Compression Check Oddities

1968 CL350
Hi guys,
Rode 7 miles today. Noticed my breather tube spitting some white smoke, and opened my crankcase dipstick, white smoke was coming out there as well. Oil smelled like gas slightly. So I decided to check my compression. I know I'm running rich. I'm thinking maybe unburnt fuel is leaking past my rings and into my crankcase. So, cold compression on both cylinders is 155. When I add oil to the cylinder, compression jumps way up to around 240. Should it be jumping that high? I know the oil temporarily seals the gaps from worn rings, but all the way to 240? Seems odd to me, but I've never done this check before, only read about it.
Confused,
Andrew

Holy Crap Batman! is 155 and 240 in PSI???? in 1968 the bike came with 190PSI compression.... by the way, my breather tube smokes the equivalent of 10 Cuban cigars, its supposed to 8).

240 is extremely high. 155 is not too bad for a cold compression. Not sure how it got so high with the bit of oil though, how much oil did you add?

Regarding the gas in the oil, it could be caused by the carbs overflowing for some reason (float height, stuck needle, etc.). Don't run it until you find the problem and change the oil.

Yeah, I couldn't believe the 240 psi either. I did it twice to be sure. I added a cap full of 10w 30. I feel like the cold compression is probably ok too. I will run the test again with the bike hot. The gas smell in the oil is slight, but after a long ride, I get white smoke from the crank case as well when I pull out the dip stick. Like I said, I know I'm running rich, but the bike runs well. At first I was worried that the bike was running hot and burning oil. My carbs are brand new VM30s. I will double check everything, but given the design of the floats I don't see how they could be so out of speck as to be causing gas to flow to the crank case. I'm confused.
Andrew

So, quick question. Is ANY difference in PSI after adding oil supposed to point to worn rings that need to be replaced? It seems like some difference is to be expected due to the added oil adding volume to the chamber, thus raising the compression. I could be completely wrong.

OK how bout this.. MAKE sure you have your valve clearances set correctly COLD as a witches tit and then do the test again after you WARM the engine up to running temp. NO oil added to the spark plug holes. See what you get.

ANY time you SMELL FUEL IN YOUR OIL then CHANGE IT RIGHT AWAY, no questions asked. Nothing will kill an an engine faster than fuel diluted OIL. Well other than running NO OIL. EVERY time you shut the bike off you should turn off the fuel supply IE set the petcock to OFF. Every TIME.

If you end up with the same readings then follow the manual. It says to check for a number ABOVE normal and pull the head and clean out CARBON deposits. CHECK for BELOW normal levels for POOR compression and repair or rebore. AND anything MORE than 10% difference between both sides means that SOMETHING is FUCKED UP and needs worked on.

...yeah, the running no oil thing. About that...

Don't do that either.

Something I just thought about: The oil in the engine now does have seafoam added to it. I forgot I added it last oil change. Perhaps this has something to do with the fuel smell? Maybe, maybe not.

Next steps: Change oil, check floats and float level, check valve clearances and reset if needed, warm bike to running temp. Recheck compression.

My only question are these: If I get a good compression warm, which I expect I will based on the cold compression, should I run the test again after adding oil to the cylinder?
Like I said, the bike has been running great. Strong pull though all rpms and cranks on first button push cold or warm.

Additionally, is the fact that I am running a rich in the mid throttle positions a possible reason that a small amount of fuel could be getting to the crank case? Are there other reasons that I would be getting some smoke from the crankcase when I remove the dipstick?

I learned my lesson long ago about leaving the petcock on. I check and double check every time I stop. I am sure that the petcock has not been left on while parked.

I will post my results from my running temp compression check in the morning.

Thanks guys!

Where are you?
How cold and damp is it?
'smoke' is probably condensation

....... a whole cap full? sir, are you crazy? no wonder your test showed 240...... on my 72 cl350, i got 153 and 145.... your bike is fine. why did you even do this test? you only add that much oil to a bike that has been sitting for 10+ years in a barn, then wait 24 hours, then attempt to slowly turn it over to see if the motor is rebuild-able. unless your compression is 110psi or less, no adjustments or parts are needed. What are the bikes symptoms? will it not run? you just need an oil change and POSSIBLY a carb adjustment. dont start the bike till you get the oil out of the combustion chambers! you will hydro lock it if you dont

and really, the smoke out of the breather tube is normal, bikes now-a-days have little emissions filters on them to filter the shit out before its let out into the environment. your bike is over 40 years old, they didnt care about the environment back then....

arudeseal said:

Something I just thought about: The oil in the engine now does have seafoam added to it. I forgot I added it last oil change. Perhaps this has something to do with the fuel smell? Maybe, maybe not.

Click to expand...

Well, Duh!
Why do you have Seafoam in your oil. A Seafoam treatment is for an engine that has specific problems, and you don't leave it in there. Also, how much did you add? Could certainly do more harm than good if you added too much.

arudeseal said:

Like I said, the bike has been running great. Strong pull though all rpms and cranks on first button push cold or warm.

Click to expand...

So, what is your problem? Sounds like you are trying to find a problem where none exists.

Your compression reading is just fine. Best practice is to do a compression test on a warm engine. Adding oil for a second test is only done if your compression readings are low. Adding the oil is only for the purpose of determining whether the low compression reading is due to rings or valves. Your reading isn't low, so there is no need for the second test with oil.

Change out that oil that you contaminated with a non-lubricant. (Seafoam makes copious quantities of white smoke, BTW.)

Running rich will not contaminate your oil with raw fuel. It will cause carbon buildup on your pistons and heads. The fuel smell you are detecting is the Seafoam. Seafoam in the oil should be only about 1 1/2 oz per quart of oil. If you added more than that, change your oil.

Oil changed, no Seafoam this time. Valves checked: good. Jet needle lowered one clip. Idle circuit air screw reset. I haven't started the bike yet.

How do I make sure the oil is cleared from the combustion chambers? Turning over by the kick (ignition off of course) several times?

Gonna go for a short ride once I'm sure the oil is cleared from the chambers and then check my plugs, oil, and compression after. I added a couple of capfulls of Seafoam to the crankcase last oil change, about 60 miles ago (my average trips are around 3 miles). I also added a capful to the compression chambers and let them soak before turning the bike over by the kick to clear the excess. However, now I realize that Seafoam ended up past the rings. This explains the fuel smell in my oil. Lesson learned. No non-lubricants with the oil, and fresh oil whenever there is any sign of contamination.
Thanks for all the help,
I'll post the warm compression check results in an hour or so.
Andrew

PJ,
I'm in north Georgia. It was 63 with about 50% relative humidity yesterday.

To get the oil out of the cylinders just take the plugs out and kick the thing over a few times with a rag over the plug holes, it will blow it out. Take a lighter or a cold propane torch and smoke the oil out of the plugs as well.