Bonneville America Forums Forums Technical Forums Performance Mods Lugs is first gear???

Hey guys, I have been trying to figure out what is causing my bike to do this, When I take off normal from a stop in first gear my bike will like lug or be really sluggish then seems to catch up and take off just fine. Now I have the stock pipes all gutted, gutted airbox with the bottom cut out, 150 jets and some fresh plugs. Do you think I would benefit form the TBS needles?? I have shims but I don't rally know what they do, I am guessing more fuel?? I build some 11 and 12 secound cars and tune them myself but this is just a new type of carb to me... thanks

150's might be a little to big for stock pipes gutted? it could be bogging?

Jets are to large!!!!!

If your engine is too rich, then you should be belching black smoke out the ex. pipes when it "bogs"/lays down.

All carbs are pretty much alike, except Holleys have fewer jet adjustments than bike carbs or Webers. (The jets are there, they're just fixed.)

I suggest you go back to a stock main jet and start from there. Only go up a jet size at a time, just as you would with a race car carb. Be sure to keep notes on what you've done, too.

NOTE: If your spark plugs are fuel fouled because of too-rich a mixture, either clean them well or install a fresh set.

From what I have learned from the Dinq master. The size of the main jets should not be an issue in first gear take off. Has more to do with air/fuel mix, or that little hidden fuel filter. The jets may be too large for stock but I don't think that is what is happening.

If your pipes are just plain gutted, you need something in there for backpressure.

Mixture problems at low engine speed are caused by the pilot jets or maybe a clogged air bleed that feeds through the idle and transition ports. The 150 mains might be a little big but, since it seems to be OK after you get going, they probably aren't the problem.
When your engine is running slow, below around 3000 - 3400, it is getting gas from the idle jet and a couple of transition ports located just outside of the throttle plates, all fed by the pilot jets. There is an air bleed port running from the inlet end of the carburettors all the way in to the idle port that syphon gas from the pilot jets. Once the engine picks up speed, the slides start to open and fuel feed moves to the needles and main jets. At high speeds, enough air is flowing through the carburettors that the idle and transition ports begin to feed fuel again, acting like the power enrichment valve on car carburettors.

well the stock jets are way to lean, so i tried 140's and they were still a bit lean, now with the 150's the plugs look just perfect. I would bet a little more fuel would net me a few more ponies but I don't have anymore jets... Maybe if I drilled out that vacume port??