Yep another jetting/tuning thread

R

Robe338

Guest
So heres where im at:
04 bonneville black
TOR's
K&N pods
No air box
145 Main
40 pilot
Thrux needle
1 shim
2.5 - 2.75 turns (somewhere between the two)
No air injection

Heres how it runs:
starts good
Idles good
Runs awesome. all gears all rpms. No complaints.

Heres my concerns:
Really white plugs. Maybe a slight tan tint very faint if it is.

I started it up this morning. Choke on. Warming up. I went back out side to check on it and the first six or so inches of the the headers were glowing red.

Seems to me it needs to be a bit richer. Ive tried a 148 main. It ran like crap all rpms. I tried two shims not any better.

Ive searched and im not sure what to try next.

Any suggestions or thoughts on things I might have missed?
 
bluesforchallah

bluesforchallah

Rocker
You said you were warming it up while you went inside. How long were you letting it warm up with the choke on? I only run mine for a minute or two. Then cut the choke.
 
R

Robe338

Guest
Three to five minutes maybe. Long enough to get my gear out of the house.

Think it idling on the choke too long would have caused the glowing pipes?

Ive done it before and never noticed them glowing (before air box removal).

Ive rode it twice since the air box removal. It warmed up 2 - 5 min with the choke on. I didnt notice the glowing pipes but it wasnt dark out either.

The glowing pipes made me second guess riding to work today. I was suprised to see it like that with it running so good.

Thanks for the input.
 
bluesforchallah

bluesforchallah

Rocker
Just a suggestion... I've heard you don't want to leave these engines running at a stand still for very long. You gotta get some air moving across those fins.

Also, according to this link, plugs Light brown, tan or grey firing end are good indicators that the plug is functioning correctly and general engine conditions are good.

http://www.spark-plugs.co.uk/pages/technical/diagnosis.htm

However, if the plugs are really white, it could be an indication that it's running too hot.
 
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BlueJ

BlueJ

Blue Haired Freak
Robe338 said:
So heres where im at:
04 bonneville black
TOR's
K&N pods
No air box
145 Main
40 pilot
Thrux needle
1 shim
2.5 - 2.75 turns (somewhere between the two)
No air injection

Heres how it runs:
starts good
Idles good
Runs awesome. all gears all rpms. No complaints.

Heres my concerns:
Really white plugs. Maybe a slight tan tint very faint if it is.

I started it up this morning. Choke on. Warming up. I went back out side to check on it and the first six or so inches of the the headers were glowing red.

Seems to me it needs to be a bit richer. Ive tried a 148 main. It ran like crap all rpms. I tried two shims not any better.

Ive searched and im not sure what to try next.

Any suggestions or thoughts on things I might have missed?
Click to expand...

Yep. You forgot the pilots. At idle, that's all there is in play. Mains are for WOT, and shims are for midrange. Go up to 42 on the pilots and you should be fine. And yes glowing headers on stock pilots with free flowing pipes is not unheard of. Definitely lean at idle. My opinion is that you're dangerously lean but opinions vary on the danger part.
 
R

Robe338

Guest
Thanks for the input everyone.

Ive heard to not let them run for too long at a stand still also. I didnt think the amount of time it sat warming up was that long.

Ive got 42 pilots on order. When I saw glowing pipes I was thinking bad lean. Doing some searching I though 40 would have been ok. Ill try the 42 and see what happens.
 
R

Robe338

Guest
So ive finally got around to test riding with the 42 pilots. No more glowing pipes. It does seem a bit sluggist when accelerating from a cruising speed (like passing another vehicle). Plugs still seem a bit off white or very light tan. Overall runs good.
 
T

Trinorman

Scooter
Robe338 said:
It does seem a bit sluggist when accelerating from a cruising speed (like passing another vehicle).
Click to expand...

How many turns out are your mixture screws? Are they the same as when you had your 40 pilots in? if so, try turning them in maybe a half turn at a time to see if that eliminates the sluggishness.

Letting your Bonneville, or any air cooled engine, idle for more than a few minutes is asking for trouble. As mentioned before air cooled engines need moving air to cool them and the only way that happens is if you are riding. How long would you be comfortable idling your car engine if you had no coolant in the system?

Chris
 
BlueJ

BlueJ

Blue Haired Freak
I was going to suggest turning in the screws (certainly you should have done it anyway when going to the bigger pilots), but the sluggishenss from the OP sounds like it's under heavy throttle (passing at highway speeds), so is more likely mains at that point.

But, yes, you need to turn those screws in a bit - potentially one or more full turns from where they were if you went from 40 to 42.
 
dschief

dschief

750cc
Going bigger on the pilot means the main mixture is now richer too. It is all additive on the top end, go with a smaller main.
 
dschief

dschief

750cc
Ok, I gotcha now. He should be able to drop a size or (maybe) two on the main with the Thruxton needles, compared to using stock needles. Like I said before, fatter on the bottom and middle make it fatter on the top. The circuits are cumulative.
 
BlueJ

BlueJ

Blue Haired Freak
dschief said:
Like I said before, fatter on the bottom and middle make it fatter on the top. The circuits are cumulative.
Click to expand...

I'm not sure about that, Chief. Jenk's Tuning guide doesn't say anything about that at all, and they've got a plot that shows at what fraction of WOT the different parts of the circuits are in play. In fact, they (and Haynes, and other sources) say you should sort out your main FIRST, to get WOT working right, and only then go down and futz with the pilots and potentially shims. If it really did all add up then changing the pilots would eff up the mains. That's also not my personal experience - I've adjusted pilots and shims and only found a difference at the very low end and mid-range, respectively, with no impact on how it felt at WOT.
 
dschief

dschief

750cc
Actually, if you look at the Jenks Bolts chart (top of page 10), the recommended main and pilot jets for stock needles are bigger than those recommended for the same setup with Thruxton needles. The circuits are not cut off as you open the throttle, they roll together.
 
BlueJ

BlueJ

Blue Haired Freak
That's because if you look at the graph on the middle of page 5 you'll see that the *taper* of the needle and the needle diameter have an influence across the board. But the needle isn't a jet. That same graph shows that the pilot jet stops playing a role before 1/4 WOT, and the main jet doesn't even start playing a role until after 1/2 WOT.

The original conversation was about whether or not you had to change the mains just because he changed the pilots (not).

The very same chart on page 10 shows, for stock needle *or* thrux needle, that as you open up the airbox/exhaust, you need a bigger and bigger main jet even though their recommended pilot didn't change.

And on page 9 it clearly states, first do the mains, then adjust the needle (which means adjusting the clip or adding or removing shims), then look at the float setting, THEN deal with the pilots. And in the section about the pilots, it even says if you have to move the pilot screw more than 2 turns you should put it back where it was, get new pilot jets (either bigger or smaller depending on which way you turned the screw), and continue your pilot adjustment. At no point does it then say, "go back and re-do the mains to take into account the new pilots." It does however say (on p.12) that if you adjust the mains or needle, you will need to adjust the pilot screws.

Bottom line? It's complicated. :) And to be sure there is some interaction between all the components, but my own experience supports Jenks - start with the mains and work backward to get the best performance.
 
dschief

dschief

750cc
I'm not arguing the procedure, in fact the reason we got on this subject was he did change the pilot, and it got blubbery on the top. If the Main was borderline rich, the larger pilot might have pushed it over the top of being too rich, they do interact: allow me to show you all the Mikuni VM jets I have in my drawer! Hahahaha.........
 
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