Rotax cylinder conversion

[HondaATC500X]

I remember a thread here from a few months (year?) ago about the rotax cylinder conversions. What all is involved in doing that? Obviously welding/machining, my question is to what extent and what rod setup should be used?

[jon370r]

Cases need to be welded up to move the base studs and narrow the transfer port area. Rotax cylinder need to be machined to accept a water neck in the rear like a 250R cylinder and you need custom head, intake, and exhaust manifolds. No problem!!!

[jon370r]

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[jon370r]

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[jon370r]

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[slamdak8782]

which rotak cylinder is it piston rod bearing combo. How big is it? Have you dynoed it? Ok that was a lot of questions

[jon370r]

Originally posted by slamdak8782
which rotak cylinder is it piston rod bearing combo. How big is it? Have you dynoed it? Ok that was a lot of questions

2002 Skidoo 800, +4mm Hot rod stroker crank, 82mm Honda Oddessy piston. There are alot of odds and ends to make this work but runs and makes great power with pump gas.

[Higgy87TRX425]

That motor looks sick! How hard was it to put together? I guess the real question is how much did it cost? I'm looking at spending about $3000 on a PUMA motor. How do you think that your motor compares to a Puma 431, on race gas?? What kinda HP are u putting out? I'm only asking because I'm building a motor real soon so I wanna get all the info I can, please answer as many questions as you can it would really help me!! Thanks!

[jon370r]

I have aprox $1200 into the complete engine including the bottom end that I purchased off Ebay and brand new crank. Keep in mind that I did all my own machine work so the cost of that isn't included and would add up quick. I lucked out on some of the speciality parts but it took me about 6-8 months of trial and error to put together my 1st prototype wich was base on a stock stroke crank and a single cylinder off a 700. It ran so well I took it back apart after riding it twice to build the 800 cylinder version on the same cases. I would say it makes about 60HP but it is built very mild, no port work done and 160lbs compression so I can trail and gravel pit ride with pump gas. I shipped my quad out to Glamis from Maine 2 years ago and road all week and it quit on the the last evening I was there because of a pulled base stud that caused a coolant leak. I was an easy fix an I improved on the design in the process. Base studs havent been a problem since.Below is a pic of the 700 cylinder version which would be a 350cc.

[HondaATC500X]

Jon, thanks a lot for the reply, you were who I was thinking of when I made this thread but I couldn't remember for sure who it was! I really think I want to give this a whirl...I've got a lot of tig welding experience and I'm fair on a bridgeport so I should be able to do what needs to be done. You mentioned the studs pulling out, was that because of the proximity to the inside of the crankcase (transfer tunnel, etc), or ? Also, where the heck is the front studs on those cylinders at, is it down inside the water jacket? I looked at the one piece 2 cylinder heads on ebay some and I'm pretty convinced i can even modify one of those and make it work...

[HondaATC500X]

By the way, yours is in a Laeger narrow chassis which is exactly what I was wanting to do with mine :)


What do you run for a pipe? I want mine to be as reliable as possible, its going to be a rider. I'll keep compression low, probably not even port it.

[slamdak8782]

Thats really awesome I wish I had saw it before I started my polanda project

[jon370r]

I origionally welded up the honda stud holes and had problems with the weld quality and the cylinder bolts pulling out. The rears were the problem so I threaded a 5/8 billet plug into the cases and sunk the bolt holes into that. Yes the front bolts are inside the waterjacket. I have several of the custom single head, dome and intake manifold you will need for this project and will try to post pics of them tomorrow.

[HondaATC500X]

Jon,

Any chance you were able to take some pictures of that stuff? :)

[jon370r]

You asked for it, you got it.

[jon370r]

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[jon370r]

sorry about the grainy pics. Our camara got broken this weekend.

[jon370r]

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[HondaATC500X]

Very Nice! Might be in the market for one of those heads and intakes in a month or two :)

What pipe are you running on yours?

[Xowner]

DAMN! thats nice work right there!

[slamdak8782]

I am still so jealous. I want one