dyno jet kit

[DannyB]

i have a dyno jet kit in my carbs on my xj. i have the 138 main jets that came with the stage three kit. i am have problems getting the bike tuned and i am only getting 22 to 24 mpg. i used the information giving in here to figure out that with the mods done to the bike i should be using 122.5 main jets. i dont understand why dyno jet would put the jets in the kit if they are WAY to big. am i doing the math wrong? i have a 4-1 header and k&n pods. i was also wondering why the xs has bigger main jets then the xj.

[natemoen]

Dyno jet had a different numbering for their jets the Mikuni does, dont ask me how its different cause I dont know I just know is different. 24 MPG is pretty low even for this bike! Dyno jet expects that you will know what kit to order for you bike so they just have the kits pre packages, its the person buying the kits that needs to know what they need in order to get the right jets.

On another note. Put the year and model of your xs in your signature line. different year xs's have different jetting so then its easier to give you year specific advice!

[TomRodgers]

Check your plugs....that low of mpg my guess is your plugs are damn near black.......on the plus side, you wont be running lean that way

On 'Sunshine i have a good plug color with the setup in my signature... im going to experiment on 'ghost' with larger mains and see what happens...

[tinman905]

I have never seen anyone who needed to use the stage 3 kit of the Dyno jet kits on a stock bike with just a 4 into 1 and pods(But that just here where I am) If your engine is stock I would try the #128's make sure your float levels are correct ,idle screws are out 4 to 4 1/4 turns and then have a look at your plugs after taking it out for a good run.

In my case I went to #128 main jets with a Mac 4 into 2 with pods and my plugs looked good but when I put my bike on the dyno I was running rich the #124 mains were right on for my set up. I am at 1800ft above sea level with my set up .

With the low gas mileage you are getting I would think you have other issues besides going too big on your main jets. What was your gas mileage with your stock carbs?

Clean your carbs check you float heights if that hasn't been done in a while.

[DannyB]

plugs looked ok. just went on a 500 mile ride, header turned black, riders behind me reported smelling gas. i have never rode bike with stock carbs. got bike in a basket and a few cardboard boxes. the slides are drilled out for the stage 3 kits will they still function correctly with smaller jets? or is this done for the needles that come in this kit?

[crazy steve]

... I was also wondering why the xs has bigger main jets than the xj...

The different years of XS/XJ carbs aren't the same internally, as well as having different ignition curves, cams, etc, so that's why the different jetting. Emission standards changed over the years also. Due to the carb changes, you want to stay close to the jetting that came in the carbs, not the motor.

Dynojet.... hmmm. I've seen any number of people use these over the years, and while some folks love 'em, many more have had nothing but problems with them. I'm not a fan, as the one bike that I owned that had one (installed by PO) never did run right until I removed the kit. If the slides have been drilled, 'fixing' them can be expensive. And nate is correct, their jet numbering system is entirely different from OEM. And IIRC, you can only use their jets, as OEM won't fit...

'78E original owner

[tinman905]

plugs looked ok. just went on a 500 mile ride, header turned black, riders behind me reported smelling gas. i have never rode bike with stock carbs. got bike in a basket and a few cardboard boxes. the slides are drilled out for the stage 3 kits will they still function correctly with smaller jets? or is this done for the needles that come in this kit?

Carb slides are drilled when you install a Dyno jet kit , stage one is just the #124 and #128 jets, stage 3 is with #138 jets. So it's not a problem as for drilled slides. You might want to check if the proper air jets (#190) are installed at the back of the carbs or the filter side.

Dyno Jets mains are the same as small Mikuni main or air jets but the number to jet size are different.

Anyway if using #138 jets is too rich it would not affect your gas mileage that much. You are about 12 to 18 mpg lower than you should be .

If your carbs are stock for XJ they should have the drain screw on the side of the bowls. There is a drain on the bottom or the bowls if you put a clear tube over the drain nipple you can see where your fuel level is by putting the clear tube up against the side of your carb bowls, the fuel in the clear tube will rise to the level inside the bowl. Make sure your bike/carbs are in a level position.

[petejw]

im running a dj kit in my 81,
i also found the 138 main jet was to big,
you could try the 128 mains, i didnt end up
using the 190 air jets, i found that these jets
caused flat acceleration so i left the stock air jets,
readjusted my float levels, im running 1 and half turns
out on the mixture screw.

from memory the stock main jets are the same for the xs
and xj 110, i think the pilots are 47.5 and the air jets are 210?
compared to 142.5 pilots and 185 air jets.

if that is the case i wouldnt use the air jets that came with
the dj kit, just the needles and main jets.

what position have you got the clip for the needles in?

[tinman905]

im running a dj kit in my 81,
i also found the 138 main jet was to big,
you could try the 128 mains, i didnt end up
using the 190 air jets, i found that these jets
caused flat acceleration so i left the stock air jets,
readjusted my float levels, im running 1 and half turns
out on the mixture screw.

from memory the stock main jets are the same for the xs
and xj 110, i think the pilots are 47.5 and the air jets are 210?
compared to 142.5 pilots and 185 air jets.

if that is the case i wouldnt use the air jets that came with
the dj kit, just the needles and main jets.

what position have you got the clip for the needles in?

XJ's have 112.5 mains ,47.5 pilot jets and 170 air jets or at least the ones in North America did.