Bigger main jet ?.


Active Forum User
Non-VOC Member
I have been adjusting the carbs, a 229 on the front and a 289 on the rear. The off side sets up well, with slightly rich off peak leaving the air screw about 1 turn out. On the front finding the same point leaves the air screw tight in with no adjustment left. By fitting a larger main jet (180 at present) would that allow the screw to be backed off to regain some adjustment. The holes in the jet block are clear.


Well Known and Active Forum User
VOC Member
Hi Ben, not sure about 229 and 289 (before my time) but I'm fairly confident the the main jet only affects about 3/4 throttle and above. If it's run ok before, check float level, otherwise I think you're in pilot jet teritory.


chankly bore

Well Known and Active Forum User
Non-VOC Member
Yup, check pilot jet, then the large washer under the jet block, then the float level- does tilting the carb affect running? Then check your ignition!! As someone once said; "70% of carburetion problems are electrical." If still no good, come back online for a few hundred more opinions/solutions. Cheers, F5AB/2A/7945 since 1970 (and F10AB/1B/2304 a long time ago) The main jet should not affect this portion of the carb adjustment at all.You may also be able to alter the float level by adding or subtracting washers on the float bowl arm. I would suspect float too high or leaky float or poor float needle seating.