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Discussion Starter #1 (Edited)
I've had some more time to ride and use the P700 for firewood chores than usual and I thought I'd revisit some of modifications and settings on my P700. I'm sharing my findings, hopefully it's not old news, and looking for some fine tuning tips!

2004 P700
Mods that affect jetting:
Napa 7335 air box hose mod and a 3" intake tube on the right side of the intake box.
Big Gun full exhaust with race core.
Dyna CDI?
Fuel: ethanol free 90 octane
Elevation: 1900'-2000'

The original jetting that I ran for years was a 145 front and 148 rear keihin main jets with the needles shimmed out 0.074". The pilot screwes were tuned by ear according to NYROC's jetting guide. I always thought it ran pretty well with this setup, most of my riding was pretty wide open and higher speeds. It would occasionally stall coming down from a WOT run. Fast forward to pulling a trailer full of firewood and it was woefully apparent my jetting was off. It was loading up, stalling and generally running poor when creeping up steep hills pulling a load. I attempted to adjust the pilot screws which didn't help the situation. Time to revisit the shims on the needles.

Needle shim impressions
0.074" Too rich, stalls coming to stop.
0.065" Still too rich, loads up when pulling the trailer.
0.055" Mid-range felt better, finally getting somewhere with the shims. I thought it lost a bit of power up top though.

At this point I grabbed the wideband O2 sensor I had bought for getting my old car road tuned and figured I'd stuff it down the tailpipe and see what was going on.

145 front and 148 rear jets and the needles shimmed 0.055" afr's
Idle ~13.5
1/8-1/2 throttle ~10.5
1/2-WOT afr's went from 10.5> 13.5 I was only able to test up to ~45mph

The only area that looked ok to me was the idle. Everywhere else needed some drastic changes. My midrange was way too rich and I was lean up top. I did some searching on here about needle shims and others jetting sizes. I tried to find people who had used a wideband to jet their atv.

I was targeting WOT afr''s of ~12.5:1, a full point richer. I didn't really know how many jet sizes I would have to go up on the mains. But the percent change from 13.5 to 12.5 is ~7%. I found a jetting diameter chart on jets r us and calculated the area of each jet and chose jets that were ~7% bigger. This worked out to be 150 front and 152 rear jet. A jump in jet size equals ~ 3-3.5% in area, more fuel in theory. I would remove the shims due to the rich conditions they were causing. Bigger main jets with the same size needle should let more fuel in anyway.

150 front and 152 rear jets and the needles with no shims afr's
Idle ~13.5
1/8-1/2 throttle ~11.1 leaning out to ~12.2. ~11.1 at low speeds(5-20mph) and less throttle leaning out to ~12.2 to with more throttle and higher speeds(30-40mph)
1/2-WOT ~12.5-12.8 at 52mph. I occasionally saw a 13.0 flash on the gauge but it was mostly in the mid to high 12's.

I'm pretty happy with the results from changing the mains. I 'd like to lean out and even up my 1/8-1/2 throttle afr's. I'm not entirely sure how to do this? I took some measurements of the factory NAZH needle and sent it to jetsrus but they weren't able to cross reference it with anything. I know dynojet has an adjustable needle but I don't think I can purchase them separately, the whole kit is about $100. That's a waste to just use their needles to experiment with. I admittedly don't know how many turns out I am on the pilot screws. If I'm backed out around 2.5 turns is it possible that larger pilot jets with the screws turned in more would give me better control of the off idle afr?


Here's a picture of the spark plugs after riding around for a few weeks and doing some clutch work, WOT runs. The front plug is on the left and the rear on the right. I don't have the ability to monitor the afr's in each cylinder and I was concerned about overall eveness of the cylinders. The front cyclinder looks a touch leaner to me, I'm thinking of getting another 152 main and putting it up front. I'm debating bumping up to 152/155 jets just to be on the safer side of things but I think that will make my rich off idle and midrange worse.


TLDR: I need to lean out just off idle and my midrange, Im running the factory needles with no shims.
75190
 

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Add a shim back on the needles. If you go much over 0.045 (being two typical shims), it will be dumping fuel in at an idle.
Start by tuning the top end with the main jets, and work down from there. Ignore what the A/F ratio is saying, and try tuning by how it's running. Chasing the gauge for every RPM and throttle setting will give you fits.
 

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I just re-read your post........ if you have a second 3" opening in the airbox, it's going to jet more like the 12-hole airbox mod; you need to go considerably richer, or cover the 3" opening.
 

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Discussion Starter #4
I ordered a few more jets, 152, 155, 158 and 160. I'm hoping they get here for the weekend!
 

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The 158/160 may not be enough. If it's not, start taping over the 3" hole a little at a time.
 
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