91' CR 125 engine swap into 99' CR 125 frame

I think I found the right place for this question. Anyway I have two bikes a 1991 CR 125 and a 1999 CR 125. I want to put the 91' engine in the 99' frame. I know the engine mounts are larger (no big deal for me) but I need to know what pipe to use and what electronics and ignition(CDI, stator, flywheel, and coil) do I use? Will a 99 stator bolt onto the 91' engine? Are the carburetors interchangeable? Both are Keihin? What's the easiest/ best way to do this swap? Thank you

I think I found the right place for this question. Anyway I have two bikes a 1991 CR 125 and a 1999 CR 125. I want to put the 91' engine in the 99' frame. I know the engine mounts are larger (no big deal for me) but I need to know what pipe to use and what electronics and ignition(CDI, stator, flywheel, and coil) do I use? Will a 99 stator bolt onto the 91' engine? Are the carburetors interchangeable? Both are Keihin? What's the easiest/ best way to do this swap? Thank you

Easiest is to bolt everything off the '99 onto the '91. I'd try to have all parts off the same year still together. But '91 electrical parts will also work on a '99 engine. I'd just stay away of mixing parts from various years.

 

Carburetion is almost identical. It should work either way.

 

With exhausts just remind you that older bikes had the rear mount of the exhaust farther back in between the rear subframe/main frame while newer models (also your '99) have the rear mount farther forward just above the kickstart lever. Also the bends of the exhausts differ. They are basically all equal but they have a different bend. 90-99 are basically interchangeable but a old exhaust will not fit later years as it's bulb in the front is too high and will interfere with the lower radiators of modern bikes. It's easy though to have the rear mount re-welded if that should be a problem. However it's not possible to mount a older exhaust (90-92) on a 98/99 as it will touch the radiators above.

 

That said a modern exhaust up to '99 will also fit a '90 (except for the position of the rear mount which needs to be relocated).

Edited by nino

Ok. This is some great hard to find info here. Thanks a ton. Im relieved to know I can run the 99' electronics on the old engine. Thank you.

Well I got the '91 engine into the '99 frame. I used the '99 electronics on the '91 engine. But now I have NO spark. Nada, nothing.. so I tried the '91 stator, CDI box, and coil on it as well.. and nothing, no spark whatsoever.. which is weird because before I took the bike apart both of my bikes were getting spark. Im stumped.. i un- hooked the kill switch too, still no spark! What in the heck??

New spark plug? Cap screwed on coil lead properly? Could lead screwed to coil properly? Coil earthed?

Yes. Two new plugs, the coil is grounded and wires appear to be hooked up right. I've went above and beyond to make sure everything's right. I think the stator may have been on its way out on both the '91 and '99 and thats why I'm getting no spark

Possibly a stator, believe I will just buy a new stator, then try it..

Disconect kill switch?

Yes

Ok, new stator is in now I am getting spark!! Waiting on waterpump gasket to get here and I still need to do some minor modifications to the pipe and tuck the wires in neatly and other small things and then try it out.

Ok, so I tried the bike with the new stator, fired right up. Let it idle for a few minutes, and it acted like it wanted to load up.. so I revved it to clean it out it got better. Rode it over a couple acres and it ran great, but something didnt seem right it was a little sputtery or something.. after one pass it died suddenly and had no spark again. So I'm buying a coil

Bought a brand new ignition coil.. still no spark.. Checked the reading on the brand new stator with an ohm meter can't get a reading on the pulse generator part of the stator. And the exciter coil reading is out of spec.. so Im assuming I fried a brand new stator?? Looks like the wire colors are backwards on my male and female plugs on the aftermarket stator they sent me(the part that plugs into the CDI box) so....... I don't know what the heck to do, I can't have any luck. The stator I bought was a mister electrical brand

FOUND THE PROBLEM! After much testing I found the new stator I bought had a defevtive pulse generator on it.. my pulse generator on my old stator tested out OK so I put that on my new stator and the bike runs like a charm and doesn't foul plugs anymore! It's nice to have a 6 speed engine in the newer aluminum frame too. Thanks everyone who helped me figure this out!

Bike runs great, but has a rich condition that I need to correct. But thats another story. But the swap was successful

FOUND THE PROBLEM! After much testing I found the new stator I bought had a defevtive pulse generator on it.. my pulse generator on my old stator tested out OK so I put that on my new stator and the bike runs like a charm and doesn't foul plugs anymore! It's nice to have a 6 speed engine in the newer aluminum frame too. Thanks everyone who helped me figure this out!

Cool.

I am also a fan of the six speed transmission in the CR125. I have an 05 with a 97 transmission. See my thread:

http://www.thumpertalk.com/topic/1086470-cr125-six-speed-tranny-swap/

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