Have questions on removing the camshafts; with crank at "T1", both 1 & 3 camshafts gears have the lines level with the head...exactly where they are supposed to be, cylinder #1 is at TDC, but cylinder #3 is not as the intake cam lobe is just beginning to open the valve.
So is the 1 & 3 camshafts removed with #3 not at TDC?
I have not checked, but I assume that 2 & 4 are going to be the same, with #2 at TDC, but not #4.
Just want to be sure I am not missing something before I remove the cams so as to correct valve clearances.
Are you sure the Intake Valve of #3 is opening? It should be closing, you might be turning the engine in the wrong direction! because in 180deg #3 is at TDC on compression stroke.
Same would be for #2 and #4, as #4 is also 180deg after #2.
Firing Order is 1-3-2-4.
Cylinder #1 at TDC + 180deg = #3 at TDC + 270deg = #2 at TDC + 180deg = #4 at TDC + 90deg back to #1 at TDC.
Removed one cam at a time, removed the shims that needed to be, measured it, then put everything back, cam holders in place, just not torqued down. New shims on order.
Of the 16 valves, 8 were needing thinner shims to increase the clearance.
Removed one cam at a time, removed the shims that needed to be, measured it, then put everything back, cam holders in place, just not torqued down. New shims on order.
Of the 16 valves, 8 were needing thinner shims to increase the clearance.
Is this normal?
It would be smart to measure the rest for two reasons:
- You might not need new shims
- It is easier next time; no need to remove cams to order new shims
When you get the new shims and replace, then I would measure the remaining shims
I did remove and measure all of the shims; made a spreadsheet of original measurements/shims and then the ones I changed.....ready for the next time.
Overall job was not all that bad....never dropped a shim. I did get the front intake cam off a tooth as I did not allow for the position change when the cam holder is tighten.....but saw it after I had tighten it down....so I got to take it back off, move the cam a tooth and do it again.
Rotated engine many times and watched the cam/valves/pistons through the firing order....all was good.
Got a tube of the HondaBond for the half-circles on the head covers, put everything back together.
Connected my carb synch lines, waited a few days so the HondaBond to set, then applied power to the fuel pump to fill the carb bowls, then hit the START button, engine fired-up pretty quickly.
Over about two days I adjusted the carb synch, got the carbs levels within 2mm...called it good.
Put side fairings on, waited for a warm day to take it out, which was yesterday.....ran good but with a hot start problem....starting new thread.
So you got to the finish line without nasty surprises 🙂
On this old Nimbus you don't need a micrometer - hell, you don't even need a feeler gauge: first adjust so no gap, then return screw 1 turn back on exhaust and 1/2 turn back on intake, secure with counter nut - job done 🙂
So you got to the finish line without nasty surprises 🙂
On this old Nimbus you don't need a micrometer - hell, you don't even need a feeler gauge: first adjust so no gap, then return screw 1 turn back on exhaust and 1/2 turn back on intake, secure with counter nut - job done 🙂
Love it! actually if one knows the screw pitch for any screw-adjusted tappet, I guess you could work out how many degrees of rotation from zero clearance would get the required clearance.
Love it! actually if one knows the screw pitch for any screw-adjusted tappet, I guess you could work out how many degrees of rotation from zero clearance would get the required clearance.
You got it - that is exactly the trick used. It's a metric 0.75 pitch screw. So that gives you 0.75mm for exhaust and 0.375mm in intake - which is about what you need.