Bonneville America Forums Forums Technical Forums Performance Mods TBS needles

i just installed them on the 05 speedy and i can't help wondering why i got no benefits over the stock needles with one shim. I tried the TBS also with one, then 2. With one the midrange wan't quite as strong as stock and with 2 it was about the same, tho possibly still less. So i may go back to stock. This is with UNI filter, drilled filter/airbox bottom, snorkel removed and 130 mains, tho i just now put in 125's which helped the top a bit but of course had no effect on midrange. The 130's were a bit rich i think.

I noticed 2 things about the TBS compared to stock....they were longer and the taper seemed thinner, but very very slightly to the point where it was visually hard to see. I'm thinking the extra length is the reason for the less than spectacular performance. Thats whay i added 2 shims. But thats not nearly enough to shorten them compared to the stock needles with one shim so i wonder if i need maybe 4 shims. But i never heard of anyone using that many. These are .5mm shims by the way. heres my theory as to why i didn't see the improvmant so many here have cited.The 05 speedy has NBZY needles while the pre 05's have NBAD. Could it be my stock needles were already much closer to the richness the TBS give than the pre 05 speedy's needles? Or if not, what are your thoughts on this situation?

Good theory!! I could send you my stock needles to compare if u want, or if someone is closer... In fact, if you find someone local with an older speedy but similar filter/jetting, it would be a great experiment. I was also thinking that maybe the guys with the freak see a more drastic effect because of the higher airflow and jetting? But I like your needle theory better.

Yea, i believe thats it. The same thing with the hole in the slide everyone was drilling out for better throttle response. i was about to consider doing that when i finally read a post saying the 05's are already drilled bigger. so i guess they rectified a few carb things in 05's that they saw everyone was wanting. Sadly i think my quest for more power might be over. I decided against the freak, so theres really nothing left to try ! Bike runs nice but i never did get it quite to the point where i'd imagined it being when i first got the bike. Close, but no cigar. but there still seems to be a flat spot in a certain point in the midrange depending on the RPM and gear i'm in. Getting rid of that was what i'd hoped for with the needles.

The Freak and Big Bore kit will take care of that flat spot and you'll have more than enough power to haul you up those hills. Take a look at Harley and Star motorcycles. Their stage 1 and 2 kits are not that much different than our Frk and BB Kits. fredlevy@hotmail.com

I didn't get any huge performance increase from the TBS needles on my 03 America, but they did cure 2 things.. a very minor flat spot at mid range, and a "stumble" that would occur if I blipped the throttle between downshifts.
Your theory may be correct. Your carbs may already be more responsive than the 790cc carbs are stock.

Sounds like the carbs are better, but wasn't someone saying the cam profiles are different and may be the limmiting factor in the 865?

Here is the reference I always refer to when adjusting carbs. Very helpful. Start with the top speed and work down until you get it going the way you want in all throttle postions.

The peaks of the curves are when the different parts are doing the most work.
By looking at the chart, you can see that main jets and a small bit of needle taper effect the gas flow the most at WOT. Do the main jets first, then figure out which needles/taper run the best at 1/2 to WOT, then maybe add a shim then maybe fatten or thin the needle main body (but be sure the taper is the same as before) for the low end. The pilot circuits are one of the very last things you do, just before you balance the carbs.

I'm not sure about the differance between the TBS & Thruxton needles but after putting the Thruxton needles in my 03 America the throttle response from 1/4 to full is much smoother and the speedo needle climbs over those numbers much faster than before.

Well, i added more shims to the TBS needles in order to get the same length as i had with the stock needles with one shim on them. It worked....flat spot gone, chirped the tire shifting to 2nd. definate improvment.