NO power below 6000rpm

Thanks for all of the advice everyone. Y'all have given me a very good idea of what I need to do to fix/diagnose this problem. I'll keep you updated as to the progress and results of my tinkering. Thanks again.

Well guys, I just checked the compression and things aren't looking so good.
#1=75lbs, #2=82lbs, #3=85lbs, #4=80lbs
After adding a small amount of oil to the #1 cylinder to confirm that there was no valve seating issue, the compression reading was 150lbs. Looks like it's time for a rebuild or re-ring. Does anyone know where I can find cheap pistons and rings?

Did you take the carburetors off or open the throttle all the way when checking compression? If not, the numbers will be low. If you did open the throttle, and the oil test indicates ring issues, then the next step is to figure out what to do. DO NOT start spending the family savings quite yet. First, you will need to remove the cylinder head and block. Buy a digital caliper and some tee gauges. These things are NOT expensive. Measure the cylinder per your Kaw factory service manual. Do it at three levels and at two different orientations so that you can determine if the cylnders are round and what the diameter is. You will use the tee bore gauge for this (with the caliper). Measure the piston diameter.

Now that you know what the piston and bore diameters are, you can start making decisions. There are two basic alternatives.
1. The piston to bore clearance is within spec.
2. The piston to bore clearance is OUTSIDE spec.

If the piston to bore clearance is outside spec, you have options. One is to buy oversized pistons and bore the cylinder and then install new rings. This is a very expensive prospect. The alternative is to buy another used block/piston set where the clearance is within spec and just re-ring and hone. This is a much less expensive alternative.

If the piston to bore clearance is within spec, re-ring and hone.

You will need a base and head gasket at a minimum. I would also pick up a valve spring compressor and replace the valve stem oil seals and clean the combustion chambers and lap the valves while I had the engine apart. It might also be a good time to replace the old cam chain. You can buy a new one with a master link... it is easier to change a master-link chainout for the old one when the block/head are off.

If you don't buy new pistons/rings/bore, the whole job isn't really that expensive and I personally think that ANY used pistons / block within spec will work JUST AS WELL AS NEW STUFF! Anyway, if you need any help/tips, I am glad to help. ---ONE last thought before you run off to disassemble that engine... HAVE YOU CHECKED VALVE CLEARANCES YET? You might want to, in spite of the clues that indicate your rings are suspect. If you have no clearance on any of the cylinders, adjust clearances before the disassembly and recheck compression, just for grins.

Post edited by: wiredgeorge, at: 2006/06/23 09:23