Triumph Rat Motorcycle Forums banner
  • Hey everyone! Enter your ride HERE to be a part of September's Bike of the Month Challenge!
1 - 5 of 5 Posts

·
Registered
Joined
·
3,617 Posts
Discussion Starter · #1 ·
Need some help from the gurus at RAT. I have put the BC air box removal kit on my 790 T100. Bike has TOR's. Jets were up-sized. Idles & starts great. Blip the throttle and it stumbles a little. Bike breaks up at 6000 rpm. Any body have some jetting/idle screw settings? Main is now 150. Pilot is now 42 (I think). One shim on needles. Thanks in advance!
 

·
Registered
Joined
·
683 Posts
On 2007-01-04 18:49, Brooksie wrote:
Need some help from the gurus at RAT. I have put the BC air box removal kit on my 790 T100. Bike has TOR's. Jets were up-sized. Idles & starts great. Blip the throttle and it stumbles a little. Bike breaks up at 6000 rpm. Any body have some jetting/idle screw settings? Main is now 150. Pilot is now 42 (I think). One shim on needles. Thanks in advance!
Dinqua's jet calculator comes up with a 154 main, "assuming" the 42 pilot info is correct, and those are stock needles, and you are at or below 1000'asl

Dinqua's calculator is super cool.....check it out. But I'd confirm those pilots and needles first.
 

·
Registered
Joined
·
3,588 Posts
From your description, I would guess your problem is with the pilot circuitry--not the needles or main jets. If you did put 42 pilot jets in the carbs, you will likely need to turn the pilot screws in to lean the mixture some. My 790 has 42 pilots and the screws are only out about a turn. Having said all that, I did have the screws out about 3.5 turns before I got it on a dyno, and it ran good. If you still have the stock 40 pilot jets, you will likely have to turn the pilot screws out some to richen the mixture. You might want to recheck everything done in and around the carbs...look for vacuum leaks...make sure the vacuum nipples are all on, etc.

I know nothing about the TOR's, but I wouldn't be surprised if the 150 mains are a tad rich with the TOR's. However, all bikes are a little different, and my OLD butt dyno is not sensitive enough to get the mixtures at optimum--only a good dyno with EGA. :-D

'03 T-100: Nark, NH Togas, 158 mains, 42 pilots, stock needles--no shims...dyno'ed at 745 ft. elevation.

Larry

edit: Just reread your post...what does "breaks up at 6000 rpm" mean? At that rpm you should be running mostly on the main jets--that is the rpm that mine really turns on--like it is lifting the front wheel off the ground. When I had too small main jets in, mine ran about like stock--but no stumbling or anything like that. The largest size main jets I have run were 160 and I couldn't tell a difference between them and the 158's the dyno run liked the most. The old rule of thumb is to get the main jets sized correctly first; second, get the needles correct; and last do the pilot (idle) mixtures.

I started my jetting with 135 mains and Thrux needles, and like I said it ran about like stock until I put in the 150 mains.

[ This message was edited by: RedBird on 2007-01-04 20:17 ]
 

·
Registered
Joined
·
361 Posts
Brooksie,

With the 42 pilots 1.5 to 2 turns out should be good and you may not need the shim. 3 to 3.5 turns out on the pilot screws if you're running 40 pilots. As far as the problem at about 6K try running with the choke out slightly to see if that solves the problem. If it does your running too lean obviously and if it doesn't help you're probably running too rich on the mains. My guess is your mains are too big especially if you're running Thruxton needles in the carbs. Get it on a dyno if you can to try for an Air/Fuel ratio of about 13 to 13.5 to 1.

Good Luck,

Bill
 

·
Registered
Joined
·
3,617 Posts
Discussion Starter · #5 ·
You guys are the best. Will try it this weekend. I am getting a 904 kit put in it next week but want to ride it while the weather here is in the 50's. Thanks again!!
 
1 - 5 of 5 Posts
Top