Pilot Jet Woes

Dec 5, 2005
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I am in the final stages of my '73 commando 750 rebuild.The bike had stood for many years prior to my acquiring it, and as such the carburettors were badly gunked up. After copious quantities of carburettor cleaner, compressed air and probing with thin copper wire I can now get air and cleaner fluid to pass through the air passage and also through the pilot jet to the two small orifices at the front the carburettors, when I insert the tube of the carb cleaner aerosol can in the opening left where the air adjuster screw fits. However, no air or cleaner fluid will pass through the small threaded hole under the body of the carb. I assume this small hole is where fuel will pass through the pilot jet into the mixing chamber. How do I rectify this problem?

First the jet itself is a .016 hole and needs to be drilled clean back to it's size with a #78 drill. The drill is small and must be epoxyed into the end of the red plastic tube that comes on airosol cans( brake clean , carb clean). lots of twisting very light presure. Now it's factory size. not juast a hole in some dirt. I woud use a drill on the other passage ways as well than lots of blown cleaner out of a can. Sometimes somone has already drilled the jet out too far and the #78 drill will let you know things are not right. When this happens I just drill them out to .030 and use the old stye jet in the hole you can't get spray out of now. #25's also have .016 hole.
Thanks Norbsa. I acquired a #78 drillbit and it has done the job. Fuel now flows through the pilot jet. Now need to extract the digit and complete assembly of the bike. Got an insentive to finish the job when I called on my pal Richard last night. He has completed the restoration of his 74 850 and it looks a treat. Iam sure you will hear from him on this site as he puts it through road tests.

Bazz, do you know Combat Pete? Got to stay with him on a visit some time ago. He showed my boy and I around Your town nice place. If you see him tell him Greg and Evan said hi. Glad the #78 did the deed.