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honda300EXtreme
03-27-2008, 08:12 PM
i know me and others have answered many of the same questions over a short period of time, so i figured if there is one reference chart with a majority of 300ex frequently asked questions, in theory this could save everyone some time, i will keep adding to the list feel free to add something useful! :)

ok, here we go remember this all 300ex info, some corresponds to the 250x some doesn't.


stock valve lash =.004
Stock jetting = 122 main , 120 main (high alttitude), 38 pilot, stock needle position - 3rd groove
Wheel offsets - front = 4/144 rear =4/110
Stock gearing = 13 / 38
stock spark plug # - DR8ES-L

stock carb 32mm keihin with accelerator pump.

Ignition: CD with electronic advance
(300ex CDI will not work on 250x)

Ground Clearance : 4.6 in. (stock)

Will 400ex a-arms work?
yes, you will need a-arms, tie rods, and 400ex length shocks (16.25), and a shock relocator bracket, 400ex spindles are not neccessary but are an improvement with this set-up,and yes stock brakelines will stretch far enough.

will a 400ex steering stem work?
yes, stops on bottom need cut off beacuse there 180* off, and the little washer about 3/4 will need removed, it is roughly 1'' longer

will a 400ex carb work?
yes, i recomend it for engines that have atleast the basic mods, such as pipe. filter, ect.. stock boots will stretch, all you need to do is rejet, and i recomend a 42 pilot jet

Hardweld rockers are only necessary for a hard weld cam -
EX. web cam, billet cams such as hot cams do not require hard weld rockers, they will actually cause damage to your cam

What is max. compression piston on 93 octane. - 11:1
any thing over is pushing and detonation could result.

engine idle speed = 1,400 +/- 100 rpm
stock pilot screw setting = 2 1/4 out from closed

engine compression with stock piston - 171 - 200 PSI

engine oil capacity -
oil change only - 1.6 quarts
oil and filter change - 1.7 quarts
totally engine dissambly - 2.11 quarts

*if you run a oil cooler about 2 quarts even on basic oil and filter change*

Suspension
Front: Independent double-wishbone with dual hydraulic shocks, 5-position spring-preload adjustability; 7.1 in. travel
Rear: Swingarm with single shock, 5-position spring-preload adjustability; 7.9 in. travel

Fuel Capacity- 2.2 gallons, with a .5-gallon reserve

chain free play - 1 3/4 in. at most

heres a gearing calculator to show how variables such as rev-limit, tire size and gearing affect speed
gearing calculator (http://home.earthlink.net/~gellett/mph.htm)

here is the link from the tech section on how to rig your reverse set-up, used when you use a aftermarket clutch lever & perch or if you are just tired of hurting yourself when you try to engage reverse
reverse bypass (http://www.atvriders.com/articles/reverse300ex.html)

quad clicks when start botton is engaged -
its can usually be narrowed down to 2 things, assuming your battery has a proper charge, and it putting out correct voltage at (100% it should be reading about 13 volts)
now, its either your solenoid, or contact brushes in your starter

Common Rear end Swaps:
A 01 raptor rear shock will work but they are famous for blowing bladders on the 300ex

a 450R swingarm will also work, how ever this set-up requires tabs to be welded or bolted to the frame to accept the linkage. You WILL have to use a 250R rear shock, linkage is up to you, the 250r or the 450r linkage will work, carrier and axle, and rear brakeline will also be needed. the swingarm is around 3 inches longer
the 350x rear end will also work
same as 250r
more info will be added by me constantly,, don't be shy feel free to add anything you think would be useful

QUAD BOGS WHEN IN WATER?
alot of times it is your carb vent tube. the one that hangs down behind the motor. the problem is this tube gets submerged, you can either trim the tube shorter, or put a T splittler on it and add a different length hose.

ridered92
03-27-2008, 08:29 PM
Originally posted by honda300EXtreme


Will 400ex a-arms work?
yes, you will need a-arms, tie rods, and 400ex length shocks (16.25), 400ex spindles are not neccessary but are an improvement with this set-up,

[/B]

you will also need a shock relocator with the 400ex a arms and shocks

honda300EXtreme
03-27-2008, 08:37 PM
^ good call cody, i knew i was forgetting something

ridered92
03-27-2008, 08:39 PM
not a problem mike great thread

2muchquad
03-31-2008, 11:58 PM
What is max. compression piston on 93 octane. - 11:1

This is debateable.engine set ups along with location are just a few of the variables to add to this.Did i mention cam as well?Valve overlap plays a huge factor in ACTUAL compression.Im at around 12 to 1 with my 385ex and i have never ran anything more than 93 oct.Thats almost $3.50 a gallon and that enough let alone paying for race gas.Of course the higher the compression the more strain it puts on the bottom end so i shoot for a happy medium;)

honda300EXtreme
04-01-2008, 04:13 PM
i agress 100% that there are too many variables with particular engine set-ups,

saying 11:1 is the highest you can go is a broad statement, but on the other hand is a good general rule of thumb.

im trying not to get technical in this thread,, its just used to answer a bunch of the basics to save me and your self some time,

MY FYN 79
04-06-2008, 08:01 AM
Maybe its just the car nut in me, but I find it easier to understand the difference in our gearing if we use a ratio rather than the sprocket sizes. Treating this the same as rear gears in a car, heres a list I made going from lowest gearing (numerically higher) to highest gearing (numerically lower). The ratio numbers dont really mean anything other than giving a good idea how drastic of a change we'll make.

12/38 - 3.17
12/37 - 3.08
12/36 - 3.00
13/38 - 2.92
13/37 - 2.84
13/36 - 2.76
14/38 - 2.71
14/37 - 2.64
13/34 - 2.62
14/36 - 2.57
14/35 - 2.50
14/34 - 2.43

mudrat454
05-03-2008, 11:23 PM
to the top for all to see!

Uphill Rush 450
06-02-2008, 08:52 PM
up!

theres alot of great info in here :eek2:

panther99
06-10-2008, 10:02 PM
ttt

SET THE STAGE
06-12-2008, 11:00 AM
am i the only one that runs a 33t rear? :p

atv70x
06-18-2008, 06:50 PM
Great info., but I need more. How can I figure what sprockets to use at the TT national over the fourth? I heard it has a 1000' straight away. We have a 300ex with a TC motor and are running 14 in the front and 37 in the rear. This works great for mx and 1/4 mile oval. The tires are 18x10x8. Also, what is a good max RPM?

honda300EXtreme
06-19-2008, 11:12 PM
well it sounds like you have a good motor, so i would drop one more tooth in the rear go to a 36.

a 300ex with a well built motor can greatly benefit from a 1000 RPM increase, that is if you still running stock box with stock rev-limit

other than that, you could possibly go to 20'' rear tires but if your running stock width rear end that could hurt you racing TT cuse the 300 is known to be a tad tippy

Uphill Rush 450
06-21-2008, 12:26 AM
honda300EXtreme you seem to be good with the 300's

i have been pondering the thought of rebuilding my 250x for quite some time,

now im starting with a stock motor, what do you recomend doing, budget is really no concern at this point, i want to make this thing run strong, i was thinking 11:1 piston, and maybe port and polish,

what do you think about over sized valves and that sort of stuff and what about exhaust and cam?


thanks alot bro, this thread has helped me alot, this should be pinned at the top of the page!

honda300EXtreme
06-23-2008, 08:40 PM
ok..

i would first go to four stroke tech and get a 80mm piston kit, it includes sleeve, piston rings, circlips, and head gasket
this kit uses a 11:1 piston and the valve recesses are large enough to accomodate oversized valves,
next i would send my head out to a reputable builder and have them install +1mm valves, all 4 oversized valves will allow alot more airflow to your engine, and show a nice increase across the board, and also have them port and polish your head, for your riding style, then your gonna need HD valves springs because it sounds like you want an aggressive cam, also remember to have them replace your valve seals because it added insurance and there cheap.,

also look into a 400ex carb because the stock will hold you back once you start going this far into it

as far as exhaust, curtis sparks and hmf are both great pipes for the 300 and add great power, just remember to get a full system because 300ex headers are very restrictive,

as far as cams go,
personally i had a hot cam and wasn't impressed, so i would find something a bit more agrressive,

web cams are good, FST can make you a custom cam, curtis sparks sells them and there are many others, you will also need hardweld rockers

hope this helps

Uphill Rush 450
06-23-2008, 08:47 PM
thanks alot,

i appreciate all the help

if the wife gives me the okay i might just have to tear into it



thanks again

honda300EXtreme
06-24-2008, 11:18 PM
no problem

happy to help

;)

dabomb_350x
06-27-2008, 08:40 AM
The Stock carb on a 300EX is as followed. '93 though '98 (49-states), Non emissions, is a 28mm Keihin '98(California) thought current, emissions, is a 32mm Keihin. All shock 400EX have a 38mm Keihin.

Spark Plug gag is .024-.028.

I have a sevice manual if any one need more info. I try to get it for them.

honda300EXtreme
06-27-2008, 01:42 PM
:confused:

to the best of my knoledge the 300ex carb has always remained the same (32mm with acc. pump) in every state, in 1998 i believe they re-routed the crancase breather to the air-box to make it more "emissions friendly" i guess.

i know in certain parts of the country they jet them a bit lean for lower emissions.

again im not calling you a liar. i just have never heard this, and to be honest i dont think it is accurate,

dabomb_350x
06-27-2008, 02:35 PM
Carb model number on non emissions is QB02A and emissions is QB04A. 4 mm is not a very noticable difference unless you get a set of mics out and measure.

It list them different in the service manual and a article I have from that Mickey Dunlop in '96 that said you need to put a 32mm carb. on the bike in place of the 28mm.

I look in my owners manual to see it that spec is there or not.
And get back to you. I have both models.

Uphill Rush 450
06-28-2008, 12:25 AM
never heard of this either???


why hasnt this been stickied yet? this is the only post in this section that is actually helpful its like my on line service manual :p

dabomb_350x
06-30-2008, 07:31 AM
I was right and I was wrong, it is not a 28mm. In the service manual it says it has a 29mm ventri dia. carburetor.

And a link from on here.
http://www.exriders.com/vbb/showthread.php?postid=218084

dabomb_350x
06-30-2008, 03:01 PM
I think the difference, in the size of the carb, is to get the clean air to gas mixture, as close to being the same, as it was on pre-emissions add on. On the emissions bike, they are adding blow-by gas back into the air intake, which would cut into the clean air mixture, so they increased the carb size to offset this issue.

honda300EXtreme
07-01-2008, 10:56 PM
glad this helped

as long as it helped one person it makes this thread worth the time put into it

sparks427
07-13-2008, 12:26 PM
hey all would it be better to widen the front or rear of the 300 first cuz i'm gonna do somthin w/ the suspension but i got to thinkin bout it and dont knwo what to do first. thanx

SET THE STAGE
07-13-2008, 12:37 PM
front for sure. widening the rear will make it handle horribly

sparks427
07-13-2008, 12:38 PM
right on well then i think i'll find some a-arms then. how much wider are +2 400ex arms than 300s?

SET THE STAGE
07-13-2008, 12:41 PM
+2 400 arms on a 300 would be about +3.25 (so about an extra 6 1/2" added)

i run them on mine
http://www.uscconlinealbum.com/photos/photo01/9d/71/5a417563f589.jpg


you'll also need a relocator bracket and 400ex shocks. you can get the bracket from jb racing or diamond j's (i think that's what it's called)

sparks427
07-13-2008, 12:43 PM
ok for one dude thats bad ***. i'd like to set mine up like that and i foud a couple 400ex a-arms for a pretty good price. is ur rear widende?

honda300EXtreme
07-13-2008, 10:18 PM
yea, the 300ex's front end is to say the least a weak point,
the shocks are terrible, and the front end is too narrow for any real kind of aggressive riding (IMO)

+2 400ex a-arms with stock offset wheels should put you somewhere in the 47-48 inch range i do believe

i personally run +1 400ex a-arms and with stock offset wheels i measure in at 45''

sparks427
07-14-2008, 05:10 AM
awsome well i just bought repomans +2 400ex lonestars so they should be here in a week. i need 400ex shocks and a relocater bracket and brake lines now so i'll be doin all that here soon. thanx guys for all ur help.

NV300ex
07-21-2008, 05:02 PM
ok i have a question only cause im searchin n lookin for it.. maybe im overlookin it... wheres an online download for service manual on the 300ex?

honda300extreme, what brand are your foot pegs, im diggin them.

dabomb_350x
07-22-2008, 07:24 AM
In all my searching I was never able to come up with a manual for the 300EX, I ended up purchasing one off ebay. I did come up with a few other models, but they are no long available either do to copy write issues.

NV300ex
07-22-2008, 06:26 PM
dabomb---- looks like im going have to do the same exact thing myself...

honda300EXtreme
07-22-2008, 06:51 PM
my footpegs are stock, i did make some foot peg extensions but there not pictured.. if you mean my heel guards there IMS

as for the online manual, most of the sites got shut down,
your best bet would be one off of ebay

honda300EXtreme
07-24-2008, 11:13 PM
one more thing,

a IMS oversized tank will not work with a lonestar anti-vibe stem
:mad:

SET THE STAGE
07-25-2008, 12:24 AM
have you tried a clarke? mine's only a 2.7 gallon (half gallon more) and it seems like there would be enough room for an aftermarket stem (especially if it were longer)

honda300EXtreme
07-25-2008, 12:54 AM
yea i figure thats gonna be my last option, i loved that 4 gallon ims tank . but i like the stem even more. so i bought a stock tank untill i can find something better
the stocker wouldn't be so bad if it wasnt metal

honda300EXtreme
07-27-2008, 08:30 PM
thanks

the nut for the clutch basket is 81 FT. LBS.

and the clutch spring bolts dont have a actual torque spec. just get them snug with a ratchet. the spring tension is what holds them in place, just remember dont get them too tight, (4-5 ft. lbs is your determined for a number)

sparks427
07-27-2008, 08:40 PM
hey for all who helped me out w/ my questions on my front suspension i want to thank you. i figured i'd post some pics of it so you all could see it. i know the caster camber is probly off but i'm still waitin on the bushings for it so i might change it all then.

honda300EXtreme
07-27-2008, 10:11 PM
yea, some adjusting on the front and you'll be set

it looks great man.

sparks427
07-27-2008, 10:13 PM
where should the caster/camber be set too? completlely straight up and down or slightly in at the top? thanx for the compliment.

honda300EXtreme
07-27-2008, 10:23 PM
i personally, set my wheels straight up and down

some perfer more caster and some more camber,
i shoot for a happy medium,

sparks427
07-27-2008, 10:24 PM
right on well thanx for the help yet again haha.

honda300EXtreme
07-27-2008, 10:25 PM
no problem, happy to help

JohnT_98300EX
07-28-2008, 06:02 AM
With the fronts tipped in the way they are you should be getting s real quick initial turn in and then it "pushes" (goes straight) The straighter up and down you get them the better it will handle over all. If you go to far it will get real quick and twitchy.
On my 250r upper arms I found that UNI Lug type wheel spacers work great as shims.

sparks427
07-28-2008, 06:11 AM
right on well i'll get it all set and if its not good enough i'll try them spacers. i'll just have to play w/ it a little bit haha.

Uphill Rush 450
07-29-2008, 12:13 AM
hey, my 250x has a brand new wiseco piston, and recently new valve seals, but it still smokes untill warm is this normal?

thanks for any help

honda300EXtreme
07-29-2008, 12:40 AM
the 2 most common sizes for oversized valves for a 300ex are +1mm and +2mm,

i personally like the +1mm intake and exhaust valves, it provides a nice increase across the board, but some prefer to only do the intake valves for more bottom end, and the exhaust valves for more top end

i have seen people run valves as large as +3mm but at that point you would be running extremely hot and sacrificing reliability,


all builders have there own preferences, four stroke tech for example uses +2 mm valves.



but with these air cooled motors you need to find a balance between peformance and longetivity



heres the link from the tech section on removing the choke ;)
http://www.atvriders.com/articles/choke400ex.html

honda300EXtreme
07-29-2008, 12:42 AM
will a 400ex bumper work?

yes, however a few spacers will most likely be requied to fill some space

very easy and common swap

honda300EXtreme
07-29-2008, 12:45 AM
Originally posted by Uphill Rush 450
hey, my 250x has a brand new wiseco piston, and recently new valve seals, but it still smokes untill warm is this normal?

thanks for any help

yes this is normal, the rate at which aftermarket pistons expand differs from that of the stock pistons,

different metal types : (cast & forged) are the main factors in this

Uphill Rush 450
07-29-2008, 12:51 AM
:blah: (sigh of relief) thanks so much man,

i aprecaite all your help


this thread needs stickied, theres alot of info to be learned here, i guess the mods forget about the little old 300ex section :p

honda300EXtreme
07-29-2008, 12:55 AM
no problem man, glad i could help

honda300EXtreme
07-29-2008, 12:57 AM
how could i forget the 2 main things

stock speed - 54-55 MPH

stock horse power 15-17 (:( )

sparks427
07-29-2008, 07:31 AM
those are horrible, how much more power do ya get w/ a 330 big bore, a stage 3 web cam, port and polished head, oversized valves, an oil cooler, sparks x-4 pipe, and k&N filter w/ 400ex carb. not sure if the hardened rockers and the HD valve springs figure into that but if they do how much more does that add.

honda300EXtreme
07-29-2008, 11:08 PM
with that set up, anywhere from 28- 31 HP is respectable,
(stock 400 range)


the engine builder plays a huge factor into this though

sparks427
07-30-2008, 10:44 PM
right on well i'm pretty much plannin that set up this winter hopefully if all goes right. so i would be able to keep up w/ my brothers suzuki 400 easier?

honda300EXtreme
07-30-2008, 10:56 PM
^^^yes sir
build it right and you might be waving goodby as you pass him :p

sparks427
07-30-2008, 10:58 PM
haha i know it and that would piss him off soooo bad, i thought about that FST 380/390 kit but i duno if i wanna go that big i read that it gets unreliable but i duno i still have a few months b4 winter i still have riddin time left to decide that so we'll see.

honda300EXtreme
07-30-2008, 11:03 PM
so you get that front end straightened out? how do ya like it?

sparks427
07-30-2008, 11:05 PM
not yet i'm still tryin to get the ball joints broke loose from the spindle, no such luck w/ that yet tho. it do like it with the way it is but i know its not right and i need to get it fixed but its really nice so far. i was gonna ask you too if a 300 bearing carrier and axle will fit in the 450 swinger, i'm sure its a long shot but thought i'd ask.

honda300EXtreme
07-30-2008, 11:11 PM
nope, your gonna need the 450r carrier and axle. 300ex stuff wont work right.

at least everything is going good for your quad, mine is turning into a big headache

:grr:

sparks427
07-30-2008, 11:15 PM
ok thats what i figured i just wasnt sure i thought mabey i'd be able to use my nice billet carrier in the 450 swinger but i guess not oh well.

whats the matter w/ urs.

they seem to be never ending and the worst part is i'm just gettin started on mine. haha.

honda300EXtreme
07-30-2008, 11:24 PM
ok, i got my motor all finished and broke in, cam chain tensioner goes, snaps the cam chain and takes out a valve spring and valve ( all parts have very little time)

buy new valve and had to order brand new valve spring kit, cuse they wouldnt send me the parts i needed

get everything back together

running hot, oil pump is shot, fries my cam and rockers (badly)

so thats where i stand right now

i was gonna get aftermarket cam and rockers soon but not this soon. oh well the only part that sucks is. i wont get my refund for the core charge on the rockers


so thats been my luck latly


:(

sparks427
07-30-2008, 11:29 PM
oh geezz man thats startin to make me think about just replacin all that while i have it apart just to prevent that from happening. that really sux man well i hope you have it back up here soon, you have to nice of a quad to be just sittin around w/ a blown motor.

honda300EXtreme
07-30-2008, 11:47 PM
yea that tensioner bit me in the ***, the cam chain was brand new,

yea do it right and replace what you can,


thanks for the kind words

she'll be up and running eventually. im gonna give her one more chance

sparks427
07-31-2008, 05:49 AM
right on well good luck with it man i hope you get it up and running. that sux really bad.

honda300EXtreme
07-31-2008, 08:36 PM
thanks man,

ill post up some pics of the damage

sparks427
07-31-2008, 09:02 PM
right on man well that'll be intresting to see.

honda300EXtreme
07-31-2008, 11:22 PM
interesting yes , pretty no!

ill get some tomorrow

if any one has some useable rockers let me know!

honda300EXtreme
08-02-2008, 06:32 PM
well i decided to part it out :(

i have it posted in the 300 section and the forsale section

sparks427
08-02-2008, 06:33 PM
no way man why in the world are you doin that?

honda300EXtreme
08-02-2008, 06:37 PM
sent ya a pm

i need to move on, this thing has turned into a money pit and i need to get out of it. i need a new vehicle. and the list goes on.
it breaks my heart but you gotta do what ya gotta do :(

sparks427
08-02-2008, 06:39 PM
sent ya one back bud.

honda300EXtreme
08-03-2008, 07:55 PM
well anyways heres some pics of the damage

honda300EXtreme
08-03-2008, 08:05 PM
heres one of the cam :grr:

sparks427
08-03-2008, 08:12 PM
dude that really blows.

sskustomz
10-16-2008, 12:39 AM
lotta great info ttt

10-16-2008, 07:50 PM
Originally posted by honda300EXtreme
yea, the 300ex's front end is to say the least a weak point,
the shocks are terrible, and the front end is too narrow for any real kind of aggressive riding (IMO)

+2 400ex a-arms with stock offset wheels should put you somewhere in the 47-48 inch range i do believe

i personally run +1 400ex a-arms and with stock offset wheels i measure in at 45''

wow dude were did u get those plastics!!!!!??????????????

honda300EXtreme
10-23-2008, 07:02 PM
those front fenders were maier customs with maier 250r scooped hood

tomtom79
11-14-2008, 05:15 AM
here is a compression ratio calculator www.rosspistons.com/calculator.php

Supergumby5000
12-02-2008, 12:13 AM
wow, awesome thread

this is really going to help me with my 250x/400ex frankenstein build.

dbc112
01-15-2009, 08:24 AM
Anyone know if 450R front spindles will fit 400ex a-arms and tie rods? I am looking to replace the complete package..

450R spindle, Caliper, Breaks, rotor.. basically remove my entire setup and bolt on the 450r, connect break lines (bleed), put wheels back on and roll.

hondaracing0144
01-16-2009, 04:46 PM
hey i heard that the400ex graphics will fit on a 200ex with cutting buti was wondering if there was curtains years or not

hondaracing0144
04-04-2009, 11:14 AM
whats the best front tire for mx that you can put on the front stock rims

dbc112
04-04-2009, 11:17 AM
21x7x10 or 22x7x10.

Are you asking what is the best brand for mx or size? A ton of discussion in the other topics regarding tires of all types.

hondaracing0144
04-04-2009, 11:20 AM
both because i have 18'' Turfs on the back and i wanted around a 20'' front but i dont want to buy a new front rims

chargercalvin
04-08-2009, 08:10 PM
good thread, very good thread. i have learned alot. i have some quick questions. can i put a 450r or 250r hood on my 300ex? it has stock front plastics and no hood at all. i had to make one out of a floor mat lol.

also, what is this thing??? it is loose. i can pull it right out with ease. should i put a little liquid gasket on it?

http://i39.tinypic.com/30xabee.jpg



and...my ex runs ok but hesitates in low rpms and backfires like crazy when i let off the gas in high rpms. it has a fmf megamax pipe with the end cover on. i adjusted the mixture screw a while back but i set it to stock today and its still doing it. it isnt leaking at the slipon conection or header...so?????
i have already done the little things like clean spark plug and carb wich pretty much checks out. and the floats are good, the idol screw does not work so i just adjust it at the throttle. anyway, what could be making it run like crap?

Quadkid440
04-08-2009, 08:57 PM
Originally posted by chargercalvin




and...my ex runs ok but hesitates in low rpms and backfires like crazy when i let off the gas in high rpms. it has a fmf megamax pipe with the end cover on. i adjusted the mixture screw a while back but i set it to stock today and its still doing it. it isnt leaking at the slipon conection or header...so?????
i have already done the little things like clean spark plug and carb wich pretty much checks out. and the floats are good, the idol screw does not work so i just adjust it at the throttle. anyway, what could be making it run like crap?

Runnin rich. Try taking your airbox lid off and see if it gets any better.

chargercalvin
04-08-2009, 10:39 PM
i tried it didnt help, someone even drilled some holes in the airbox so it doesnt do much anyway. i tinkered on it a little today. its not hesitating anymore but the backfire is still really bad. what is the thing i took a picture of?

thanks,
calvin

dbc112
04-09-2009, 08:22 AM
when you put the exhaust on, did you make sure to tighten down the header bolts? Also a ring should be in front of the exhaust where it connects to the header pipe...


Did you rejet when you upgraded?

Stock slow and main?

chargercalvin
04-09-2009, 10:07 PM
well i bought it with the pipe and filter. im not sure if a moron who had it before me jetted it or not. im thinkin i atleast need a bigger slow jet. i think that would help the backfire and yes i tightened everything down just to make sure. i guess its runnin lean maybe? it prob needs a good carb rebuilding and jetting.

cr480r
04-20-2009, 09:43 AM
will a 400ex axle work in a 250/300 carrier?

QuadCobbler
04-23-2009, 03:32 PM
Originally posted by cr480r
will a 400ex axle work in a 250/300 carrier?

If your wanting to just take out a 300ex axle and slap in a new 400EX than no it will not fit, If you want to take an extra brake rotor hub and use it as a spacer to take up the extra space on the splins then probly. Oh and run the same thikness spacer on the oposite side wheel so your axle will be even.

slocalduner
04-30-2009, 12:11 AM
hey what is a shock relocater? i have a friend who has a 300ex and i have all my stock front suspension?

thanks

dawg
05-11-2009, 12:23 AM
will the 400ex nerf bars work on my 300ex?

josh79z28
06-05-2009, 11:34 PM
hey sparks427 what size sparks jet do u have in your bike i have a 300ex with a full sparks pipe and i dont think it is jetted

wideopenracing5
06-11-2009, 04:29 PM
Originally posted by dawg
will the 400ex nerf bars work on my 300ex?

i dont think they will

IRISH-RACER-14
06-11-2009, 04:37 PM
Originally posted by wideopenracing5
i dont think they will

it will work with forward a arms and a longer swingarm. or else if ur 300 is stock then u must have 18 rear tyres and 20 in the front

dns1764
06-12-2009, 04:47 PM
What's the redline with the stock cdi box?

hisi
06-15-2009, 09:56 AM
If I install houser +3 longtravel a-arms on a 300ex what will the wheel base be? I am trying to keep it 50" or a little less!

Also what is the maximum size piston that I can go up to to stay under 300cc for Nationals. 75mm or 76mm???

SET THE STAGE
06-15-2009, 10:48 AM
+3 for a 300 will be under 50 inches. no worries. a lot of people run +2 400ex arms which leaves you almost at 50

hisi
06-15-2009, 01:01 PM
What about 400ex +3 long travel?

SET THE STAGE
06-15-2009, 03:18 PM
well i think even on a 400ex, +3 would be about 51 or so. +2 400ex arms on a 300 is pretty wide. it's what i run and i've had it on it's side wheels maybe twice. no worries.

adelmer
06-28-2009, 01:37 PM
We recently purchased a 2005 Honda 300 EX, I dont get to take it out everyweekend and from time to time forget to put it on the charger, its really easy to bomb start, but was wondering if you can get an aftermarket pull start kit, or kick start kit?? Thanks in advance for any input on this! Thanks and have a great day :)

SET THE STAGE
06-28-2009, 01:41 PM
Originally posted by adelmer
We recently purchased a 2005 Honda 300 EX, I dont get to take it out everyweekend and from time to time forget to put it on the charger, its really easy to bomb start, but was wondering if you can get an aftermarket pull start kit, or kick start kit?? Thanks in advance for any input on this! Thanks and have a great day :)

there are no kits per se, but you can convert the 300ex into a kickstart. the 1987-1992 trx250x had the same engine but a smaller stroke and it was kickstart. you would just have to find a good bottom end and swap some parts over. sadly, this involves cracking the cases to be done properly because one shaft that holds a gear is absent in our newer bottom ends.

hondaracing0144
06-28-2009, 02:01 PM
i got gas leaking from the overflow line when i hit mid 3rd and its leaking on my swingarm. i heard that my jets or float s might be stuck in the carb. is there any way to stop it from leaking

adelmer
06-28-2009, 02:16 PM
Originally posted by SET THE STAGE
there are no kits per se, but you can convert the 300ex into a kickstart. the 1987-1992 trx250x had the same engine but a smaller stroke and it was kickstart. you would just have to find a good bottom end and swap some parts over. sadly, this involves cracking the cases to be done properly because one shaft that holds a gear is absent in our newer bottom ends.



Thanks so much SET THE STAGE for the quick reply! Its muchly appreciated :)

Edited to add: Since I got such a quick reply, does anyone know if you can get a twist throttle for the 05 honda 300? Thanks again, this site is great for info!

hondaracing0144
06-28-2009, 02:31 PM
http://www.partsforatvs.com/default.asp?p=1375&c=715&cn=M3Q+300EX%2F250X+BARS+%26+CONTROLS

SET THE STAGE
06-28-2009, 03:37 PM
Originally posted by hondaracing0144
i got gas leaking from the overflow line when i hit mid 3rd and its leaking on my swingarm. i heard that my jets or float s might be stuck in the carb. is there any way to stop it from leaking

not sure if you've ever messed with a carb before but it's very easy. take your carb off (or loosen it away from the boots so you can move it upside down) take off the bowl (the bottom part. should be 4 screws) and just make sure everything is moving freely that looks like it should be moving lol make sure you keep it upside down while you're doing this though. you don't want anything falling to the ground. i once dropped a tiny pin that keeps the float attached and it took me a few days to find it.

hondaracing0144
06-28-2009, 03:54 PM
my friend told me i had to rebuild it

SET THE STAGE
06-28-2009, 04:08 PM
Originally posted by hondaracing0144
my friend told me i had to rebuild it

that's what quitters say (just kidding)

in order to rebuild it, you'll have to do everything i said anyways so i think it'd be worth your time to at least give it a shot and possibly save some money. if it doesn't work, then a rebuild kit may be in need

my best guess is something blocking the float, though. that's what ultimately controls the overflow i think.

hondaracing0144
06-28-2009, 04:09 PM
okay thanks

reconmaster
07-17-2009, 09:03 PM
heres what i did for a 400ex front end. its more reinforced than what a bolt on relocator would be. cut the shock towers and raiser them about 3 inches roughly. tack them on 1st and line everything up. one you get the desidered set up weld the towers on and make a brace in between the frame rails as you will see in the pics to help with strenghtening of the frame. you will have to remount the front fender brackets but they will support the fenders better. also use round tubing to gusset the frame as you will see in the pics. i got this done on my old 300ex back in 05 and from what i understand its still holding up for the current owner.

cut towers
http://i1.piczo.com/view/5/l/7/y/p/2/o/j/n/3/d/img/i70051796_45523.jpg

everything welded with the raised front fender mounts
http://i1.piczo.com/view/5/l/7/y/p/2/o/j/n/3/d/img/i70051820_77205.jpg

http://i1.piczo.com/view/5/l/7/y/p/2/o/j/n/3/d/img/i70051814_56897.jpg

heres the round tubing guessets
http://i1.piczo.com/view/5/l/7/y/p/2/o/j/n/3/d/img/i70051804_47254.jpg


hopes this helps for anyone whos on a budget so you don't have to spend too mcuh money on a 300ex before you grow into a 400ex/z400 450etc

wideopenracing5
08-18-2009, 08:32 PM
can a 400 or a 250r hood fit in my stock plastic?

wideopenracing5
08-18-2009, 08:33 PM
can a 400 or a 250r hood fit in my stock plastic?

born2ride14
08-18-2009, 09:21 PM
Originally posted by SET THE STAGE
well i think even on a 400ex, +3 would be about 51 or so. +2 400ex arms on a 300 is pretty wide. it's what i run and i've had it on it's side wheels maybe twice. no worries.


400ex +2= 47 ish
400ex +3 = 50 ish

thats with 4-1 offset wheels

Tommy Warren
08-18-2009, 10:03 PM
awsome thread lots of info guys great job. I just wanted to add one thing and I don't know if it matters or not but the 250R had 2 different sized linkages. the 88 linkages is about an inch longer than the 87 or visa versa. don't know if it will affect anything but it may. just a heads up for the guys doing the 450R swinger

QuadOwner
08-18-2009, 11:44 PM
stock rev limit?

QuadCobbler
09-15-2009, 12:34 PM
bump :D

414tinner
10-11-2009, 04:52 PM
Has anyone done the 450R swing arm with the 450r shock and linkage, instead of using the 250R shock and linkage?

If so what needs to be done other than welding a bracket to the bottom of the frame to mount the linkage. Basically I am asking if the upper shock mount on the 300ex frame is in a close enough location to mount the 450R shock or is that all thrown off by the 450R shock and linkage.

I currently have the 88 250R rear end on a 300ex and I would rather have the 450R on there if it all works.

Thanks!

shiley55
10-11-2009, 08:39 PM
didnt see an answer abotu the 250r hoods on the 300 but do you have to run the new style plactic or can you use the old style plastic

sparks427
10-11-2009, 09:00 PM
i've seen it done on the old plastics, i was gonna b4 i got rid of mine, it just takes some work to make it work and i dont think the new plastics fit on the new bikes w/o alot of work. but ya it should work, and then just cut a hole in ur stock fenders to make the scoop functional.

honda300EXtreme
10-11-2009, 09:15 PM
414tinner
the 450r shock would not be useable, if i recall correctly the resiviore of the shock hits the tabs that the shock is supposed to be mounted to.. a 250r shock is about the only option and if you have a few extra bucks to spend get the shock rebuilt and you'll be set.

hondaracing0144
10-11-2009, 09:16 PM
anyone know how to hook this up i know it goes to the stator and i know the other think but where are you suppose to connect it into at like where on the stator

shiley55
10-11-2009, 09:33 PM
cant you still use the 01 raptor (660 cause ppl ask) shock with the 450r swing arm

m0t0xk1d
10-11-2009, 10:26 PM
no cuase that would be the same lenth as a stoch 300 shock. with the 450r rear end you would be able to use a longer shock.

QuadCobbler
10-12-2009, 07:09 AM
It's not that you would be able to use a longer shock. The 01 raptor shock has the same eyelet on the end of the shock as the 300ex. The 250r shock has a fork on the end the goes on the out side of the rear link. I guess the 250r shock could be longer, but I never really looked.

honda300EXtreme
10-12-2009, 11:56 AM
hondaracing0144
to wire a kill switch into your stator wire, just simply remove some of the insulation off of the wire, do not cut it and splice or solder into the appropriate wire.

you can also splice into the positive side of your coil i do believe

sameltoe
10-13-2009, 04:04 PM
Originally posted by adelmer
Thanks so much SET THE STAGE for the quick reply! Its muchly appreciated :)

Edited to add: Since I got such a quick reply, does anyone know if you can get a twist throttle for the 05 honda 300? Thanks again, this site is great for info! check your messages:D

shiley55
10-13-2009, 08:36 PM
this is what i say to a rwist throttle http://www.youtube.com/watch?v=5B55YK_Ux_o



make sure you watch it with the volume on

sameltoe
10-13-2009, 10:41 PM
That's why it's for sale! lol i hate them fing things! This 300 i bought had it on their. . first thing off !!

shiley55
10-17-2009, 11:53 AM
bump

Uphill Rush 450
10-18-2009, 10:57 PM
hey,
i just got an oil cooler for my 300ex does any body have any pics on how they ran the hoses. im not sure what oil line there supposed to go to

any help would be appreciated

honda300EXtreme
10-19-2009, 06:20 PM
heres what pics i have that might help you.
you just cut the black line and attach the hoses make sure you cut the line while removed and blow it out with compressed air to avoid metal shavings in the motor.

Uphill Rush 450
10-19-2009, 06:29 PM
thats exactly what i needed thanks alot

this thread needs to be a sticky it answers almost every question in this forum

great job guys

thanks!

shiley55
10-21-2009, 06:42 PM
bump

shiley55
10-22-2009, 12:47 PM
in this thread it says you do not need hardface rockers for web cams but on there site they require hardface rockers for all of there cams for the 300ex

honda300EXtreme
10-24-2009, 09:37 PM
i never saw that post,,, and if it was me i was probably half asleep haha


any agressive cam requires hard weld rockers, that way the rockers match the hardness of the cam

let me expand on this,

most aftermarket cam companys will start with a stock core, they will add material to this cam then machine them down to the desired size, cam lobe size and so on.

a hard weld rocker is a similar process they build up the material on a stock rocker and then machine it to spec.. this way they all have the same hardness

shiley55
10-24-2009, 11:13 PM
yea its in the main section i just didnt want someone to get a cam and not think they need to get the hard face rockers cause thats what they read on a website . for anyone who wants to know the diffrence what hard face means is that it is a much harder metal and if you had hard face cam and not hard face rockers it would slowly mash the rocker everytime they touched and it would casue or valves to not open correctly over time and also the tiny bits of metal wouldnt be good floating around in the motor eather and if you had hard face rockers and not cam the rockers would eat up the cam

QuadCobbler
11-16-2009, 02:27 PM
bump:D

4x4_war
11-16-2009, 08:17 PM
Originally posted by honda300EXtreme
how could i forget the 2 main things

stock speed - 54-55 MPH

stock horse power 15-17 (:( )

How fast would a 330ex with an fmf slip-on megamax 2 with k and n airfilter, and 14/38 sprocket, with 20in back tires go?

SET THE STAGE
11-17-2009, 12:50 AM
close to stock.

QuadCobbler
11-30-2009, 06:43 AM
:D

4x4_war
11-30-2009, 12:38 PM
no, it actually goes 65 now. i ran alongside a car, and tested it on a radar. it does 60-65.

4x4_war
11-30-2009, 12:38 PM
no, it actually goes 65 now. i ran alongside a car, and tested it on a radar. it does 60-65.

reconmaster
12-09-2009, 09:54 AM
Originally posted by shiley55
in this thread it says you do not need hardface rockers for web cams but on there site they require hardface rockers for all of there cams for the 300ex

you need them i destroyed my stock rockers and the cam...got the hardweld rockers and still holding up for whoever has it now

Big_Guy_Green
12-19-2009, 12:24 AM
bump

honda300EXtreme
01-10-2010, 08:57 PM
bump

venomrider57
01-18-2010, 11:27 AM
this could have already been asked but i was wondering if 450 a arms could fit on a 300?

honda300EXtreme
01-18-2010, 01:46 PM
not without modification they wont, 400ex is the only common swap that is a direct fit

QuadCobbler
01-19-2010, 01:51 PM
The mounting tabs on a 450 frame are wider than a 300ex. You would have to cut the tabs off and move them about 1". 250r and 400ex arms both fit the 300. The is some one on here that had a frame moded to fit 450 arms.

bsolomon918
05-26-2010, 05:16 PM
Plastics question. will honda 450r or 400ex work on a 300ex?

4x4_war
05-26-2010, 05:21 PM
GET SOME

sameltoe
05-26-2010, 05:44 PM
I just bought a set of 250r prp longtravel a-arms, And they DID NOT fit. So hopefully 400ex ones will....