Low RPM surge what causes it?

Discussion in 'Technical' started by ray23, Aug 31, 2009.

  1. ray23

    ray23 Ol'Timer

    Bought a Vulcan 800, smooth as silk when it's in the power band. I have an engine surge when I'm at low RPMS.

    I had the timing checked, the carbs cleaned, new plugs. It's got a K&N airfilter that was cleaned. Lessened it but it's still there.

    The bikes rideable but it is annoying I like a bike to be right.

    Any guesses?

    I'm thinking the carbs might not be syncronized.

    Been suggested there might be a difference in compression from one cylinder to the other
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  3. gobs

    gobs Ol'Timer

    Hi Ray,

    I think it can only happen with air/fuel intake devices... Meaning mixture problem...
    As far as I know carbs not synchronized make lose power... As does a compression default in one cylinder... Engine not balanced and rough/weak...
    But we learn every day, doesn't we?

    So, what I can say:
    1) Did you check and adjust pilot screws on the carbs? No incidence on High rpm, but on Low rpm and starts, yes...
    Or maybe one (or two) torn or "broken" or O-ring...
    2) Did you check for an air intake in the rubber hose or seal between carbs and engine?.. Or air intake by loosen axle on the body of the carbs...
    3) Did you check choke system (don't know specs of your bike though) and "choke circuit" on the carbs?..
    4) Did you check "depression chambers" (if any on the carbs), needle, circuit and rubber?..

    Mmmmmh... Make me remember some recurent problem on my previous Honda CB1... A long, long time of cleaning and adjusting before finding a slightly torn O-ring on a pilot screw...

    My 25 satangs, if can help... :roll:

    Good luck,

    PS: sorry Ray I'm not a native English speaker, so sometimes a bit difficult about mecanic...
  4. ray23

    ray23 Ol'Timer

    That may in fact be a good 25 satang. The bike sit idle in a garage for years while not in use. Clean a carb is not a rebuild. Now to find a kit, the search is on. I have friend going back to the states and will return in a few months, he can pick it up for me there.

    Anyone got any ideas where to find a Carb rebuild kit?

    Based on the costs here might be cheaper just to replace them, off a thrashed bike, it's a 97
  5. thaicbr

    thaicbr Ol'Timer

    Ray... why not try Kawasaki in Bangkok. you never know they may have it in stock. otherwise one of the big outfits in the US. like Dennis Kirk.
  6. ray23

    ray23 Ol'Timer

    Thanks that is one I will try to get around the shorty widshield is $500.00 from Bangkok.

    But, expensicve still got to pay that import tax of 30% really adds top cost. The 900 is fuel injected so they may not have the parts. But, can order them.

    Proabably will be cheaper to just order it from the states and pay 30% minus one companies profit margine.

    I'm lucky I have the Tech manual to the bike so it may be here already don't know I doubt in a kit form though.

    I've already removed must of it with a simple hose change. It's one of those things I know it's there and I know it can be solved. Anybody who buys bike me is getting a better bike then the one I bought. That's just me and my Mia Noi's as I call my bikes :wink:

    The goal is to come out of this with a primo bike for under 250 K. Paid 170K for the bike with a good book, rideable when I bought it Now it's down to fine tuning so I think I can easily do that.

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