Aprilia Rs125 urgent help neede.

[cliff]

A good friend has just broken down in farnborough riding back his Rs. It won't start. He said the engine is turning over but it just won't idle. Do they have a kickstart? Any ideas? I know it is very vague but it was a quick blurred phone call. Any help appreciated.
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Sweet reggae music.

[G]

They do have a kickstart. (I think... hmmm, dunno actually, my 250 does, but completely different engine.

If the engine is actually going, but just won't idle... well first thing I'd think is out of petrol, or running on fumes at least.

If it's not that and it's just that it won't idle... well he can get it home at least.

[Shaun]

They do not have a kick start!

[Jack2004]

Might not be enough charge in the engine to turn it over, or as G said he might have run out of petrol.

[cliff]

Right. I went and met him, the bike was ruinning ok. It stalled 5 minutes later, a blackspot at 6000rpm, suspected gone off petrol. We walked it back to my house. I have left it ticking over outside, is it wise to run the petrol through for a period of time?
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Sweet reggae music.

[G]

If it's gone off or contaminated petrol you want to be draining the tank and the carb if possible.

It could be water in the petrol, which is clogging up the carb.

[Wave2k]

i had a wierd problem a while ago.
it would ride but as s00n as you stop instead of idling it stalled i pulled over and checked all the fuel pipes and wiggled them and it fixed it
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RS125->CBR400->RXS100->GSXR750K2->Ducati749S->CBR600RR5->TL1000R->DRz400->RSVR1000->Honda VTR SP1->CBR400->GSXR1000K6->Honda H100->CBR600RR3->Ducati1299

[Kickstart]

Hi

99% of RS125s do not have a kick start (only the SP version has a kick start and they are quite rare).

First thing to try doing is to increase the idle speed a touch. The is done using a knob on the side of the carb. Screw it it to increase the idle speed (not much, maybe half a turn at most).

Check the fuel filters. However if these start to get blocked then I would expect the bike to idle OK but not be able to rev (whereas this seems to be the opposite problem). Same for water in the fuel.

If it is a newish RS125 then it has the PHBH28 carb. There is no drain screw on these. There is a large bolt on the bottom of the carb (use a 14mm spanner) which locates the float bowl (and also holds the main jet). Undo this and the petrol in the float bowl will pee out all over the place (make sure you turn the petrol off first).

Check the fuel pipes are not kinked and check that the fuel tank breather is not blocked (open the fuel cap and then try starting the engine, but don't try riding it like that).

If it is an early RS125 with the Rotax 123 engine then the ignition system does not care about the state of the battery. However I think the later ones do, but if the bike it turning over on the starter motor OK then this is unlikely to be the problem.

After that you get on to more serious problems. This is possibly likely. The engine needs to produce very little power to idle, which means a tiny loss of power will prevent it idling, yet a loss of power at higher rpm will have a less noticeable affect (as you will compensate for it by opening the throttle more). Get hold of a compression tester and try that.

All the best

Keith
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[G]

The rs125 has an electric start and a fuel filter?
Meh, my 250 doesn't have any luxuries like that .

[Kickstart]

Hi

Yep. Aprilia have been fitting electric starts to their 125 sports bikes for years (eg, my 1987 model AF1s have electric starts).

The fuel filter is in the carb. Where the pipe joins the carb there is a banjo shaped cover with a bolt in the middle. Undo this cover and you will find a 20p sized gauze filter.

All the best

Keith
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