Did a compression test on my bike.

Bike runs. It sounds like my cylinder may be misfiring but I'm not sure. Sending my carbs to be cleaned today.

Compression test after bike warmed up:

Cylinder #1 (Left side when sitting on bike)
Dry: 145 psi
Wet: 205 psi

Cylinder #2:
Dry: 110 psi
Wet: 195 psi

Valves just adjusted and are in spec.

I don't have a leak down tester, I may consider buying one, but not sure if a leak down test could tell me much more than the compression test.

Wondering if there is anything else I should check. If I do end up needing to replace piston rings, how many days should I reserve if I worked all day on getting the rings on? I've never torn down an engine, closest thing is doing valve adjustments myself.

Does this look like a probable piston rings replacement scenario?
I've heard of those products like Rislone Compression Repair additives, but do they actually work? Could this be a temporary solution (help for 10,000 mi)
Can I replace piston rings with the engine still on the bike?

Don't use any magic-elixirs in bottle. They'll often cause more damage than cure.

Other possible cause of low-compression is burnt exhaust-valves and/or seats. A leak-down tester will give you confirmation if leak is going past rings or valves. Then you'd have better idea of which areas to inspect.

A lot of times, ring-leaks are caused by carbon from too-rich mixtures or burnt-oil clogging rings. One hail-mary operation before tearing engine apart is to do piston-soak to dissolve some of sludge which may be clogging rings and preventing seal. Do both cylinders:

1. spray in PB-blaster for 5-sec down spark-plug hole
2. crank engine 1-sec to spread it around
3. follow with 3-4cc of acetone
4. lightly lay spark-spark over hole to prevent evaporation
5. let sit for 3-4 hrs

6. follow with 3-4cc of 50/50 acetone/ATF mix
7. let sit for overnight (6-8hrs)

8. follow with another PB-blaster/acetone mix
9. let sit for 3-4 hrs

10. crank engine to blow out any residual mixtures
11. re-install plugs
12. warm-up engine and re-do compression test.

Depending upon how much improvement you get, it will be additional data for diagnosis.

https://drive.google.com/uc?export=download&id=1F0svISsyRHKOwY6SnOKiyGxDYl9YG7pz

DannoXYZ thanks for the write-up. I'll do the soak once I get my carbs back from cleaning.

I'll waiting on a leak down tester that's coming in the mail tomorrow, I'll post results after

DannoXYZ sidenote, does it need to be PB Blaster or could I use another penetrating lube like liquid wrench?

I’ve found PB Blaster to work best. Frees up rusted bolts & nuts better than anything else. So cleans cylinders & rings best too. Got my wife’s Corolla with one 60psi cylinder back up to 195psi. Similar car with same issue picture posted above. I was able to skip the teardown.

I think you can remove pistons with engine in frame by removing head and dropping oil-pan. But it’s a lot quicker and easier to remove engine 1st.

I did the leak down test and got some results I don't quite understand.

With the leakdown regulator set at 100 psi, the cylinder pressures I got were:

Cylinder #1: 99 psi
Cylinder #2: 99 psi

No air leak from intake, exhaust, or radiator cap.
Air only coming out through oil filler cap, both cylinders tested had this problem.

I rechecked compression and got:
Cylinder #1: 155 psi
Cylinder #2: 160 psi.

Cylinder #2 was the cylinder which was originally testing at 110 psi. I'm guessing after I did a wet compression test described in my first post, even though I ran the bike to blow out the excess oil for 45 min, that maybe some oil is still there helping the piston rings seal and that's giving me my better numbers?

I also was kinda confused about trying to find TDC on cylinders when I didn't have the valve cover off to see the camshaft lobes, so I ended up trying both cycles of 1T and 2T and chose the one didn't have air blowing through the intake.

My carbs are in a land far far away right now being cleaned, so I can't run the bike

Excess oil should be scraped off by rings within seconds when running engine.

Hmmm, you may have had some grit or carbon chunk holding valve open earlier? Couple months ago someone reported something holding their valve open and giving really bad numbers. Then it freed itself and blew through.

At this point, I'd do piston-soak anyway. These bikes run really rich in high-end and has lots of carbon build-up.

Excess oil should be scraped off by rings within seconds when running engine.

Hmmm, you may have had some grit or carbon chunk holding valve open earlier? Couple months ago someone reported something holding their valve open and giving really bad numbers. Then it freed itself and blew through.

At this point, I'd do piston-soak anyway. These bikes run really rich in high-end and has lots of carbon build-up.

Awesome, I'm gonna do the piston soak once my carbs come back. I'll post compression test results

I did the piston soak. Couldn't warm the engine up yet, carbs don't come back till tomorrow, but I got some improved compression test-wise.

Pre soak:.
Cylinder #1: 155 psi
Cylinder #2: 160 psi

Post-Soak:
Cylinder #1: 164 psi
Cylinder #2: 169 psi

Gained 9 psi on both cylinders!
:dancecool:

That's good results! With warmed-up engine, you should be in 180psi range, which is perfect!

Btw, you’ll want to do an oil-change.

Btw, you’ll want to do an oil-change.

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