1997/1999 CR250 engine swap

[Kev_CR]

My sons '99 CR250 engine siezed. When I took it apart I found that the piston skirt broke and busted up both L/R engine cases internally.

I found someone who is selling a '97 engine complete with carb and electrical for a decent price. My question is will this bolt right into the '99 frame? If so, any suggestions on if I should just use the bottom end off of the '97 and the electrical, cylinder and carb off the '99? From what I've read the '97's porting is more aggressive, so should I use the '97's cylinder if I wanted more top end? Or what combination of parts would be recommended?

[dogger315]

The '97 motor will bolt right in to your '99 frame. The '97 motor does have
a bigger hit and a little more overrev than the '99 which had a rider friendly
usable powerband, but was a little weak on top.

I recommend using a Stealhy flywheel to smooth out the "hit" a bit. That
way you get the best of both worlds without any permanent changes like
porting. The flywheel will help the bike hook up better and delay the onset
of rider fatigue/arm pump to later in the moto.

The '97 used a Keihin PWK carburetor with TPS. Honda got the "boost"
timing wrong with that setup which only added to the explosiveness of
the powerband. I'm not sure if that problem still exsisted in '99 or if the
port timing change was the fix. Since you have a perfectly good ignition
on your '99, I would swap that over to the '97 along with the '99 coil
('97 coils were prone to failure).

Sounds like an interesting swap, good luck with it.

dogger

[ctroger24]

I actually did this swap myself. I bought a 99 roller that the engine was almost beyond rebuilding, but found a good deal on a 97 engine. I swapped everything from my 99 over to the 97 engine ie: carb, stator, ecu, fly wheel, and coil. Everything fit and worked perfectly. I didnt even have to mess with the jetting. The cases between the two are itentical so fitment is not an issue. Once your done you can sell the rest of the 97 stuff on Ebay to help pay for the swap. Good luck!!

[Kev_CR]

Thank you both for the info!

I've got a Stealthy flywheel weight on the '99 engine that I'm definitly going to move over. That was one of the better mods I've done.

[Kev_CR]

Well, I went and picked up the '97 engine for $400 with carb and electrics. I'm going to rebuild the top end on it and get it installed sometime this week hopefully. I'll post the results.

[Woody_393]

Right on! Good luck with it.

[Kev_CR]

I put the engine in today using the parts from the '99 that ctroger24 did with his swap. Everything went smooth, except I had to travel a distance to get a flywheel puller .

Anyhow, the bike fired right up and rides good, jetting feels to be close if not spot on. I'll have to do some throttle chops to confirm.

[Woody_393]

Right on... that sounds like it wasn't too bad at all. Well, with the exception of the flywheel puller

[AJ_YFZ]

Sound like you spent less rebuilding with the donor motor than you would have with a rebuild....Congrats Man...

[Kev_CR]

Thanks all, yeah it ended out working out good. I spent about 3 hrs doing the work and I was taking my sweet time. I didn't do a new piston/rings yet though. I inspected the piston as much as I could through the intake and exhaust ports and it looks to be good. The compression tested at 175 ish, which is pretty close to what my old engine did with my compression tester with a new broken-in piston/rings.

I'll do a top end within the next couple weeks though just to start fresh. First I need to clean up some of the old parts and get em' on ebay.