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Poor running

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2wheelsteve
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Joined: 05 Feb 2010
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PostPosted: 21:22 - 03 Oct 2010    Post subject: Poor running Reply with quote
I have an inline four maxim, four carbs, it was running like shit on and off like running on three, anyway I cleaned the carbs and it ran brilliant but when travelling fast'ish it gets a bit lumpy after a while like its being starved of fuel to one of the carbs, if I slow down or stop and turn it off, two minutes later its great again, plugs initially were sooty but they are ok since I cleaned the carbs that were pretty gummed up by the way, any ideas would be good, cheers.
PS stinkwheel mentioned in a previous thread something about how you find the offending carb?????
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0l0dom0l0
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Joined: 21 Oct 2009
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PostPosted: 21:32 - 03 Oct 2010    Post subject: Reply with quote
spray wd40 on each header. it will burn off on all cylinders that are running and wont on the one that isnt. have you checked the air filter, and changed the plugs?
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2wheelsteve
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PostPosted: 21:47 - 03 Oct 2010    Post subject: Reply with quote
0l0dom0l0 wrote:
spray wd40 on each header. it will burn off on all cylinders that are running and wont on the one that isnt. have you checked the air filter, and changed the plugs?



Yeah Ive done checks and cleaned the plugs but tomorrow its wd40 on the heads. I think I will invest Smile in a set of plugs and see what happens
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stinkwheel
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Joined: 12 Jul 2004
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PostPosted: 00:24 - 04 Oct 2010    Post subject: Re: Poor running Reply with quote
2wheelsteve wrote:
when travelling fast'ish it gets a bit lumpy after a while like its being starved of fuel to one of the carbs, if I slow down or stop and turn it off, two minutes later its great again


Could your fuel tank breather be blocked? If it's blocked, a vacuum forms in the tank as fuel runs out with no air getting back in again to replace it. Eventually the flow of fuel slows down/stops. Happens more at higher speeds because you're using more fuel.

Simple way to check is to try riding with the fuel cap undone. If the problem goes away, it's a blocked breather. The breather can be a hose running from the tank that's got trapped somewhere or it could be as simple as a small hole in the petrol cap.

If not that, sounds like fuel starvation, either in general or on a particular carb (a general fuel starvation issue would usually make one carb drop out at a time anyway. I'd check the fuel tap and fuel filter first off.

If you have drain screws on the carbs, it's easy to check the float heights to make sure all the cartbs are filling properly. Attach a longish bit of clear tube to the drain stub and hold it up along side the carb. (the top of the hose should be well above the height of the float bowl). When you open the screw, fuel will run into the tube to the same height as it's sitting in the float bowl. Measure it from a fixed point of reference (say the edge of the join where the float bowl attaches). Should be the same height on all four. If one of them is low, there's your problem.
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Frost
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Joined: 26 May 2004
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PostPosted: 01:49 - 04 Oct 2010    Post subject: Reply with quote
I had this on a bike i rebuilt. The fuel hose i used was a bit thing and kinked in one place when the tank was put on. It wasn't noticeable as it was hidden under the tank, and once the tank was lifted up it straightened itself!
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2wheelsteve
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Joined: 05 Feb 2010
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PostPosted: 16:49 - 04 Oct 2010    Post subject: Reply with quote
DaFrostyOne wrote:
I had this on a bike i rebuilt. The fuel hose i used was a bit thing and kinked in one place when the tank was put on. It wasn't noticeable as it was hidden under the tank, and once the tank was lifted up it straightened itself!


I will check that but it was good and the tanks been on and off several times so I would have to be pretty unlucky to twist it each time, just done 60miles down the motorway with three pots on and off, its shit but Im gonna check out the points stinkwheel suggested, firstly have the fuel cap open and see when happens, ride safe
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Gone
Nearly there...



Joined: 01 Sep 2010
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PostPosted: 16:57 - 04 Oct 2010    Post subject: Reply with quote
A good dose of carb cleaner in the tank cured my old GSX 1100 of similar tendencies. Could just be some crap in one car causing the trouble.
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2wheelsteve
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PostPosted: 17:12 - 04 Oct 2010    Post subject: Reply with quote
FinnDave wrote:
A good dose of carb cleaner in the tank cured my old GSX 1100 of similar tendencies. Could just be some crap in one car causing the trouble.



Yeah I gave them a good full clean but yep its worth a go, cheers
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2wheelsteve
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PostPosted: 20:30 - 06 Oct 2010    Post subject: Reply with quote
New plugs, air filter, cleaned carbs, undone fuel cap while riding, checked fuel hoses and still f**ked up, I believe there is a silly problem, gonna check inlet manifold for leaks, and check electrics. shit man I hate this when it could be millions of things and a matter of elimination
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