rebuild suggestions

[chamberlain31c]

i've got an 87 250r, going to do a complete rebuild, planning on installing all new bearings, esr's new 310 cylinder, cr ignition, new clutch, will be riding mostly trails and some mx any suggestions on anything i should replace why i got it apart? tranny gears, etc.. just want a good reliable machine!

[All250R]

With the detail oriented mind I have, it's hard for me to give advice that's not complete, but here is my broad way of thinking how to approach an engine you're taking the time and money to rebuild. I'd like to say that it's fun to jump in with a wrench in one and hand and your di*k in the other, and just have fun with your engine, but taking a detailed comprehensive approach to the rebuild/maintenance is the best way to make sure it runs its best for the long haul.

If you're not sure of the condition of the engine overall, you should go through everything. The service manual will take you through the entire engine letting you know what to look for and how to measure it. that will cover most things pretty well. Here are some broad categories of things to look for:

Bearings and seals (mains in particular) are mandatory like you said. - don't forget the counterbalancer bearings

Have someone inspect the crank with the correct tolerance numbers.

Rebuild the water pump if you're not sure of its age

Clutch components; fibers, plates, basket, lifter system

Trans gears; dogs, mating surface tolerances

Top end; bore, piston clearance, compression, ring end


This is just a loose list. Again the service manual fills in the cracks. You really aren't going to be able to do a complete job on your own without it and some good quality measuring instruments.

p.s. don't forget to do perform a leakdown test to check your gasket surfaces. Lapping the surfaces is a nice touch and generally prevents you from having to fiddle with gasket sealer.

2c.