Best carb jetting for stock airbox / bike - Triumph Forum: Triumph Rat Motorcycle Forums
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post #1 of 12 (permalink) Old 10-01-2019, 06:13 PM Thread Starter
Grand Prix 125
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Best carb jetting for stock airbox / bike

Hi,
I haven't found the thread on this topic so: Is the factory jetting ( pilot jet 38, main jet 98) the best for the Keihin carbs on TB which has no other mods? Some threads mention 40 pilot jet....but what about main jet. Is there any space for improvement, for pushing stock machine up to best limits?

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post #2 of 12 (permalink) Old 10-01-2019, 08:32 PM
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To give you an idea, I am running 125 mains in a bike that has an opened up airbox and stock pipes, so it would have to be a bit smaller than that. Cannot go too far because the airbox is so limiting. I wanted to keep the stock pipes on mine so I just cut a giant hole in the right side of my airbox opposite where the intake is on the left side. Cheap power. ...J.D.
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post #3 of 12 (permalink) Old 10-01-2019, 11:47 PM
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Every bike will be slightly different. How does yours run now?

I have a 1996 Thunderbird converted to Keihin carbs, stock jetting with the fuel screws out 2 3/4 turns and it runs beautifully with a stock airbox.

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post #4 of 12 (permalink) Old 10-02-2019, 01:51 AM Thread Starter
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Hi,
I run the stock jets 38/98, runs nice, but maybe could even better with orig.airbox...that's why I asked..

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post #5 of 12 (permalink) Old 10-02-2019, 06:50 AM
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Stock airbox w/ K & N filter along with a set of Sprint slip on mufflers, stock jetting and she runs great!
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post #6 of 12 (permalink) Old 10-18-2019, 05:40 PM
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Jet kit

I'm converting my 99 Legend to pods and I went with a stage 3 6-sigma jet kit. They offer stage 1, 2, 3, and 7 kits.
https://www.6sigmajetkit.com/

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post #7 of 12 (permalink) Old 10-18-2019, 10:55 PM
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I threw away the pods and bought the stock airbox and 38 pilots, and 100 mains. I may buy the 98 mains. I'm just trying to put it back to stock, the way my friend's 2000 TBS runs so well. I have a K&N element for the box and also the stock element. They tried everything on this bike over its checkered past, even plowing a bunch of holes in both airboxes. I should never have bought this bike, but it was orange and beautiful. The way I understand it is that the bikes are supposed to pop on closed throttle, so don't try to "tune it out"...
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post #8 of 12 (permalink) Old 10-19-2019, 01:33 AM Thread Starter
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I've tried open KN airbox, 40pilot j., 150main j., 3 shims( 0.6mm each) under the needle, Free flow muffers...info got from Proven set up thread.......but it didn't run well...kot kot kot..from low end and very poor in mid range....too reach?...don't want to split carbs x- times, relying on Proven set ups failed, so far so back to stock 40/98 jets etc where it runs well,
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post #9 of 12 (permalink) Old 10-19-2019, 02:26 AM
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OP was wondering if there was any point in going larger on the mainjet to get more hp or something. These bikes are all about torque with the cams to suit... If you want more power, get a bike with more hp. I rode Buddy's bike 200+ miles one day in moving, and the bike was perfect stock, with TORs and stock jetting, airbox etc. Meanwhile everyone else is talking about bikes with modified airboxes. That's where the "Proven Set-ups" threaded people are supposed to live
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post #10 of 12 (permalink) Old 10-19-2019, 02:28 AM
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Ooops, hope I'm not out of line... Not "everyone" is talking about set-ups for modified air cleaners... My bad
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