help with valve shims.

[roger]

Good question Mike and I should clarify. You roll the motor forward until the cam lobe pushes down on the shim/bucket. This lowers the shim/bucket in the hole so that you can install the tool. It is fastened in place with one M6 cap screw that is provided with the tool. If installed correctly, the lower tip of the tool holds the bucket down in the lowered position.

You must now roll the motor back slightly until the cam lobe is pointing away from the shim allowing you to remove and replace the shim. If the tool has too much "meat" in the area that I highlighted in red it will actually touch the cam.

If the tightened tool touches the cam because it too thick in the area I pointed out in red and you are trying to turn the motor, you will experience a drag much like Roger described. It could even be damaging. However, it was never established if the tool was actually in place during rotating the motor. It's just a possibility. The Motion Pro tool can be out of spec. Mine was junk and I tossed it.

I didn't have the tool on the valve, I just had the cam lobe turned away from the shim. I couldn't move it at all to start with but I finally got it to start moving its just harder to turn than the others.

[Radioguylogs]

Then Bikerphil's advice might make you worry less. (post #9)

[DEEBS11]

Sometimes coffee enhances my enthusiasm.

[Ccitis]

A 275 shim would put you at .21, the low end of the range.
A 270 shim would put you at .25. the high end of the range (better choice)

Sometimes it is not possible to get to the center of the range.

Help me understand this... first time doing shim over bucket valves... why is the high end better... just because looser valves are better? All my valves are silly tight (bought the bike last year as a non runner, 32k kms) Only 2 are in spec (#2 ex .21mm and #3 intake .14mm). I will still replace the #2 exhaust at the lower end of the range. The bike is a 1980 G model, so there are supplementary specs for one side... I forget. Waiting on my shim tool to come and then will figure out what shims I need using the manual.

[DiverRay]

The valve lash DECREASES as it wears. With tappet valves, they would INCREASE. You now see the difference.I always set my valves as close as possible to the high end, even over a little bit, 0.26. A little noisy at first, but they ALL wear down as the valve keeps pounding the seat. With these bikes, a little valve noise is good, and no noise can be a big problem.

[DEEBS11]

Above all else you need the valve to sit closed and tight on the valve seat when the cam lobe is faced away from the lifter. It needs the gap to compensate for heat expansion. If there is too little or no gap the valve can stay slightly open and burn the seat because of escaping combustion. Very bad. It also reduces compression for a loss in power. Use the motor long enough in this manner and even a proper valve adjustment won't bring back compression because the seat is pitted and damaged. This is when the head has to come apart for a proper valve job by a machine shop to re-grind the seat and possibly replace the valve guides depending on wear.

[Ccitis]

Thanks alot... This indeed does help. I will certainly err on the side of loose. Bike will not be run until all is well in the valve train.

[Ccitis]

Where are we all getting Shims from? Any to stay away from... I was eyeing Mikes XS.

[cajun31]

Where are we all getting Shims from? Any to stay away from... I was eyeing Mikes XS.

The ones on Mike's are the cheapest I have seen them. Not a bad selection to start with either.

[DiverRay]

Once you know what shims you need, let me know. I don't have a lot of them. but I'm willing to trade sizes with you. Just shoot me a PM with your mailing address and I can send what will fit to you. All I ask is the return of the shims you cannot use, so I can send some to the next owner that needs them.

[Ccitis]

Once you know what shims you need, let me know. I don't have a lot of them. but I'm willing to trade sizes with you. Just shoot me a PM with your mailing address and I can send what will fit to you. All I ask is the return of the shims you cannot use, so I can send some to the next owner that needs them.

Thanks for the offer, but I have already ordered from Mikes... next time! I do have one more question. One intake is at .07. If I go up 5, I go to .12. Spec on a 80 g model is between .11-.15... sooo if I go up 10mm I go to .17... is that too loose, or just go looser on that one and spare the trouble later. I am leaning that way. Thanks.