2 stroke motor in YZF frame

Who makes the cleanest conversion using the latest 250F chasis with the Yz 250 2-stroke motor? I want to build a killer like this with a gorr 295 kit and revalved SSS kyb suspension for scrambles racing.

Who makes the cleanest conversion using the latest 250F chasis with the Yz 250 2-stroke motor? I want to build a killer like this with a gorr 295 kit and revalved SSS kyb suspension for scrambles racing.

I don't know it will be the cleanest conversion or not, I just started it now.

I've already got the latest 250F chasis and the Yz 250 2-stroke motor with EG295 kit.

And I'm grinding its lower engine mount to decide the 2-stroke motor alignment.

121210b.jpg

Next, the thing that I should do is to solve a lower frame issue that is the maximum problem on this plan.

I've arranged to get an used 2-stroke frame for it, and i'm waitig for its arrival.

Not sure why one would go through all this effort, when the 2 stroke comes with an aluminum frame...Do you think the thumper frame is lighter..?

Do you think the thumper frame is lighter..?

No. It's rather heavier more than 2lb.

I've rode my 2-stroke YZ250 since 2006, so I've been a little bored with its shape of the frame.

I do not think that there is so much benefit in this effort, too.

But I just want to something "new" for my 2-stroke. :-)

Edited by kmtr

After reading a couple of threads about CRACKED al. frames, I'm not sure I'd do it....but thats just me. Especially if you're a balls out SX/MX rider that weighs much over 200lb.

No. It's rather heavier more than 2lb.

I've rode my 2-stroke YZ250 since 2006, so I've been a little bored with its shape of the frame.

I do not think that there is so much benefit in this effort, too.

But I just want to something "new" for my 2-stroke. :-)

Why not a VDlaar kit instead then?

Why not a VDlaar kit instead then?

I also think the VDlaar kit is one of awesome solution for guys who want the appearance of a new 4-stroke style.

It's just replacing the exterior. It's easy except for the cost. And there is no risk of broken frame you've spent a lot of money either.

As a matter of fact, I had thought to make a copy of the kit. To make its tank and subframe is not so difficult for me.

However, among the new something I want, there are not so many percentage of appearance. I love the look of the old-style 2-stroke YZ rather.

I've ridden on the new 4-stroke of course. I want to know the performance of the YZ250 2-stroke motor with a new designed frame therefore.

Both center of gravity and the characteristic of the engine are different from 4-stroke though it is not to saying.

Also different dimension and stiffness of the frame itself. I expect those differences would bring something new to me.

And most important thing of all, I want to try to make it by myself. :)

Edited by kmtr

Local guy has one, believe its an 08-09 250f frame with an 04 yz 250 motor. Said surprisingly everything lined up pretty well only had to modify one of the two engine mounts, believe a few spacers around swingarm/motor to make it track straight with chain.

No. It's rather heavier more than 2lb.

I've rode my 2-stroke YZ250 since 2006, so I've been a little bored with its shape of the frame.

I do not think that there is so much benefit in this effort, too.

But I just want to something "new" for my 2-stroke. :-)

how many lbs is the frame?

how many lbs is the frame?

It's about 23lbs. I measure two stroke frame before. It was about roughly 20-21lbs in my memory.

A 2-stroke frame that will become victim may arrive my garage in about ten days later.

At that time, I'll comparing measure their lbs again.

Edited by kmtr

It's about 23lbs. I measure two stroke frame before. It was about roughly 20-21lbs in my memory.

A 2-stroke frame that will become victim may arrive my garage in about ten days later.

At that time, I'll comparing measure their lbs again.

thanks, have you thought about a 06-09 450 frame? my 144 motor fits right in, i ground off the lower mounts and machined up new ones, this wee the fram goes to welder ill post up pic by next week.

thanks, have you thought about a 06-09 450 frame? my 144 motor fits right in, i ground off the lower mounts and machined up new ones, this wee the fram goes to welder ill post up pic by next week.

I've read your thread. And I'm looking forward to its progress.

How did you decide the engine alignment? It's important for the movement of a rear suspension as you know.

I copied the position of the counter shaft , a swing arm pivot, and a rear axle shaft from YZ-F.

And, I'm adjusting it now.

121212a.jpg

Actually, I also have a frame of 07YZ450F.

Though I have not decided the usage of the frame, there are a few motor in my garege.

TY250Z,TTR125LWE and DT230. They do not seem so attractive combination... :(

Edited by kmtr

any updates, progress?

Have you seen my thread KMTR? I bought a yz250AF that a guy did himself, frame broke right away, then I bought a MPS frame.

You radiators will have to be customized too.

any updates, progress?

I'm sorry to have kept waiting all.

The YZ frame as victim finally arrived in my garage yesterday. It spent about three weeks by so lazy USPS and JPO.

At first, I'll make some jigs with this frame. Afterwards, a necessary part will be cut out from it.

I plan to start those works next week.

how many lbs is the frame?

I compared its weight with the YZF frame.

05-YZ250 18.9lbs

10-YZ250F 22.5lbs

Yes, 3.6lbs heavier. :(

But I don't care about it is as I've already written.

Have you seen my thread KMTR? I bought a yz250AF that a guy did himself, frame broke right away, then I bought a MPS frame.

You radiators will have to be customized too.

Ya, I'm lookig forward your thread.

I confirmed the problem while waiting for arrval of the YZ frame. I'm thinking which radiator of YZF and YZ to customize.

And, I'm thinking about how to make under pipes of frame.

If I don't mind about the much clearance with the engine, it doesn't have the problem like YZF either.

However, I want to ensure ground clearance as possible, I'm going to re-create that part.

If it is possible, could you show me some pics of the part of your frame? It would be very helpful reference for me.

To complete this plan, I should solve various problems besides.

If someone want to put 2stroke motor in YZF frame, I would strongly recommend to buy a complete frame from MPS.

They seem to have enough experience and skills for this work.

Though it is interesting for me to solve various problems by myself, but I'm nuts to do the same work with the pay for their work.

Edited by kmtr

I went a different route on my AF. This started as an 04 CRF250 that I put a very modified CR500 in. Got to ride it once then the kick mechanism failed and busted out the center and primary cases. I had this spare YZ motor in another chassis (1st gen CR250 chassis Motard) and dropped it in. It was a little harder in some things especially getting the air boot to clear the shock spring but I finally got it. I found the ultra rare aluminum pipe on flea bay and the Ohlins on Craigslist. It sports a Rad Valve, milled head and a 9 oz flywheel. Only got to ride it once but hopefully I can get it out soon. The 500 had an aluminum fuel tank I made also. It handles well and turns better than my 01 YZ250. BTW, I snagged an 05 YZ250 frame off flea bay and will start putting my 01 stuff on it. :goofy:

Craigus

Happy New Year

cryz2-1.jpg

I went a different route on my AF. This started as an 04 CRF250 that I put a very modified CR500 in. Got to ride it once then the kick mechanism failed and busted out the center and primary cases. I had this spare YZ motor in another chassis (1st gen CR250 chassis Motard) and dropped it in. It was a little harder in some things especially getting the air boot to clear the shock spring but I finally got it. I found the ultra rare aluminum pipe on flea bay and the Ohlins on Craigslist. It sports a Rad Valve, milled head and a 9 oz flywheel. Only got to ride it once but hopefully I can get it out soon. The 500 had an aluminum fuel tank I made also. It handles well and turns better than my 01 YZ250. BTW, I snagged an 05 YZ250 frame off flea bay and will start putting my 01 stuff on it. :goofy:

Craigus

Happy New Year

cryz2-1.jpg

how did you solve your airbox issue, did you make a new one, i just got all my carbon fiber materials today and should get the fram back by wed this week, im off all week so ill have some late nights mocking up everything than sending to powder coat.

not sure what the big difference is but I had a CRF450/CR500 conversion and I could not get it to turn well at all, so I changed to a YZ 250F platform, and OMG what a difference. The YZ turns on a dime.

not sure what the big difference is but I had a CRF450/CR500 conversion and I could not get it to turn well at all, so I changed to a YZ 250F platform, and OMG what a difference. The YZ turns on a dime.

I've tried to say that before in these threads and there is always someone that thinks the mod is about using the new plastic, etc. It is a much bigger change than something as superficial as new shrouds and tank. I think my bike handles great and I won't go back to a conventional YZ and I have one! The other YZ250 sits in the garage in basically new condition after a complete rebuild but it doesn't compare to the new one.

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