Finally removed the stock air box!

fender

fender

Street Tracker
Wish I did this earlier in the riding season. Used a hacksaw blade and dremel. The hardest part was getting the screws out of the side panels with the airbox on the bike. Once past that it was really easy.

The change in performance was quite noticeable. Pulls really hard up to redline, I'm still working on the jetting and needle height, but so far I'm quite happy with the results.

pilot 42, 3.5 turns out on mix screw
Thruxton needles w/ 2 .5 shims
155 mains

Once I feel like I have it closer with the jetting I'll take it in and have it dyno'd to get the A/F right on. The combination of Predators and air box removal really changed the personality of the bike. I've been running the bike for the past two years with Preds and stock air box. Loved the sound but need a little more performance.
 

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S

SCBonneville

Two Stroke
Also, just for good measure... with 42 pilots, turn the pilot screws between 1 and 1 1/2 turns out...

I did the "carve" a while back... I'm now running 3 1/2 turns out on the pilot screws, 40 pilot jets, Thruxton needles with 1 Keihin (very thin) shim and 145 main jets. K&N pods, EPCO peashooter exhaust and a reworked igniter...

I had a dyno run a couple of weeks back (prior to putting the shim under the needles and going from 138's up to the 145's) and was spot on A/F ratio wise up to 5k rpms.. then it went lean up on top. I've added the shims and 145's and will get back on the dyno in a couple of weeks to check the jetting - A/F ratio and confirm some VERY nice hp/torque figures... It's running balls to the walls right now!
 
fender

fender

Street Tracker
Thanks for the input!

I've got various jet sizes that I running through to see which one feels the best. I didn't really notice a difference between the 150's and 155's so I'll be dropping down to 150's and then to 145's and see what feels the best. Then on to the needle and eventually the pilot and mixture before I hit the dyno.

BTW is a 05' 790
 
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S

SCBonneville

Two Stroke
fender said:
Thanks for the input!

I've got various jet sizes that I running through to see which one feels the best. I didn't really notice a difference between the 150's and 155's so I'll be dropping down to 150's and then to 145's and see what feels the best. Then on to the needle and eventually the pilot and mixture before I hit the dyno.

BTW is a 05' 790
Click to expand...

Fender... if you choose to go the Thruxton needle route (HIGHLY recommended on the 790 engine w/o air box), you can reduce your main jet size between 5 and 10 points... The more slender profile of them "richens" the mid range and up to the overlap area where it mixes with the main...

Do a google search for "tuning Keihin carbs"... There is a lot of information about how the carbs/jets work and inter-relate through the different throttle ranges...

Also, I recommend that you look into having your igniter's advance curve "reworked" and the rev limit raised... 8400 rpms is a nice round figure...
Google "Triumph Twin Power" and contact Mike (he is over in the UK but shipping is not a problem), he has the ability to reset both for just a bit more than you can buy a Procom unit off e-bay... But you retain all the smooth starting of the stock unit and you don't get "spitting back" through the carbs as you do with the Procom... Plus the top end rush is better too... You will be surprised what your 790 will do with the pods/Thrux needles/juiced igniter/Pred. exhaust set up...
 
OregonThruxton

OregonThruxton

750cc
FYI, I know you have a Bonnie, but British Customs recommends 42 pilots, 135-140 mains and 2 1/2 turns out, on a Thruxton with Predators and K&N pods.

Why did you use a dremel and hack saw? I got mine out by removing one side panel and pulling out the back.

There's a couple of great How-To videos on the BIR website: http://www.britironrebels.com/video.htm
 
fender

fender

Street Tracker
I looked at buying one of the kits but figured I could put the $200 plus savings to better use. Cutting it up was really easy and only spent $80 on the filters. I did end up buying several jet sizes and the thruxton needles but I'm still much further ahead.

SCBonneville said:
I recommend that you look into having your igniter's advance curve "reworked" and the rev limit raised... 8400 rpms is a nice round figure...
Click to expand...

I'm liking that idea since it now quickly hits the rev limiter and it still pulling hard when it does.

The only sad part is the weather is going back to normal temps this weekend mid 40's from the past week of 60's. So my tuning rides will be much cooler. Hopefully the snow holds off to later in Dec this year.
 
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