jetting bs34 on 81 750ltd pods and 4-1

I switched to a Mikuni BS34 carb on my bike it came off an '82 750R1 and had 110 main and 37.5 idle jets. I switched to 140 main and 42.5 idle jets with individual pods and a 4-1 exhaust, I thought better too rich than lean.

It is running rich, I can smell the gas ( and my wife too inside the house :S ) and I get puffs of white smoke out the exhaust when accelerating.

I thought about dropping just the idle jet to 40 and try keeping the 140 main, if that doesn't do it then drop the mains to 137.5 ?

Thanks for any suggestions

When rejetting I've always started with one size bigger pilot and 2-3 sizes bigger on the main.

I suggest a #40 pilot jet and some 115 mains. Normally the mains weren't too lean from the factory since no emission testing took place at WFO. Definitely ditch the 140 mains.

Perhaps WG or someone else can chime in here.

Later, Doug

Post edited by: StreetfighterKz, at: 2007/08/13 07:20

#140 mains and #40 pilots. The bike won't pull 6K rpm with #115 mains as was suggested. The richness is from the #42.5 pilots I suspect. Also, double check the carburetors when you replace the pilots to ensure there is no passageway from pilot well to main jet well... This is a about a 1mm passageway and on models eqipped with this hole between the two wells, a plug must be used or the carbs will be very rich. I think the GPz carbs came without this hole but you may have a set from another application. There is also a type of BS34 out there (not sure its orignal application) with a richer mid-range and a #130 main jet is the one to use when rejetting. If you have the jet needle badge numbers I could likely tell you if you have this type or the more common configuration(s) that require a #140 main. You can also tell because the bike can't pull redline cleanly if it has the wrong main jet after rejetting.

Post edited by: wiredgeorge, at: 2007/08/13 08:12

The carbs seem to have the passageway between pilot and main jet, the idle jet was plugged.

The number on the needle reads 4BE4.

Thanks for the replies.

I have the BS34 with those jet needles down for the 83 KZ750 and 82 GPz 750. Use the #140 mains as suggested and #40 pilots. I think the jet needles have clip slots... clip on 3rd slot.

40 pilots it is then, I don't remember seeing clip slots on the needle, I'll check when I replace the pilots.

Thanks for you time.

I'll let you know what happened.