Need jetting suggestion; data is included.

K

Kframe

Street Tracker
My Bonneville ('07) has been running pretty well, but I've known for awhile that it's not quite on with the jetting.
I haven't had time to mess with it, so to keep myself sane I have had a sock over the AF gauge for awhile.

Today, 62°F and calm, elevation 1000 feet, I pulled the sock off, took some visual readings and these are my results:

Idle 1000rpms = 13.5
1/8 throttle at 65 mph and 4000 rpms = ~12.2
1/4 throttle about 70 and about 4400 = ~12.7-12.8
WFO from 40mph to up over 100mph 13.9-14

Main DJ-124 (= K132.5)
Pilot K42
IMS screws 1/2 turn out
Needle is the stock NBTZ (aka 'Thruxton needle')

My assessment is that I'm a bit rich at cruising speeds when the throttle is barely open - and I'm a bit lean at WFO.

I've got the smaller 40 pilots, and I have various mains from K115 to K145.

Would you:
A) Leave it, it's close enough.
B) Decrease the pilot size.
C) Increase the main.
D) B & C

I probably won't have time to try this right now (mid terms next week :crazy: ) but I'd like to hear your suggestions and reasoning.

Thanks!
:wave:
-K
 
PieMan

PieMan

Two Stroke
Keihin 138 mains should get you close WOT. If you put the 40 pilots in for leaner cruise, then the mains will need to go to 140 or 142's. This will keep WOT on the mark and cruise will most likely be 14:1 ish AFR.
 
A

Aussie_T100

Banned
Dropping back to 40 pilot jets will probably go a long way towards fixing the richness at 1/8th & 1/4 throttle, you'd need to re-adjust pilot screws of course. Increasing the main jet a couple of sizes should solve the leanness at WOT and once you've got the mains sorted you can figure out what needs to be done with the needles to get it right in the 1/4 to 3/4 throttle range.

Mains then needles then pilots is the way it should be done. If you have a set of Dynojet needles they offer more adjust-ability but they should be fitted before doing your mains not after.

Having an A/F gauge makes it a lot easier.

Edit: I see the master has spoken while I was posting - he'll fix you up for sure.
 
K

Kframe

Street Tracker
Thanks for the replies.

I used to have DJ needles in there, but was having weird issues.
On clip position 3 (from the top) it was running very rich, 11-12 at cruise.
On clip 2, it was so lean I had trouble pulling away from my driveway.
I put a 0.5mm shim in, and then it would cruise around 14.5 or more.

After I put the stock needle back in, I'm between 12 and 14 everywhere, so I know I'm getting close.

The AF gauge needle wavers much less with the stock needle than with the DJ, I don't know if that's just my imagination though.

I think, when I get a chance, I'll take out the '132.5's' and put in K135's.
Probably won't swap out the pilot at that time though, I like to make one change at a time and judge the effect.
If that enrichens the 3/4 to WFO to about right, then I'll put the 40's in.
If that leans out the cruise, and the WFO a bit, then I can go up to 137.5's.

You've been a lot of help thinking me through this, thanks!
-K
 
You must log in or register to reply here.
Top