Check for sumping?

[Big Dan]

I suspect my bike may be sumping. It's running crazy hot and has a weird "thok-thok-thok" sound to it. Hp & torque were also a little less than I expected when it was on the dyno, but that could just be my "no-name" heads. I know that to check it I need to pull the crankcase plug and measure the amount of oil that comes out. I believe 4 ounces is okay, and more than 4 ounces is bad. Is this correct?

Also, I believe I need to run it for a bit before I pull the crankcase plug so that the pump has a chance to scavenge all that it's going to. Can it just idle for a minute or two, or do I need to take it out and ride it for a bit? And, do I need to drain the oil from the pan first? I can't think of a reason why I would have to drain the pan, but I'd like to be sure that when I check it, I do it properly.

As always, thanks for the help.

[djl]

Take it for a ride, get it hot, bring it home, pull the crankcase plug and watch what comes out. If it is sumping, you will know it.  Is it running hot?  Be careful removing and reinstalling the plug.  I screwed up last one I had open and put the wrong o-ring in the scavenge port; major sumping.  Once corrected, it ran like it shed 500 pounds and cooled down to normal operating temps.

[KingofCubes]

Yes, take it out and ride it first. 4-6 normal ounces without power loss, 8 ozs. you will only loose a little power, 2-3-4- horse. At 10-11-12 ozs. down 3-4-5 horse. No braking action was felt until 20-24 ozs. and down 25-30 horse.

[se]

it also depends on how much power you have to lose to determin if its sumping like that... also do a compression check.