Sticky throttle

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Sticky throttle

Postby Andy51 » Tue Aug 06, 2019 8:55 pm

Hi All, having trouble with a sticking throttle. I have a '54 18 S fitted with an Amal Concentric Mk 1 carb, which worked perfectly for a couple of years. Earlier this year it started 8 stroking, missing and generally running badly, diagnosed as blocked idle jet. This has been fixed and carb cleaned with carb cleaner, and I am now fitting it back on. I have been running it on its worn original 89N carb. Having fitted the Concentric back on, using the same twistgrip and throttle cable that worked on the Concentric previously and the 89N, the throttle sometimes sticks just open when I twist the throttle and let it go. If I jiggle the cable it shuts completely. I have lubricated the cable thoroughly, the inner slides easily in the outer, the carb slide moves freely in the carb barrel. All is assembled correctly in the carb. Any suggestions? Cheers, Andy

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Re: Sticky throttle

Postby dave16mct » Tue Aug 06, 2019 9:25 pm

One of the usual causes is overtightening of the nuts holding the carb to the manifold. If you ease the nuts off slightly you may hear the slide drop.
Dave.

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Re: Sticky throttle

Postby Mick D » Wed Aug 07, 2019 7:05 am

Hi

Have you altered the cable run at all / nipped it a bit when re-fitting the tank?

Regards Mick

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Re: Sticky throttle

Postby MalcW » Wed Aug 07, 2019 7:48 am

dave16mct wrote:One of the usual causes is overtightening of the nuts holding the carb to the manifold. If you ease the nuts off slightly you may hear the slide drop.
Dave.


I had exactly this on my twin; slackening off the manifold nuts a bit fixed it. Also check the cable run. Lastly, check that all is well at the throttle end. A friends bike was doing this, and the cable outer was coming out of the throttle and catching on the throttle body if the throttle was closed quickly.

Malc

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Re: Sticky throttle

Postby 56G80S » Sun Aug 11, 2019 6:12 pm

I had a problem like tis with a Concentric that had done a lot (and I mean a lot) of miles.

I bit the bullet and bought a "correct" Monobloc from the Spares Scheme - what an improvement on all fronts.

Johnny B

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Re: Sticky throttle

Postby poplargreg » Sun Aug 11, 2019 6:50 pm

When I was eighteen, I upgraded to a AJS 500cc from my 1936 22 250cc. On the way home I blipped the throttle before changing down when approaching some traffic lights - throttle stuck wide open.
Exhaust valve lifters can come in handy sometimes BANG! BANG! BANG!
Never happened since.

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Re: Sticky throttle

Postby 56G80S » Sun Aug 11, 2019 7:17 pm

Yep and I've fitted a kill button from handlebars to the SR1 magneto.

Unfortunately it doesn't seem to affect the other road users who are irritating me.

Johnny B

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Re: Sticky throttle

Postby REW » Sun Aug 11, 2019 8:01 pm

:rofl:
Ron

1951 Matchless G3L, thumping round the Durham Dales

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