Bonneville America Forums Forums Technical Forums Performance Mods CV Carb Tuning

@B02S4

Greetings Sir,
Coolfogman here from the TriumphRAT forum. I want to thank you for your response to my query regarding my carb troubles!
Following your recommendation, I up-sized the pilot jets in my CVK's to #45 (keihin). Idle circuit thumbscrews are each ~2.5 turns out. (Also cleaned and re-oiled my K&N pods.) Took her out for a 30-mile test ride at varying speeds... found that the at-cruise miss/stumbling is much improved but still there as well as the power-robbing wind gust symptom - although the intensity of that also seemed lessened. 🤨

Thinking that the denser foam element of Uni's might have a positive effect in regards to the wind-gust issue - I purchased and installed a pair of Uni pod filters (#4229), from a local shop and took her out again... performance-wise the bike responds much the same as having the K&N pods on it (with slightly quieter intake suction noise).

Here's where things are at currently:

'06 Speedmaster 865
8042 miles on odometer
Stock motor, head and cams
Airbox completely removed
Uni Pods (#4229)
Air Injection removed
EVAP/Emissions removed
Sceptre pipes
TTP Stage I Igniter
Nology coils
New Bonneville "Premium Spark Plug Wires"
NGK BPR8EIX-9 Iridium plugs gapped to the .8 - .9mm spec
#45 Pilot jets (Keihin)
#148 Main jets (Keihin)
Idle Screws 2.5 +/- turns out each
Thruxton (NBZT) needles w/1 shim
Stock slide springs
Vacuum slides - wings sanded to remove surface variations (unknown cause), using 3M automotive premium wet-sanding paper from 800 - 3000 grit (sanding 90° to previous grit), finishing in direction of movement and then polishing wings and bodies with Flitz polish
Vacuum slide bleed holes at 3mm (drilled by previous owner)

The bike starts easily with no choke and idles well with no popping.
Acceleration is smooth up through the gears with no perceptible hesitation or flat spots
At highway cruise (~4200 rpm/70mph), there is a slight stumbling happening, but if I roll into the throttle it accelerates without hesitation

In addition to the at-cruise stumble, the other symptom I'm still experiencing is: when I get hit with a wind gust - from any location other than head-on or directly astern - the gust immediately seems to suck the power out of the motor and I have to roll into the throttle to maintain speed!

As I stated previously, the above two symptoms are much improved with the installation of the larger pilot jets but still there.


I'm hopeful that you or another forum member will have a resolution?!

Thank you and much appreciation in advance to all who may have input!

Best Regards,
John Wentworth
"Coolfogman"