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Aprilia Rs125 wont rev over 8000rpm

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Johan12fly
L Plate Warrior



Joined: 24 Mar 2009
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PostPosted: 11:09 - 24 Mar 2009    Post subject: Aprilia Rs125 wont rev over 8000rpm Reply with quote

I've searched the web and this forum but cant find a similar fault. My son's RS125 K2 was running fine, but suddenly it wont rev over 8000rpm. Checked the PV-it is working fine. Replaced the spark plug. Choke is ok. Clean fresh fuel in tank. Opened the carb. Cant see anything wrong there. If I close the fuel tap it starts to rev normal until the carb runs dry. Open fuel tap-problem back. Engine sounds normal. All services up to date. Please help. Thanks
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Walloper
Super Spammer



Joined: 24 Feb 2005
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PostPosted: 11:17 - 24 Mar 2009    Post subject: Reply with quote

Throttle cable adjustment.
Air filter restriction.
Tachometer(Rev Counter) reading incorrect.

I know hee haw about Aprilia 125s so what is the 'PV'?
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asdf
Nitrous Nuisance



Joined: 06 Nov 2007
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PostPosted: 11:44 - 24 Mar 2009    Post subject: Reply with quote

The powervalve.
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KTM EXC 125 Supermoto, Honda Cub90

Past - Aprilia SR 50 Ditech, Derbi Senda SM DRD, Aprilia RS125 x 2, Aprilia RX 125
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Billing
World Chat Champion



Joined: 12 Mar 2009
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PostPosted: 11:47 - 24 Mar 2009    Post subject: Reply with quote

Could the float have gotten damaged? it sounds like its running rich, then when you shut the fuel off it runs leaner, and therefore back to the normal ratio (ideal is 14.7:1) until it runs dry. I'd double check the float isn't sticky or anything Thumbs Up
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Johan12fly
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Joined: 24 Mar 2009
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PostPosted: 11:57 - 24 Mar 2009    Post subject: Reply with quote

I have taken the power valve out. It wasnt sticky at all. The cable is ok. Tested the solenoid. Also ok
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Johan12fly
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Joined: 24 Mar 2009
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PostPosted: 12:08 - 24 Mar 2009    Post subject: Reply with quote

I have cleaned the carb with carb cleaner. The needle and seat seems ok. I'm suspecting that maybe the float level isnt at the right height, but I dont have a manual on how to set it correctly or to check whether it needs adjusting at all.
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Billing
World Chat Champion



Joined: 12 Mar 2009
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PostPosted: 12:09 - 24 Mar 2009    Post subject: Reply with quote

Did you check the float aswell? It's in the bottom of the carb and it sounds like its damaged and letting too much fuel in, which is why when you turn the fuel off it stops the problem, because the mixture leans out again. This may not be the problem, but it seems a good place to start to me. =]
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'84 TS50X, '91 TZR125, '89 CBR400RR, '91 VFR400R NC30, '98 R1
"Hey copernicus! Why don't you navigate yourself to the back of the line with your feet and stand there with your shit."
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stirlinggaz
World Chat Champion



Joined: 22 Jul 2007
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PostPosted: 12:18 - 24 Mar 2009    Post subject: Reply with quote

hi,
im presuming you have checked that the solenoid is operating correctly.
& moving at approx 2000rpm (self cleaning) & 78000rpm.
At what throttle range is this happening?
have you returned the carb to the standard settings?
have you done any mods to the biket? (exhaust/airfilter?)
was it ok before?
what airfilter is on it & is it clean?
if anyrthing has been upgraded/modified, i'd suggest up jetting.
cheers.
GAZ
edit- just re-read the original post-definately sounds like the float height is incorrectly set & there not cutting the fuel off when there supposed to.
is it the 28mm carb?
i have the float height somewhere.
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stirlinggaz
World Chat Champion



Joined: 22 Jul 2007
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PostPosted: 12:30 - 24 Mar 2009    Post subject: Reply with quote

here you go https://www.owners.heskethmotorcycles.co.uk/technical/dellorto%20PHF%20carb/dellorto_3_2.html
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