I am currently attempting to fit a new camshaft to see if it improves the hill climbing abilities of my Jupiter but I am having a problem with setting the valve timing. From the manual I understand that there shoul be 13 thou of lift at the inlet valve at N1 cylinder at the twelve degree mark on the flywheel, and that the fixing holes in the chainwheel are elongated (oversize actually) to allow adjustment, but I find that the holes do not permit sufficient movement of the chainwheel to achieve this condition when the dowell is shoved into a suitable hole in the boss. Am I missing something?
If one is using this method does one dispense with lining-up of the arrow and and the two dots on the chainwheel and crankshaft sprocket respectively. At the moment I am getting about 10 thou lift at TDC but no lift at all at the 12 degree mark on the flywheel. As I wish to get to the National at the end of the month some clarification from one of our experts will be much appreciated.
Valve timing
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Brian Cole
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Valve timing
As a member of JCC and JOAC i wish to join to take part in on-line discussion and to improve my knowlege and understanding of the jupiter mark.
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Re: Valve timing
1. Check you are on Top Dead Centre of No 1 and not some other cylinder by checking position with wire through spark plug hole.
2. Check that you are on 12 degrees before TDC by marking crankshaft pulley using a protractor. Check this coincides with flywheel mark.
3. Set up dial gauge on rocker arm and check movement of valves corresponds to inlet cycle. This assumes you have already pegged the camshaft and put on chain. See below if not.
4 Rotate through to almost 2 revolutions so that you are just before inlet cycle again, looking at dial gauge to prove you are moving from the base circle.
5. Usually the valve springs force back the camshaft so you need to keep torque on crank pulley nut. The lift ramps up very quickly, so turn slowly.
6. If lift is wrong, then take off chain and peg clamp and remove peg.
7. With crankshaft at 12deg before TDC, turn camshaft as for steps 3 and 4 above, and then do 5, but turning camshaft.
Note that a couple of degrees either way is acceptable as the ramp is very steep. Just find the peg hole alignment that is best.
This method disregards any marks that there might be, but once it is checked this way the marks may align, but not necessarily.
2. Check that you are on 12 degrees before TDC by marking crankshaft pulley using a protractor. Check this coincides with flywheel mark.
3. Set up dial gauge on rocker arm and check movement of valves corresponds to inlet cycle. This assumes you have already pegged the camshaft and put on chain. See below if not.
4 Rotate through to almost 2 revolutions so that you are just before inlet cycle again, looking at dial gauge to prove you are moving from the base circle.
5. Usually the valve springs force back the camshaft so you need to keep torque on crank pulley nut. The lift ramps up very quickly, so turn slowly.
6. If lift is wrong, then take off chain and peg clamp and remove peg.
7. With crankshaft at 12deg before TDC, turn camshaft as for steps 3 and 4 above, and then do 5, but turning camshaft.
Note that a couple of degrees either way is acceptable as the ramp is very steep. Just find the peg hole alignment that is best.
This method disregards any marks that there might be, but once it is checked this way the marks may align, but not necessarily.