Fast Idling.

[Gucci1710]

Hi Folks, I am a site Newby,but the proud owner of a 1972 ES250/2. The problem I am having is that the bike starts and generally runs OK, but after a few miles, when I pull in the clutch, the engine revs rise quite a bit, which makes the next gearchange very difficult. The bike is standard and carb set up seems OK. Any ideas what to look for please ? Many thanks, Gucci, Shropshire.

[DAVID THOMPSON]

throttle cable routed incorrect some of these the cable adjusts the idle i think
and is the choke or fuel enrichment lever working correct

air leak in the carb to engine connection

on a 2 smoker leaks in the exhaust system can cause this
and carb adjusted to rich is another thing ??

[Blurredman]

The idling speed is controlled by the throttle cable on the ES carbs, but since it starts to increase in speed, It could indeed by a slight passing of fuel through the choke mechanism (check the choke slide and rubber).

Make sure there are no air leaks from where the cables enter the carburettor, and also the top is screwed on nice and tightly (not too tight though-should have a paper seal really), and like David said, it could also be a leak between the carburettor and the head. I believe ES's like most MZ's have cast alluminium manifolds and there could be a leak between the flanges that circle around the carb outlet.

I put some vasiline grease around the carburettor outlet collar and then tighten up nicely on the manifolds. Makes a nicer air tight seal! I used to have an issue with high idle, but after doing these things I no longer do.

[Gucci1710]

Thank you both, I will check and get back !

Gucci.

[Gucci1710]

Hmmmm, I checked the above and all seemed right. I then let the engine warm up properly, noticing that the tickover rose as it warmed up. I adjusted the throttle cable until the revs went back down to tickover when warm, and that seems to have cured the problem.

Many thanks for your help, Gucci.

[Blurredman]

Yes, that is also a problem, as the engine warms, it can burn less fuel, and more efficiently, thus, as it warms, and the same amount of petrol gets sucked in, the idle rises, thus why it's always better to 'basic tune' an engine when it's warmed up.

Good going