86/89 tranny differences

[ESR250R]

i have a 86 250r that is getting the bottom end completely rebuilt and honda has discontinued 5th gear on 86 models. i believe they still make the 89 5th gear. i was wondering if i could buy new (89) gears from honda and if they would fit in my 86 tranny ok. i realize that the later years had a shorter 5th and 6th gear and that doesnt bother me at all.

[beerock]

ahh yes, Finally a good technical thread.

I actually did the reverse of what you have to do.I went from a 88 tranny to a 86 tranny for a lil more top speed.

I blew 3 gears in my tranny and my friend had a new 86 tranny So I was very hapy, I wanted to swap years for a while.


I was going completely nutz when I swapped out the gears though! my tranny kept binding up when I put the cases together.I thought 6th gear counter shaft was the same, it turned out that 6th counter shaft gear has the same amount of teeth (23t) but the inside splines are slightly rotated and that makes the tranny not shift properly(the dog bone on that gear forces another gear against the case with the wrong year gear).

So In order to do the swap you have to swap out....both 5th main shaft and 5th countershaft, 6th main shaft and 6th countershaft.

the difference in gears is as follows:

1986: 5th gear mainshaft 24t
1986: 5th gear counter shaft 26t
1986: 6th gear mainshaft 26t
1986: 6th gear counter shaft 23t


1988: 5th gear mainshaft 23t
1988: 5th gear counter shaft 25t
1988: 6th gear mainshaft 25t
1988: 6th gear counter shaft 23t- same amount of teeth but splines are rotated slightly

I hope this helps......
;)

[ESR250R]

so it can be done i just need 5th and 6th gears from a 89, and i need a 89 main shaft, countershaft for both these gears correct.

[beerock]

yes both 5th and 6th for both mainshaft and counter shaft.......

good luck!