4th GEN camshaft removal

[Lannyl81]

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.

[Grum]

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.

 

[Lannyl81]

Grum: you are correct, #3 is closing, not opening....forgot that cams turn CCW when I wrote above......duh!.....thank you.

 

Will be removing the rear cams this afternoon.

[Lannyl81]

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?

[RC36B]

59 minutes ago, Lannyl81 said:

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

[Lannyl81]

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.

 

Thanks again for all the help.

[RC36B]

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 🙂

[Terry]

8 hours ago, RC36B said:

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. 

[RC36B]

3 hours ago, Terry said:

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.

[Lannyl81]

Ahhh....those were the days.....