knocking noise at RPM above 3000.

[dbeardslee]

I always check the dumb stuff first. Before swapping out parts you might want to check to make sure the pointer for the timing wheel is indicating correctly by checking TDC with a dial gauge against the timing wheel and pointer, and then checking the timing with a light. JAT

[Bonz]

tqs335, has it been established you have the correct vacuum cannister line connection to the #2 carb boot?

[motoman]

Re-read all above, and I suspect the vacuum hose is misplaced on carb boot and not on #2 carb where it's supposed to be. If that is hooked correctly, I highly suspect either seriously out of sync carbs..........or rubber internal diaphram of vacuum advance has a hole in it and is trash.

[Bonz]

^^^This^^^

Like Motoman said and my post above it, is the vacuum line connected to the #2 carb boot?

Buehler... Buehler... Anyone? Anyone?

[motoman]

^^^This^^^

Like Motoman said and my post above it, is the vacuum line connected to the #2 carb boot?

Buehler... Buehler... Anyone? Anyone?

Uh......Hi Howard! A happy Holidays to ya'!

[jetmechmarty]

Hi fellas!

The vacuum line goes to the nipple on the carburetor, and not the manifold or boot. Correct?

Happy holidays!

[Bonz]

Yes, #2 carb and not the #2 intake boot. Sorry, I really DO know better... I totally messed up my wording.

Still waiting to hear back from the OP?

[motoman]

Hi fellas!

The vacuum line goes to the nipple on the carburetor, and not the manifold or boot. Correct?

Happy holidays!

Yeppers........ported vacuum, not manifold vacuum. Old school vehicles are the same.

[motoman]

Hi tqs335, and welcome to the forum.

I have 2 xs1100LG's (MNS)
One has the same knocking around 3 to 4k rpm.
The other one doesn't!

Disconnecting the vac advance seems to minimize the knocking but also
seems to have a negative affect on overall performance.

This problem has caused me to start knocking my head against the wall!
and that didn't help either!

Good luck tqs335..
Please let me know if you find a resolution...
I'll be watching this thread closely!

Carbs seriously out of sync will cause the same thing........and a bread-tie for initial throttle plate setting does NOT cut it.

[Ranger_xs1100]

Thanks motoman for the tips, I used the same home made "tubing on a board" synching method on both bikes and at least 3 other bikes previously. I know it is not the most precision accurate method. but it has always worked well for me. The knocking bike runs great!, no hesitation no throttle hanging , no apparent performance problems whatsoever. The knocking is just annoying and worrysome even though the service bulletin states that there is no harm in it.

[motoman]

Thanks motoman for the tips, I used the same home made "tubing on a board" synching method on both bikes and at least 3 other bikes previously. I know it is not the most precision accurate method. but it has always worked well for me. The knocking bike runs great!, no hesitation no throttle hanging , no apparent performance problems whatsoever. The knocking is just annoying and worrysome even though the service bulletin states that there is no harm in it.

If that noise is that annoying, I'd definitely investigate a bit farther.

[ViperRon]

I want to ask if you are sure it is internal to the engine. I ask because several things can cause a knock, motor mounts and even exhaust, especially if you have the original exhaust which has an internal pipe that can break loose. I had a horn one time on the original mount that would tap the frame at a certain speed once and drove me nuts because I looked at everything else.

Can you get the knock sitting still or does it only happen under load. Do you have a stethoscope. I am asking because normally what the other guys have mentioned resolves the problem from detonation issues.

[Ranger_xs1100]

I don't mean to hi-jack the thread (I am not the original poster)...But I hope this helps him as well...

In my case, the knocking is only under load, I cannot duplicate it sitting still, and it is louder when the engine is hotter.

I have banged around on the pipes and was not able to create any rattling sounds, I have taken off the heat shields and looked for cracks or breaks in the pipes and found none. I have read where someone else had that problem with the internal pipe, so even though I cannot verify that as the source, it is still possible. The pipes are original and all in very good solid condition on the outside though.

I do not have a stethoscope.

I checked the timing awhile back and i remember it checking good at idle and advancing at a higher rpm, however i remember reading somewhere that the degrees of advancement is different between the specials and the standards. I probably should recheck that.

I have checked the vac advance wiring for breaks both physically by hand as well as by ohm meter tests.

The bike only has 25k miles on it. It is very hard to isolate the source of the knocking when riding but it sounds like it comes from the lower right side of the engine , and only under load between 3 and 4 k rpm.
The knocking goes away at higher or lower rpms. So I just normally shift up or down when I hear it thus changing the rpms to avoid listening to the knocking.

It seems worse in 2 and 3rd gear, I don't hear it in 1st 4th or 5th, but that may be just because of the different load and rpm ranges in those gears. It's a mystery for sure!

[Bonz]

Could there be anything related to the cam chain being loose going on here? Just thinking out loud.

[Ranger_xs1100]

That's a good thought Bonz, However I did adjust the cam chain tensioner, Thanks