Triumphrat

Gary_spain

I can assure you that with my setup a shim is certainly needed. Open pipes, thrux needles and de-baffled air box + breathe.

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07 Thruxton: TEC 2 into 1, K&N, TTP Breathe Bellmouth, 135 mains, 40 pilots, std. needles, 1 shim (0.65mm). All baffles removed. Bitubo Fork Cartridges. Bitubo Rear Shocks. TEC Steering Damper. 3 Pot Nissin (Honda) brake caliper.

PieMan

But you're using a 40 pilot Gary, if you moved to a 42's you possibly wouldn't need a shim.

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Mike (UK)

04 Bonnie Black Special

http://www.triumphtwinpower.com

Bron-Yr-Aur

After reading many, many posts on this, when setting up my bike, here's what I came up with...

For 865 motors, pods and open exhaust, the guys who were tested and tuned, I saw this pattern: mains, range of 140 to 155. This varied greatly depending on location and weather, but this is the most important factor in tuning, because everything else is affected from the mains down. The mains have to be correct (WOT) to get the low (idle to 1/4 throttle, pilots) and mid range (needles) power right. So I started with a 147.5. (I ended up needing 152's) With Thrux needles, I never saw a member use shims, and my dyno/sniffer confirmed this. With 42 pilots, I saw most members between 1 and 2 turns. Mine is happy around 1 1/2, until lately with crazy weather changes. And the only reason I question them now is difficulty starting when below 40°.

By no means am I a genius at this, which is why I research like I do, but I'm just sharing what a couple of months of research yielded for me. I'm sure others may have a different experience, but I tried to take all things into consideration, at least to establish some sort of baseline. Hope that helps, at least a little.

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(The artist formerly known as kreemsicleT100)

"Ya can't have 'no' in your heart. Life's a garden. Dig it." - Joe Dirt
"If y'ain't first, yer last." - Ricky Bobby
Bron-Yr-Aur Garage

gjones

Sure, and I appreciate your input.

My existing set-up is working very well for me. Having found the right configuration, it provides the performance benefits that I expected.

However, I find that in top gear at speed, when I want to pass traffic, given the choice to gear down and accelerate, or to just accelerate, I tend to choose the latter.

So my question regarding shims was to discover whether, theoretically, an extra shim would increase acceleration under these conditions, or not.

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B02S4

IMO, if the current mains are too small for optimum WOT performance (& I believe the 140's in yours probably are sub-optimally on the lean side), then yes, it is theoretically possible.

An AFM in actual on-road conditions will show AFR indications that you simply can't feel, & the difference between "OK" & "WOW" can sometimes be just a step or two off.

Also IMO, you can get to "good" with seat of the pants carb tuning, however if you want to get to "great" there really is no substitute for tuning with a AFM.

gjones

well, that's quite motivational.

hmmm.... I have 145s in my box that I could try.

thanks, GJ

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sonicboom

I would think the larger jet would give better roll on throttle response if that is what you are looking for. Try it out and decide for yourself. Can't hurt anything. Having the bike tuned on a dyno is the best way to go and then you are not guessing at this stuff. But then what happen to all the fun with a dyno. LOL.