more on MPG & carb settings

alisch80 at alisch80 at
Tue Jan 15 15:53:12 PST 2008

Ditto everything Steve wrote plus: 
1) If you get the Dyno Jet carb kit (or any others I thinks) DON'T use the
diaphragm springs included.  Just reuse your stock diaphragm springs.  The kit
springs are too light letting the slide open too fast resulting in a major bog
when the throttle is opened. 

2)  I have had very good performance using the #38 pilot jets.  I have the stock
air box, Dyno-Jet kit with #108 mains and the clip in the middle groove, stock
engine, V&H exhaust with louder baffle and I consistently get high 40s mpg.  The
#38s will almost eliminate the lean flat spot around 3-4k rpm without hurting

Art in DM 

----------------------  Original Message:  ---------------------
From:    "Steve Northrop" <blackgpz at>
To:      <gpzlist at>
Subject: Re: more on MPG & carb settings
Date:    Tue, 15 Jan 2008 22:57:18 +0000

>      Bill, do you know what brand jet kit? It's important for the main jet 
> size. Do you still have the stock airbox or pods? If he put in what I think 
> he put in, NONE of which is available in a standard jet kit for the GPZ, you 
> are very, very, very rich. I'm surprised Hugo Chavez hasn't sent you a 
> personal thank you note. The 35 slow refers to a #35 pilot jet, which is the 
> stock pilot jet. If he put in a #40 pilot jet, you are extremely rich in the 
> 0-4000 rpm range. In my bored out, 12:1, ZX11 cammed, pod filtered motor, I 
> only use a #38 pilot @ 1 1/2 turns out on the mixture screws. A #40 pilot at 
> 2 turns is way too much. If he gave you the #35 pilot jets back, you need to 
> put them back in, especially if you have the stock airbox, and set the 
> mixture screws at 3 turns out. Now for the main jet (150 main). If it is a 
> Keihin/Factory Pro main jet, a #150 is way too rich. Again as a reference, 
> in my highly modified motor, I only use a #140 main jet. The jet size 
> numbers don't cross reference exactly between the Keihin/FP and Dynojet 
> mainjets but a #150 would still be too large. The Dynojet main jet they 
> supply in their Stage 1 kit to be used with the stock airbox and a 
> performance exhaust is a #108. This makes you very rich in the 7500-11000 
> rpm range. There is no mention of replacing the needles or even shimming 
> them for proper mid-range (4000-7500 rpm) fueling. So, you're very rich on 
> the bottom and the top and probably lean in the middle. No wonder it runs 
> like crap. I suspect your bike was re-jetted with whatever they had laying 
> around, certainly not with a kit specifically for the GPZ. No kits for the 
> GPZ are supplied with pilot jets (you must purchase them separately) and no 
> kit has 150 main jets in it. The biggest main jet supplied with Factory 
> Pro's Stage 3 kit for the GPZ is a 142.
>      Alas, all is not lost. If memory serves me correctly, you have a 
> performance exhaust and the stock airbox. Keep your eyes open for a Dynojet 
> Stage 1 jet kit on ebay, it works very well for your configuration. If you 
> didn't get the #35 pilot jets back, go here and 
> buy four of them for a Keihin CVK carburetor. When you feel up to it, I'll 
> walk you through installing the kit. It is not difficult at all, the hardest 
> part is getting the carb rack on and off the bike. You've learned the hard 
> way and I will reiterate it for everyone else's benefit here: YOU CANNOT 
>      Bill, don't give up your GPZ for a $100 worth of parts and a couple 
> hours of your time. It'll run good again, really it will.
> Steve in Western NY
> '96 GPZ1100
> '02 Daytona 955i
> '08 KLR 650
> "You Can't Fix Stupid", Ron White
> ----- Original Message ----- 
> From: "Bill Magitz" <corbie at>
> To: <gpzlist at>
> Sent: Tuesday, January 15, 2008 4:01 PM
> Subject: more on MPG & carb settings
> after reading the recent postings on mpg/miles per tankful I found out what 
> I already knew, my GPZ is not well. I had a jet kit installed and after a 
> few stops at mc shops I got it close but not to my liking. I get about 
> 110-120 miles before I hit reserve ( mild riding , hitting the throttle will 
> yield less than 100 mile tankful ) which is @40 less than before jet kit and 
> tinkering which translates to 10-15 mpg less. also I'm spewing some serious 
> fumes wherever I go. see if this makes sense to anybody , the last mechanic 
> who set the carbs wrote this on the work order ,  35 slow 40 slow 150 main 
> and 2 turns out on mixture , I'm to the point if I can't fix I won't keep 
> it. will the proper setting help me get the mileage I desire ?  thanks much 
> to anybody who can pass info on, the GPZ is a blast to ride and I'd prefer 
> to keep it and upgrade the Intruder 700.   --bill m  in joisey still getting 
> out on the weekends !!!!
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