Bevel gears timing marks

[ecurbruce]

When setting the four timing marks on the bevel gears to time the crankshaft and the camshaft,,, does it require the camshaft to be at top dead center on the compression stroke? Or does it matter, or can be set at any top dead center? After having some timing and carburetor issues, I decided to check the cam timing, and found the marks to be off. (there was lots of reversion through the carb and could not get a reliable idle.) I recently had the head off , and suspect I may have put the oldham coupling 360 degrees out???

Bruce

[Jordan]

All the timing marks don't line up except every 5 crankshaft revolutions.
Try turning the engine until the bottom coupling's flat surface is straight in line with the bike, male semi circle to the outside.
Check that the points are near opening point for ignition.
Then on the head, turn the gears until the marks line up, piston near TDC. The couplings should match.
This could save you having to remove the timing cover.

[machten]

+1 on Jordan's post. If you haven't done anything with the bottom bevel or the ignition timing gear, (as it seems you haven't) that's the way to sort out any mismatch. Line up the valves logical postion with the the ignition. You'll work it out, Bruce!

Kev

[DewCatTea-Bob]

[quote= ecurbruce ...
" When setting the four timing marks on the bevel gears to time the crankshaft and the camshaft,,, does it require the camshaft to be at top dead center on the compression stroke? "

____ Yes, otherwise you could-not align-up ALL the timing-dots !



" Or does it matter, or can be set at any top dead center? "

____ Any actual TDC (with valves closed) could work,, BUT, if not the originally-intended TDC, then the upper tower-shaft & camshaft bevel-gear timing-dots will NEVER line-up.



" I decided to check the cam timing, and found the marks to be off. "

____ Chances are that that situation will be the most-likely case, if ya do-not know exactly what you are doing,, (as only one out of five power-stroke TDC-points will actually happen to show the upper bevel-gear pair with their timing-dots set to properly match-up) !
__ Ya always ought-to align the upper bevel-gear timing-dots for the cyl.head (by turning-over the engine), BEFORE removing the cyl.head. _ That way, ya can then always do as Jordan has indicated with the lower tower-shaft, (which with the upper bevel-gear timing-dots fixed-aligned, will then allow for perfect fore-&-aft alinement between the upper tower-shaft half-moon male-coupling tip-end along-with the corresponding lower-shaft tip-end male-coupling, every ten crank-revolutions).



" I recently had the head off , and suspect I may have put the oldham coupling 360 degrees out??? "

____ It is next to impossible to discover any other crankshaft & camshaft timing-relationship that could still allow the engine to possibly run any at all by simply reinstalling a cyl.head incorrectly-timed, (unless ya had also un-meshed any of the bevel-gear pairs AND just happened to re-mesh them back together just a single tooth out of normal timing).


Hopeful-Cheers,
-Bob

[DewCatTea-Bob]

[quote= Jordan ...
" All the timing marks don't line up except every 5 crankshaft revolutions. "

____ I believe that what Jordan must have actually meant to indicate, is that the upper & lower tower-shaft coupling-tips come to properly-align only every "5" Otto-cycles -(or power-strokes), which is actually 10 "crankshaft-revolutions" !


Dukaddy-DUKEs,
-Bob

[ecurbruce]

Thanks, guys for the responses.
After removing and reinstalling the head assembly without disturbing either set of bevel gears in the process, bringss me to realize that the lower pair had to be off before the head removal.
I'm also understanding that the only way all bevel gears can be in time is on the compression stroke, because of the dot on the upper-most gear will only align when the cam is in that position.

After correcting the lower bevel mesh, the engine will idle, and the reversion issue is better. I'm just trying to figure out when that timing got out. No matter, problem solved...

Bruce

[DewCatTea-Bob]

[quote= ecurbruce ...
" I'm also understanding that the only way all bevel gears can be in time is on the compression stroke, "

____ Once the gear-timing has been properly set, their 'timing' will always remain set. _ So rather, you must've meant that the timing-dots will only possibly become 'aligned' at the compression/power-stroke TDC, (no more than ONCE every five Otto-cycles/4-strokes).



" I'm just trying to figure out when that timing got out. No matter, "

____ Actually, that mystery ought-to be pondered-out !


Hopeful-Cheers,
-Bob

[Jordan]

[quote= Jordan ...
" All the timing marks don't line up except every 5 crankshaft revolutions. "

____ actually 10 "crankshaft-revolutions" !

Oops, actually I think we're both wrong, Bob.
Looking back at my notes, it's every 5 turns of the bevel shaft that all the dots line up.
For crankshaft revolutions, the number is 14.

The main thing to know is that the coupling can go together, but that doesn't necessarily mean the crank-cam timing is correct.

[DewCatTea-Bob]

[quote= Jordan ...
" Oops, actually I think we're both wrong, Bob. "

____ DewCatTea-Bob actually be wrong ?
__ I first learned (when I was a teenager) back in the '60s about those shaft's half-moon coupling-faces coming into fore&aft*alignment (in parallel-direction with the split between the crankcase-halves), EVERY ten rotations of the crankshaft, (so that the cyl.head could then be properly installed with it's-own bevel-gear timing-dots pre-aligned) !
(* The coupling-faces also align as well every 5 crank-revs, but with those shaft's half-moon tip-ends set on the opposite-side.)



" Looking back at my notes, it's every 5 turns of the bevel shaft that all the dots line up. "

____ I assume you're only meaning just the timing-dots of the bevel-gears ?
But even just-THOSE should all line-up far less often than just "5 turns", (as the tower-shafts must turn slower than the crankshaft, [yet faster than the camshaft] ) !
It's rather the CAMshaft that actually turns only "5" times, for the tower-shaft to finally reach one of the two fore-&-aft coupling-face alignment-arrangements that's the correctly phased one.
__ (I gather that your "notes" were hastily written-down, thus allowing you to misinterpret whatever you had originally meant ?)



" For crankshaft revolutions, the number is 14. "

____ I sure don't know how you possibly came-up with THAT-figure !



" The main thing to know is that the coupling can go together, but that doesn't necessarily mean the crank-cam timing is correct. "

____ I sure as-heck learned that-FACT back when I was a teenager (before I bought my first Ducati workshop-manual), which is how I had learned that installing the cyl.head without having the lower tower-shaft's male-tip PERFECTLY-set (in properly-timed orientation), will most certainly lead to some way-off cam-timing that will-NOT allow the engine to start & run !


Dukaddy-DUKEs,
-Bob

[Jordan]

I'd better stop it with the rev numbers, relying on sketchy notes, and maybe confusing with bevel twins' timing.
Next time I'll pay better attention.