anybody considered swapping in a 4 stroke?

[Vernon Head]

I personally don't think it's any faster. But the insurance is for a 125 shifter and no larger. I think this can be corrected in the future.

[Kirk Schenck]

Welll to answer the question, yes it has been done. Yamaha is offering a complete wr250f kit. It comes with a motor mount, Oil res (the bike uses the frame) exhaust (very heavy) battery/electronics box (battery not inc)starter,carb,radiator,hoses,fule pump, fuel line and hardware. Just add battery, oil, gas and a strong person to lift the back of the kart. I must say it isn't cheap at around $5,300.00. It would appear that you could take one out of a bike cheaper but you would have to find a pipe, oil tank, and battery box and motor mount.
I purchased one of the kits after my CR125 blew the bottom end at the beginning of a three day event. I road race with the people who sell and run the kit. Their kart has been competative and as fast or faster on a straight pull on a slow start long straight. We road race with a car club and have numbers in the high 20s. We will have at least 10 125s. Most of us are experienced (aka fat). Their kart with the kit and a 185 lb driver were always competative. I was competetive with a strong 125 and a 213lb ass. With the kit installed on my kart it seams that everyone that I was equal to just walk away from me now. Some what depressing after spending $5,300.00. I figured the thumper would compensate for my fat ass. I have only run with it a few times and have not tweaked it at all. I must say I like the starter as I am alone most of the time. I had to install a winch in my car port to lift the kart off of the bed cover on a Toyota 4x4. I use to be able to wrestle it off by myself onto a kart stand. That bas tard is heavy. I think the pipe must weigh 12 lbs. I ditched the battery box with a heavy cast aluminum base for a light weight Tupper Ware container. I found the power band to be very flat and very short. It just does not wind up like my 125. In a effort to help this I installed a Rekluse slipper clutch. So now it acks tike the my old Honda CT90. No clutch put it in gear and go. My expectation was to dial in the slip below power band to widen it. I have only run one practice day with it and the engagement was to low. When I get off my butt after writing this post I have to replace one of the plates with a thinner one to bring up the RPM engaugement. As is it helped the downshifting big. Before it down shifted much like a 125 upshifted at WOT. It didn't. In order to down shift you had to blip the throttle or use the clutch. Now you just hammer downshifts while compression braking. The slipper softens the jolt from gear to gear also.
So in closing I must say I miss the extra HP of my moded 125. For $5,300.00 I could have bought the one sweet Sweedtech or a 149cc stroker from Eric Gorr. It did not help the fact I have a fat ass. I took the motor out of the box and ran it. I have done nothing more than move the clip on the needle. I hope there is more HP to be tuned out of it. I would highly recommend it to anyone that adds weight to their kart. I would guess that it adds 15 lbs to the kart. I have not weighed it. You need some really good friends at the track otherwise all you hear is crickets when it's time to lift. It would make a great school kart with the slipper clutch.




http://mtdkarting.com/Merchant2/graphics/00000001/sr5bvyam250_dhpsk2c.jpg
_________________
Kirk Schenck
Tempe Az.


There has got to be a better way!

[Scott Nagler]

cool, yeah that is pricey and 15lbs wouldn't be too bad considering I may need to add weight anyways. You can buy a WR250 bike for like $3g or so. It sounded to me like there is more power in doing the gray wire mod, throttle stop mod, exhaust, and airbox mods. Then I'd be curious to see if there's different cams you could slap on'r. Keep us posted man, you seem to be paving the way so far.

Maybe I'll have to hit you up next spring when I'm in Tempe... Training for my company, I plan on hitting up Bondurant while I'm there too.
_________________
Still a noob, but can't wait to be "on the pipe"

[Josh Schultz]

[Scott Nagler]