300ex/350x conversion

[1998300ex]

Hey guys, sometime next year I am going to hopefully buy a 350x motor to swap into my 300ex chassis. I just wanted to know what is all required in parts to succesfully complete the conversion. I have read stuff about like a 350x wiring harness or something like that, but I am not for sure what all I need to swap the motors and make the 350x motor run when it is in the 300ex frame. All I want is a list of parts that are needed to make this conversion a succesful one. Thanks in advance guys.

[dork]

i just finished doing one on my 300ex. you'll need at least a 350x motor, 350x cdi, 250x harness or 350x harness, 250x or 350x kicker, some engine mount spacers, and a custom headpipe. if you want to run lights you'll need a 250x (if you run a 250x harness) or a 350x (if you run a 350x harness) voltage regulator, and if you want the honda style on/off light switches then you'll need a 250x or 350x unit(if you keep the 300ex unit, the engine will only run in the off positions and i think the connector is different). thats the short story.

http://i8.photobucket.com/albums/a18/strato-streak/000_0242.jpg

[ZeroLogic]

Originally posted by dork
i just finished doing one on my 300ex. you'll need at least a 350x motor, 350x cdi, 250x harness or 350x harness, 250x or 350x kicker, some engine mount spacers, and a custom headpipe. if you want to run lights you'll need a 250x (if you run a 250x harness) or a 350x (if you run a 350x harness) voltage regulator, and if you want the honda style on/off light switches then you'll need a 250x or 350x unit(if you keep the 300ex unit, the engine will only run in the off positions and i think the connector is different). thats the short story.

http://i8.photobucket.com/albums/a18/strato-streak/000_0242.jpg

that is one of the cleanest 350x conversions i ever seen nice job man:macho

[Trevor]

That is awsome! But it dosen't sound like a weekend job.

[Honda TRX250ex]

Originally posted by dork
i just finished doing one on my 300ex. you'll need at least a 350x motor, 350x cdi, 250x harness or 350x harness, 250x or 350x kicker, some engine mount spacers, and a custom headpipe. if you want to run lights you'll need a 250x (if you run a 250x harness) or a 350x (if you run a 350x harness) voltage regulator, and if you want the honda style on/off light switches then you'll need a 250x or 350x unit(if you keep the 300ex unit, the engine will only run in the off positions and i think the connector is different). thats the short story.

http://i8.photobucket.com/albums/a18/strato-streak/000_0242.jpg
i was thinking about doing that too, do you have any close ups on the engine. and how much fast/more power does the 350x engine give over a 300ex?

[exrider008]

Originally posted by dork
i just finished doing one on my 300ex. you'll need at least a 350x motor, 350x cdi, 250x harness or 350x harness, 250x or 350x kicker, some engine mount spacers, and a custom headpipe. if you want to run lights you'll need a 250x (if you run a 250x harness) or a 350x (if you run a 350x harness) voltage regulator, and if you want the honda style on/off light switches then you'll need a 250x or 350x unit(if you keep the 300ex unit, the engine will only run in the off positions and i think the connector is different). thats the short story.

http://i8.photobucket.com/albums/a18/strato-streak/000_0242.jpg

nice job that engine look brand new i want to do that so bad but im a little short on money

u should make a video of u driving it so we can see it in action

[dork]

http://i8.photobucket.com/albums/a18/strato-streak/000_0236.jpg
if you look at the rear motor mount, you can see i didn't cut the case like most do to fit the rear motor mount. instead i cut the old frame mount off and made a detachable one so i can use any 350x cases, and its easier to install the motor. as far as power goes, a stock 350x makes about 23-25hp, and high 20s low 30s with some bolt ons(piston, cam, exhaust, carb) plus you have 6th gear. but you can also get that with a 330 kit in a 300ex, but the 350x has more potential and is 5lbs lighter(plus 10lbs for the battery and electrics for the 300). i would say a 350x with a pipe, 10:1 piston, and a 400ex carb would run with most 330ex's. my advice would be to ask yourself if you're going to keep it, if yes then maybe the 350x would be worthwhile. but if you want to move up to a bigger chassis, then just save up. if you take your time and use a good motor its just like the factory did it. they're different and work great for play riding and trails. mines at 452cc's so it holds its own against the newer bigger stuff, and i like the small chassis so it fits me.

[reconmaster]

sweet quad man looks super clean ya she should be quite the improvement in the power/speed department now for handling

[Honda TRX250ex]

Originally posted by dork
http://i8.photobucket.com/albums/a18/strato-streak/000_0236.jpg
if you look at the rear motor mount, you can see i didn't cut the case like most do to fit the rear motor mount. instead i cut the old frame mount off and made a detachable one so i can use any 350x cases, and its easier to install the motor. as far as power goes, a stock 350x makes about 23-25hp, and high 20s low 30s with some bolt ons(piston, cam, exhaust, carb) plus you have 6th gear. but you can also get that with a 330 kit in a 300ex, but the 350x has more potential and is 5lbs lighter(plus 10lbs for the battery and electrics for the 300). i would say a 350x with a pipe, 10:1 piston, and a 400ex carb would run with most 330ex's. my advice would be to ask yourself if you're going to keep it, if yes then maybe the 350x would be worthwhile. but if you want to move up to a bigger chassis, then just save up. if you take your time and use a good motor its just like the factory did it. they're different and work great for play riding and trails. mines at 452cc's so it holds its own against the newer bigger stuff, and i like the small chassis so it fits me.
thanks, i probly wont do it because im almost 6 foot and 185lbs so ill probly move on to a 400ex and make it 426ex and set it up for mx
BTW you did a really nice job on that quad great job

[bwamos]

Very very nice 350x bro. I'm impressed.

Has that "sleeper" look to it. Until you start it up anyway.. lol.

[lefthander12]

Will the 400ex exhaust work for the 350X motor in the 250/300ex chassis? I know about powroll and hacking a stock 350x pipe, but I'm cheap and don't want to cut the only X pipe I have. Thanks.

[Ripitupfilms]

for anyone whos doing this mod wait untill you have to try to fit the engine in..

[bwamos]

Originally posted by lefthander12
Will the 400ex exhaust work for the 350X motor in the 250/300ex chassis? I know about powroll and hacking a stock 350x pipe, but I'm cheap and don't want to cut the only X pipe I have. Thanks.

I'm sure it fits just like OJ's glove. :P

[dabomb_350x]

A 400EX headpipe is shaped the same way a 350x headpipe is so you have to hack on the 400EX headpipe as well but it will work. A 350x motor can be installed in a 300ex frame, same as 250x frame.

[dabomb_350x]

Pic of my conversion.

[dork]

you can use the 400ex header, it just needs to be lengthened to go around the frame tube. also the engine goes in about the same as the stock motor, its just a little tighter around the head. take off the left peg, go in/out throught the left side, use lots of masking tape and its not bad.

dabomb350x, looks nice. heres mine again.
http://i8.photobucket.com/albums/a18/strato-streak/000_0243.jpg

[Sjorge450R]

correct me if Im wrong, but I believe that a 400ex header has two ports?? So how would it work on a single port head???

[exrider008]

Originally posted by dork
you can use the 400ex header, it just needs to be lengthened to go around the frame tube. also the engine goes in about the same as the stock motor, its just a little tighter around the head. take off the left peg, go in/out throught the left side, use lots of masking tape and its not bad.

dabomb350x, looks nice. heres mine.
http://i8.photobucket.com/albums/a18/strato-streak/000_0242.jpg :huh :huh WTF u just posted a pic of his Quad and said it was urs.:huh

[Ripitupfilms]

350x has to ports for the pipe

[Sjorge450R]

Originally posted by atvracer9m
350x has to ports for the pipe

oh alright. I didnt see two ports in the pics.

[dabomb_350x]

The bikes are close but are two different bikes, there are a few defferents.

The 350X motor has two exhaust port like the 400EX. Out of the frame a 400EX headpipe is a direct bolt up, in the frame the headpipe has the same issue that the 350x head pipe has. They both hit the down tube of the frame, so they both need hacked and roughly 2 inches added between the flange and the bend in the pipe.

The ports are even across the motor and both bike look like they have the Powroll headpipe, which connects the exhaust port together before the bend of the pipe which causes it to look like a single port. Great for sleeper bike.

Another pic.

[dabomb_350x]

Another pic

[Ryanwolfe911]

You forgot about the part where you have to dent the hell out of the pipe where the kickstarter rests, or it will never fold all the way in and it will keep kicking out and smacking you in the shins.
Even the Powroll pipe has this dent in it, if you look closely.

[Xeller8]

I THOUGHT about doing this to my 300ex...however...I just can't convince myself that it is worth going back in time to kickstarting my quad....LOL!

VERY nice job though! :)

[Tri-valleyracin]

im thinking about doin this to my 300ex. Can i use a stock 400ex head pipe and have no problems with the down tube of the frame? im not to shure if i should do this hybrid or should i build up my 300ex motor. im going to be racing in the open class so i need good power. The 350x motor seems more able to take more mods.

[Ryanwolfe911]

If you're really worried about kick starting it, Goki, still makes an electric start kit for the 350X. It's about $400. Personallly, Id like to have it myself. I own a 250X and 300ex. I hate kick starting the stupid 250x, since i'm so used to electric start.

[2muchquad]

Yeah i have a 350x motor thats just laying around that i had in a 250x frame at one time.Its tempting knowing that i can get almost 500cc out of it with a bore and stroke but i really like the electric start and reverse of my 385ex.Im always tinkering in the shop so who knows what i'll end up doing..;)

[bigbadbrad]

hey do either of you guys that have done this conversion still have your 300ex motors? and if so are they still in good runing condition? I need one for mine, and i can not see ruining a good 350x just to get the motor out of it. If I could get a 350x, I would be running it as a 3 wheeler, but that is just me.

[dabomb_350x]

I do not have a 300EX motor. I pieced together my bike. I purchased a rolling 250X chassis for a base of my bike, and I purchased a crated 350X motor, to build the bike around.

Does any one know if you can put the crank and top end from a 350X on a 300EX lower end, which would allow the hop ups and electric start with reverse.

The stock 400EX headpipe can not be used without modifing it or the modifing the down tube. The headpipe need hacked and roughly 2 inches added between the flange and the bend in the pipe. Then you have to beat on the pipe to make room for the kicker.

Here is a pic of the powroll pipe

[2muchquad]

you can put the 350x head on a 300ex cylinder as long as it not the stock size cylinder.Mine is 86mm so the cylinder was big enough for the valves to clear the lining.You will have to use a timing chain from a atc 250es(big red) because the 300ex chain will not fit the 350x cam,its fatter.the thicker chain works fine on the 300ex crank gear,they both have the same pitch,the big red chain is just thicker,same as the one for a 350x,just 110tooth instead of the 114tooth that is stock on the 350x.;)

[Xeller8]

Sounds like that could be opening up a huge can of worms..

I think I'd just stick to building the 300...you can get tons of power out of the 300 as it is.

[Ryanwolfe911]

I don't think you could put a 350X crank in a 300ex bottom end.
I know you can't put a 300ex crank in a 250X because the crank bearings are much larger. Chances are you can't do it with the 350X either, allthough, I have never personally taken the bottom end apart on a 350x and compared it to a 300ex. I may do that in the future, just to see if it can be done. It wolud be pretty sweet to have a 350x/300ex hybrid with reverse.

[zell250x]

How much of the case do you need to cut out? and what mounts do the spacers go in at?

[JIMFROMTEXCO]

ruffly 2 1/4 inchs ive got my bottem end in and all lined up wating on my head and piston to come back

[SWIGIN]

that powroll pipe is 1 3/4'' this is a pic of the pipe i built...its on a rx but i have built 2'' pipes for 250x hybids and the kicker does not hit...you just have to hug the frame

[250X_project]

Originally posted by Ryanwolfe911
I don't think you could put a 350X crank in a 300ex bottom end.
I know you can't put a 300ex crank in a 250X because the crank bearings are much larger. Chances are you can't do it with the 350X either, allthough, I have never personally taken the bottom end apart on a 350x and compared it to a 300ex. I may do that in the future, just to see if it can be done. It wolud be pretty sweet to have a 350x/300ex hybrid with reverse.

You could just get a stroker crank and have a longer stroke than the 350X. Though a 350X stroker would be longer. Also, ask yourself which is more important, reverse or 6th gear?

Is there a 6th gear kit for the 250X/300EX engine?

Very nice build!! Very clean! What carb are you running? Did you get the FST 92mm big bore? I have thought of this many times, after I am done with my 250X engine. What other mods? How would you compare it to a 450R? (you've got me interested)

[zell250x]

has anyone used a 300ex or 250x carb on a 350x motor? What jetting do you have to run?

[250X_project]

It can definitely be done, but I don't know the specific jetting.