Bonneville America Forums Forums Technical Forums Performance Mods Any performance gain with switching needles/mains?

Running thruxton needles and 140 mains. Dyno A/F says that I am near dead on. Not being one to leave things alone, was wondering if switching to dnyojet needles and 145 mains would show any performance increase? According to the Jet Calculator the dynojet needle takes a larger main. So given that, does a larger main mean more gas - i.e. more power?

That is nearly impossible to answer without knowing exactly what your bike did on the dyno run, absent an onboard a/f meter. Can you post the a/f print?

No onboard a/f meter. The dyno was a slightly wavy line over the 13 to 1 red line. Going to have to dig around, and scan it.

OK, however if your run shows on or about 13:1 a/f during the dyno sweep test, then you're pretty close to optimal.

Wish I kept mine but I didn't have the forethought to save it. I have been told I can't get the HP and TQ that I am with stock bore. I seemed to lose some with the TBS needles that was why I went back but no dyno run to back that up.

I swapped to Thruxton needles after my 4th dyno run, but haven't been back to see how it did. I was rich (I think?) in the middle and it was a touch flat, the Thrux needles felt like they improved the midrange, just need to verify. Don't remember if there is a shim under each needle or not.

I was looking to fix a small flat spot mid way but it just seemed to make me too rich.

what's rich, higher or lower than 13, I forget which way it goes

Less is richer. Before anyone says it too I did play with different jets with those needles and if I got the top right the bottom was off and vise versa.

okay, so I was rich in the middle and the Thrux needles are slightly fatter which should lean out the mix and bring it closer to optimal


in theory

Right the Thruxton needles are fatter - which would lean it out.

well youhave to remember that with carbs you will have to make some compromises. you run the risk of being to rich so if you are near perfect you had better stay. Go to stuff like a performance clutch,changing sprockets, or cutting some excess wieght of the bike.
A battery relocation kit will drop a few pounds, also go to some light wieght pipes. I had mine made at a custom exhaust shop for like $40 bucks. they are just 18" turndowns. You can bob the rear fender and drop 10 to 15 lbs. If you get creative you can drop nearly 40 lbs.
If you haven't yet get rid of the air injection.

lol, I can't remember all the crap I've done to my carbs. sorry to give out inaccurate advise. whatever my problem was, the Thruxton needles were supposed to help, and it seems like they have. again, I have no dyno run to support that since I swapped them out, but it feels like it fixed it.

Go to the jet calculator its pretty accurate. I did exactly what it said. the only diff was I had to go up to a 130 main when it said 127.5. Its really close.

uhh.. The Thruxton needles are thicker then Dynojet needles.