Help Diagnosing where my exhaust leak is - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 7 (permalink) Old 06-27-2011, 12:53 AM Thread Starter
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Help Diagnosing where my exhaust leak is

OK, first off, sorry about the new thread for this topic, but I am so frustrated/stumped on this one.

I have an exhaust leak. This I am 99% sure of. Bike pops on decel, a lot. Like 5-6 times after I let off throttle. It happens more when the engine is warm (perhaps b/c the pipes are hot?)

I cannot determine where the leak is.

More Details:

Bike was completely stock when I got it. Popped like a popcorn machine - but nothing abnormal based on what I have read, reed valves were the culprit.
I coastered, popping mostly stopped. I De-goated, started popping like crazy on the right side, front cylinder.

I adjusted carb screws from factory setting to 2.5 turns, then out to 3 turns, and finally 3.5 turns, only minor affect in popping if any at all.

Couldn't get a good result from cigarette smoke test.

Thought I determined that it was the connection between the added pipe and the muffler. Tried sixteen ways from Sunday to repair that connection. Each time it seemed to stop popping briefly (5-10 minutes into ride it would start again) In retrospect maybe this was wishful thinking that I fixed the problem.

Got frustrated and decided to replace exhaust with V & H Cruzers since I wanted to get them eventually anyway. Used HD gaskets as recommended here. Either there were no stock gaskets in there in the first place or they had completely fused with the inside of the exhaust manifold, because I could not find anything resembling a crush gasket, or any loose parts for that matter between the manifold and the stock pipes anywhere. Seating of the new pipes seemed to go well.

For about 2-5 minutes of first test ride there was no popping, then it was back. Still no results from the smoke test. Played with air/mix screws and no major difference between settings from 1.5 turns all the way to 4 turns.

Now I am beginning to wonder if when I did the De-Goat perhaps I loosened or damaged the exhaust manifold or the exhaust manifold gasket while taking the muffler off for the first time. I remember I needed to do quite a bit of twisting and rocking to get it to break free. This does not appear to be in a very accessible location to get access to it.

How would I go about testing/removing this part to check. Do I need to do an engine pull? Does anyone have any suggestions on what might be the problem if it is not the exhaust manifold? Should I recheck the coasters, or perhaps put some RTV red silcone in them to ensure the leak is not there?

I thank you all in advance for your advice / comments

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post #2 of 7 (permalink) Old 06-27-2011, 05:38 AM
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Is the popping still only coming from one side or is it from both sides? Maybe your exhaust manifolds are secure and fine......on these carbs there is a small diaphragm for the enrichening circuit......it adds a extra amount of fuel to the cylinder when you let off the throttle to keep the ultra lean condition from happening. Maybe one or both of these small diaphragms are not working or damaged? I believe they can be checked without removing the carbs.
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post #3 of 7 (permalink) Old 06-27-2011, 08:01 AM
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Vacuum switch valve could be broken.

JM2001

" Loud Pipes Risk Rights "

2001 Vulcan 750
marbled
TOC upgrade on ACCT
Air/fuel mixture set to 2 1/2 out
rectifier relocated
splines lubed
iridiums
decals removed
upgraded mirrors
Pic up coil mod done
degoated
All LED lighting
Upgraded Mosfet rectifier
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post #4 of 7 (permalink) Old 06-27-2011, 08:28 AM Thread Starter
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Quote:
Originally Posted by BRET H View Post
Is the popping still only coming from one side or is it from both sides?
Best I can tell it's still only coming from the right side


Quote:
Originally Posted by JM2001 View Post
Vacuum switch valve could be broken.
Which vacuum switch, how do I check this?

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post #5 of 7 (permalink) Old 06-27-2011, 10:44 AM
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Quote:
Originally Posted by KidChaos View Post
Best I can tell it's still only coming from the right side




Which vacuum switch, how do I check this?
I don't have a manual and can't tell you where it is on this engine exactly. It is part of the emission controls and is there to prevent backfiring and a lean condition when decelerating.

JM2001

" Loud Pipes Risk Rights "

2001 Vulcan 750
marbled
TOC upgrade on ACCT
Air/fuel mixture set to 2 1/2 out
rectifier relocated
splines lubed
iridiums
decals removed
upgraded mirrors
Pic up coil mod done
degoated
All LED lighting
Upgraded Mosfet rectifier
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post #6 of 7 (permalink) Old 06-27-2011, 11:37 AM
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did u plug or cap the air hose thats goes to the carb. that stopped my horrible popping problem.
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post #7 of 7 (permalink) Old 06-27-2011, 12:51 PM Thread Starter
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Quote:
Originally Posted by dbking321 View Post
did u plug or cap the air hose thats goes to the carb. that stopped my horrible popping problem.
Which Hose.

I plugged the Hose under the seat with a rubber stopper and a Hose clamp around it.

I capped the vacuum port on the carb with a plastic cap.

Should I add some silicone around these plugs to ensure no air is leaking through?

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