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Author Topic: CV carb surging  (Read 999 times)

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Offline trueblue

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CV carb surging
« on: November 13, 2013, 01:11:56 AM »
A mate of mine has a Honda 300cc quad (ATV for you Yanks ;D), it sat for some time.  I cleaned out the rotten fuel and varnish out of the carb.  Now it idles perfect, when you give it a good fistful it goes like a dog shot in the arse.  But when you come back to a cruise it surges, like you are giving it full power then backing off repeatedly.  It had a couple of holes in the diaphragm that was in the carb.  He has another complete bike out there we removed the diaphragm and slide from it and fitted to the runner, but it is still doing it.  I'm just about out of ideas, the only other thing I can think of is that the slide is sticking a little and causing it to jump.  I haven't had a chance to get back out there to check it though.   :-\
« Last Edit: November 13, 2013, 03:00:50 AM by trueblue »
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Offline Bankerdanny

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Re: CV carb surging
« Reply #1 on: November 13, 2013, 06:57:04 AM »
We call em quads here too.

It could be a sticking slide, are there any marke on the slide that indicate wear from one particular park of the slide bore?  I would look hard at the connections between the carb and the head for vacuum leaks. I would also check the slow jets again.
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Offline Maurice

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Re: CV carb surging
« Reply #2 on: November 13, 2013, 07:15:48 AM »
Air leak somewhere? Use a can of WD-40 and spray around the carb and notice where it changes RPMs (they'll pick up a bit when you find it). Likely it's the carb boot, could be throttle shaft seals, etc...

Good luck
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