Hi Guys,i'm a new member looking for some advise , i have a locost zx9r which i have had built for a while now , i have an ongoing problem which is driving me crazy !, one other guy on here posted the exact same fault but i don't know if he resolved it ,basically i can drive the car nice and slow stop starting in traffic no probs ,full bore acceleration no probs , cruising at 50 /60 ish car starts to misfire and eventually die altogether no power at all ,pull to side of road switch off wait less than 30 secs then it'll go ok again for a little while longer then repeat again very frustrating i've checked breather in tank replaced pump and filter bypassed pump relay getting desperate now seems so much like fuel but need help ,it has a dynojet kit and i've tried circlips in various positions but still the same ,also did it before i had dyno kit on this is second set of carbs too ,any help greatly received regards steve b .

[Edited on 29/9/08 by exclusive964]

Sounds like a mixture problem. I think you're referring to Roadrunners problems before. On my engine, it wasn't enough to just dynojet the carbs, I had to alter the mixture using the screw beneath each float bowl.
I've also had to balance the carbs and I used one of those Gunson glass spark plug things and engine seems to tick over nice now.
To be fair, I haven't yet driven it, still waiting for my trial run.

Hi thx for that ,yes done all them things you mentioned ,very frustrating fault thought it may be carb icing so tried additive but still no good going on track day thurs day but looks unlikely unless i can sort :-)

Have you blocked off the main air jet when the dynojet went in and what size jets are you using out of interest?

i blocked them off yes, too be honest i can;t remember jet size off hand i'd have to check ,car was set up at tts and made good power 118 bhp at wheels but they were baffled by problem too ran out of time while we were there so unresolved .

Are the float levels all correct?

It sounds like a fuelling problem to me. If the main seems fine but you can't find a needle setting that's right at middling throttle, then the main could be wrong. I had too small a main jet and had the needle very rich to compensate. I couldn't find a spot that was right at all speeds. You could also have a main that's too big and are compensating with too little needle. A session on the dyno will help.

Other than that, check you've blocked the right jets. Check there are no air leaks, check that the slides move freely and the diaphragms are OK.


[Edited on 29-9-2008 by smart51]

Hi thx for your suggestions , i'll check out the things mentioned i would like to hear from riggins on here is problem is exactly as mine to a tee thx again

Just a possibility but I had a similar problem with my race bike at the TT tried all the things you mentoined to no avail then found that that the fuel filler had been sealed using silicon - which when immersed in petrol assumes a form something like jelly - net result was part throttle ok then full throttle pulled the mass of gel against the outlet . Misfire followed by engine cut out, wait a minute or two then off we went again only to experience the same again. I have known the same fault caused by a piece of plastic protective film which was not cleaned off the tank before welding.
Its always difficult to diagnose from a distance but might be worth a look.
regards
Andy

thx for that yes i'm seriously thinking of getting tank out and cleaning it can only see through top obviously and outlet is pretty small may be worth a go

Unfortunately I still haven't solved the problem and haven't had the time to try everything I would have liked.

I sent a U2U with some more details

Thx for that i sent u message back regards steve

Just like to say thx to all who replied to message ,problem fixed !yippee took fuel tank out found a piece of stick same diameter as outlet ! my theory is that under very light throttle stick wouldn't be sucked to outlet ull bore fuel sloshing around so stick all over the place ,cruising fuel stable stick finds it;s way to outlet and blocks it off ! what a pain in the ass to sort !,message to riginns check very carefully all parts of fuel system for blockage,ps haven't a clue where stick came from probably broke off four BRANCH manifold !lol sorry !steve b

Back again !to eat humble pie been on trackday at curborough today car cut out a t least a dozen times on the way !once at the track i could do one flying lap then it would missfire and cut out ,i need help !lol is it possible i have a faulty sensor somewhere ? ny more ideas very much appreciated

Is it possible you got another piece of wood or sawdust/wood shaving stopping up the fuel system anywhere else. Filter, carbs?

thx for reply yes i'm going to have to strip the whole lot apart to get to the bottom of it really does seem like fuel starvation wondering now whether myfuel pipe is restricted in engine tunnel will have to take covers off this weekend