2-Stroke Engine Rebuild

deano,
If you bought a complete gasket set, it probably did not include a shift shaft seal, and you may want to replace that. There are also two oil seals not included in the gasket set - for my '99 they were part #91201-Ka4-004 and 91205-kz3-861.

On Honda CR250s, an OEM new crank/rod assembly is usually pretty reasonably priced (around $160 or so from Service Honda) so it makes sense to go with a new crank and not bother putting a new rod on your original crank. FWIW, the shop manual says to replace the crank every year for racing...I understand the CR250 cranks are difficult to split/reassemble and may require special care/labor to do right. It sounds like you already have a new rod though.

You should also plan on new crankshaft bearings, there are 2 of them about $30 each. I have a spare that I would sell for below cost (had to buy a new crankcase half that already had a bearing in it).

Oops, double post.

Also, your vibration problem might be motor mounts/head stay.

I've seen the output shaft bearing in poor shape on the older bikes I've done. Other than that, I would just plan on replacing the usual, Main bearings and seals along with the crank. And inspect the other bearings while you're in there, shift forks too.

if the rod is tight and doesn,t have any play in it put case bearings and seals in it and go for it,it is a honda you know.if it aint red it,s dead

If it aint red, your ahead. :D

plysWfire said:

How much risk is there in not replacing the crank? I'm kinda trying to do this on a budget. In all reallity, I only expect to ride this bike for the next 6 months to a year, without a lot of serious race time.

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If you are trying to do this on a budget then trying to replace the bottom end rod bearing is going to bust your budget either way. That is, unless you are all set up to split and re-true the crank yourself with, press, surface plate, v-blocks, bronze chisels etc. And I believe dirtbikedave is right, I think you need a special fixture to re-assemble those CR250 cranks.

$160 for a rod/crank assembly is pretty cheap. I doubt if you can hire the crank split/re-true done for much less.

Check the transbearings. when was the last time they were replaced. Warm up the bike, Put it in nuetral and rev the motor.If it vibrates excessively and you feel it in the handle bars and foot pegs then the lower end bearings do need to be replaced. I would also replace the bearing behind the clutch. It will cost you more in the long run if you skip things that should be replaced.