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revs slow to fall
b3nny - 1/8/14 at 07:14 PM

Noticed this over the last couple of trips out, once warm the revs seem very slow to fall to idle from around 3k and also now idles at 1k when warm when normally she sits around 900rpm.

Any ideas? She's a 2.0 black top twin 45 webers.

pmc_3 - 1/8/14 at 08:20 PM

Air leak somewhere I would have thought

adithorp - 1/8/14 at 08:28 PM

quote:
Originally posted by pmc_3
Air leak somewhere I would have thought


That would be my first thought. Check around the inlet manifold.

Sam_68 - 1/8/14 at 08:41 PM

Check the obvious too - sticky throttle cable, something seized or binding in the linkages or throttle butterflies/shafts?

rick1962uk - 1/8/14 at 09:17 PM

have you checked the carbs are balanced

jeffw - 1/8/14 at 09:25 PM

Air leak....

philfingers - 1/8/14 at 10:07 PM

Not too rich? Could try dropping the idle mixture screws 1/8 turn. Easy to put back if it isn't!

b3nny - 2/8/14 at 12:29 PM

Carbs where balanced only a couple of weeks ago, I'm going to try the idle mixture screw next time I'm out but from what I have read it's more than likely a air leak.

Is there a easy solution to finding this or would a smoke test be advisable?

Sam_68 - 2/8/14 at 12:50 PM

quote:
Originally posted by b3nny
Is there a easy solution to finding this or would a smoke test be advisable?


In the olden days, the standard technique was to go around the manifold gaskets/O-rings spraying easi-start or WD40, and when the revs picked up, you knew you'd found your leak.

I've heard suggestions that you can do the same thing with rather more safety and precision by using an unlit blow-torch, with the nozzle played around the joints, but I've never tried it myself.

If you're on Webers, top suspects would be the carb mounting O-rings/misab plates. These are basically service items anyway, so I'd be inclined to replace them (with new mounting rubbers/thackeray washers) before even trying anything else.

bumpy - 2/11/14 at 04:13 PM

And the answer was?