My front cylinder showed 210 PSI in a recent compression test. I thought this was pretty high, but didn't think much about it until I looked at Haynes manual. It shows something like 156 PSI as a maximum compression.
The manual suggested carbon deposits were a likely culprit. I sprayed a can of Seafoam spray and upper cylinder lube in my front cylinder. I haven't had time to check compression again. I thought I ask the forum about their experience correcting high compression, as I don't have much faith in a can of Seafoam to serve as a panacea to my problem.
Any advice would be great. My bigger picture problem is hard starting when hot. Just trying to cross things like large differences in compression off the list (210 front, 110 rear (I hope more on rear now that I have put some miles on bike)).
Did you do the test more than once? I distrust single readings of things like tire pressure and cylinder compression because they can be a bit shaky in the process. Especially when the test is the least bit difficult to make.
Six tests on two different days. K
Same gauge?
What did the front cyln. plug look like regarding color and carbon deposits? Cheers.
The plug that is in the bike now looked pretty normal, but I replaced it about 20 miles ago. Unfortunately, those 20 miles took me since August 2016 to put on the bike. I think the previous plug was oily.
Maybe I'm the only peasant with only one compression tester, but yes, same gage each time.
Does anyone have any experience correcting high compression?
Can you borrow a gauge from Auto Zone? It might be better than chasing the wrong problem. I would have serious doubt about any reading above 170.
Yep, I'll go borrow a gage. I am crazy busy at work next 10 days, so it will be a while before I can get the numbers. If it is my gage giving bad numbers, than the rear cylinder at 110 PSI (which is below lower limit, but I was hoping would come up with some miles on the motor) could be well below this number, and even more of a problem.
Since I have about 10 days before I can really put my hands on the bike, but would like to gather ideas about what to do once I have new compression readings, does anyone have experience correcting high compression?
Have you checked valve clearance lately? Too tight valve clearance could cause low readings and, as someone already said, carbon deposits could cause high readings.
Oily plug is not a good sign. If the combustion chamber gets a lot of oil you likely have carbon deposits. Excess oil can be from worn out valve stem seals, bad rings, or scored cylinder. IF you have carbon deposits you will likely have to take the head off. For sure the head will have to come off if you need rings or cylinder work.
Quote from: fret nut on April 26, 2017, 02:18:13 AM
IF you have carbon deposits you will likely have to take the head off. For sure the head will have to come off if you need rings or cylinder work.
I know that Yamaha and Vesrah do replacement valve seals, but rings? Can you get replacement rings?
eBay sometimes. It's why I have a couple extra motors.