Larger case bushing for 1986 engine found

[blackz34]

So I wanted to get some larger bushing to fit the 17 mm pivot bolt of the AF.Honda doesn,t sell the bushing themselves but Yamaha is so I ordered some from a YZ250 2001 (17mm pivot bolt).

Part # 90387-1712Y-00

According to partzilla, these fit on:


1998 RACE KART - YZ125K-SK CRANKCASE-YZ125-SK
1998 RACE KART - YZ80K-SK CRANKCASE-YZ125-SK
1998 YZ125SK CRANKCASE-YZ125-SK
1998 YZ80SK CRANKCASE-YZ125-SK
1998 MOTOCROSS 4-STROKE - YZ400FK CRANKCASE
1998 WR400FK CRANKCASE
1998 YZ125 - YZ125K1 CRANKCASE
1998 YZ250 - YZ250K1 CRANKCASE
1999 COMPETITION - YZ250L1 CRANKCASE
1999 MOTOCROSS 4-STROKE - YZ400FL CRANKCASE
1999 WR400FL (DEEP PURPLISH BLUE SOLID E) CRANKCASE
1999 YZ125 - YZ125L1 CRANKCASE
2000 WR400F - WR400FM CRANKCASE
2000 YZ125 - YZ125M1 CRANKCASE
2000 YZ125M CRANKCASE
2000 YZ250 - YZ250M1 CRANKCASE
2000 YZ250M CRANKCASE
2000 YZ426F - YZ426FM CRANKCASE
2001 WR250F - WR250FN CRANKCASE
2001 WR426F - WR426FN CRANKCASE
2001 YZ125 - YZ125N1 CRANKCASE
2001 YZ250 - YZ250N1 CRANKCASE
2001 YZ250F - YZ250FN CRANKCASE
2001 YZ250N CRANKCASE
2001 YZ426 - YZ426FN CRANKCASE

So I got some measurement with my caliper (note that my 1986 bushing is not in very good condition and was bored to 17mm so I don't have original ID):

YZ250 2001 bushing: CR500 1986 bushing:

Lenght: 25.48mm ~25.70mm
Flange thickness 3mm 3.22mm
Flange OD 32.75mm ~31.60mm
Bushing OD 21.94mm 18.99mm
Bushing ID 17.14mm ~15mm


I was worry about the flange thickness before I received them but after I measured them, 0.22mm (~0.008") isn't gonna be a problem I think. And thinking of it, my 1986 bushing is a little ressed (is it from the factory?) and I didn't took it into account when I took my measurement, so they may be about the same then...

So only thing to do is to bore the case for the new larger bushing.

[blackz34]

YZ250 2001 on the left, bored CR500 1986 on the right:

[maddog1927]

Good to know, but if it were me I would not bore the cases. I bet the Honda engine you pullout of the af has direct swap bushings.

[blackz34]

Never got the engine, just a roller. And I believe the CRF bushing have a larger OD too so...

[MojaveRider]

Good to know, but if it were me I would not bore the cases. I bet the Honda engine you pullout of the af has direct swap bushings.

How do you suggest dealing with the bushing size mis-match?

[maddog1927]

I think the 125 and 250 2 stroke bushings a a direct swap. Not sure.

[MojaveRider]

I think the 125 and 250 2 stroke bushings a a direct swap. Not sure.

I'm new to 500's so I'm certainly no expert, but I thought even with the right size Honda bushing the smaller 500 cases had to be bored out.

If anyone knows for sure, post up!

[MojaveRider]

Did you ever get these bushings into the 500 cases? I'm curious if this worked.

[blackz34]

I had to sent the cases to my machinist because I didn't have the right size tool to bore them out. I should get them back sometimes this week I hope.

[blackz34]

I forgot to update this, bushing are in the case and engine is in the frame, everything went well for me.

[cr500binks]

I wish I knew about these bushes when I did my 86 conversion ! things like this can make a build much easier !

[paddy's lad]

I just used these collars on my conversion& drilled the case (assembled)
With a 7/8 step drill worked great.the collars are tight and the correct size to fit in the 85 case. I'm installing a 85 motor in a 05 crf250 frame.

[paddy's lad]

This is how I drilled the case on my 85 motor for the yz250 bushings first thing I did was drive the factory collar out with a punch.
I used a step drill with a final size of 7/8" and a ratchet and did it by hand
Takes about ten minutes for both sides. The bushing fits perfect in the case with no movement. Hope this helps anyone contemplating using an early motor. Cheers, Pat

[blackz34]

I'm glad that my findings has helped another hoon!

I have re-upload my pictures while I was on this topic.

[paddy's lad]

I'm glad that my findings has helped another hoon!

I have re-upload my pictures while I was on this topic.

You da man! Thanks, made my conversion a lot easier
Cheers, Pat

[Roostius_Maximus]

you done good