51 "B" timing question

CP1 · Mar 16, 2015

Is turning this engine over with the flywheel and listening for the mag to snap a good way to check the timing? This is what we did and then when it snaps and we look at the timing marks they are off from tdc. The marks are right cuz I went by the piston coming up on the left side. We were real careful in checking every thing, then went and rotated the mag but we're not able to get it turned far enough to get it timed this way, of turning it over by hand till the mag snaps. Also when the piston is at tdc, I notice the slot that drives the mag is not parallel to the ground, it's leaning ahead. What could have caused this to get off. Or possibly been put together wrong years ago? Also it won't hand start right now,have to use a belt to start it, but runs good then. We're going to put in points and condenser even tho the spark does jump 1/4 inch. Fuel is there and will sometimes get flooded in trying. Haven't tried shutting the peacocks when cranking, but seems to have enough compression when cranking. Just a question on the timing and then we'll work from there. Thanks

soldiertom · Mar 16, 2015

Same deal on my 45 b. Someone before I got it had put the flywheel on ONE tooth off. When we replaced the flywheel to the proper position, it really made a world of difference.
Good luck
Walk in peace
Tom

Pete in MD · Mar 16, 2015

That's a way to check "start" timing.

If the drive slot for the mag is not horizontal when the left hand cylinder is at TDC then the governor shaft is not in time with the gear that drives it. The drive gear has a small punch mark, a dot, on the outside tip of one of the gear teeth. The governor gear has a small punch mark at the root between to gear teeth. The two punch marks have to be right opposite each other when the left hand piston is at TDC. To check on this take off the mag and then take off the left side cover of the governor. Rotate the engine until the left piston is at TDC. If the marks don't line up then you need to unbolt the governor and raise it up enough to turn the governor shaft until the marks line up. After you get the marks lined up and the governor bolted down, put the left hand cover back on and then remount the mag.

If it doesn't hand start now the "start" timing adjustment on the backside of the mag may need adjusting. Post back if that's the case.

Mike(NEOhio) · Mar 16, 2015

Pete's got it right but you should also check the flywheel to crankshaft marks. While you're at it check the clutch drive disc to crankshaft. They really shake if those are off.

John T · Mar 17, 2015

IFFFFFFFF the flywheel is on the correct crank spline, when the Flywheels Left Hand Impulse (LHI) mark is at 3 o clock lined up with the mark on the tractors side

THE LEFT PISTON SHOULD BE AT TDC

Then if the cam to crank are in time (likely are) and the cam to governor are in time (may be off it sounds like in your case) the governors female slot (where mag mates) should be flat horizontal fore and aft. If all else above is correct (flywheel on right spline and cam to crank is correct) but the slot isn't flat fore n aft when the Flywheels LHI is at 3 o clock ID GUESS YOUR GOVERNOR IS OUT OF TIME WITH THE CAM.

If the flywheel were on the wrong crank spline you would get a bad vibration when running.

YES the mags impulse should SNAP right as the LHI passes the 3 o clock mark. That's a way to set the initial start/impulse timing.

The advance run timing is determined by which drive cup you have (like a 25 or 30 etc) plus the mags rotational position on the governor case plus points gap plus wear etc

Rotating the mag in the governor case changes BOTH start and run timing.

John T

51 "B" timing question

CP1

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soldiertom

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Pete in MD

Well-known Member

Mike(NEOhio)

Well-known Member

John T

Well-known Member

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