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Topic: Phantom air leak on Weber carb (Read 86 times) previous topic - next topic

Phantom air leak on Weber carb

On a recent trip to Edinburgh (roughly 430 miles) my 1.6 Weber carb MK2 didn't miss a beat all the way there, aside from a rear wheel bearing that was easily fixed.

3 Days later we left on the trip home. Started fine, pulled away fine, then as it reached just above 20 mph it started cutting out.

Tried tightening the carb down, carb flange is new and in good condition, checking spark plugs and spark. Checked the dizzy cap and rotor arm but all okay. Ended up calling RAC and after 40 minutes the guy suggested an air leak on the right hand side of the carb. Tested by spraying that side of the carb while the engine was running and sure enough it conked out.

So looking for ideas on what it might be and some advice on fixing it.
To confirm the bits on that side of carb are the throttle and choke cables

Would really appreciate any help as this has me stumped
 

Re: Phantom air leak on Weber carb

Reply #1 –
Normally when you get an air leak with a carb it will run, but it will not idle, as the extra air being sucked in means its not getting enough fuel.  But it will still run if you keep the revs up higher with the throttle.  That does not sound like your symptoms to me, unless I'm misunderstanding.  If it will run at idle but wont get passed 20mph, that suggests a lack of fuel, for example a blockage, or a tired fuel pump resulting in the float bowl being half empty.  Another thought is there some crap has got into the carb and is blocking the jets up.  I'm assuming its running smooth and it isn't an electrical issues (duff dizzy cap, bad coil, lead or plug etc).  An extra thought, make sure the vacuum hose is not split.