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[zonggong]

I'd appreciate some suggestions with this problem. My current project is a 1990 350 iron barrel 4 speed that was imported into Australia from India. I'm having trouble with the tuning. I'm pretty certain that the timing is OK, new points and condenser, bob weight springs seem OK, used a dial gauge and lamp to get 0.8 mm before TDC static timing. The carby is Mikarb. The bike started and idled but did not really want to accelerate. To save time I ordered a new carby. The only difference was the throttle cutaway which was 3.5 on the new one and 2.0 on the original. Same jets (47) and needle in the middle groove. I've tried both throttles in the new carby without any significant difference. It starts reasonably easily, sometimes spits back through the carby and sometimes will just cough and 'die. If the throttle is opened to say 1/2 then it will start to die but recover and idle again when the throttle is returned. If the throttle is opened a few times it will rev up OK. It seems to me that it could be starving for fuel but not really sure what to pay attention to next. The mixture screw is set at 1 1/2 turns out. The float level was as per the spec. Opening the 'enricher' circuit when warm makes it die rather than run better.I haven't been able to ride this one yet and I want to get it 'roadworthy' - our MOT test - soon. Thanks for your suggestions

[Presto]

If the problems you had with the original carb continue with the new carb that seems to eliminate the carb from being the main source of the trouble. And timing seems, from what you say, also to be correct. This type of running problem can sometimes be due to burnt exhaust valve and loss of compression. That’s a ‘maybe’.

[Freddo]

This issue was covered at great length at http://www.hitchcocksmotorcycles.com/vi ... orumorder=

The solution appeared to be to take the carburetor apart and soak the metal parts of the carburetor in carb cleaner for several days.

[simon]

If you are setting the static timing at bob weights out ie full advance position then 8mm isn't enough for a 350 should be 7/16" to 1/2" and I always set mine to 1/2" without issue. Reset to just shy of 13mm (1/2 of 25.4 to be precise) and see how that goes

[zonggong]

Thanks for the suggestions. I had followed Simplo's problem with his 350 carb with great interest, however, that wasn't the problem I was having. It turns out that it was running too rich. By lowering the needle and making the mixture a little leaner, and retuning the mixture screw, it seems to have solved the problem. Lowering the needle helped because it starts to become effective in the early throttle openings. I may also investigate a slightly leaner throttle cutaway at some later stage.