Bike idles but won't rev

[Alexlib]

Finally sorted mine today , it was the coil . I also put electric ignition on. The bike is running really well . All the misfires gone

[EddieDay]

"Thought everyone knew that carburettor problems are usually electrical and electrical problems are almost certainly due to the carburettor. "

I am beginning to believe that John.

Good luck with yours too Steve.

The new coil will arrive tomorrow so fingers are crossed. If it doesn't do the trick I am going to sit in a dark room and think through what could have been disturbed. It might be a bad connection somewhere in the ignition circuit.

[EddieDay]

Whoopee. Problem solved. Bike running well again. 60mph uphill. I will take that.

Chatted in the Bulls Head (one of the Surrey section pub evenings) last night with Duncan. He asked if the float needle tended to stick up. I noticed when I put the float back in that the needle seemed to be a bit sticky, so while I was waiting for the new coil to arrive I decided to open the carb again. The float needle was fine so I took out the main jet and pilot jets again. The main jet had a tiny piece of crud in it, so I blew it out. Reassembled everything, including putting the old coil and HT lead back on, and hey presto - bike started and ran beautifully. I guess there must have been a stray particle somewhere in the carb after I cleaned it before. So now I have a brand new spare coil and HT lead. But I am happy.

[Duncan]

Result, I glad you are up and running again, looks like there are some sunny days ahead to get some miles in.

[Expat]

Rather late reply but ended up taking carb off again, cleaned out loads of rusty sediment and lapped the carb face and face of spacer. Re assembled with new o ring and gasket against head and she now starts and runs great. I think because the tank was left almost empty for ages, when it was partially filled for the initial start up, surface rust was washed into the carb.
A possibility?

[clive]

Thanks for all your suggestions.
I took out the pilot jet and it was clean. The float chamber emptied itself when I took the end cap off so I take that as a sign that the passage to the pilot jet from the float chamber is clear. Same symptoms. (With choke open).
Checked that the weights on the advance mechanism are free and will open. Checked timing. OK. Checked points gap. No difference.
Changed the spark plug to an NGK B7ES after reading several threads on the topic. It was a B6ES. No difference.
Checked that the connections to the coil were tight and the HT lead in place. No difference.
Just ordered a new coil and HT lead. The old coil is stamped 2016. Not that old IMO but I am running out of ideas.

Seems a very through check. Just a thought, I service a G3LS for a friend each year. This year he complained it would start and tickover but not rev after standing for the winter. I said bring it over and was about to start similar checks to yours however one tap was leaking a bit because the Cork had gone dry. I thought I will replace the corks but when I turned the tap on the main side to drain the tank only a dribble came out. Turned the reserve tap on and nothing at all. Investigation showed both taps had no filter and had simply filled with rust until blocked. Cleaned them out and new corks then cleaned rust from the tank ( a dozen nuts and bolts in the tank vigorous shaking and count them out again followed by flushing through with the old drained petrol.). Cleaned the filter on the carb and it then started, ticked over, and revved freely.

You do mention finding the carb filter blocked but not checking the flow from the tank. Good luck.

[Expat]

Thanks Clive.