Triumphrat

DharmaLion

I have the Jenks tuning notes, but I wonder what you guys are actually running in terms of jetting/ shims/ mods etc for a hi power output with no lag in the powerband.

Here's what I've got; 18tooth counter sprocket, rubber velocity stack, AI eliminator, iridium plugs, 125/42 jets, 3 turns out, hi flow filter. TORS. unifilter with airbox in.

I have a slight lag in the low RPMs. No problems in the pull in higher revs, and mostly happy with with I've got.

What Are you running/ and what are the mods you have on the 790cc bonnie and what works best in terms of jetting and airflow.

Thanks to All!

Dean

Dave2001

As you will have noticed from my other posts, I don't see any advantage in snorkel removal, but having said that...

If you remove the snorkel you will have to compensate for the effect that the snorkel was designed for i.e to help the mid range power - others will no doubt advise on this, but I may be able to add something else to the mix which may help the idle situation.

I removed the AI very early, and always had a sort of lumpy idle, and problems starting despite retuning the airscrews. Recently, in a fit of stockmania, I put the AI back on, and was surprised to be rewarded with a really smooth idle, easy starting, and an increase in idle speed when the choke was out.

My conclusion is that despite the general wisdom, removing the AI DOES have some effect on performance: or at least the stock bike is set up to run best with the AI on. I now believe that you DO have to rejet if you remove the AI.

Sorry no dyno results to back this up though....

Dave

6dock6

I have been thinking about this to as i changed the pipes and removed AI at
9km i don't know enough about how the AI is supposed to work but i would think if it worked at idle it would help the engine scavenge better an there for idle smoother unfortunately i fell down the stair and broke my foot with 200km on the bike and cant ride it for 6 weeks to see if it makes any difference

oldroadie

That slight lag in power at low throttle is likely a rich condition, why not turn those screws in by half and see? 42s are just a wee bit on the fat side if you haven't opened the air box up but you could compensate for that with the air screws.

__________________
2001 Bonneville
2004 Bonneville America

ohiorider

Here's a summary of the Air/Fuel results from my dyno run in Aug 2007. This was jetted 125/42, with one shim under each needle. As you can see, as the rpms climbed, the A/F continued to go rich. I suspect it went leaner at 7000, since I'd asked the dyno operator to cut the run at 7000, but this is only a guess on my part.

RPM A/F Ratio
3000 14.21
4000 13.07
5000 11.67
6000 10.90
7000 11.43

A couple of the long-time rejetters suggested I drop my mains to 122s or 120s, and remove the shim. To date, I dropped to 122 mains. Bike runs better. No dyno run to support this statement. I do have a set of 120s I may install, just for 'butt dyno' comparison ... not always accurate, unfortunately. I will first remove the shims.

Check my signature and you can see how my 790 is configured.

Bob

__________________
2003 T100 (790cc) Lucifer Org and Silv: 122/42 jets, TORs, 17T, UNI filter, no AI, Polaris bellmouth, Metzeler ME880 tires, Progressive 440 shocks (105/150 springs),11-1126 fork springs, gaiters, MotoTwin low bars, 6024 lamp, htd grips, 12v outlet.

uzidzit

make sure you have the needle you think you have(nagb), and ditch the 18 tooth countersprocket, that is were the low rev. lack of guts is coming from. the hardest pulling least flat setup I had was, D&Ds, uni, 2 shims, nagb needle, 42 pilots, 135 mains, snorkel out, restrictor plate IN, 17t counter, 44T rear. this set up had no flat spots and started perfectly, idled well, and warmed up fast.

I have never had idle problems, rember RE-BALANCE the carbs after any carb work!

Currently I am running the D&Ds, no restrictor, uni, airbox, nbtz needle, .5mm shim, 125 mains, 40 pilots, about 3 1/2 turns out, 17/43, 3mm air hole, softer slide spring. this is just a little mushy below 2,000 but the 790 doesn't make power that low any way. My last dyno slip has this setup at 12.9-14.0 from idle to the rev limiter, ps I run stock ignition, and cheap ngk plugs.

I would not worry with power, until the suspension and brakes were up graded esp the front end suspension, treat yourself and raise the front tubes about 15mm, you will like the difference.

__________________
"Peter, It seems like you have been missing a lot of work recently, well Bob I wouldn't say that I've been missing it"
ENOUGH, go out and ride!

mikeinva

Most of the time you have a lag its because you are to lean you might try a shim to get it to open up alittle quicker.What pipes are you running? If the shim helps it take off and you are runing stock pipes you may want to try a 115 main you might be to rich on top.The only real way to get main jet size right is to get it dynoed with a sniffer.
The 18t wont hurt a thing dont let anyone tell you it will.
The AI dont help it run any better it just puts air in the head at the ex port and makes pipes blue and ex pop.
If when you adj the idle mix screws you can hear eng. change you are prob. ok on the pilot all though with stock pipes stock pilots would be ok
You should get carb balance stright after any carb work every thing you do could change it.

__________________
Why do I feel young on my bike

DharmaLion

Thanks for the advice. It runs fine now at 125/42 with TORS and 2.5 turns out. the Jenks tuning notes say to shim, but not by how much, .5mm? I have a foam unifilter, rubber velocity stack and it pulls pretty good all the way to full open.

Here's a question, with the stock 05 Bonnie 790 needle in, what is the effect of shimming? More fuel at what point in the band??

On various posts Ive read, not to shim with 18 tooth front, or when riding two up.

Thx!
Dean

Bottle_Fed

Dean, a word of advice. If you are happy with the performance, leave it the way that it is. If you want an "optimum" setup, bring it to a dyno to find out what your af ratio is doing. You will drive yourself nucking futs trying to get it spot on without a dyno.

Greg

__________________
2001 Black Bonneville 1200cc "High Tuned Son-of-a-Bitch!"


Bored, Stroked, and Injected!
Life always gets better after a few gears and a shot of nitrous....

DharmaLion

Gotcha.
Thanks