Timing the head on the 750 GT round case - Ducati.ms

RockingM · Dec 7th, 2011, 6:04 pm

Ok, I had to pull the vertical head to do a insert on the spark plug hole.
I thought I had used the correct marks on the bevels but what I used was one mark on one and the key way for the other. I did notice the exhaust valve was just closing when it came off. Anyway I lined my marks back up on the head
and reinstalled without turning the crank in the meantime. I've lightly snugged it down and turned several times through the cycle and no valve clash.
I also checked and it's firing at 10degrees BTDC on the compression stroke. (Both valves closed and spark) and the timing marks on the bevel gears are lined up. The correct timing marks I must add since after I had it off I found the other correct mark.

Am I good to go? Or can someone take me through the whole timing sequence
if not?

DesmoDog · Dec 7th, 2011, 6:57 pm

I'm not sure what you're trying to say but if you lined up the cam the same before and after, and didn't move the crank in the meantime, you're fine. It doesn't really matter what marks you used as long as you didn't move anything in between.

You can't change ignition timing by pulling a head so there's no reason that would change. If the correct marks line up (only happens once every six revolutions remember) then I don't see the problem. Line up the marks on the crank and the cam on the head you didn't pull, and the other cam should be good too.

RockingM · Dec 7th, 2011, 7:06 pm

Quote:

Originally Posted by DesmoDog

I'm not sure what you're trying to say but if you lined up the cam the same before and after, and didn't move the crank in the meantime, you're fine. It doesn't really matter what marks you used as long as you didn't move anything in between.

You can't change ignition timing by pulling a head so there's no reason that would change. If the correct marks line up (only happens once every six revolutions remember) then I don't see the problem. Line up the marks on the crank and the cam on the head you didn't pull, and the other cam should be good too.

I can't even find any marks on the crank. The only thing I've got is the crank end with the bolt hole to attach a degree wheel. Maybe you can tell me what I'm missing. Sure is much simpler with a rubber duck.

wdietz186 · Dec 7th, 2011, 9:04 pm

Go over to the other side of the engine and pull that cover off. You will find a whole bunch of gears on that side. On those gears are dots that should line up with each other when the dots on the vertical head are aligned. The crank gear aligns with the distributor gear [dots on both] above those gears are the gears that drive the towershafts. They also have dots that will line up with each other. These are hard to see as they are close to the case [a good penlight helps]. As DesmoDog stated you will have to turn the engine over about six times to get everything to align. But since you haven't undone any of the gears and moved them,it all should pop back together easily. Do the head nuts up to 30ftlb.I usually do it in 3 stages 10,20,30. Check your valve clearances while you are in there too.

DesmoDog · Dec 7th, 2011, 11:47 pm

Ah, sorry, I thought you had the side cover off to check the timing marks. the two crank gears have their marks highlighted in yellow in this shot.

There are also marks on the central bevel gears. this shot also shows the rotor for the alternator which might make it harder to see the dots on the crank gears. You can see the yellow dots on a few of the gears in this shot.

When I said the dots only line up every six revolutions, I meant ALL the dots only line up every six. The two lower gears, the three central gears, and the two sets of cam gears.

EDIT: There is a slight chance someone has timed the cams by deliberately offsetting the gears a tooth or two. If this is the case... the dots will not line up when the timing is correct... my bike is set up with squarecase cams so the gears are NOT indexed per stock specs (and the cams use offset keys). Anyone who tries to time it using the factory dots is screwed... in any case if you did make marks and use them without shifting anything in the process, you're good to go.

RockingM · Dec 8th, 2011, 6:02 am

Thanks for the info fellows and great pics Craig. I mistakenly used the one bevel mark and the key way on the upper bevels. I've rotated through several times and no clearances issues. Also checked to see if it is firing just as the marks lined up on the bevels for that cylinder and it did. I'll also pull the other head and decoke it while I'm at it.

pulled the cover to double check too. I'll sleep better at night.