Top Dead Center


Information and questions on GL1100 Goldwings (1980-1983)
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jeremysmith035
Posts: 28
Joined: Mon Jan 07, 2019 7:14 pm
Location: Norfolk, VA
Motorcycle: 1983 GL1100i

Top Dead Center

Post by jeremysmith035 »



I was removing my timing belts. While doing so I lined the pulley facing up and along with the marks on the side. When I looked at the fly wheel it showed # 1 and under that it had the letter F.
Is the correct position for TDC on the #1cylinder?
What does the "F" mean?
I know there are other similar discussions on the forum, however I did not see anything describing the letter "F" under the #1 on the fly wheel while looking through the timing hole. :?:

1983 GL-1100 Interstate


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Aussie81Interstate
Posts: 1178
Joined: Thu Nov 27, 2014 2:34 am
Location: Penrith Australia
Motorcycle: 2001 GL1500F6C Valkyrie
1982 CX500 Turbo (Historic registration - finally)
1981 GL1100 Interstate (sold)
1988 GL1500 (sold)

Re: Top Dead Center

Post by Aussie81Interstate »

F stands for FIRE..........
jeremysmith035
Posts: 28
Joined: Mon Jan 07, 2019 7:14 pm
Location: Norfolk, VA
Motorcycle: 1983 GL1100i

Re: Top Dead Center

Post by jeremysmith035 »

Does that mean I am at TDC?
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DenverWinger
Posts: 1831
Joined: Thu Jun 23, 2011 2:20 pm
Location: Denver, CO
Motorcycle: (s)
1980 GL1100 STD Vetter (2005-)
1993 GL1500 Aspencade (2017-)
1983 Trav-Lite Camper (2010-)
Past rides
1972 CL350 (1980-1988) sold
1978 Suzuki GS550 (1985-2005) sold
1977 GL1000 (2002-2006) sold

Re: Top Dead Center

Post by DenverWinger »

There's four marks on the flywheel, T1, F1, T2, F2. The T marks are TDC for cylinder 1 or 2 and the F marks are where cylinder 1 or 2 ignition would fire with no spark advance. The F marks particularly used on the GL1000 for doing static timing adjustments on the points.

You can turn the crankshaft with a wrench on the crank bolt to find the T1 mark. It is very close to the F1 mark. It won't hurt anything turning crankshaft by hand with the belts off.

When putting the belts back on, note that the timing marks on the cams will rarely line up "Exact". You'll know they are correct if moving the belt one cog in either direction the timing marks line up "worse".

Just so you know, these engines will run without damage if the timing belts are +- one cog off... they just won't run "right".
♫ 99 Little Bugs in the Code, ♪
♪ 99 Bugs in the Code. ♫ :(
♫ Take one down, Patch it around, ♪
♫ 127 Little Bugs in the Code. ♫ ♪ :shock:

~Mark
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ekvh
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Joined: Thu Apr 29, 2010 9:52 am
Location: Grand Forks, ND
Motorcycle: 1977 gl1000

Re: Top Dead Center

Post by ekvh »

“It won't hurt anything turning crankshaft by hand with the belts off.”

If the crank is turned with a valve(s) open very much, it will likely bend a valve.

There are points where all the valves are 98% on the base circle and safe to turn the crank. Up mark at 2 o’clock on the right side and 8:00 on the left side has all valves closed or nearly closed. At that point it’s safe to turn the crank. Right and left are as sitting on the bike. However, if you don’t know where the crank is, it may not be safe to turn the belt pulleys.

Carefully turn the crank 90 degrees away from T1, whichever way you can without contact, then you can turn the cams without contact to their respective marks on the belt covers. (I turn the crank counterclockwise from T1, adjust the pulleys to the marks, then turn the crank clockwise back to T1 after aligning the marks. ) With the right side cam on the mark, the #3 intake valve spring will walk the cam clockwise a little. Let it go where it wants, then you can bring the crank back to T1 in the opposite direction of the way you turned it above.


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