Simple Engine Mods

[ZR2]

ok right now my motor is comp stock and i am ordering a cam from tc (cross country) and a pipe from him (supertrap). i wanted to know what else can i do to wake up the motor without boring it out and all that. just something simple maybe a piston, head gasket, i want to still be able to run pump gas. any suggestions would be helpfull.

p.s. the type of riding i do is mostly racing around a homemade track with the guys sometimes we will go to a motorcross track and race that but just for fun, and i dont want to bore or anything because this bike will event. go to the wife, thanks alot

[YZROOSTINYA]

HIGHER COMP PISTON 10.8:1
remove the choke, higher flow filter
jetting
gearing
smaller rear tires
holes in airbox

[Cannonball08]

while you have it tore down putting a cam in it you might as well take it the rest of the way down and put a hi-compression piston it also, ( the cam will benifit well with the piston), Use a XR400 head gasket, other little tricks would include holes in the airbox lid K&N airfilter, removal of the choke and grinding out the welds in you head pipe, all of this with the correct jetting will really bring the EX to life!

[ZR2]

ok is it real hard to change out the piston, ive never had to deal with valves and timing chains and such, dont want to putit back together and it blow up. also what piston should i get, some say wiseco but :confused: thanks

[Cannonball08]

You should beable to change all this out yourself, go buy the book that shows how to do all this in detail if your not sure you can do it yourself. I would buy a JE 11:1 piston, Just my Opinion

[YZROOSTINYA]

the wiseco is a 11:1 and a mix of race gas should be used. my friend has a 11:1 and NEVER ran race gas. he beats the piss out of it and we ride in hot weather and do climbs all day. he has 4 yrs on his motor with one on the top end. he also has a all-around web cam.

the je is a 10.8:1. there basically the same but you get some people with preference.

the piston swap is not too hard but def get a manual if you have never done his before. i have no prob doing it but patiance is def sumpin you need the first time. just mark your bolts and take pictures. once you do it you 'll be like why did i ever pay that guy $$$ to do this. its really not that hard. if you have a decent understanding of mechanical things you can do it. also get a torque wrench

[ZR2]

thanks for the quick reply i will try to find a manual for the 400 and while i had it a prt i was going to do the choke, grind welds and all that. and unless anyone says otherwise it will be a je 11:1 piston and a xr400 gasket to go with the pipe, filter, cam. thanks

[stocktires]

I wouldnt even put in a cam without a high comp piston, But I guess thats just me.
Here are all the cheap/free mods I know of

-Remove choke
-k&n/uni/twin air filter
-drill/take off airbox lid
-grind welds in header
-xr gasket
-gearing and rear tires
-adjusting your throttle (if it has too much slack frum tha factory)

[stocktires]

O yea, If you do any racing (play or not), you might wana look into some nice tires (smaller ones), nerfs, bars, and maybe even a nice axle, a-arms and shocks depending on your budget.

[ZR2]

yeah i got some 18in holeshots in the back and 19s in the front,douglas 190s with the plus 1 offset in the front, and it handles alot better. i plan to get some plus 1 arms to go with the offset on the rims and a plus 2 axel with some elka shocks. i dont want to go to wide so i can still ride in the woods some.

ok so lets get this straight here is what im getting:

cross country cam from tc
supertrap pipe from tc
xr 400 head gasket
and still a little foggy on the piston YZROOST said that a wiseco 11:1 would need at least a mix of race gas i dont want to have to run race fuel.

so should i go with the je 10.8:1

(man 2 strokes were so simple)

[416ex_ba]

What do you gain by removing the choke and grinding the welds.

[MOUSE]

better air flow, the faster you get air and gas in and out of an engine the better the power

[MOUSE]

the choke and welds in the pipe are resticting to air flow thru the bike

[Jblazin98]

Is it really that hard to remove the choke and grind the welds and is it a really noticable power difference.

[MOUSE]

there is a thread on here that has the procedure to remove the choke and you have to bump up the jetting on it, the welds are real simple just unbolt the head pipe look into it where it bolts to the head and youll see the welds, get a dremel and go to work

and you can tell the diff. with the responsiveness

[Doibugu2]

If I swap out the piston for a higher compression, do I have to have it bored? Or can you buy one that fits the stock cylinder wall?

[MOUSE]

you can gget one to fit the stock bore as far as i know if im wrong someone will correct me:D

[ZR2]

wich piston do yall think the wiseco 11:1 and do i need race fuel with this one or the je 10.8:1 should run with pump gas fine right?

[Houser Cannondale]

if you run premium pump gas 93 or 94 octane it shoud be fine but defanatly no less. if the motor is not very old you can probably use a stock bore piston and rings. but if it has some time on it you might want to take it to a machine shop and have it bored and fitted with the next size larger piston and rings. boring is usually only 25 or 30 bucks and it will be just like it came from the factory when your done.

[yellowrider]

hey man,

i know a couple of people that run piston ratios 10:5:1 and run race gas, dmc dull system, web cam.

that thing is pretty fast i dont know if he can beat raptors or anything.. but you can tell night and day difference hill climbing you have so much more power and control of the bike... it woknt lug as easily either..

his motor oil most of the time reads 210, but if he gets it up to 270 he stops... for a couple of minutes and everything is fine again...

i think it is a nice motor! he does alot of drag racing also...


anyways what ever you decided to do just make sure you check around for prices and stuff before you rush into it,.. cause you could find a better deal and more power if you just wait..


i am to cheap to do any mods to mine:devil

i have a 97 chevy 1500 4x4 that is still stock and i need to do soemthing about that...... and junk is not cheap and neither is gas!!:D

so i just come on here and check out what other people are doing to there ex ,.....

[YZROOSTINYA]

supposedly your supposed to run race gas with pistons that are 11:1 or higher. my friend has a stock bore 11:1 with a web cam in his 400ex and has never ran race gas. he has benn beating the piss out of for almost 2 years now with no probs. for safety sake if i were you i would get the je @ 10.8:1

i just ordered a wiseco 11:1 416 kit for mine and i am getting a hot cam stage 2 cam. the only time i will be running race fuel is in the summertime when it is really hot. and my mix will be 1 gallon to 4 gallons.

if you run 93 or 94 you will have no probs. i am also gong to get a aftermarket oil cooler set up for added durability.

alot of people take the race gas thing way too seriously. it does help with the cooling of the motor and does burn cleaner but with such a minimal compression jump it really does not do all that much. if your motor is not PINGING, DETONATING, KNOCKING then you DO NOT NEED IT! besides from what i have read the 11:1 is not really 11:1 when you take in to effect the cam and and duration and all that stuff. my 99 yz250 would ping like mad on pump fuel, my aircooled ex has yet to do it and i beat the piss out of it everytime i ride.

[Cannonball08]

You shouldn't have to run race gas with a 11:1, If you could afford it I would mix half race and half 93 octane. I would only go with the 18 inch tires if your going to run MX if not then just run a 14 tooth sprocket

[Jekyl_22]

I have an IMS 440 11:1 Kit. With Premium pump gas, it pre-detonates (pings). I run a 50:50 mix of race gas and pump gas. Does anybody have any comments about Octane Booster? I have used it a few times when I didn't have any race fuel.

[stocktires]

I used octane booster for a while on my R.
As long as you mix the right amount, it works great!

[BigThumper33]

I run an xr gasket with a wiseco 11:1 and run fine on 91, no pings, knocks, nothing.