Timing problem

Classic short-frame models

Timing problem

Postby Otis » Mon Oct 29, 2018 12:19 pm

I’m try to time a 66 XLCH and to get it right in correlation with the advance timing mark on the flywheel the magneto body is touching the rear cylinder push rod tube. There is no further room to retard the mag for starting because it’s already touching. If I jump one tooth clockwise it hits the air cleaner. I don’t know what’s in the motor but even if it had 1000cc flywheels the 5 degree difference in the marks shouldn’t change location that much. I’m thinking one cam could be a tooth out possibly. Interestingly enough the front cylinder compression is slightly lower. Tested the rings and they seemed good, pulled the head and seated valves with no noticeable difference. Maybe the cam is holding valve open at wrong time. Something is out and I’d rather not completely disassemble the motor without an idea what to check and a plan in place. Any help is appreciated.
P.S. the bike runs ok but is near impossible to start.
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Re: Timing problem

Postby xlh59 » Mon Oct 29, 2018 3:20 pm

I just went through the same problem, took cam cover off, checked for the gasket of the adapter plate (as height matters as well) and tried a dozen times to find the "right" tooth ... at the end it was the point gap, that was to wide that caused the problem. Of yourse I adjusted that before, but something went wrong. Check the point gap first ... if this is too wide, you will not find the right timimg.

Good luck!
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Re: Timing problem

Postby Ferrous_Head » Mon Oct 29, 2018 4:03 pm

Verify that the timing mark on the flywheels is accurate. This is a simple job done with an inexpensive tool. Piston Tdc tool. You can even make one yourself if your a real cheapskate. An old spark plug and small piece of rod. But you can buy one for about 20 bucks and they are handy for checking cams etc. FSM gives you the length (11/16's ?) That gives you correct firing point no matter what the wheels say.
Your 66 should have a Tillotson on it. HD1A. That has a phenolic spacer to help space the carb out. The air cleaner, if using the ham can should have a small cutout on the bottom for magneto clearance.
If the cam timing is out the engine won't be happy at idle or low rpm. It will run ut won't be a "happy" engine. These things do tnd tp be hard to start.
Set the points gap very carefully. Should be .015. Plugs at 0.020. New plugs help. I set my magneto timing with a buzz box from Morris Mags. One of the best tools I've ever bought. Save your ciggy papers for your dope. your battery and light setup looks like a little kids toy as well.
Your engine should have the adjustable advance retard mechanism as well. The mag and the mount have to be assembled correctly for all of this to work.
"I know only too well the evil that I propose, but my inclinations get the better of me."
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Re: Timing problem

Postby Otis » Mon Oct 29, 2018 6:12 pm

All you have told me is correct and I do have a Morris tester and find it much more precise than cigarette pack cellophane that works fine on big twins. I ordered a dial indicator today to check flywheel mark. My question is what is the exact angle of the spark plug hole? To get the 11/16” BTDC I will have to triangulate it because the gauge will move a bigger distance. It looks to be about 40 degrees but I’m not sure that’s exact.
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