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1951 fl timing problem

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Joined: Mon Apr 16, 2007 11:12 pm

1951 fl timing problem


Post by sla0001 » Tue Jun 12, 2007 10:19 am

I know very little about the variables possible when building these motors,i hope its that simple...

First off its a 51 panhead that other than an overbore is stock that i know of,,i purchased it assembled from someone that had a well standing i didnt have too many worries.
The problem is i was verifying the timing/gapping the point set{single}
and with the flywheel timing slot at the rear edge of the left case timing hole,and the front cylinder piston 7/16 from tdc,and a few degrees after the front intake valve closes i understand it all should be,the dist shaft slot at the top should have pointing at the point set rub block,ready to fire that cylinder,at full advance or not, at least close.instead it was 180 degrees out,pointing at the cylinder.
Instead of pulling dist and relocating it,i removed the gear cover and found the timing marks way off,i then rotated the engine and found they did line up,but the flywheel timing slot was nowhere to be seen in the hole,i then checked the front piston location,seems when they line up the front piston is 7/16 about from bdc,instead of ready to fire at about tdc.
it seems the pinion shaft is 180 degrees off...
Can it be installed that way by mistake?
Any ideas will be more than appriciated...
I hope im missing something right in front of me,other than it needing a teardown.
its taken me 9 years to get to this point,i just want to ride and show it!

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Post by Cotten » Tue Jun 12, 2007 1:50 pm

The pinion shaft is keyed to the flywheel, so it would be very hard to get it 180 degrees out. (But anything is possible, such as someone in the past having recut a keyway due to damage, etc.) Even flatty wheels wouldn't be an even 180, although the mark would be off a few degrees.

It is quite easy to be confused by the internal marks, as they only resolve twice during the four cycles of the motor, and they do not coincide with the appearance of the timing mark in the hole.

I think you almost had it when you found the circuit breaker pointing the wrong way. It sounds like you were indeed upon the compression stroke (few degrees past the closing of the front intake), so lifting the circuit breaker base and re-inserting it to align the cam and follower would be required.

(PS: With today's low octane fuels, I suggest static timing with the line in the middle of the hole, or strobe timing with the line slightly forward.)

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Post by fourthgear » Tue Jun 12, 2007 1:59 pm

Any thing is possible ,but that should be a keyed shaft in the fly wheel , unless is was not installed incorrectly ( no key )or spun , or wrong shaft if that's possible . I would not worry too much about the 7/16 measurement and just rotate the motor until you see the timing mark come just into view. I use a one piece plastic pen ( no guts ) or straw to feel the piston coming up so I don't pass the mark up ,cause it goes by fast if you don't .As long as the timing marks line up in the cam chest ( gear case ) according to the manual you should be OK .Once you have the timing mark where it should be in the timing window you can set your circuit breaker ( distributor ) up right.Of course with the circuit breaker at full adv. (all the way forward , if you have a manual adv. unit ) the point cam should be just opening the points. Hope this helps.

And I see Cotten was faster on the type.

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Post by sla0001 » Fri Jun 15, 2007 8:09 am

Thank you Cotton and Fourth gear,
It made no sense to me that it was 180 out...too many distractions and way too late at night to do this for me,i second and third guess to much.
and ill take the timing advice Cotten...
Do you recommend any way other than what ive been doing to set it?{ what forthgear recommends is the way ive been attemping it}
Thanks again to you both.

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Joined: Mon Aug 26, 2002 9:09 am
Location: Central Illinois


Post by Cotten » Fri Jun 15, 2007 2:03 pm

Just for clarity:
Re-install your cam chest with the gears lined up and forget about them.

The cam determines which stroke your front cylinder is on. Just after the front intake valve closes, find the line in the timing hole as you did before.
Then install the circuit breaker so that the follower aims at the small lobe's mark.

Please be aware that the piston comes up on the exhaust stroke too!
Timeing by the piston alone gives you a 50/50 chance of installing the circuit breaker 180 degrees out.

Proceed then to static time it.
I prefer to strobe it perfect after it is running.


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Joined: Mon Apr 16, 2007 11:12 pm


Post by sla0001 » Fri Jun 15, 2007 11:20 pm

Thank you for taking the time to explain it,
Ill do it tonight.
Thanks again,

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