My buds and I, back about four years ago stuffed a CR 500 into a 250x frame, well, mostly, then we had to create and weld up our own sub-frame. Vibes were totally our enemy. The thing practically bounced around just while idling and after every ride, there were more cracks in the frame and more broken welds. We could not keep up with this thing breaking the frame, but damn, I had never seen such a monster with such power. It was faster than the other builder's Zilla and could climb hills that most people would not even think possible for any quad. It was funny too, he'd go flyin down the road (not the smartest of guys, but a helluva rider) and got going so fast, the plastics were bending up as if little wings getting ready for take off. He had fun on it, then we scrapped it due to the frame's inability to contain the monster motor. My advice, if you have the motor and a frame, take your time and add lots and lots of frame supports and don't worry about the weight, you'll need the extra weight to keep you from taking off!! Have fun.

 

I picked her up last night seems like a really solid bike ,awsome condition just need to get used to that goofy kick start , it's got some pretty good snap.
thanks for your guys's input I appriciate it. I know a buddy who put an 86 CR500 into an 87 LT250 frame, other than lengthining the swing arm 8 inches he has been riding it for two years. He can beat my Zilla.

 

As far as the chain being on the right side of the engine...

...is it possible to just flip the axle over? I realize you may have to fiddle with the rear brake assembly, but is this possible?

Sounds like a fun project. Just don't tell your insurance agent.

 

...and while we're on the subject, why is it again that these engines don't vibrate so much in a motorcycle frame as opposed to an ATV chassis?

I know ATV engines have counterbalance shafts, but I just was wondering why "good vibrations" are not a problem on motorcycles. Why not just but counterbalancers on all engines? And, which motorcycles do feature such handy items? (YZ426, CR450F, KTM520, and a few others come to mind...what else though?)

 

MALOCHALA,

The culprit of vibration on the quads with MC engines is due to increased contact area with the ground. [4 Tires instead of 2]

The ATC models with these engines also suffer from vibration, but not as much as a quad.

 

A friend did a swap and went to a ton of try this to cure the bad vibes but nothing worked.
the best thing was rubber bar mounts and an antivib insert into the bar ends but the vid through the pegs and seat was enough to drive you nuts.
If you can find a 250R motor b/c it has a counter balance and then bore you will be very close in performance and not have the bad vibs, that is why you do not see many swaps done other things work better.

 

Thanks KNOWSALOT! That makes a good deal of sense! Thanks for explaining.

What about flipping that axle over? Seems like I read years ago about someone making a similar conversion with an engine that's chain was on the opposite side and their solution was to flip the axle over.

I have to say, though, if I had an old motocross bike in good working condition, I wouldn't do a thing to it but ride it. I just don't think I could molest a good example of an old dirtbike. I'd fix what needed to be fixed on it and keep it forever.

Now, if it was in bad shape except for the engine, yeah, I'd do it too.

 

Why not just but counterbalancers on all engines?

The reason for not putting counterbalancers in all engines is rotating mass. If you have a one pound counterbalance you do the same thing as adding 7 pounds more to the bike. Not good when you are spending big money on R&D trying to figure out how to have the lightest bike made.

 

I'm not sure about flipping the axle over. i have never done this or seen one first hand.

I suppose if you didn't have a sprocket flange with an offset and the same with the brake rotor hub, it could be done.

If that didn't work, you can always spend the dough for custom offset sprocket flanges and rotor hubs to be made........that is IF the splines on both sides of the axle are the same as well.

I haven't a clue.....I'm just rambling. I got myself lost just thinking about this one.... [img]i/expressions/face-icon-small-tongue.gif[/img]