Shimming stock needles changed lean spot rpm.

[Kratos]

:ummm:
I would like to thank everyone for guiding me to this point, but I still need carb help. Have an 07 Max with 2K on the clock. Everything is stock except for the below listed mods. I noticed after I installed the exhaust and air filter that it seemed to be running lean around 4K or so. After doing the Peashooter, Shotgun, taking apart and cleaning the carbs, and running Seafoam/Techron cleaner, although slightly less noticeable, the seemingly lean condition still existed at 4K. Checked all the rubber connections and diaphrams, everything looks to be OK. I finally decided to shim the stock needles. This seems to be the only change I?ve made that actually caused a result. The plugs or plug wires did not seem to make any difference. When I shimmed the needles with a washer that is the same size as the washer on top of the stock needle, the lean condition has moved to 3K ? 3.5K or so. The fuel screws were set to 3.5 turns out, I have changed them to 4 turns out but have not ridden it since I made that change. Will ride later this week to see if that helps. Anyone have any other suggestions?:confused2:

2007 Vmax
K&N Filter
Supertrapp slip-on exhaust with 8 discs and off road open end caps
Nology HotWires
E3 Diamond Fire spark plugs

 

[maleko89]

What are the symptoms? Does it cut out at full throttle at 3-3.5K? What did it do at 4K with stock needle position? Did you do the needle tests? 4K in 5th gear....count to 5 and then whack it to WOT. Any delay in aceleration and needle is rich. Now, 2K in 3rd gear. Do WOT. If it seems to lag in 4-5 range then needle is rich. Sputtering at 4500 or so and needle is lean.

 

[Kratos]

I haven't done the needle tests yet, will try when I ride later this week. Symptom seems to be that it is right on the edge of popping and crackling when holding at a constant speed/rpm in the range specified, used to be at 4K, now is at 3K-3.5K after shimming needles. I can hear it in the exhaust, it is smooth sounding at any other rpm, but changes at the specified rpm range. I forgot to mention that I did sync the carbs after putting them back on the bike.

 

[PATMAX]

Dang Kratos, any letter color BUT black dude. You're making me go blind before my time! PatMax.

 

[maleko89]

I haven't done the needle tests yet, will try when I ride later this week. Symptom seems to be that it is right on the edge of popping and crackling when holding at a constant speed/rpm in the range specified, used to be at 4K, now is at 3K-3.5K after shimming needles. I can hear it in the exhaust, it is smooth sounding at any other rpm, but changes at the specified rpm range. I forgot to mention that I did sync the carbs after putting them back on the bike.

Kratos, I think your shims are probably too thick. At most, they should be .024 inches thick. It sounds like you are pretty close. Probably just an idle screw adjustment and/or PFJ2 reduction.

 

[Kratos]

Sorry PATMAX, I'll watch my letter coloring next time.

 

[Kratos]

I think I had seen it on here, but don't remember. Where can I find a washer of that specific size. I looked at Home Depot, and found nothing. I found the washers I used at a local True Value hardware store, but they did not have anything thinner.

 

[PATMAX]

Check out "Paul's Precision Shim Kits" by google or email him at [email protected] 30 bucks and free shipping to VMOA members.

 

[maleko89]

I got mine here: Shim Kits!

It's a bit pricey but making your own is a pain in the ass. If you do want to go that route the 1/2 clip shims are about .013 inches and the 3/4 clips are .0195 inches thick.

 

[Kratos]

Great, thanks for the info and the link!

 

[Kratos]

Just measured the washers I got from True Value, they are slightly thicker at .028 inches.

 

[Kratos]

The lean spot a 3K - 3.5K is all but gone now, seems if I could turn the mixture screws out another 1/4 - 1/2 turn or so, it would be gone completely. They are already set at 4 turns out, how much is too far before other changes should be made? Now that it seems my carb issue wasn't due to carb cleanliness, would I be able to squeeze any more power out of the bike by going down in main jet size? I've seen that some have gone down to a 147.5, I think. Did the needle tests and there is no hesitation going WOT from 4K in 5th gear, there is a very, very slight spot at around 4K when going WOT at 2K in 3rd gear, probably due to the washers being slightly too large. For now I am happy, but would like to get it dialed in, and of course add some more ponies if possible.

 

[gamorg02]

no way an expert on any of this, but would the open end supertrapps affect any of this? It basically negates the idea of disks eh?

 

[Kratos]

Well, since the end cap's opening is smaller than the inside diameter of the discs, there would still be some back pressure from the turbulence of the air between the end of the baffle and the end cap since the exhaust has to be forced out the smaller diameter hole in the end cap. At least that's my logic, and I am in no way an expert either. I would think that it would flow much better than having solid end caps, although there may be a loss in torque but a gain in horsepower in the higher rpm.