TDC 180 degrees off?


Information and questions on GL1100 Goldwings (1980-1983)
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robertdawber
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Motorcycle: 1983 GL1100 Interstate

TDC 180 degrees off?

Postby robertdawber » Sun Jun 19, 2016 9:42 pm



With the heads off--is there a way to tell if I am at TDC or if I am off by 180 degrees?
I am changing the heads for two reasons, but prior to this project, I tried to set the timing and the bike sounded like crap. The pistons have indentations on them as though they were being hit.
Hence the question.
Before removing the heads I double checked and checked along the way to keep things lined up. It occurred to me today that I could be 180 degrees off though.
Bob



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ekvh
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Re: TDC 180 degrees off?

Postby ekvh » Mon Jun 20, 2016 6:57 am

No there' s no way with the heads off to tell. When at T1 in the sight window, are both pulleys' "UP" marks facing up? T1 is the same all the time for the crank. With the belts installed, cams move half the speed of the crank, so the T1 comes up twice for every full turn of the cams. It is important when adjusting the valves. Quite a few get confused with the T2 mark which has no real purpose. When setting ignition timing you use F1 and F2, but for setting valves, you set four valves at T1 where the pulleys' UP marks are up, and the other four at the next T1 when the UP marks on the cams are down.

A compression test will tell you if you did something wrong along the way, such as rotating it at the wrong time in the process.

robertdawber
Posts: 285
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Re: TDC 180 degrees off?

Postby robertdawber » Mon Jun 20, 2016 8:05 am

ekvh wrote:No there' s no way with the heads off to tell. When at T1 in the sight window, are both pulleys' "UP" marks facing up? T1 is the same all the time for the crank. With the belts installed, cams move half the speed of the crank, so the T1 comes up twice for every full turn of the cams. It is important when adjusting the valves. Quite a few get confused with the T2 mark which has no real purpose. When setting ignition timing you use F1 and F2, but for setting valves, you set four valves at T1 where the pulleys' UP marks are up, and the other four at the next T1 when the UP marks on the cams are down.

A compression test will tell you if you did something wrong along the way, such as rotating it at the wrong time in the process.

I am replacing the heads.... that is the reason they are off. I would bet the farm it was 180 off prior though. It ran, but with a clanking noise and the pistons have marks , indentation, from the valves. Anyone else have a thought on this? ( The clanking and the marks)
As always, thanks for the support.

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spiralout
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Re: TDC 180 degrees off?

Postby spiralout » Mon Jun 20, 2016 9:42 am

With the heads off, it doesn't matter as long as you're on T1. The motor won't know or care. It's the valve train that determines the what stroke the pistons are on.

robertdawber
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Re: TDC 180 degrees off?

Postby robertdawber » Mon Jun 20, 2016 9:52 am

spiralout wrote:With the heads off, it doesn't matter as long as you're on T1. The motor won't know or care. It's the valve train that determines the what stroke the pistons are on.


That makes sense-but what should I do then? Set the valve train up before the reinstall?

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spiralout
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Re: TDC 180 degrees off?

Postby spiralout » Mon Jun 20, 2016 10:24 am

Correct. (20 characters)

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Maz
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Re: TDC 180 degrees off?

Postby Maz » Mon Jun 20, 2016 2:38 pm

robertdawber wrote:With the heads off--is there a way to tell if I am at TDC or if I am off by 180 degrees?
I am changing the heads for two reasons, but prior to this project, I tried to set the timing and the bike sounded like crap. The pistons have indentations on them as though they were being hit.
Hence the question.
Before removing the heads I double checked and checked along the way to keep things lined up. It occurred to me today that I could be 180 degrees off though.
Bob


I'm not clear whether you have had the bike for long and if it has ever run properly while you have owned it.
With regard to the "clanking", this could just be that the bike is not running on all 4 cylinders. The internal chains etc make a hell of a racket when these engines are not running smoothly, so you could just have a carb or ignition fault.
The pistons SHOULD have indentations to clear the valves. Are you saying that yours have extra indentations?
Both possibly silly questions, but more information on the history of the bike may help.
Maz
Nostalgia is not what it used to be!

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RBGERSON
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Re: TDC 180 degrees off?

Postby RBGERSON » Mon Jun 20, 2016 3:10 pm

For FUTURE reference mark the crank pulley before you re/move anything..at the T1 with the cam wheels in line to their marks..then you'll know when the T1 is the right T1..for reinstall. Just gives one peace of mind!!
HAD LOTS OF GOLDWING 75-83
NOW INTO 1500'S..RIDING A 1998 SE

FAIR WINDS,
RB

robertdawber
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Re: TDC 180 degrees off?

Postby robertdawber » Mon Jun 20, 2016 5:39 pm

I have owned it for about ten years. I changed the clutch out and synced the carbs-I believe that when I did this, I messed up the timing (maybe) because it was making a racket. When I would give some gas it would not rev up properly. I had the new heads anyway so I took the old ones off.
I did (Berg) mark the spot prior to removing the timing belts, etc. The problem, of course, is that I did not do this when it was running smooth a couple of years ago when I changed the belts.
ANy other suggestions are more than welcome!

How will I know how the drive train should be set? Set it as though it is at TDC?
Are the indentations on the pistons an indicator that it was out of time?

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Johnyy Smoke
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Re: TDC 180 degrees off?

Postby Johnyy Smoke » Mon Jun 20, 2016 5:54 pm

Can you send a pic of the indentations on the heads?
Regards, Johnny

robertdawber
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Re: TDC 180 degrees off?

Postby robertdawber » Mon Jun 20, 2016 6:02 pm

Johnyy Smoke wrote:Can you send a pic of the indentations on the heads?
Regards, Johnny

Did I say the heads? I meant the pistons

robertdawber
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Re: TDC 180 degrees off?

Postby robertdawber » Mon Jun 20, 2016 8:23 pm

Like this only not as deep and on all 4 pistons. Clearly valve marks

http://www.drivecult.com/uploads/piston.jpg

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RBGERSON
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Re: TDC 180 degrees off?

Postby RBGERSON » Tue Jun 21, 2016 8:04 am

Wow..bent valves likely ??? definitely out of time..me thinks!!! Could have been off a 2 teeth and did that..not sure about 180 off...??? what that would do..
HAD LOTS OF GOLDWING 75-83
NOW INTO 1500'S..RIDING A 1998 SE

FAIR WINDS,
RB

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ekvh
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Re: TDC 180 degrees off?

Postby ekvh » Tue Jun 21, 2016 3:31 pm

At 180 degrees off on one cam, they will run. Not great, but they won't do any damage. Being off a couple teeth will do the valves in (bend) and maybe Pistons in. Not sure how you're seeing the prisons unless you have a camera/scope.

robertdawber
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Re: TDC 180 degrees off?

Postby robertdawber » Tue Jun 21, 2016 4:12 pm

ekvh wrote:At 180 degrees off on one cam, they will run. Not great, but they won't do any damage. Being off a couple teeth will do the valves in (bend) and maybe Pistons in. Not sure how you're seeing the prisons unless you have a camera/scope.

The heads are off




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