Valve adjustment woes - Star Motorcycle Forums: Star Raider, V-Max, V-Star, Road-Star Forum
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post #1 of 23 (permalink) Old 01-24-2016, 10:33 PM Thread Starter
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Unhappy Valve adjustment woes

Howdy gents, I'll try to keep this a short as possible: anybody who's checked and set their own valve adjustment, I need your help.

I followed the Yammy repair manual's valve adjustment guide from 650ccnd to the letter. First problem: the repair manual says to find TDC by aligning both the camshaft sprocket with it's mark on the cylinder head (the dot and pointer) AND the T/I on the rotor with the the AC magneto cover (the T/I mark and the notch), but I cannot do both; when one is aligned, the other is approximately 10-25 off! When the head is aligned, the rotor is 25 off to clockwise; if I align the TI/I and the notch on the rotor, the head is off by around 10 to counterclockwise!

Assuming the camshaft sprocket on the head was more important, I went with that. With hesitation, I continued.

After taking my first measurements, I found that both the intake and exhaust valves were within spec (intake was right on the minimum at .07 mm, exhaust was .14 mm, both within tolerances). I then rotated the crankshaft through 3 full rotations in order to recheck my measurements, expecting no difference, since I hadn't made any adjustments; THIS time the intake was at .05 mm (.02mm out of true) and the exhaust was at .15mm!

My measurements are good, I checked several times, both times, using the "go/no go" method. My feeler gauges are good; I borrowed a second set just to be sure. Both times I (rather comically) stuck my eyeball three inches from the sprocket and lined up the pointer with the center of the dot to the absolute stupid best of my ability, probably accurate to a half-mm or better.

What could be causing these two phenomenon? Are they related? Am I incompetent? Is this a manufacturer's defect, or a parts failure? Do I need to do something different? As is, I'm inclined to simply put the head covers back on and forget I ever mucked with it. While I'm just an amateur, I just removed, rebuilt and reinstalled both carbs and greased the rear drive splines without a single peep of trouble, and after those confidence builders, I'm kinda shocked that things have gone sour so quickly. The manual is not helping me here. Any suggestions?

Last edited by Arnold_Kupferkopf; 01-24-2016 at 10:48 PM.
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post #2 of 23 (permalink) Old 01-25-2016, 07:52 AM
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I hope I can help without sounding as if I am trying to insult your intelligence. Remember that the crankshaft makes two full revolutions for a single revolution of the camshaft. Any angular error on the crank (rotor, flywheel) will be twice the angular error on the camshaft. At least on the bikes I have worked with, the rotor usually has at least two marks. One is TDC; the other is the timing mark for the ignition. The timing mark is usually somewhat advanced from the TDC mark so the spark plug fires before TDC (ignition advance). On V-twins there may be a timing mark and a TDC mark for each cylinder.

The surest way to find TDC is to remove a spark plug and stick a plastic soda straw down through the hole so it rests on the piston. Turn the engine slowly in its normal direction of rotation (this makes sure the timing chain stays tight) and observe the straw. When the straw stops rising, the piston is at TDC. You can usually get "close enough" by using a flashlight to look through the hole so as to actually see the piston. Remember too that the intake valve will have closed probably 150 degrees before TDC and the exhaust valve will not open for probably 150 degrees after TDC, so a few degrees isn't likely to matter.

For every operating cycle of the engine, the crank makes two revolutions and there are two TDC events. At one TDC, both valves are closed and there will be "play" between the lifter and the valves; at the other it is likely both valves will be slightly open and you won't be able to get a feeler into the gap. When you check or adjust the valves, make sure to rotate the crank some multiple of two revolutions before you recheck.

Completely unrelated: How do you get the little "degree" mark into a post?
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post #3 of 23 (permalink) Old 01-25-2016, 08:05 AM
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i just rotate the engine until one of the valves just begins to open, then adjust the opposite valve on that cylinder. when an intake valve is starting to open the exhaust will be on the heel of the cam (no lift) and vice versa. a valve can be adjusted any where along the heel of a cam, and the heel of a cam is 180 degrees of the cam circle. auto engines are adjusted by watching the action of valve rockers so i use the same method on motorcycles. it also says in the manual , adjust to the tighter end of the specs for the best performance. also the flywheel marks should line up at very right edge of the hole not the middle. and the front cam will appear to be off by a half tooth with the flywheel line up correctly, this is normal. i set mine at 3 thousandths intake and 4.5 thousandths exhaust. i know the exhaust is a bit tighter than allowed but it's the only way to eliminate the ticking. i'v rode many thousands of miles with that setting with no problems. i check my clearances every winter and after the 15000 mile mark they never seem to change more than 1/2 thousandth . (.0005) inch

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post #4 of 23 (permalink) Old 01-25-2016, 04:38 PM Thread Starter
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Thank you both, gentlemen! You've given me some excellent information to chew on as I head back into the garage. I'll post my results when I'm finished! *crosses fingers*
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post #5 of 23 (permalink) Old 01-25-2016, 04:43 PM Thread Starter
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Quote:
Originally Posted by Charon View Post
I hope I can help without sounding as if I am trying to insult your intelligence.
No insult taken at all, sir. I'm happy for every little tip when I'm elbows deep in an engine for the first time. You were wise to dumb it down for me.

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Completely unrelated: How do you get the little "degree" mark into a post?
Simple, I copied it from the Wikipedia article. Nerd alert.
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post #6 of 23 (permalink) Old 01-25-2016, 08:01 PM
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Charon,
For the degree symbol hold the alt key and then 248. (could be the control key)

Last edited by StarDriver242; 01-25-2016 at 08:08 PM.
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post #7 of 23 (permalink) Old 01-25-2016, 08:06 PM
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Pauli466 are your measurements in mm or thousandths? because 3 ans 4.5 thousandths lash seems a bit tight to me but i work on large diesels.
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post #8 of 23 (permalink) Old 01-26-2016, 07:23 AM
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Quote:
Originally Posted by Charon View Post
I hope I can help without sounding as if I am trying to insult your intelligence. Remember that the crankshaft makes two full revolutions for a single revolution of the camshaft. Any angular error on the crank (rotor, flywheel) will be twice the angular error on the camshaft. At least on the bikes I have worked with, the rotor usually has at least two marks. One is TDC; the other is the timing mark for the ignition. The timing mark is usually somewhat advanced from the TDC mark so the spark plug fires before TDC (ignition advance). On V-twins there may be a timing mark and a TDC mark for each cylinder.

The surest way to find TDC is to remove a spark plug and stick a plastic soda straw down through the hole so it rests on the piston. Turn the engine slowly in its normal direction of rotation (this makes sure the timing chain stays tight) and observe the straw. When the straw stops rising, the piston is at TDC. You can usually get "close enough" by using a flashlight to look through the hole so as to actually see the piston. Remember too that the intake valve will have closed probably 150 degrees before TDC and the exhaust valve will not open for probably 150 degrees after TDC, so a few degrees isn't likely to matter.

For every operating cycle of the engine, the crank makes two revolutions and there are two TDC events. At one TDC, both valves are closed and there will be "play" between the lifter and the valves; at the other it is likely both valves will be slightly open and you won't be able to get a feeler into the gap. When you check or adjust the valves, make sure to rotate the crank some multiple of two revolutions before you recheck.

Completely unrelated: How do you get the little "degree" mark into a post?
wipe the oil off the dimple and paint it with white out, it will then be highly visible in pics

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post #9 of 23 (permalink) Old 01-26-2016, 07:40 AM
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Originally Posted by StarDriver242 View Post
Pauli466 are your measurements in mm or thousandths? because 3 ans 4.5 thousandths lash seems a bit tight to me but i work on large diesels.
those numbers are in thousandths of an inch. overhead cams allow for very close tolerances. the manual shows ( .0028-.0047 inch ) for intakes and (.0047-.0067 inch) for exhaust on a 650 engine. the only way you can hear the tick on mine is with a stethoscope.some tick is absolutely necessary or the valves will burn but i don't like hearing it over the exhaust. did you ever have to shim the side covers on a cummins to set the clearance for injectors? also the using a straw to find TDC is better than trying to line up flywheel marks. at least with a straw there is no guessing.

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Last edited by pauli466; 01-26-2016 at 08:06 AM.
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post #10 of 23 (permalink) Old 01-26-2016, 10:39 AM
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Quote:
Originally Posted by pauli466 View Post
those numbers are in thousandths of an inch. overhead cams allow for very close tolerances. the manual shows ( .0028-.0047 inch ) for intakes and (.0047-.0067 inch) for exhaust on a 650 engine. the only way you can hear the tick on mine is with a stethoscope.some tick is absolutely necessary or the valves will burn but i don't like hearing it over the exhaust. did you ever have to shim the side covers on a cummins to set the clearance for injectors? also the using a straw to find TDC is better than trying to line up flywheel marks. at least with a straw there is no guessing.
Yes; I have timed the cam followers on the Cummins engines a time or three. A lot of barring the engine back and forth.... so much fun

I am getting my list together and going to add valve adjustment to my preseason maintenance this year.
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