My bike won't rev up -sorry, not AMC

Janet · Post by **Janet** » Sat May 24, 2003 4:37 pm

I apologise because my problem relates to my LE Velo, not an AMC bike, but I think it is not a marque-specific problem, so someone may be able to help.

When I lift the throttle off tick-over, or when changing gear, the revs initially dip and then pick up, after which the engine revs beautifully until I back it off again. This happens with no load, even before I let out the clutch. If I blip the throttle before each change of gear or when I want to accelerate it is perfectly rideable, but I'd like to get it right as it can be inconvenient.

It's got an Amal monobloc carb on it which I've never touched since I bought the bike two years ago, apart from checking it is clean.

Has anyone any ideas what may be causing this?

Biscuit · Post by **Biscuit** » Mon May 26, 2003 6:33 pm

Hi Janet, In the absence of expert advice, your'll have to do with me. According the literature I have read, the problem occurs when the engine is coming off the pilot jet on to the slide cutaway, as the latter remains the same, it must be to do with the pilot jet. Apparently this jet has two bleed holes which provide a compensating action and provide a well of fuel for snap acceleration. So I reckon you need another clean or pilot screw adjustment. A good way of cleaning small hole in carbs is a multi cigarette lighter gas refill, just press the nozzle against the hole, push and whoosh - the hole is clear, pongs though, don't do this near a naked flame.

Janet · Post by **Janet** » Mon May 26, 2003 7:11 pm

Thanks Alan, I'll give it a try, although the concept of snap acceleration when talking about an LE isa little optimistic.

Biscuit · Post by **Biscuit** » Mon May 26, 2003 9:29 pm

Well I did confess I was reading from the book, and I didn't want to be rude about your Vespa, sorry, Velocette

silverarrow · Post by **silverarrow** » Tue May 27, 2003 2:14 pm

Janet, 2 things come to mind. 1) are you using old petrol, it goes off nowadays (progress!) 2) clean out the carb with Carb Cleaner which comes in aerosol cans from any motor accessory shop. It shifts the gunge that unleaded petrol leaves behind and will find muck that anything else bar ultrasonic cleaning will not. After this treatment you may be amazed. (Ask me how i know?) Les Smith

Janet · Post by **Janet** » Tue May 27, 2003 11:18 pm

Thanks for the replies chaps. I seem to have found the cause of the problem. Les I didn't think it could be the sludgy petrol because I've just done 1000 miles on it this month. I did take the carb apart because both you and Alan thought the problem was there, and you were right. I found that the clip on the needle was sitting halfway down instead of in its groove. I put it back and appeared to have cured it. While I had it apart I gave it a good clean for good measure.

Thanks again.