Why a 165 main jet and 38 pilot jet?

A reference for the PWK carbs...
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sthutch
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Why a 165 main jet and 38 pilot jet?

Post by sthutch »

Hello all,
Just finished jetting for the first time. Followed the guide and it worked like a charm. I was surprised to go so lean on the pilot jet and so rich on the main jet. Any ideas as to why? Here are the specifics

Year: 2001
Model: KDX 200
Riding Altitude: 600'-900', 50F-90F, Central and Northern Michigan
Mods: Top end rebuilt
Boyesen 607 Reeds
FMF Woods Gnarly
FMF Turbine Core 2
Mix: 32-1 Super M, 91 octane fuel
Pilot: 38
Main 165
Needle: 1st Clip, R1174K 2AFKG (stock needle)
Airscrew: 1.75 turns out

Notes:
-Just finished jetting today. 0 to 3/4's throttle is great, but 3/4 to full is not quite there yet. Lower end is crisp, smooth, and aggressive.
-Plug color is on the dark side of brown, but not black after high speed chop tests.

Sthutch
Sthutch

1st Bike: '72 Arctic Cat Whisker (rode it to the wheels fell off)
2nd Bike: '76 KT250 Trials (gone, but not forgotten)
3rd Bike: '01 KDX200
4th Bike: '96 DS80 (okay, my 9yr old's and it's gone)
5th Bike: '04 RM65 (okay, he's now 10 and it's gone)
6th Bike: '08 KTM 105xc (okay, he's now 13)
7th Bike: '06 KTM 200xc-w (okay, he's now 16)
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rbates9
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Post by rbates9 »

I would try going down to a 155 or a 152 main and see what that looks like. I might even try a lower clip on the needle after you drop the main.

Also check to make sure the fuel is getting to the carb like it should.
sthutch
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Post by sthutch »

rbates9,
I tried a 155 and it was nearly white, went to a 158 and it was more grey than brown, followed by the stock 160 which still was lighter than it should be. I jumped to the 165, skipping the 162, and got the dark side of brown.

I think I will go down one clip, as I didn't get the performance today that I think I did when I was on the second clip.

Sthutch
Sthutch

1st Bike: '72 Arctic Cat Whisker (rode it to the wheels fell off)
2nd Bike: '76 KT250 Trials (gone, but not forgotten)
3rd Bike: '01 KDX200
4th Bike: '96 DS80 (okay, my 9yr old's and it's gone)
5th Bike: '04 RM65 (okay, he's now 10 and it's gone)
6th Bike: '08 KTM 105xc (okay, he's now 13)
7th Bike: '06 KTM 200xc-w (okay, he's now 16)
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rbates9
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Post by rbates9 »

Every bike is different but it seems that a 165 is very rich. Ride it for awhile and see how dark the plug gets. If it's not running good with the 165, how is it with the smaller jets?
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scheckaet
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Post by scheckaet »

seems odd to have such a wide difference between pilot and main compared to every other jetting I've seen on this site.
Could it be an air leak on the main circuit or something?
sthutch
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Post by sthutch »

I am going to check the airboot next. What is the best way? I heard that Brake Cleaner sprayed on the boot will work. It causes the bike to lose RPMs. Anyone have experience with this process? Any other himts?
Sthutch

1st Bike: '72 Arctic Cat Whisker (rode it to the wheels fell off)
2nd Bike: '76 KT250 Trials (gone, but not forgotten)
3rd Bike: '01 KDX200
4th Bike: '96 DS80 (okay, my 9yr old's and it's gone)
5th Bike: '04 RM65 (okay, he's now 10 and it's gone)
6th Bike: '08 KTM 105xc (okay, he's now 13)
7th Bike: '06 KTM 200xc-w (okay, he's now 16)
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rbates9
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Post by rbates9 »

Yes if you spray anything flammable like starting fluid around the different joints you should see a noticeable rpm change if there is a leak. It should rev up a little but any change in rpm should be looked into.

When you cleaned the carb did you soak the carb body in any type of carb cleaner for any amount of time?
sthutch
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Post by sthutch »

I took it apart and just hit it hard with carb spray, in all the openings.
Sthutch

1st Bike: '72 Arctic Cat Whisker (rode it to the wheels fell off)
2nd Bike: '76 KT250 Trials (gone, but not forgotten)
3rd Bike: '01 KDX200
4th Bike: '96 DS80 (okay, my 9yr old's and it's gone)
5th Bike: '04 RM65 (okay, he's now 10 and it's gone)
6th Bike: '08 KTM 105xc (okay, he's now 13)
7th Bike: '06 KTM 200xc-w (okay, he's now 16)
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fuzzy
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Post by fuzzy »

Search on here for plug chops....When your main is perfect you can't really see the band without cutting the threads off the plug or using a plug scope (it will look white on the part you can see). You looking for a 1-2mm band of brown around the base of the insulator. The plug will turn a nice tan when put into service.
'91 KDX 200 Project $300 KDX
'95 KDX 200 Project $600 KDX
'94 WR 250 Always a project
sthutch
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Post by sthutch »

Started the bike up and sprayed Brake cleaner all around the carb, airboot, and intake. No change in RPMs so there doesn't appear to be any air leaks.

I put in a 20+ mile ride yesterday following my son and two of his buddies. The bike ran great, but still on the rich side. I am going to stick a 162 in it and see how it goes.
Sthutch

1st Bike: '72 Arctic Cat Whisker (rode it to the wheels fell off)
2nd Bike: '76 KT250 Trials (gone, but not forgotten)
3rd Bike: '01 KDX200
4th Bike: '96 DS80 (okay, my 9yr old's and it's gone)
5th Bike: '04 RM65 (okay, he's now 10 and it's gone)
6th Bike: '08 KTM 105xc (okay, he's now 13)
7th Bike: '06 KTM 200xc-w (okay, he's now 16)
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fuzzy
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Post by fuzzy »

I found some old threads on here that used to have pics of good plug chops. Googling found this....Just good pics of what you're after, and why your plug looked white(without cutting the threads off). You don't ahv eto be that anal, but you can likely go into the 150#'s on your main.
'91 KDX 200 Project $300 KDX
'95 KDX 200 Project $600 KDX
'94 WR 250 Always a project
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