Technical Engine over-revving / racing

[Kiwi Denzil]

Hi,

I'm sure this is covered somewhere but i'm not much use at navigating around the site....yet.

My 500F engine over-revs / races when it is hot. The throttle and choke linkages are free. It's quite an oily engine and I'm wondering if the engine is consuming excess oil vapours through the intake and causing the over-revving. I had this happen on a landy due to excessive crankcase pressure. Has anyone come across anything similar?

 

[oopsadaisy]

Never heard of this before but that doen't mean I am right!

Sticking throttle cable maybe?

 

[ecdy]

If your dipstick stays in place I doubt you have crankcase overpressure. Maybe the throttle return spring is weak; easy to replace. Also clean and lubricate with engine oil all components of the throttle linkage. Things do expand, and get hung up, when hot.

Ecdy

 

[Kiwi Denzil]

Dip stick remains in place. Linkages all free. I'm stumped.
:bang:

 

[Bambino]

You could get to the point where it is over-revving and have a look at what is happening - that is, open the engine lid and see what is moving freely, what is stuck etc.

I've heard of this in old injected cars when the throttle valve intermittently sticks.

Chris

 

[Kiwi Denzil]

Folks, all sorted. Did what Bambino suggested and had a look while it was gunning it. throttle not fully against the idle stop. sorted the spring and cleaned and lubed the cable and all sweet again.

 

[Kiwi Denzil]

Its always the simple things that get you mixed up huh?

 

[Bambino]

Glad it's sorted. My other thought was that maybe the beast wanted to be unleashed and was champing at the bit.

Chris

 

[Kiwi Denzil]

Actually I think that was it. New tyres, new brakes, new dizzy cap, rotor and leads and a complete rewire. It certainly feels more responsive - although that could be psychological.