Tappet clearance & compression

[Guest]

Please help. I just adjusted my tappets for the first time and I think I made a mess of it. My piston's compression have either dropped or gone away. Will poor tappet clearance cause this?

Thank you for your help.

[Steve]

Yes it can.

First of all, WHAT BIKE????

What method did you use to adjust the valves?

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[BigVic54]

Its a 1982 GS1100LG. I used a feeler gauge, measured the existing tappets, did the math and put new ones in. However, I think I screwed the pooch as one piston that was at 140LBS now has none and another has dropped significantly.

[hampshirehog]

I think you're going to have to take us through the maths to start with. It could be your method but it's easier to start with the maths.

[Steve]

The "maths" part is easily taken care of by taking advantage of the offer in my sig.

The "method" part might need to be explained, as the process can be easily misunderstood by a first-timer.

Most don't understand that you set the cam lobes in the position shown in the manual and measure TWO clearances without moving anything. Not measuring with that method can easily give you wrong readings.

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[hannibal]

Maybe you put in massive shims and the valves aren't closing. Can't see how you'd lose compression otherwise.

[BigVic54]

My #3 cylinder wasn't firing. I cleaned & adjusted the carbs, adjusted the tappets and put everything back together. Before I did this the compression in #3 was 140lbs, now its almost 0. It would seem it was the tappets. Could the carbs affect the compression?

[Steve]

Could the carbs affect the compression?

If you forget to hold the carb open, it could.

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[tkent02]

Perhaps, but it wouldn't read zero.

[JTGS850GL]

Perhaps, but it wouldn't read zero.

Agreed... Typically it would read low, like in the 90's, but not zero.

[8ball]

Go back and check clearances, again....according to the exact method in the manual. Chances are you have a couple too tight.

[BigVic54]

I opened it up and checked the clearances again. This time I paid more attention to the location of the lobes on the cams. The gaps were anywhere between 1.0 and 2.0. I've moved some around and will order some new ones. Does anyone think this would be enough to lower the compression?

[hampshirehog]

How are you measuring those gaps? They're huge.

[BigVic54]

How are you measuring those gaps? They're huge.

I switched a decimal point, sorry. I should have said between .1 and .2

[8ball]

I switched a decimal point, sorry. I should have said between .1 and .2

Still huge! Should be .03 -.08 mm (.001" - .003")