Idle speed. What have I done?!

[ProXimaCore]

Yet more problems. My fault this time. I don't know how to sort it though. After I took my bike to bits in search for the intake restrictor on the weekend I've put it back together and now the idle isn't right. I remember I fiddled with the idle screw wondering what it was (oops) but now I can't seem to get it back the way it was. Maybe someone could give me an explanation on how it works. Here's what happens:

From cold engine
Press the ignition without the use of the choke. Doesn't start. Take out the choke and the bike starts but the revs sit at 5000rpm. If I take the choke off then it slowly falls down then goes off.

From warmed up engine
I just drove it for a while keeping the revs going round the town for a bit till it was warm. No choke used. Each time I came to a stop at a junction or traffic lights the revs rested at 4000rpm when it was warmed up.

After it was warmed up and I got home I tried adjusting the idle speed and I got it to 1500rpm. I thought great, that's that sorted. But then after riding around town again it idled at 4000rpm again when I stopped.

The other thing that's not right is if I rev it, the revs take ages to come back down again. Before I messed it up, the revs came right down quickly when i released the throttle. Now it takes a few seconds to settle.

I know it's got to do with me tampering with that screw but whatever I do it just doesn't seem to sort it. Please help!
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Honda NSR125R -> Suzuki GSXR400R GK76a -> Kawasaki ZX636 B1H -> Honda CBR400RR NC29 -> Nothing

[Ian (GPX)]

Did you put the reed block back in (complete) ?

Sounds like too much fuel / air going in via some route, either by air screw or mixture screw. Not to sure if there is a setting on the choke.

Could also be a cable thats got trapped / snagged under fuel tank, make sure all cables are free.

[ilovens125f's]

Hi ProXimaCore ,
Did you take the intake restrictor out or not? This could be what is doing it, or did you take the idle screw right out? If so some crap might have got in and jamed you floats open. If you have taken the restrictor out then you might need new jets to make it run right. The only other thing is if you have created an air leak in which case the bike would just rev to a certain point!


Hope this helps.

Kev
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Kev the Ns125F lover!!
!!!Dont ignore me!!!

[Kickstart]

Hi

Sounds to me like you have fiddled with the mixture screw as well as the idle screw. For a brief overview of the Dellorto carbs see here.

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[ProXimaCore]

[ProXimaCore]

[Kickstart]

Hi

That is the mixture screw that you screw in all the way (lightly) then back out. Set that one, start the bike and then adjust the idle screw to get the idle speed correct.

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[ProXimaCore]

Great. Thanks I'll try that tomorrow!
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Honda NSR125R -> Suzuki GSXR400R GK76a -> Kawasaki ZX636 B1H -> Honda CBR400RR NC29 -> Nothing

[ZaphodBeeble]

If it isn't what the other guys have said then it seems like it's drawing air after the carburettor. That would cause the bike to keep revving even if the throttle is closed as air is being sucked in on the engine side of the carb.

Hopefully it will be the mixture screw though as that will be easy to do.
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Current bike: VTR1000F Firestorm. Previous: Firestorm (written off) - XJ600 Divvy - NSR125 - DT125 and a load of offroaders.

[AcIdBuRnZ]

Just thought, if it is too much air as someone suggested, then check that you have connected the rubber duct from the carb to the cylinder inlet properly, perhaps its drawing in air here?

I know from experience that its fiddly working on the NSR engine (maybe its my big hands?) so perhaps it ain't on right. Always worth a check.

Hope you get it sorted,
Mark
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Past: Honda NSR125R >> Kawasaki ER-5a2 >> Kawasaki ZZR-600e1 >> Suzuki GSXR-750Y >> Honda VTR 1000 Firestorm
"Chickity China the Chinese Chicken..."

[ZaphodBeeble]

[Crash it for fun]

Do you need to adjust the Carb screws/jets if you have de-restricted the bike? (NSR125R) Bearing in mind that the engine appears to run fine and idles at about 1500rpm.

I think I might have answered my own question.

[ProXimaCore]