Fuel Mixture

[johnfrancis898]

I’m having trouble tuning up the carbs. Tick over has always been a bit erratic and the old girl has always smelt a bit rich, however acceleration and power has been good but I have recently noticed fuel consumption has got worse. So today I decided to fit a set of new needles and clean up the dash pots. I then balanced the air intake with my carb balancer and established a good tick over. After reassembly she started fine but on a test run a misfire was evident on acceleration and also loss of power. Further adjustment to the jets has cleared the misfire. I have them set exactly 2 turns down from when they are flush at the bridge. Power and acceleration is now good as before but on tick over it’s still smelling rich and I can’t establish a good tick over. Any pointers or tips welcome!

[Alec]

Hello John,

the two turns is an arbitary setting, i.e. a starting point, and should be adjusted to get the right setting. That said it shouldn't be far away from ideal. Presumably your air cleaner element is clean also as this affects the mixture.
When you have got the mixture where you want it, try small adjustments to the timing as mixture affects what timeing works best.

Alec

[johnfrancis898]

Many thanks for your reply Alec. I have done some further investigating and found the problem is when I use the choke. When the choke is pulled it pulls back the jet to richen the mixture for cold starting. I found that on the front carb the jet was not returning fully. The misfire then disappeared after ensuring the jets were in their correct position. I’ve now ordered a full refurb kit from Burlens.
Thanks again. John.