I'm adjusting the valves for the first time on a 2gm20f the book says align the 1t Mark for first cylinder then 2t Mark for second. To make sure they are on compression stroke. Are they on compression stroke every time marks are aligned or does flywheel have to go around more then once to get comp. stroke? Thanks for any help.
Yanmar valve adjustment
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every other time the crank goes around you are on a compression stroke for a specific cylinder - you can tell because both rockers can be moved, if just one valve has play - rotate another 360 and both should have play. (unless you have a Detroit Diesel or other 2 cycle)
I do not use the marks on the flywheel but like Leslie indicates I manually turn the engine after flipping the decompression levers until both the intake and exhaust rocker arms are loose and both attain their maximum gap . I turn the engine with a wrench in the direction of rotation of the belts and pulleys. I verify this gap with a feeler gauge and will adjust to specs if needed. The final test is a smooth running engine with no loud taps. Loosen the adjuster nut, insert the feeler gauge and turn the adjuster until contact is made (a little tight but the feeler gauge can be slid out) Then carefully tighten back the nut without allowing the adjuster to turn and foul up the correct gap. I always after completing the adjustment will run the feeler gauge to insure the desired gap was attained.
Check your flywheel mark just once to find TDC for either cylinder. Mark the cylinder number and location at the exact top your crank sheave. The photo below shows my engine at ANY LOCATION. It is not being checked for lash.
The other cylinder will be at exactly 180deg. from the first mark. Mark that one as well.
When you want to check the lash on #1 cylinder, place the #1 mark at the top and make sure the rocker arm doesn't move when the engine is slightly turned. If it does, rotate the engine 180 deg.
Below is an extract from a Seloc manual which, in this case, might be a little clearer than the Yanmar shop manual.
Page 3-40 (below) is the start for a 2GM
The other cylinder will be at exactly 180deg. from the first mark. Mark that one as well.
When you want to check the lash on #1 cylinder, place the #1 mark at the top and make sure the rocker arm doesn't move when the engine is slightly turned. If it does, rotate the engine 180 deg.
Below is an extract from a Seloc manual which, in this case, might be a little clearer than the Yanmar shop manual.
Page 3-40 (below) is the start for a 2GM
Two more questions about valve adjustments on the Yanmar. Do you open the injector lines as a precaution against the engine starting while rotating to find TDC? ( mine doesn't have decompression levers) And, approximately how long does this job take in entirety?
I have comp. levers, but did not release them, I will next time, but you turn it over slowly so I don't think it will start. It tool two of us, one to turn over and one to watch flywheel mark. About an hour's time.
I will use one of the above ways in the future.
I will use one of the above ways in the future.