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Discussion Starter · #1 · (Edited)
Dyno'd the bike this evening. 2008 Bonnie Black, only mods done to it are Specialty Spares TT Exhaust and the AI Removed. Everything else is completely stock.

The pilot jets are 45, and the mains are stock 110.

What are your thoughts and suggestions with the reading below...
also - is it safe to assume that if the a/f ratio is like this at WOT - that the a/f ratio will be similar under normal driving conditions?

What do i need to do to get the a/f closer to 13.1?

Also - the bump @4000 rpm in air/fuel ...is it something to be concerned about under normal driving if I chose not to rejet?

Thanks for the input.

 

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If I were you I'd revert to the 42 pilots and increase the main jet size to 115-118. What is your elevation above sea level?

Dick
 

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I stand by my 115/118 educated "guess" since you are at sea level. I think many people are running their bikes too rich to obtain maximum dyno power but in the process give up a bit of drivability (doesn't apply so much to direct pull slide carbs) Jets are cheap; get both and try the 115 first and then after a lot of riding, switch to the 118's and see how it feels.

Dick
 

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Is there a particular reason why you selected the 45 Pilot Jets? Way too rich at the low end. See the dip in torque corresponding almost exactly to the over-rich condition. I'd say 40's for your bike's current state of tune.

Intake and exhaust mod's need to match. Doing one (exhaust) without the other places the pulse waves out of kilter.

Try removing the airbox snorkle. Maybe switch to a K&N or Unifilter intake air filter. Finally, try removing the airbox interior baffle plate.

Otherwise, maybe you can go back to 108 Main jets?

Oddly, your horsepower curve doesn't seem to relate to your Torque curve.
 

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Discussion Starter · #6 ·
I asked about my torque curve, the operator said my chain may be loose - i checked and the free-play is within spec.

So i believe the torque curve to be incorrect... because even when i'm at WOT - its a continuous pull.. no flat spots.

As for the 45 pilots - this is what was suggested by Specialty Spares with a stock bike.
 

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Well the 45's are clearly too rich, as can be seen by your low down a/f curve. 40's should work (stock pilots) 42s would be a bit rich, but probably OK.

The a/f curve says your main jets are too big too (running rich) - but at 12 not disastrous.

I think if you put 40s back in, you will flatten things out over the whole range, or as Gob-ny-geay suggests, pull the snorkel as well, which will probably get you very close to 13 a/f ratio over most of the range.

While the bike may pull well now, it will probably pull even better if you do that.
 

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Discussion Starter · #8 ·
So, if I change the pilots to 42 - and remove the snorkle.... i should be close to 13.1? --- what about the main jet? remain at 110?

and what about the a/f from 2500-4200 --- wouldn't that by putting in a smaller pilot and removing the snorkle, make that jump to excessively lean?
 

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2500 to 4200 is influenced a lot by needle, in conjunction with main jet as the revs increase.

I don't think you will go way lean. It may be best to add the 115 main jet as well as pulling out the snorkle, that will help even it out everywhere. Alternatively, lift the needle up by placing a shim under it while keeping the 11o, and removing snorkel. That will help richen the mixture over that rev range.
 

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Too many changes at once will confuse you. Go back to #42 pilots and add the 115 mains. Ride it for a while - you may need needle shims, abut there is no way to know without first getting your mains straightened out and the pilots brought down. This is not precise, rocket science; it is trial and error. The more of this you do the more comfortable you will become in assessing the impact of the changes.

I do not recommend pilot jet, needle shims and main jet changes all at once.

Dick
 

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Generally when setting up carbs you should get the main jet sized right first, but your pilots are obviously way off, so it's reasonable to put those back.

It's a good idea not to mess with the needle until you have tested the change to the mains and the pilot, and take it from there. These are simply possible adjustments to be borne in mind when you get to that point.

This post has a rather good description of the setup sequence:

http://www.triumphrat.net/twins-technical-talk/106325-carb-jetting-question.html#post1232729
 

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As has already been stated, keep it simple and dont do too much at one time.
Get the course adjustments right then go for the fine-tuning with needle type/position/shims etc.

IMHO you definitely need to get those 45 pilots out!
The stock 40's are what should be in there.

Give the engine some more air by removing the snorkel.
If you feel inclined then fit a Uni or K&N filter, but the difference wont be that great.
You'd be better off with 115 mains with the above.

Use all that as a starting point, and maybe dyno again if you need to clarify the accuracy of this set-up, then progress (if you want to) with further opening of the intake and rejetting to suit.

The "Great sources of info" sticky is where all the required relevant info can be found.

NB.... Your torque curve certainly doesnt make sense!!
Something must have slipped!!


V.
 
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