Please help. Kymco pulsar lx 125 splutters and wont go into

[Lyndsay]

Can anybody help solve this problem. My chaps kymco pulsar lx 125 58plate. We bought it and soon realised tht theres some sort of problem. It wont go into the red in any gear and splutters like its trying to. First he tried redex which made a slight difference and it went from only goin to 5000revs to 6000 revs. He then cleaned the carb and air filter but its stil doin it. Hes changed the spark plug aswel but hes jst checked it and its all dirty. He replaced that about 2wks ago (dont knw if tht tells u anything) oh and when he did the carb i dont think he took the pin out, should he of done? Could it be that? Is there something else we could try? Any advice is greatly appreciated. Tia
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Lyndsay crossley

[Reservoir Dog]

Always "someone else's bike" when it needs fixing

[Rogerborg]

Hi Lyndsay. Has it ever run well, or was it bought in this condition?

You've done the right stuff, but it sounds like the fuelling is off. I assume that it's idling OK, so don't touch the idle mixture - that won't be influencing the response when it's on-throttle anyway.

I'd get back into the carb and check that:

The main jet is secure (and present, for that matter). If there are any markings on it, check that it's the right size. You probably want a 90 or 95, but it really does depend on the bike.

That the float is free to open and close, and sitting at the correct height. Sorry, I don't know what carb is on there, but it looks like the common Mikuni or Keihin 26mm - if you google for specific advice on whatever carb you have then you should turn something up.

That the needle is secure, and set in the middle position by default. If it's already there, and the plug is fouling, then I might try moving it down a notch, although it sounds like your problem is at wide open throttle, which suggests the main jet is too large (or loose), or that the needle is badly worn.

The other option is that given the low cost of these carbs (£25 if you have a Mikuni VM22, less if you buy direct from China), you could realistically consider just throwing a whole new carb on and hoping that it saves you a lot of time in guesswork. Worst case, it doesn't help, but you'll then be able to tune one of them off the bike and swap it in to try and narrow down the problem.

Sorry that there's no "Do this, bike will work" answer. Fuelling problems need diagnosed step-by-step.
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Biking is 1/20th as dangerous as horse riding.
GONE: HN125-8, LF-250B, GPz 305, GPZ 500S, Burgman 400 // RIDING: F650GS (800 twin), Royal Enfield Bullet Electra 500 AVL, Ninja 250R because racebike

[Pjay]

A lot of smaller bikes wont go into the red, due to rev limiting.
It may never get there, even when running at its best, so it's not a good indicator of it running well.