Powroll 350X

[wilkin250r]

Has anybody done the powroll engine conversion for putting a 350X engine into a 250X? Was it very difficult? Did you use the stock 250X carburetor? What jetting? Did you use the powroll exhaust, or did you make your own exhaust?

[300exazzkikr]

do a search for this it's been covered many times. it's not hard, you have to cut the back motor mount otherwise it bolts right up. somepeople use 400ex headers and modify them or they have a kit exhaust but it's madd $$.

[SBC101]

I know you don't use the 250x carb but you can use a 400ex carb that will work or a 39mm Kehin FCR Carb for the 350X-250X Conversion but the conversion is simple with the right tools and time but fairly eaxy I have to ask my friend did two of these conversion I will ask him what he did.

[wilkin250r]

Originally posted by SBC101
I know you don't use the 250x carb but you can use a 400ex carb that will work or a 39mm Kehin FCR Carb for the 350X-250X Conversion but the conversion is simple with the right tools and time but fairly eaxy I have to ask my friend did two of these conversion I will ask him what he did.

The powroll website says use the 250X carb. That's the whole reason I started this thread. I've done the search, and many people said "Yeah, it can be done, check out powroll. Yeah, it's real fast..." but nobody has specifics, and there is no mention of the carburetor in any of the previous threads that I've read.

[nismo]

IMO i would think when you get the 350x engine you would try and get the carb too. i wouldnt use the 250x carb unless money is tight b/c its smaller less air = less power just my 3cents

[wilkin250r]

This is the exact reason I started this thread. Is there something that makes the 350X carb undesirable? Perhaps you also need to replace the throttle cable? Perhaps the 350X carb is too tall, or doesn't fit?

In all reality, I have no problem using the 250X carb. This is going to be my spare quad, ridden mostly by my friends who don't have a quad of their own and don't know how to ride real well. I don't need 60hp out of it, but I need something bigger than the little 250X in case my 350lb buddy wants to ride with me in the sand.

I'll also be putting nitrous on it, but that's just so I can whoop my girlfriend's stock 400EX. She doesn't think I can make a 250X beat a 400EX, and she won't be able to tell that I put a 350X engine in it, she'll think it's still the 250X engine.

[01_300ex]

You can use a 250x carb, You will just need to make an extension on the carb boot so it will be long enough.

[nismo]

wont a stock 350x beat a stock 400ex? i thought so maybe i was miss led

[wilkin250r]

Originally posted by nismo
wont a stock 350x beat a stock 400ex? i thought so maybe i was miss led

I think they are pretty close. I think an ATC 350X will beat a stock 400EX, but the 350X in the 250x frame is going to be heavier than the ATC350X.

However, I don't want to be pretty close. I want to beat her pants off. I bought this 250X for $400. She says "There's no way you can make that little $400 quad beat my brand new 400EX!"

The length's I'm willing to go to prove I'm right :devil:

[SBC101]

You don't need nitrious to beat a 400ex you just need better carb than a 250x carb and port & polish or bore kit but you can pretty much beat a stock 400ex with a stock 350x you be pretty suprised of the power of the 350x don't be cheap and use the stock 250x carb .

[wilkin250r]

Originally posted by SBC101
You don't need nitrious to beat a 400ex you just need better carb than a 250x carb and port & polish or bore kit but you can pretty much beat a stock 400ex with a stock 350x you be pretty suprised of the power of the 350x don't be cheap and use the stock 250x carb .

Yeah, but I already have the nitrous on the 250x right now, installed in the carb.

[jbach72]

I've done 2 conversions so far. One was into a 250X, the other is the one I'm still working on, a 350X into a 1988 250R. The 250X is simple, I did it in two nights in my garage. If I remember right, the biggest part was making the stock 350X headpipe longer to clear the frame tubes of the 250X as well as extending the stock arrester to mount in the same position and still meet up with the stock headpipe(To get them to mate, you will have to cut the mount end of the arrester off of the 350 pipe and weld it to the 250 arrester). If you have a MIG welder and a hacksaw, it shouldn't be too hard to do. I did use the stock 250X carb as it has an excellerator pump in it(it takes out the hesitation when jamming the throttle on hard). You will have to shave the rear engine mount down and shim the rest of them to get it in there, but honestly anyone with a little mechanical know how and a half decently outfitted shop could do it. i wouldn't waste my money on the Poweroll conversion kit. I would however freshen up the 350X motor or up the displacement with a Poweroll Kit, as it is now going to be pushing a heavier front end. Stock it will still lift it in 3 out of 6 gears. Dirt Wheels did an article on the conversion way back when and I believe I still have it, if you need, I can scan it in and send it to you. The R conversion is quite a bit more challenging, but if you look around on the web, you can find all kinds of info on it too!!

Good Luck

[honda250xrider]

if u want to beat her just with your 250 all you have to do is regear it and ull end up winning on top end but i guess it all depends how long you are racing

[hondafox440]

You one crazy mothafocka to have NAAAWWWZZZZ on your quad!

[wilkin250r]

Originally posted by hondafox440
You one crazy mothafocka to have NAAAWWWZZZZ on your quad!

I did it just to try it, and if I blew it up, I was only out $400! Nitrous kits come with both fuel and Nitrous jets, and you jet the mixture just like normal jetting. Too rich and it will bog down, too lean and you can melt the piston.

At first, I had it jetted way too rich (factory reccommended jetting :rolleyes: ) so I hit the button, and it just died.

I increased the size of the nitrous jet, and when I hit the button in 3rd gear, the front end came up, and almost came over on me. Scared the crap out of me, but I had a grin from ear to ear. :D

[hondafox440]

So it injects it right into the carburetor? Thats pretty cool, but sounds annoying to tune. Did you buy the quad with the nitrous installed already?

[wilkin250r]

Actually, the way I had it set up, the nitrous was between the carburetor and the cylinder intake, so it was basically direct injection. It was a pain to tune, because I had to remove the gas tank each time to change the jets.

I put the nitrous on myself. I bought a kit on ebay. It was originally for a 2-stroke watercraft, but the kits are all basically the same. One fuel solenoid, one nitrous solenoid, a fuel pump, a nitrous bottle, an injection nozzle, and an activation switch. I did a LOT of research on the web before I installed it.

[MDE3]

TC Racing has probably done as many 350X motors as anyone I know(including for guys like Travis Spader), and every one uses a larger carb. Even with NOX on the quad you still will want the increased fuel/air mix to get the maximum performance out of the engine when the NOX is not on........

Most conversions I have run used the Lectron 44/38 taperjet carb supplied by TC racing, which is supposed to have the needle taper ground for each engine (TC's grind on the needle), but I'm sure the FCR 39 mm will work fine as well and give you more tuning flexibility. The Lectrons work great for us IMO, although others have complained they do not like them. They are about 60% or less of the price of an FCR 39 mm. If you give TC a call (if you can reach him...he's pretty tied up with Doug Gust's Suzuki these days)) and tell him what you have done to your motor, he will sell you a Lectron set up for your engine.

Fitting the larger carb sometimes involves raising the tank mounts for the fuel tank to give more clearance if you want to run the carb perfectly vertical. With the Lectron we just turned them at an angle of about 25 deg., so they fit under the hollow(there is a cable tunnel in the floor of the stock 250X /300 ex tank) in the stock fuel tank. This never seemed to hurt the performance any.

We never ran airboxes so we just used the stock intake with a K&N and outerwears attached to it. We made custom supports for the filter. We heated the carb end of the intake to allow it to stretch to fit the larger carb bore.

As far as beating a 400 ex, we raced every variety of modified 400 ex(except nos engines which are not allowed), as well as 330r's 265 r's, Banshhee's, Cannondales, YZF.s, Raptors and modded 350x's with those bikes in Flat track and MX.....those motors were still very competitive, beat some, lost to others, but never to stock bikes.

The last time we ran the smaller engined quad.only a 363 cc conversion, but still a TC racing engine, it easily outran a stock 400z. And that engine was very tired when we did that....valves sticking and piston/bore clearance way out of spec.

Using the 430 kit with a Powroll pipe should be plenty......even without the NOS. The powroll pipe is the easiest conversion for a 250X frame.

[wilkin250r]

I don't really want to put any serious mods into the engine. This is just a backup quad for friends to ride. If I was going to shell out money for a new carb or serious upgrades, I'd put it into my 250r instead.

The only reason I'm doing nitrous isjust for novelty, and because I already have it on the 250x now. The 250x carb is cheap (because I already have it) and it has an accelerator pump, for quick throttle response. I'm not worried about getting maximum performance out of this engine or carb. I just need more power than the 250X, and I like the idea of 6 gears...

[swamprider7]

Use a 400ex carb. They are cheap, give better performance, and also have an accelerator pump. You can find them cheap on ebay all the time.:D

[markeg192]

Your NOS powere 250X wants to come over in third gear but your girl beats it on her 400EX ? I think we see who is the rider in that relationship.

[cat_crap]

I am in the process of converting a 250x/350x. I just shaved the back motor bracket and it fit right in. I am using a 400ex carb. I would like to know if anyone used a 400ex carb for this application. If so what jets did you use. The engine is bored 92mm piston, ported, shaved flywheel, fst cam, and powroll exhaust. What jets should i use?

[MDE3]

A stock 400 ex carb? isn't that only 36 mm? Seems a little small for a 450+ cc motor with a big cam. Suggest you look at a Lectron 38/44, or FCR 39 mm for this motor, or you may not see the gains you expect.

Are you sure you are at 92 mm? Normally they have to cut and reweld the case, then redrill the stud bores for a 92 mm bore, or so i was told by TC. Maximum without doing this I believe was 89 mm.

[wilkin250r]

Originally posted by markeg192
Your NOS powere 250X wants to come over in third gear but your girl beats it on her 400EX ? I think we see who is the rider in that relationship.


Ha ha ha.

Actually, nitrous has an odd little quirk, but if you look at how it works, you understand.

Your engine pulls air through the carb. The faster the engine revs, the more air it pulls, and you get more power.

Nitrous is fed at a constant rate. That means you get more PER STROKE at lower rpms. At 3000 rpms, you get twice as much nitrous/fuel per stroke than you do at 6000 rpms.

This means you get more boost at lower rpms. It's possible to see a 10hp gain at 3000 rpms, and only 6hp gain at 5000rpms. I can jump off the line, but my top speed isn't much faster.

[markeg192]

J/K But I would think you might try gearing it up . My son rides an X srock bore WB cam pipe and we worked on the head and I guess with the right gearing it should be close to a stock 400.

[wilkin250r]

That's exactly what I'm thinking. Since my nitrous gives me more boost at lower rpms, I'll gear it to beat the 400 up top, and use the nitrous to beat it off the line.

[cat_crap]

Yes it is a 92mm piston. I got it from FST. The first one I installed, it ran for about tw0 weeks and I cracked a valve. That piston and head got torn up. luckliy i slavage the cylinder and sleeve. I just got it back together and now i cant get it to run right. I am trying a 400ex carb first and will by a Fcr later. What jat setting are people running on a 440 kit for 400ex????

[Smokin 440]

Im at a 200 main and thats all i remember but thats the biggest jet i could getif i could do it over i would spend the extra $$ on the fcr insteads of dicking around with stock, my $0.02

[Moded86R]

I can't really help you with the the install.


However I rode a 91 250x the other day with a race built 350x engine.And let me tell you.It ran pretty dang good.I was on a short gravel road at my buddies house.

After kicking it for a good 10 minutes.(it stays outside under an overhang)We finnaly got her to fire.It was geared so the front end wouldn't come up unless you tried.But I can tell you I was in 4th gear and I was scootin.Plenty of power for that chassis.



Add a little nitrous to that and a stock 400ex is way back there:devil:

[MDE3]

In pure flat track(oval track, 1/8th to 1/3 rd mile) racing which tends to be more horsepower intensive than some other forms of racing, the ol' 350X motors are still seen frequently on 250X conversions. While of course it depends on what mods are done to the motors like any other racing, I can honestly say that in general, there were more 350X/250X's in the front half of the pack than 400 ex's.(416's 440's 490's etc.) This may be because the 350X's out there were older and had been more worked than some of the 400 ex's given the number of years they have been around, and the number of mods which had been developed for these motors, as well as the fact that TC racing who did a lot of National 350X motors, is here in Pa.

But if you consider what we spent on a used 250X/350X to make it competitive out there, we were probably $4000 - $12,000 under most of the hot machines. There were some YZF.s, lot's of modded Raptors, all kinds of modded 250r's, Big bore Banshees, lot's of 440's, Cannondales etc. Even in the open classes with unlimited cc's there was usually one or two of the old 350X's still running up towards the front of the pack, and sometimes leading it.

The typical hot bike as run by guys and girls like Jason Dunkleberger, Sue Parker(former top 3 women's pro class national mx rider and in a couple of the Huevos films), Dustin Wimmer, etc., was about a $14,000 to $18,000 bike.

Many of the privately built Raptors, 250r's 440 ex's , Banshees etc were also up there over $12,000.

For a $6000 old 250X/350X to get out there and be competitive still says a lot for that old motor. Of course if we had paid for every mod done to that quad from scratch and bought the quad new, it would be up there in the $10,000 - $12,000 too. Like so many of them we bought it already pretty trick and started from there.

[Justin St.Jeor]

I am getting ready to big bore my 400 and stroke it and wanted
to know if anyone has tried to use a crank out of an old xr500
motor. I have a guy checking on it but was wondering if anyone
knows????:confused: