350X conversion question

[quadracer04]

I know that using the Powroll kit makes it the easiest to do, but I have a few other questions.

Can you do it without that kit? With the 350X motor and carb and stuff can you use an aftermarket 250X exhaust, such as Sparks X-6? And would that 250X exhaust be better than the Powroll exhaust that comes with the conversion kit?

I need to know this stuff ASAP fellas so any help is greatly appreciated

[Tri-valleyracin]

it would be realy hard for u to do it with out the kit. the pipes the come with it are made for the aplication and a stock pipe wouldent work and a 250x pipe wouldent work eather becuse the the 350x has two out ports for the head pipe and a 250 x has one. or u can get two head pipes and muflers for a 250x and maybe make a custom dull pipes.

[quadracer04]

I remembered that the 250 has a single exhaust port after I posted. I read up on the Powroll kit some more earlier today and it seemed like the best thing.

[quadracer04]

Also, other than more power, what are the advantages to doing the switch? Does the 350 have taller gearing and go faster?

[Tri-valleyracin]

if it was me i would stay with the 250x motor and get a 390 stroker for it from four stroke tech.

[quadracer04]

Im not really into a gas guzzling motor that runs on 110 octane. I just need something better.

[kyleschonert]

You wont have to if you get an 11:1 piston. If they make it for that application.

[quadracer04]

I dont really want to stay with the 250X motor. I want to go with the 350X motor.

So if anyone knows what the advantages to using the 350X motor are, please post them:D

[bwamos]

More CC's.

[wilkin250r]

You can change your own sprockets if you just want taller gearing.

Power is pretty much it. Reliable power. But then again, isn't power enough? Why else would you upgrade the engine?

The 350X is a good motor, with six gears. No reverse. It will accelerate faster than a stock 250X engine, and have a higher top speed, too. A fully worked-over 390cc stroker would be faster, but less reliable, have a more temperamental powerband, and be more likely to overheat.

[quadracer04]

Thats exactly why I dont want a 390 kit^^ Too much hassle. I like stock motors better.

I knew about the faster top speed and more power, thats obvious, I was just wondering if there was any other reasons that only a few people know about.

[ZeroLogic]

with having a 330 big bore kit dose it blow the gaskets?

[quadracer04]

I have no clue and in case you havent noticed that isnt what this topic is about.

[TRXRacer1]

The swap is real nice but don't spend too much because you're still way better off with a 400ex. If you can sell what you have and apply that with the money your going to spend in the swap to get a 400ex then go that route. Powroll wants to much money for that pipe and it's got a crappy design. I had a headpipe made for $225 and it went to the stock location for the 250x/300ex muffler. The head pipe is a little bigger in diameter for the 350x so the end of the 250x/300ex aftermarket silencer just had to be enlaged a hair. If you're stuck on the project another bonus is that the 350x motor can be taken to 452 and still have reliability when built right.

[quadracer04]

I originally was gonna buy a 400ex, but the guy backed out at the last minute. Plus I think I can buy my friends 250X for like $800.

So I'm thinking for the basics it should cost a whole lot.

250X - $800
350X motor - about $700
Powroll kit - $515

So for about $2000 I could have a decent bike. Then Im gonna sell all the 250X parts that I dont use or replace and sell all my aftermarket blaster parts for parts for the project. Maybe even sell my blaster if I want more money.

[dork]

actually, you'll be hard pressed to build a better performing pipe than the powroll one. the head pipe is where the power's at, and their design is based off the HRC racing exhaust honda offerred for the xr500/600 motors.

the 350x has the same trans ratios as the 250x, but it has a .950 sixth gear. so you'll want to go to a 14/36 combo to start.

you can keep your 250x wire harness, you just need the 350x cdi and then reverse the wires in the 2 way connector at the cdi.

as far as power goes, if you use a stock 350x, it will be a good improvement over the 250x, but might not be as much as you expected. its easy to improve the power though, and still be very reliable. i just rebuilt my friends 350x trike, its now .080 over, 10:1, ported, 400ex carb, and supertrapp exhaust. it has stock gearing, which limits its top speed, but in a straight drag against my other friends 300ex with a FST 380 bore kit, cam, oversize intakes, fcr carb, tc exhaust, and 15/36 gearing, it will run even unitll around 4th gear where the 380's gearing and cam lets it pull away. the point is that the 350x is still understressed, it even has the stock cam, while the 300ex is pretty much maxed out.

[quadracer04]

I know about not getting a better pipe, that's why Im gonna go with the kit - engine spacers and complete powroll exhaust for $515.

I know that you just have to use the 350X CDI, but what do you mean reverse the wires?

Why should I go with 14/36 gearing? What is stock?

[TRXRacer1]

You can do better on the pipe, powroll did do a poor job on that one.

[dork]

You can do better on the pipe, powroll did do a poor job on that one.

what do you base that off of? powroll used the same dimensions from HRC's flattrack pipe for the xr motors back in the 80's. its a proven design on the honda dual exhaust port head. powroll just uses their megaphone section and a supertrapp silencer on the end of it.

quadracer04, on the harness to the CDI there are 2 connectors. one has 4 wires and the other has 2 wires. on the 2 wire connector, you just need to swap the position of the wires in the connector to work with the 350x CDI. the best way is to release the terminals in the connector with a small pick, and just swap their position. then it looks factory, no splicing.

i said use 14/36 gearing because both trannys have the same ratios except for 6th gear, and 14/36 is a good all around ratio on modified 250x/300ex's, which is basically what you'll have with the 350x. stock 250x is 13/38.

[quadracer04]

Oh i was acutally planning to go 1 bigger in front and 2 smaller in the back lol. And I am going with the Powroll kit, it seems good.

The CDI thing seems easy enough, do you know why I have to do this though? I'd never heard of having to do it before until now.:ermm:

[TRXRacer1]

Originally posted by dork
what do you base that off of? powroll used the same dimensions from HRC's flattrack pipe for the xr motors back in the 80's. its a proven design on the honda dual exhaust port head. powroll just uses their megaphone section and a supertrapp silencer on the end of it.
It's a proven design for a lighter weight machine that can bennifit from peaky power. That design robbs a lot of the mid out of the 350x. You're talking about 2 differnt animals, apples and oranges, differnt flows and profiles. You want to see a 350x make it's best power then try some longer primaries then the stubs powroll puts on and over charges you for.

[quadracer04]

Well then what exhaust system do you suggest I use on my conversion?

[notfastenuf4me]

im in the middle of doin the same conversion i bought a custom head pipe and used aluminum round stock for spacers looks great better than powroll and only paid like 200 for all not including silencer and other stuff ive done to the motor

[dork]

quadracer, the 2 wires do the same thing on both machines, its just that they're in different locations at the CDI plug. one goes to the stator and the other goes to the kill switch.

TRXracer, if you can custom build an exhaust that will out perform the powroll one, thats great, its just that the average guy whos trying to fit an exhaust probably won't. yes the powroll is overpriced, along with the install kit. i've seen some lengthen 400ex headpipes.