Timing

[sidekick1975]

I have an '80 XS1100SG and the timing seems to be off. I've pulled the cover and found that I can't move the advancement. There is two strange screws that needs a special tool or skill that I'm not aware of. Can someone help me out?

Sidekick

[Ken Talbot]

Before you go much farther, you should pick up a Clymer's manual one one of the other shop manuals available. In it, you'll see a procedure for centre-punching and drilling the bolts so you can remove them with an extractor. There are a number of other steps involved in starting at a particular alignment, putting it back together with the advance mechanism just a certain way, etc, etc. This is one of those areas you are better off waiting until you've got a manual and a good understanding of what is happening before you proceed.

BTW - what kind of symptoms are leading you to think the timing might be off?

[sidekick1975]

When it's warmed up, at idle it sounds like metal to metal hitting that gets worse as rpm are lowered. when hitting the throttle it has a slow gain of rpms. if the advancement is held it has a faster gain in rpms. I haven't yet checked the timing yet to see if it off, but thats my next step.

[Ken Talbot]

It sounds like the advance mechanism may be hooked up to one of the vacuum nipples on the carb boots instead of the vacuum nipple on the intake side of carb #2. The nipple on carb #2 is dampened by a very small orifice, while the nipples on the boots are much less restrictive. Without the dampening, the vacuum mechanism gets worked rapidly back and forth and can make quite a clattering noise.

[sidekick1975]

What does this thing look like and where can I find one. Other than that the old ones didn't have one or it fell out and I didn't know it.

Sidekick

[Ken Talbot]

I can't get out to the bike to shoot a decent photo right now, but here is a scan from the '78 shop manual:
[IMG]/forum/images/tips/20040126-advancemechanism.jpg[/IMG]
Your bike has the different screws to hold the timing plate, but it is basically the same as what's pictured here. the round can to the upper right is the vacuum advance mechanism. You can see the lever that comes out of it to move the timing plate back and forth with changes in engine vacuum. There should be a hose running from the vacuum advance 'can' to the vacuum nipple on carb #2.

Does any of this look familiar now?

[sidekick1975]

Sorry should of been more specific. I refering to the orifice. where can I find one and what does it look like.

Sidekick

[Ken Talbot]

Oops - I guess I might have been a bit clearer if I had stuck with "very small hole" instead of 'orifice'.

If you look at the four intake manifolds (the rubber parts between the carbs and the head) you'll see brass tubes approx 1/8" dia by approx 1" long sticking up and to one side. These are vacuum nipples and they have a fairly large hole through them. Three of them should be capped off with a rubber plug. One should be connected to the fuel diaphragm or 'octopus' that controls fuel flow.

Then, if you look at the body of carb #2, on the engine side rather than the airbox side, at approx the 10:00 o'clock position, you will see a similar brass tube. It is also a vacuum nipple, but it has only a very small hole through it. This small hole is what dampens the vacuum pulses and help the advance unit to operate smoothly.

[sidekick1975]

The nipples all seem to be the same size and the line is on Carb boot #2 and no leaks. Could this problem also be caused by a different air filter? Just a thought. I've put a new uni-filter in.

Sidekick

[Ken Talbot]

Okay, let's try narrowing this down a bit more. When you say "the line is on carb boot #2" do you mean:

- the vacuum line from the advance mechanism is connected to the brass nipple sticking out of the rubber manifold (sometimes called a boot) between carb #2 and the head

or, do you mean:
- the vacuum line from the advance mechanism is connected to the brass nipple which sticks directly out of the aluminum body of carb #2

The first scenario is wrong.
The second scenario is correct.

No leaks, i.e. flexible rubber hose in good condition with no cracks, is a good thing.

A different air filter will not have any effect on the operation of the vacuum advance mechanism.

[HadTX750]

Ken,
Does this configuration also apply to the '78 Standard?

Austin
The more I ride the more I find a reason to

[TonimusMaximus]

Yeah it does. I just re-tubed my '78E. Was confusing at first, but it all works now.

[John]

Originally posted by HadTX750
Ken,
Does this configuration also apply to the '78 Standard?

Austin
The more I ride the more I find a reason to

This may be a little off topic, but you had a TX750? Was it gold in color? Ha, ha , ha. You poor SOB. I had one of those back in 79-81. What a piece of s#!t! I was in the Navy, and lived in San Diego at the time. I wonder if it's the same one???? Are you new here? Well, if so, welcome aboeard, and glad to see you have decent bike now.

[Ken Talbot]

Don - the configuration for the vacuum advance is the same for standards (like your 'E) and specials. However, standards run vacuum lines from two of the manifold nipples to run the two vacuum-operated petcocks. The petcocks on a Special are not vacuum operated, but the octopus is so it has the single vacuum line from a manifild nipple.

[sidekick1975]

Thanks Ken for the info. I just got out there today little warmer. The vaccum lines must have been messed with before I got it. Now it runs smooth and no rattle.

Thanks a lot.
Sidekick