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Hello All, I performed a poor mans leak down test on the bike and I’m getting air out of my crankcase. Compression is 90 psi on all four. Guessing need new rings, if I’m right is there a set of rings that will work I know I’ll have to have the cylinders honed so when that material is removed is there rings that will work or will I have to go up in piston size. It’s hard to start seems like loss of power and I’ve been threw the carbs more times then I can count that’s why I done the leak down test/compression. If I’m missing something plz let me know. Thanks for reading

Also if it’s at TDC on the 1-4 mark shouldn’t the valves be closed on those two cylinders at the same time. The reason I ask is when I done this air came out the number 4 exhaust but not the number 1

Are you sure about the 90psi? Was the test done with the engine at operating temperature, with all the sparkplugs removed, and with the throttle held wide open? Does the gauge have the release valve near the open end of the hose?
If yes to all those, then maybe 90 is correct. There will be no way to know if oversize pistons are needed until the engine is apart, and the bores can be carefully measured with a bore guage.
When at TDC for 1& 4, the valves will be closed on one cylinder only. To checke the other cylinder, the crankshaft will need to be rotated a full turn.

My gage said 90 it’s one of the Pittsburgh ones has quick connection and the release button is under the gage it self. I done it after bout 30 minute ride from work. I did have it WOT. And all plugs removed. This is my only compression tester and I’ve read of ones not reading correctly.

That style guage can read low, and not having the throttle all the way open will also cause low readings. Still, even readings in the low 100s would be cause for concern.

Ok yea I thought the psi should be 130 to 150. So I’m guessing I need to open it up and get measurements and see if the rings are bad or the cylinder wall maybe the cross hatch is gone. I’ve seen O/S rings on partzilla and eBay has new pistons with rings that supposed to be 1.0 mm over for 285. Just ain’t sure which way to go.

Have the valves been checked for proper lash lately?

Yep bout a week ago had a couple intakes way loose, but everything is in spec at the moment. Could the timing be off I read the manual and looked at the cams and timing marks and counted the pins and I think it’s all right it that’s not my strong suit

I'm confused. Did you do a leak down or a compression test. They are different. The Compression test is measured in PSI and the leak down is measured in percentage. A leak down test is done with each cylinder at TDC in turn and that is when you would hear air coming out of the crankcase.
If your leak down percentage is at 90% across all four that is not good. If the compression test is 90 PSI I would repeat the test using a squirt of oil to see if PSI increases. Do the compression test on a warm engine with the throttle wide open. I always keep cranking until the needle pops up four times.

Ok , sorry for the confusion I did both. I have a small compressor bout 100 psi and was able to hook it straight to the quick connect that screws in to the spark plug hole. I don’t have any gages on it I could feel the air coming out of the oil filler hole I had taken the cap off so I could hear better. The compression check was done after bout a 30 minute ride and I started taking out the plugs as soon as I shut it off and also had the throttle pulled wide open. Did not try putting in the oil tho. And it’s an 86 police bike roughly 30,000 miles 4 into 1 Mac header , stock air box/filter main jet 130 and pilot 40 if that affects anything.

Is the engine using more oil than normal?

Assuming you need to change rings...I know with the 900's you can buy oversize rings in 0.5 mm increments. I imagine the same is true of the 1015 engines.

Of course that assumes you need to bore the engine. You may not need to but won't know until you pull the cylinders off and have them measured. I've done two 900 engines and they were both in spec...only needed to be honed.

Well, 30,000 is not much for one one of these engines unless maintenance was ignored. Even so, it looks like a tear down and measure is in your future.
What still seems odd to me is that this came on quickly enough to be noticed, and all four cylinders seem to have gone bad equally at the same time.
Hopefully, somebody with more knowledge will chime in soon with a better diagnosis.

The 1000P should have the J engine, 998cc.