250f Not Reving Out

[thespikeyone]

At a recent trial where alot of the sections were wet and muddy and required a whole load of right hand.

The problem comes right at the very top end of the revs when rather than keep reving it it just levels off and "hunts" around that rpm.

I also noticed there is air coming back through the fuel line from the carb toward the tank is this normal/the cause???

I have changed the plug and wire-locked the fuel lines to their respective attaching points to ensure no air getting in through the hoses and tried different carb settings but it still the same.

Anyone any ideas???

[pistonbroke]

Just a thought but is it not hitting the rev limiter ?

Phil

[thespikeyone]

Just a thought but is it not hitting the rev limiter ?

Phil

No, I thought that too but on the odd occasion it does rev out to to the limiter.(only very rarely)

[ian640]

Fuel tank breather?

[thespikeyone]

Fuel tank breather?

no tried that too, still does it with fuel cap off.

[stork955]

Gday, air cleaner OK?

Cheers,

Stork

[masso]

At a recent trial where alot of the sections were wet and muddy and required a whole load of right hand.

The problem comes right at the very top end of the revs when rather than keep reving it it just levels off and "hunts" around that rpm.

I also noticed there is air coming back through the fuel line from the carb toward the tank is this normal/the cause???

I have changed the plug and wire-locked the fuel lines to their respective attaching points to ensure no air getting in through the hoses and tried different carb settings but it still the same.

sounds like a brand new set of them fancy BOYSEN REEDS are needed!................................massso

[jse]

At a recent trial where alot of the sections were wet and muddy and required a whole load of right hand.

The problem comes right at the very top end of the revs when rather than keep reving it it just levels off and "hunts" around that rpm.

I also noticed there is air coming back through the fuel line from the carb toward the tank is this normal/the cause???

I have changed the plug and wire-locked the fuel lines to their respective attaching points to ensure no air getting in through the hoses and tried different carb settings but it still the same.

Anyone any ideas???

After checking the usual possibilities like air cleaner, electrical connections, water in fuel etc., you may also want to check the valve clearances if you are bumping the rev limiter often. The DOHC's will commonly recede the valves slightly with high-RPM use, enough to close up the clearances and affect cam timing/valve sealing. A lot of us "old timers" would expect the four-strokes to get noisier if clearances are off, but a lot of the modern OHC/DOHC engines actually get quieter as valve/seat wear causes clearances to get tighter rather than looser.

Jon

[masso]

After checking the usual possibilities like air cleaner, electrical connections, water in fuel etc., you may also want to check the valve clearances if you are bumping the rev limiter often. The DOHC's will commonly recede the valves slightly with high-RPM use, enough to close up the clearances and affect cam timing/valve sealing. A lot of us "old timers" would expect the four-strokes to get noisier if clearances are off, but a lot of the modern OHC/DOHC engines actually get quieter as valve/seat wear causes clearances to get tighter rather than looser.

Jon

..........oooppps, sorry lads,about the reeds, didn't notice.its the four stroke ........masso