Jetting Report (Part 2) And A Question

[Anonymous]

So I tweaked things from my initial settings to:

Mixture screws 2.5 turns out
Needles on 4th of 5 grooves (that is, second from bottom groove)
Mains still at 137.5

Ran much stronger this time. Very small bog off pilot onto needle when the throttle was opened suddenly from cruise to full. The bog was only noticeable in 5th gear, in the lower gears it just rips ahead without a noticeable bog. It will now almost lift the front in 1st and 2nd with a roll-on. Much better!

I also found that it will now pull through the misfire at 6000rpm in the lower gears and it ran pretty hard from 7500-9000 when it cleared. This is on a full throttle roll-on from low revs, whacking the throttle wide open at once and letting it rev out. The misfire is also less noticeable in 5th as well, which is leading me to think this is perhaps a carburation issue as well as soft coils. Ah, the joys of jetting...

Anyway, when it cleared above 7500 it ran pretty well to redline, but not as hard as I would expect it to, so I suspect I am still slightly lean on the mains. I am going to swing by my dealer and pick up some 140's at lunch and try them out tonight or tomorrow. I pulled one plug after last night's run and it was showing a more pleasing light tan color now, instead of the whitish residue I got from my first run. I want it one shade darker, but it is not bad at all, really.

So I tweaked the mixture screws to 3 turns out before riding to work this morning and it seems better again. Almost no popping on deceleration now and nice soft, smooth response to off-idle throttle changes. They were a bit abrupt previously.

Any other thoughts on my misfire/stumble/surging issue? I will change out the mains for 140's and report back on that in the next day or two.


Mark

 

[pano]

Your original settings;
Kerker 4-1 canister pipe
Pod filters
Stock carbs
137.5 main jets
47.5 pilots (stock size)
Stock needles in #3 of 5 clip position
Mixture screws at 2 1/4 turns out
Cams degreed to 110/109 intake/exhaust lobe centers (stock settings)

So I tweaked things from my initial settings to:

Mixture screws 2.5 turns out
Needles on 4th of 5 grooves (that is, second from bottom groove)
Mains still at 137.5

I really don't have much to suggest technically since you seem pretty close. Here is what I have with the same bike:
V&H 4-1 canister pipe
K&N Pod filters
Stock carbs
DJ138 main jets (dynojet which are smaller than yours)
50 pilots (put these in this spring) need less choke now
Stock needles in #5 of 6 clip position (dynojet needle)
Mixture screws at 2.5 - 3.0 turns out
Cams degreed to 110/109 intake/exhaust lobe centers (stock settings)

My bike occaisionally coughs out of one carb for a very short while when warming up I need to re look at the mixture screw I think

With the stock pilots the bike needed full choke and took longer to warm up, with the size 50 it takes 1/2 choke and choke is off in about 1 to 1.5 minutes compared to about 5 minutes before. I thought I noticed a slight hesitation off idle but I could not seem to reproduce it regularly and it was so sublte I am not sure if I am looking for something.

When I was jetting, moving from the 3rd to 4th notch from the top on the needles took out an off idle sputter but introduced a flat spot at 3.5k-5k rpm and moving the needle to the 5th notch took the flat spot out.

It pulls well in all gears at all rpms, I have no flat spots or bogging. When I was on the high way on my last ride in 5th at WOT I did not think it was pulling as well as it could have although 1-3 and even 4 seem pretty strong. I haven't tried this year to power or snap a wheelie for comparison but I could never power the front end up with out using some clutch.

 

[Anonymous]

I really don't have much to suggest technically since you seem pretty close. Here is what I have with the same bike:

Having a comparison helps a lot.

With the stock pilots the bike needed full choke and took longer to warm up, with the size 50 it takes 1/2 choke and choke is off in about 1 to 1.5 minutes compared to about 5 minutes before.

With my mixture screws at 3 turns it started this morning after about 3 revolutions on full choke and needed choke for less than 30 seconds before it would idle on its own. This was in about -1C temps. Are you working in colder temps than that or not? I let it warm up a couple of minutes while I got my gear on and rode away with no issues at all. In my experience, that is not cold blooded at all. My ZX-9 is fussier than that...

When I was jetting, moving from the 3rd to 4th notch from the top on the needles took out an off idle sputter but introduced a flat spot at 3.5k-5k rpm and moving the needle to the 5th notch took the flat spot out.

That is great info to know. I am going to try the 140 mains first, but I will reserve lifting the needle one more notch if I have to. The stumble/misfire problem seems to be alleviated somewhat by jetting, so I am thinking it is either a carb hiccup at that rpm/throttle setting or a combination of being slightly lean there and the coils going. The lean mixture is harder to light and any ignition weakness will be shown up nicely...

I haven't tried this year to power or snap a wheelie for comparison but I could never power the front end up with out using some clutch.

It is close right now. If I sat up really straight and gave a good tug on the bars in first I think it would come up. When I get the mains and ignition sorted it should be no problem. I hope.


Mark