rs125 idles at 4000rpm after its revved

[jasepugh1984]

My 2007 rs125 idles high after you rev it,it seems to sit at 4000rpm and slightly rise sometimes then fall back down after about 10seconds.if i just touch the throttle just enough that it dont rev when its idle, around the carb there is a crackling sound.the pipe that goes into the airbox has a seal around it,if that isnt properly inserted into the airbox could that cause the problem.If i quickly snap at the throttle its not as bad,but if i hold it at about 6000rpm for a couple of seconds then let goes it falls to 4000rpm and stays there for about 10sec.gonna have a look at it 2mos,just after any advice really on where to start looking.thanks.jason
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Aprilia Rs125 2007 11kw (SOLD) - Honda CBR600RR 2008 (Current Summer Toy) - Honda Cb600 2000 (Current Work Commuter)

[stirlinggaz]

hi,
have you checked the throttle cable isnt snagged?
with the engine off, open up the throttle wide + then let go quickly.
can you hear the carb slide clunk down?
if the you cant hear it & the throttle grip takes a bit to revolve back round, then its either the throttle grip (installed new grips or bar ends recently?) or the cable.
lift the tank up to make sure the cable is seated properly at the top of the carbm, sometimes the rubber boot comes loose, snagging the cable,
cheers,
GAZ

[taz4626]

i have just had a similar prob and found i had an air leak between the carbs and the block. I would say that the crackling around the carb would be your issue if you can find where exactly it is i would say that will be your leak. As for the seal on the airbox i cant see it being that as the airflow is controlled using the butterfly valve so the leak would have to be after the butterfly valve.

I had someone suggest using carb cleaner around where you think the leak is and if the revs drop or go up when you spray it in a certain area that is where your leak is as it is sucking in the spray.

[jasepugh1984]

yes i can here the slide going up and down,i will check that the cable is properly inserted into its position.
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Aprilia Rs125 2007 11kw (SOLD) - Honda CBR600RR 2008 (Current Summer Toy) - Honda Cb600 2000 (Current Work Commuter)

[stirlinggaz]

[jasepugh1984]

if theres no butterfly valve could the connection were the pipe goes in the airbox cause the problem do you think?,thanks.jason
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Aprilia Rs125 2007 11kw (SOLD) - Honda CBR600RR 2008 (Current Summer Toy) - Honda Cb600 2000 (Current Work Commuter)

[Kickstart]

[stirlinggaz]

hi,
if you have a can of easy start or similar flammable liquid,like wd40, squirt a LITTLE around the manifold. (the rubber bit that holds the carb to the bike) while the bike is running & the revs are low.
if the revs suddenly shoot up, then you have a leak at the manifold.
they are made of hard rubber & are prone to cracking/splitting.
they can be repaired by smearing them all over with instant gasket (i used the black stuff), but i would do this as a temporary repair until i got a new manifold.
a new one will cost around 25 quid.
if its not cracked or split, it may well be loose so worth checkng that as well.
but if its not the manifold thats letting in air, then, as Keith says, its likely to be the main seals,
cheers,
GAZ

[taz4626]

apologies for the butterfly valve comment was just running through in my head what was going on with my bike lol. Did it turn out to be a leak or is it still unsolved