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Thread: SR400 misfire

  1. #11
    Junior Member
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    Thanks MadMax,
    I found out a couple days later I put the fuelcock on PRIME after I reinstalled the tank. Yep I know I'm an idiot..
    I'm guessing that has to do with it. I don't see a rise in oil level and don't smell fuel in the oil tho. I'm thinking just to change oil, filter and plug anyway as it's still cutting off every once in a while. Quite annoying at traffic lights. Also what I didn't mention before is that the idle isn't very consistent varying between 1000 and 1500 rpm.
    If there's other actions you'd suggest please let me know. Thanks
    (Sorry for taking over the thread)

  2. #12
    Senior Member MadMax's Avatar
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    Quote Originally Posted by robinprins View Post
    Also what I didn't mention before is that the idle isn't very consistent varying between 1000 and 1500 rpm.
    Air leak or weak mixture, if you blip the throttle, is it slow for the revs to drop back down to idle speed?

  3. #13
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    Didn't think it was doing that. It does idle at same rpm but every time it comes back from riding it sometimes idles at 1100 rpm, sometimes at 1400 rpm. I agree that looks like an airleak but if the engine cuts out completely after running fine at 1400 it looks to me that it doesn't have to do with an airleak/ weak mixture or do you actually think so?
    Nonetheless will check the inlet for leaks first this weekend..

  4. #14
    robinprins wrote: but every time it comes back from riding it sometimes idles at 1100 rpm, sometimes at 1400 rpm

    This sounds very similar to my experience, (with different carb though, BST34.) I put it down to changes in air conditions which vary day to day, sometimes humid and sometimes fresh sea breeze. But what do I know? It's certainly intermittent. I'm following the outcome of this thread closely.
    Steve

  5. #15
    FORUM SUPPORTER thunderkat59's Avatar
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    My SR always popped on decel and had some of the running issues you mention in the OP.
    It also had one pop that shut it off when a friend of mine rode it at our last bike night.
    The previous owner had a bizarre air filter set-up that allowed a lot of unfiltered air to be sucked in.
    After I got the correct filter and readjusted the carb, it doesn’t pop on decel at all and the idle is
    is much better/stable over all. After my experience, I would agree a small air leak can have a pretty
    profound impact on the way the bike runs.
    Last edited by thunderkat59; 06-16-2017 at 10:24 PM.

  6. #16
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    Thanks guys. So I went out with my WD40 today to see if the gaskets like it or not. First of all I found my airfilter to be real loose, almost popping off. When I tightened it, it still ran the same but I found a huge leak in the inlet manifold. So I'll replace it soon and see how we go then..
    Steve, I think changes in RPM this big are too much to be caused by weather. Air pressure and humidity will probably influence performance but a change of more than 100 rpm doesn't seem plausible to me. I'm a beginner with bikes tho so don't take it for granted

  7. #17
    Mostyn's in Oz do a very good inlet manifold replacement.
    That should fix you up.
    Steve

  8. #18
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    Yeah will check Deus first because they're here in Sydney but otherwise order from Mostyn.

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