RPM's randomly when higher
Moderator: Moderator
RPM's randomly when higher
I was ridding home the other night, then all of a sudden my engines RPM's when really high and i got going 50km/h, then RPM's whent back to normal, and speed whent back down between 40-45....any idea whats up?
-1984 Spree,
Mmm. They do that sometimes when they're running hot. Pull and check your spark plug color at the insulator; what plug are you running? Might considering going cooler on it assuming there's no other mods on your bike. Do you know what main jet you have?
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Wheelman-111
- Moderator
- Posts: 11319
- Joined: Wed Oct 22, 2008 5:09 pm
- Location: Deepinnaharta, Texas
Idle Speed Enigma
Greetings:
I concur with The Noisy One and Greg on the high speed RPM issue. Vacuum leaks at high RPM are sometimes vibration-induced. Crank seals, base gasket, even a small crack in the intake or gaskets can surface only at high RPM. Sudden Hot Flashes not caused by Menopause.
I'll go one further with an interesting Flash symptom:
When I final-tuned it I let the engine warm to heat sink, set the IDLE speed to ~1800. You'd expect a warm engine to settle back to this same base Idle speed anytime you ride but
NOOO!!
Most times if it's warm out, Idle speed seems to go to 3000 initially, then settle down to 2700 or so. Then again sometimes it seems to want to stick to 1400 - barely enough to stay alive. Finally on occasion it's done all 3 during the same ride, in no recognizable order.
All I can say is that it seems to be ambient temperature-dependent. Temps on the CHT gauge always seem to settle at 275-300 at idle, regardless of outside temperature.
It doesn't seem to be a sticky throttle slide, bystarter issue or clogged carb. (The Arreche is less than 2 months old...) I'm starting to think it's the zones of magnetic (polar) forces on the earth...
I concur with The Noisy One and Greg on the high speed RPM issue. Vacuum leaks at high RPM are sometimes vibration-induced. Crank seals, base gasket, even a small crack in the intake or gaskets can surface only at high RPM. Sudden Hot Flashes not caused by Menopause.
I'll go one further with an interesting Flash symptom:
When I final-tuned it I let the engine warm to heat sink, set the IDLE speed to ~1800. You'd expect a warm engine to settle back to this same base Idle speed anytime you ride but
NOOO!!
Most times if it's warm out, Idle speed seems to go to 3000 initially, then settle down to 2700 or so. Then again sometimes it seems to want to stick to 1400 - barely enough to stay alive. Finally on occasion it's done all 3 during the same ride, in no recognizable order.
All I can say is that it seems to be ambient temperature-dependent. Temps on the CHT gauge always seem to settle at 275-300 at idle, regardless of outside temperature.
It doesn't seem to be a sticky throttle slide, bystarter issue or clogged carb. (The Arreche is less than 2 months old...) I'm starting to think it's the zones of magnetic (polar) forces on the earth...
Wheelman-111
Most of my money is spent on scooterparts. The rest is just wasted.
"ISO": '03 Vespa ET4 Malossi187 74MPH
Flash 9: 2001 Elite SR Contesta 72 ZX Tran, 9:1 Gears, Stock Airbox/Carb/Pipe 58.8 MPH
Punkin: 2010 Vespa/Malossi S78, 61MPH
Most of my money is spent on scooterparts. The rest is just wasted.
"ISO": '03 Vespa ET4 Malossi187 74MPH
Flash 9: 2001 Elite SR Contesta 72 ZX Tran, 9:1 Gears, Stock Airbox/Carb/Pipe 58.8 MPH
Punkin: 2010 Vespa/Malossi S78, 61MPH
