vacuum advance

[speedlimit85]

Last year my bike was backfiring and the Yamaha shop pinched off the vacuum advance fixing the bike.

I lost a few mpg but the bike runs great.

I am asking if the vacuum advance can be repaired or replaced.

I am also asking for opinions on leaving it alone since it works.

Thanks

[DiverRay]

The vacuum advance pot is NLA, but you may be able to find a good used one. It DOES help mileage, and allows the bike to pull like a freight train from low RPM.
I think the 80 does NOT have the same curve as the '78/'79, so I understand you do not notice it as much. for me, I would try to fix it, but as I said you will need to find one. Andreas may have a unit that is good, and they really are not that hard to change out. Just be sure you rest the timing, mixture, and carb sync once your done so it runs well.

[speedlimit85]

Found one on ebay: http://www.ebay.com/itm/YAMAHA-VACUU...5Yy~t0&vxp=mtr

YAMAHA VACUUM ADVANCE PULSE PICK-UP COILS XS1100 XS11 XS 1100 E/F 1978-1979

Mine is a 1980 xs1100 g standard. Would a different year and model be compatible?

[motoman]

Yes,,, better than not having use of one at all. 78-79 vacuum pod created a different advace than the 80-81 vacuum pods.

[DiverRay]

Look here:http://www.xs11.com/forum/showthread.php?t=46353, and send andeashweiss a PM. He may have a unit on the shelf, and it WILL BE CORRECT AND WORKING. Probably cheaper than fleabay as well.
You CAN use the earlier unit, but as motoman said the total advance is different IF you replace the complete assembly. IF you just replace the pod, it will work like the original. This is assuming it's been tested and holds vacuum....
Andreas will probably be less than half the money for just a pod.

[speedlimit85]

Look here:http://www.xs11.com/forum/showthread.php?t=46353, and send andeashweiss a PM. He may have a unit on the shelf, and it WILL BE CORRECT AND WORKING. Probably cheaper than fleabay as well.
You CAN use the earlier unit, but as motoman said the total advance is different IF you replace the complete assembly. IF you just replace the pod, it will work like the original. This is assuming it's been tested and holds vacuum....
Andreas will probably be less than half the money for just a pod.

Cool. I sent him a PM. Thanks.

[motoman]

Look here:http://www.xs11.com/forum/showthread.php?t=46353, and send andeashweiss a PM. He may have a unit on the shelf, and it WILL BE CORRECT AND WORKING. Probably cheaper than fleabay as well.
You CAN use the earlier unit, but as motoman said the total advance is different IF you replace the complete assembly. IF you just replace the pod, it will work like the original. This is assuming it's been tested and holds vacuum....
Andreas will probably be less than half the money for just a pod.

My reference was of the vacuum can itself, not whole advance assembly.
The rate of movement of vacuum can shaft assembly IS at a different rate based on vacuum draw on the early ones(78-79) than is on vacuum cans for 81. I believe the 80's, still having the mechanical advance, the vacuum can internals are even different yet as to their rate of movement, since they also have different valve timing and valve overlap timing, besides larger intake valves and slightly different combustion chamber configuration due to the larger intake valves. I say that due to some yrs. back, I compared in. vacuum draws compared to shaft distance movement with the early ones compared to the 81 ones.... just out of curiosity. Figured that valve timing and valve overlap timing since changed, vacuum can function and rate of movement did also......and it did.

[speedlimit85]

Alright. I would like to make sure I need a vacuum advance before replacing it.

1. The vacuum hose from the vacuum advance was connected to the second carburetor. The correct place.

2. With that hose pinched off, the bike runs right.

3. There is a vacuum test I will try. Sucking on the hose should make it move.

4. I will check each wire for wear.

This is what I have discovered so far. Please let me know if I am overlooking anything. Thanks.

[DiverRay]

If you have a hand vacuum pump, that is the easy way to test it. They are "cheap" at Harbor Freight, about $30. Just pull about 15 on the gauge, and watch how far the arm moves. Then just let it be for about 1 minute to make sure it stays at 15. If it drops, the pot is bad. If the arm didn't move, you may have the system rusted. that can be cleaned up and freed so it works again.

[speedlimit85]

Okay, so my vacuum advance is working again.

3. Tested vacuum by sucking air from vacuum hose and it rotated.

4. The wires have many previous repairs. I pulled on one that broke. I soldered like this says: http://www.xs11.com/xs11-info/tech-t...pictorial.html

I put a new vacuum hose through to the second carb.

Started good. Sounds different. No backfiring like I had last year before it was bypassed. I rode 50 mi.

I did not do timing or carb synchronizing. How important is it? I don't have tools for that and would need to ask a shop for help.

[IanDMacDonald]

It's the difference between a poor running bike, and a bike that runs like an raped ape in a cage.

[TopCatGr58]

Okay, so my vacuum advance is working again.

I did not do timing or carb synchronizing. How important is it? I don't have tools for that and would need to ask a shop for help.

Hey Speed,

Because you have 4 carbs feeding 4 cylinders, each cylinder can get different amounts of fuel/air to function compared to a 4 cylinder car that uses just 1 carb with a common intake manifold. And so IF the cylinders are not set to create the same amount of power then you have them working against each other instead of WITH each other, and this will affect the total power, performance, throttle response, fuel mileage, as well as possibly increase uneven wear on the bearings/crank.

SO...you might try posting a REQUEST for a local Xsive near you to be able to loan/provide a carb synch rig and/or assist you in getting it vac. synchronized as well as tuned.

T.C.

[speedlimit85]

Well, I am asking if it is important to adjust timing and synchronize carburetors right away after changing from a bypassed vacuum advance to using the vacuum advance? And any other checks to be sure the vacuum advance is completely working?

And thank you'all for helping me keep my bike alive!

[motoman]

I highly suggest with bike warmed up to operating temps., first re-setting idle mixtures, THEN re-syncing carbs, in that order. Would not even mess with the timing, unless you've, for what-ever unknown reason have messed with it.

[BA80]

If pinching off the vacuum advance stopped the backfire it's not the issue.


Sounds like you have some bad pickup coil wires and are losing contact intermittently when the pod moves the breaker plate..