Needle jet size

[Steve Minor]

The needle jet on my 38mm Bing 54 has 320 stamped on it. I assume this is the size. The manual calls for a 285. What ill effects will an improperly size needle jet cause. I'm having a terrible time with my carb loading up and suspect the float mechanism is the culprit or atleast part of the problem.

 

[Mike Lenz]

You must have the 1977 jetting in your bike. Does the needle have 4 rings on it at the top? If so your needle jet is in the ball park. On a 400 penton, running pump gas[93] and with the rubber plug out from under the seat Im running either a 322 to 324 needle jet with a 185 to 190 main. If your running the rubber plug in you will need leaner jetting. Also needle jets do wear out. Might want to order a new one and compare. You can uaually see the wear in the hole if you have a new one to compare to. Properly set the floats, then put the carb on, open the petcock. When you raise up the floats watch and as soon as the float needle  stops going in the flow should completly stop. You should not have to compress the spring in the float needle[if your needle has one] at all to stop the fuel flow. If you have to, you need a new float needle. If you have a float needle with out an internal spring, get one.

 

[Steve Minor]

Thanks Mike and yes, it's a 1977 400 GS6....I feel quite sure the jets are original, as I bought the bike new and have never changed them. The needle jet (320)is the only jet with any stamping (that I can see).I'm not sure what rubber plug under the seat you're talking about....Is that on the MC5 frame perhaps? I've never noticed a fubber plug on my GS6 frame.

 

[john durrill]

Steve,
 Give me a call if your still haveing trouble.
386-752-9290
John & Peter

 

[Steve Minor]

John & Peter....Thanks for the kind offer. I might just give you a call if I can't straighten this thing out soon.