Kettle Clinic

Irregular running when releasing the gas

I just bought a 750 gt l. A very beautiful motorcycle very well maintained. I am experiencing a problem when running the bike. When the motor is cold the bike runs smooth but when it warms up, releasing the gas, the motor tends to be irregular, I get some short acceleration. If I open the gas it disappears. It is like getting extra air or gas when the butterflies are closed. I balanced the caburators (the intake air flow) and I changed the plugs from thermal grade 9 to 7. It is a bit better but still I have the problem. I do not have points on the ignition but a pick up. Do you have any suggestion on what I could do before taking apart the carburators? Thanks,

Marco

Slow the tickover to 1000rpm and make sure the carbs are equally set, otherwise the surging is horrible.

It is the first thing I did, The air flow in the three carbs was very different, and I thought to have solved the problem balancing them and reducing the idle. The back and surge was better but didn't go completely avay.
I've been suggested to modify the carbs according to an old suzuki bulletin (back to 76). Apparently the mixture at low rpm should be reacher. This is achieved by reducing to 0.9 the air bypass jets. To do this the I need to slighly modify the carbs according to the suzuki suggestion. I I've bought the jets on ebay in the UK and as soon as I will get them,I will mount them. Do you have any experience with this procedure/ modification? Thanks.

Over to you Baz

Smart thing to do. I have modified many sets of BS40 carbs and fitting air jets usually reduces surging significantly.

I suspect that Baz has similar experience.

I pre-drill all the sets I restore tin case required.