Hello everyone, I wonder if you have any thoughts as to the most likely cause(s) of this: having not started the engine on my 1965 B40F for a month or two, I charged the battery, put in some petrol (E10 but there would have been dregs of the old stuff still in the tank), tickled the carb, and kicked it over. It usually starts first or second kick. After a few kicks it started but then died out immediately. Same happened again. Third time I kept it going by giving it revs, but as soon as I released the throttle it stopped again.
I think it might have been the last time I had it out for a ride, a few months ago, that I had trouble keeping it going. Someone at that stage thought it might be because I had held it on the clutch for a while, but now I'm thinking maybe it's something else.
Any ideas please?
The carb pilot circuit is blocked. Probably gummed up with evaporated fuel. My son had the same issue with his '59 Enfield 500 Bullet. The tiny drilling between the jet block and the engine side of the carb was blocked. The carb needed a prolonged ultrasonic clean before we eventually got it clear.
Hi Phil
I'd put my money on a blocked pilot jet. If you're using an Amal monobloc, put a small container under the carb, unscrew the jet cover then the pilot jet and you should see daylight through the hole in the jet. Give it a good clean including the cover, then replace both including the fibre washer. Tickle the carb and follow your normal starting routine and it should start and idle as before.
You'll probably have to do this every time, if the bike has not been run for a while. If my memory is correct, Amal now make a stainless pilot jet which is far less problematic with alcohol containing fuels.
Thanks for your help so far. My carb is a Concentric. To check out the pilot jet I guess I need to drain the bowl, remove the carb, and have a look. Learning as I go along! All advice very very welcome! Phil
Can I just check: to see if the pilot jet is blocked, and if so clear it, do I need to remove the carb? Any guidance would be much appreciated. Thanks in advance. Phil
It depends on whether you have an old or new type concentric. Cleaning the pilot system of the old ones is a pain. You need to strip your carb and clean it out; start with carb cleaner followed by compressed air to check for blockages. The new 'premier' carbs have a removeable jet in stainless which you can easily remove without any dismantling. On my A50 I ditched the original concentric and replaced it with a 'premier' and its made all the difference.
Useful article on rebuilding the concentric on the Amal site
http://amalcarb.co.uk/rebuilding-mark-1-concentric-carburetter
Thanks very much.
Hmmm... took the carb off, learning as I go along, but when trying to compress the throttle spring I pushed the needle from underneath and it came off its clip, so now I don't know which of the three grooves the clip was in. Any advice please? (This is probably the first of many questions!)
Phil
To be continued under fresh topic entitled "Carb queries".
one thing to look at, is , have you tried running with the filler cap off?
No, but if the carb doesn't appear to be to blame then I'll try that. I guess that's just in case the vent hole is blocked, but I don't think it is.