I'm worried I may not be getting oil to half of my crank, and I'd like to clean out the passages without pulling the engine back down.  If there is a blockage, it's probably in there really well, so solvents aren't going to cut it.  I'm thinking compressed air, but I need to know if there's a point I can blast from to clean things out.  Anyway, does anyone have an oil flow chart for the gs500 engine?  Maybe any ideas on how to tackle this?

Thanks,
GregM

What makes you think oil isnt getting to half the crank?

Best solution is to drop the motor and split the cases.

The main gallery is accessable by removing the large chrome plated bolt directly below the pick-up cover. This is the point that oil pressure readings are taken from. But if you suspect a partial blockage, blowing down it is unlikely to clear it, all you are doing is forcing it further into the engine and against and into the bearings.

As above......dismantling and thorough cleaning is the only sure fire way to deal with clogged galleries, besides which if what you suspect is true the damage will already have been done.

I was told the engine was run without oil then partially rebuilt.  When I got my hands into it I found a burnt up bearing on the crank, figured it was due to being run low on oil and just replaced the bad bearing and crank.  Now it runs but it has a hard skip.  I've checked the spark and fuel, and both are good, however, when I disconnect the cylinders one at a time, one runs at a much higher rpm.  I'm worried that there was more than a low oil issue involving the original crank (now kicking myself for not blasting out all the oil galleys when I had it apart).

Thanks,
GregM

The entire crank turns whether one cylinder is firing or two.  So your test doesn't say anything about oil flow, but it does say one cylinder is running more efficiently than the other.  Could be carb related or valve adjustment.

well, I was more worried about the rod bearing than the crank bearing.  Anyway, I'm going to double check that the carbs are synced tonight, and I know the shims all have proper clearance.

But you're turning both rod bearings and crank bearings whether R cylinder, L cylinder or both are firing, so the "one cylinder firing at a time" test shows absolutely nothing about any bearing issues. 

You may find the problem with carb sync.  Float level is also really easy to check.  Or maybe there is still a clogged jet somewhere.  Not a fun problem to troubleshoot.