Author Topic: C11G throttle travel  (Read 283 times)

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millerthegorilla

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C11G throttle travel
« on: 14 July, 2017, 15:53:33 »
Hi, I'm rebuilding a bsa c11g with an amal 276 pre monobloc carb.   I had the carb resleeved and have not used it before.   I connected up the throttle cable to the throttle and there is hardly any travel, maybe a quarter of a turn and its also quite stiff - it doesn't return.  Does anyone know if that is about right?

JulianS

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Re: C11G throttle travel
« Reply #1 on: 14 July, 2017, 19:38:00 »
That is not right.

Try losening the fixing nuts. Does this free the slide. If yes the carb flange is probably distorted.

Make sure the return spring is seated properly on the slide and in the carb top.

Check that when you fully open the throttle twist grip  the slide fully opens the carb.

Test the slide in the carb body without the cable and spring. It should move up and down quite freely. If it is tight then either the slide or bore are wrongly sized or distorted. Refer back to whoever sleeved it.

You need to get it right because a sticking throttle is dangerous and takes the pleasure out of riding.

millerthegorilla

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Re: C11G throttle travel
« Reply #2 on: 15 July, 2017, 12:29:57 »
Thanks for that.  I checked the slide, and I had it in the wrong way round.  So I took it out and replaced it, and it is still only giving me a quarter travel and not opening completely.  I think it may be that I have the wrong spring in it, so I will send of for another, but is there any chance that I have the wrong slide?  It seems that if the spring is any shorter or any less stiff as metal then the slide won't have the power that it needs to return.  Is there such a thing as a shorter slide?  I think that I have seen different slides are available at the amal site, but do you know how they are numbered and what the numbers mean?   Do you know if the slide should close fully so that there is no air passing through at all?   Or does the needle take care of closing the jet?
Also the throttle grip housing is tight, so I am going to have to figure out how to loosen that.

Many thanks.
« Last Edit: 15 July, 2017, 12:45:10 by millerthegorilla »

JulianS

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Re: C11G throttle travel
« Reply #3 on: 15 July, 2017, 14:20:14 »
The difference in the slides is the amout of cutaway - the higher the number the greater the cutaway. They are the same length.

If the twist grip is tight does it have and adjuster on the underside? If yes losen the locknut and slacken it off.

The throttle slide should be set so that the slide is just open when twistgrip is released. If it completely closes the carb there will be no airflow over the jet and no fuel will be drawn into the engine.

The Amal lists show that a standard carb was fitted for 1954 models only. Then changed to a 375 monobloc.

However the standard carb was the smaller bodied type 274 not a 276 which I think is too large to get the best running from your C11.

The photo is from the parts book and shows the carb details.