Triumphrat

RANCAM · 07-12-2007

A few months ago I removed the silencers off my 06 Bonnie and installed, what someone called a "ghetto" back pressure mod, thumbsrews. I have an extensive mechanical background in automobiles and aircraft and I understand the logic and purpose of backpressure but after testing my mod I came to the following conclusion. Prior to any mods at all I averaged 42 mpg, since the "ghetto" mod my average remains unchanged.
I personally feel my Bonnie came from the factory running extremely rich. Anyway my exhaust tip still turns black with soot, just as before the mod and my plugs show no signs of a lean condition. Just wanted to share my experience with everyone.

Hope this helps someone.

I can't wait to show you my new Bonnie Bobber creation. Pics coming soon. Just two things left to do.

Later
Randy

2112 · 07-12-2007

Post 'em up Randall!

HiVel · 07-12-2007

Get that bad boy on a dyno and check out he Fuel mixture-I bet you are lean!
You cant tell from the exhaust pipes anymore with the gas being what it is nowdays.
However, if they turn white you are close to destruction. Lean is Mean!
Plug reading is also difficult. Tan is the man here-inside the plug. Good luck

CAPTDON · 07-12-2007

I think mine was a little rich as well when new. Done some mods & did a 6k plug check. The prettiest color you can imagine & the gap was rite on!! I did oopen em up 1/2 turn in the beginning. Runs better every day!!

RedBird · 07-12-2007

I concur with the suggestion of getting it on a dyno with EGA. My '03 790 is a little rich in the mid-range (12 A/F) with the stock needles, and this is after installing the NARK and NH Togas. It runs great and gets 50+ mpg, so I haven't bothered with machining the slides to lean it some--I could find no needles that would put the mixture any closer to 13 A/F than the stock needles. I would never have believed the mid-range was rich if I hadn't gotten it on a dyno with EGA. I run 158 main jets and 42 pilot jets--40 pilot jets would work just fine.

Larry

mikeinva · 07-12-2007

wow 158 main jets on stock carbs sounds way to rich have you tried any from 138 to 150 ? Its hard to tell with unleaded gas when your to rich it should be 13to1 to 14 to 1. alot make the most hp at 14to1 but may run hot on you.most of the time when you can feel flat spots its to lean not rich.

RedBird · 07-12-2007

mikeinva,

I started with 135 mains after installing the NARK and NH Togas because then I had Thrux needles in the carbs and had read (without thinking) that one needs smaller main jets with the richer needles. It ran no better than stock with the 135's. I immediately went home and put in 150 mains and it felt like it was lifting the front wheel in 1st, 2nd and 3rd gears at 6000 rpm. I went all the way up to 160 main jets without getting a "too rich" bog when suddenly opening the throttle at 5500 rpm. I had the dyno session already scheduled so the 158 mains were what the EGA showed best on the dyno. The dyno operator has been tuning race engines as well as stock and modified street bikes for many years...it took him less than 15 minutes to get the mains where he wanted em; however, we tried different needles for hours trying to get the mid-range closer to 13. I learned quite a bit that day, and it was very interesting to see the results of all the needle changes--NONE whatsoever on the size main jet needed. :-D

Larry