Main bearings are easy enough to check. Take the plug out and turn the crank to TDC Try moving the ends of the crank. There must be a small amount of axial movement (0.1 - 0.2 mm), and little to no radial movement. Try the same a BDC to be sure.
Rotate the crank very gently at both BDC and TDC, back and forth, seeing if you can feel the slightest rumble or "catching". It should be completely smooth. If all this checks out it's very unlikely to be a main bearing problem.
As for seals, I've just done mine (again!). Method for me is to remove the clutch (or sprocket), remove the ignition stator and rotor. Put a small screwdriver through the seal by a few mm to make a couple of holes, and then use a couple of home made wire hooks (welding wire works) to pull the seal out. It's easier on the DD seals than the TAG seals, but works on both. The idea is to push the hook through the rubber of the seal, and then turn it so the hook end pulls on the steel support that's moulded into the circumference of the seal. Seals are scrap, but it's quick and easy.
The trick I'd missed that meant mine have been wearing quite fast is that you need to pack the "V" between the running surface lips of the seal with grease. I've always oiled them on 2 strokes before, but the BT82 runs quite dry on the outside of the mains, so they do need greasing.
Once you've greased the new seals just slide them over the crank and push them into their housing until the outer face of the seal is flush with the crankcase.
Given you've just had a rebuild, it might be an idea to ask the engine builder to look it over for you though. There are plenty of things other than main seals that can cause lack of power.
Liam
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Changing TKM Main Bearings by 'glittttt' (31 Aug 2010 @ 22:06)
