sputter..pop... bang... vroomm - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 6 (permalink) Old 01-14-2007, 12:06 PM Thread Starter
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Unhappy sputter..pop... bang... vroomm

Howdey and greetings from a very load and annoying rider. Ok heres my problem. After warming up, my bike likes to not Idle at 1200, infact the hoter it gets the higher the idle, if you adjust it, it starts to back fire, REALLY LOUD. and it heats up even faster. I tried clearing out the carb with seafoam. Now i dont think it needs new jets, same ears, louder slashed pipes. I think the tentioners on the timing are bad. I get a nifty thunk every once in a while from the front cyclinder. I ride this bike hard, only form of transport, right now. almost bought a kz1000 but way to many probs. I'd like to over haul the engine, shave the ears, (if it works better), and clean out the carbs, but come on, my old samauri (car) was easier to work on. where would I find a kit for shaving the ears???? how do you get the bike to not miss fire, and not back fire???? I'm ready to listen to you gurus of the VN two whell realm.
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post #2 of 6 (permalink) Old 01-14-2007, 12:21 PM
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You sure you don't have a vacuum leak? Bad carb to cylinder ring?

Jon

93VN750, under re-construction
vn750.com Member # 828

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post #3 of 6 (permalink) Old 01-14-2007, 12:31 PM Thread Starter
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bad cylinder ring is very probable, but how do you find a vacuume leak in this spagetti factory, I thought about rebuilding the carbs but then the hoses will just piss me off. if I could get it down to the basics I'd love it, no air duct, no ears, just a carb gas tank and vroom, but then there are so many fraken hoses, like reed hoses. What the hack are reads for??
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post #4 of 6 (permalink) Old 01-14-2007, 12:36 PM
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See my previous post on finding a vacuum leak. Definately sounds like that to me lean running = more heat and backfires. Reed valves are for injecting air into the burned gases like the airpumps of the 70's. They work but the system must be close to perfect for it to work. Stripping the air injection will require carb work. You can find more by reading the verses.

Rckmtn
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post #5 of 6 (permalink) Old 01-16-2007, 09:27 PM
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The carbs are already pretty much basic. The vacuum lines control the fuel flow as our carbs are a constant velocity type.
If you want to bypass the reed valve system, see the section in the verses on "coasters". Other than the vacuum lines, it's just 2 fuel hoses, one for each carb, and the vent hoses going into a T fitting with the hose resting in the right ear, but not too far in so it doesn't bottom out.
The ears are there to hold the air filters and the surge tank is there to hold the ears. Even if you do an ear shave, you wil still have a pretty tight fit for the air filters though admitedly, not as close as it is now.
As said earlier, it sounds like it may be a vacuum problem. Check the condition of the vacuum lines and their routing as well. It could be one is leaking or pinched off somewhere.
I would also recommend getting the Clymer's manual if you don't have it already and download the Kaw manual for a double check.

Jim W
93 VN 750 "Ursula"
Moved R/R 08Sep06
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post #6 of 6 (permalink) Old 01-16-2007, 09:50 PM
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Agreed that the backfiring is indicative of a lean mixture. Leaks anywhere (hoses, exhaust) will result in that; but couldn't a quick carb sync at least eliminate a possible offender, since that'll balance out the vacuum between front and rear carbs (and might account for the poor idling)?
Cisco, you said when you "adjust it" it backfires more - where are you adjusting? Choke? Air/fuel mix screws? Idle speed? Also, I just pulled my reed valve covers off and the previous owner had installed one reed in backwards - couldn't have done a whole lot to improve performance, since the air flow (intended to burn the excess fuel) wasn't set up right. You might check those and see whats goin' on in there.

C
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