Gpz 550 Jetting Suggestions

I have an '81 Gpz 550 with a Mac 4-1 Exhaust and Uni pods filters. I also purchased the dynojet kit corresponding with this bike. What do you recommend as far as main jet size and needle position to start? They recommend 98s and the third position, but I wasn't sure if anybody has already had experience with this? Also Is the removal of the air plugs necessary. Are those on the "intake" side of the carbs where air would be drawn in? Are the plugs located on the other side of the carb as the mixture screw adjustment?

Thanks,
Nate

My best suggestion is to follow their guidelines and go from there. I am sure a few of these guys have had some dynojet experience. If I remember right they want you to start your needle off in the 3rd clip, then do the testing.

I've never worked on slide carbs like these before so how do you remove the "throttle bodies" or whatever they're called from the rest of the carb assembly to remove the needles?

I just installed a K&N jet kit in my KZ550 last week ,, It took me awhile to understand the instructions at first ,, To get the Slides out you need to take off the carb tops then take the two small screws out down inside on top of the slide ,, real small screw driver needed for this one ,, once they are out the lever system comes out then you can slide out the slides to replace the needles,, The drill is used to uncover the air screws ,, they have plugs over them.. There was a chart in the instructions as to how many turns out to make the air screws as a start ,, :huh:

I own a couple 81 KZ 550 D1 (gpz).

One has had a 4-1 Kerker with Uni pods and the Dyno jet kit. I experimented with different jetting and clip adjustments. The best setup was 98 main with the clip in the third groove from the top. Mixture screws were about 1 to 1.25 turns out. (they are air-only screws)
It gave better power on the highway at high speed, but low speed torque dropped a little. I live in a city with a lot of traffic so I need the low end.

I put the air-box back on. With an airbox and stock filter with 4-1 kerker, I used a 96.5 main jet. The mixture screws were 1.25 turns out.

I also have another D1 which had the same Kerker and stock airbox, filter, jetting (94) and needles. With this setup, it seemed just right. The Kerker didn't require rejetting. The plugs looked light tan and the bike hauled ass, but I didn't have the EGA to see the real details. I later put on a Mac 4-1 with stock airbox and stock Kawasaki needle. The Mac seems to flow a little more than the Kerker. The mixture was definitely too lean. I put in 96.5 main jets and put in an adjustable version of the stock needle and lowered the clip one groove (two grooves was way too much). The air screws were about 1 turn out. This was way better, but it still takes awhile to warm up (I'm sure you love the choke setup, heh), so I'll probably try 98's and maybe even spring for another Dynojet kit for the needle.

The Dynojet needle has a very different profile from the stock one.

These settings were found using the Dynojet procedure (the one that comes with the kit), but I also used an EGA to verify them.

There were no air-plugs to remove. The drill bit was meant for removing the seals that are supposedly on the mixture screws. I've worked on many 550 D1's and have never seen the seals in place. Everyone must have taken them off after buying the bikes (or maybe the dealers removed them to tune in better idles).

My suggestion, which is mostly a guesstimate, would be 98 mains, needle in third groove from top, maybe 4th. I don't like using shims on the needles because they lock the needles and they can't wiggle in the hole. This leads to abbrasion on the side of the needle if it's not perfectly aligned. Air screws probably 1.25 to 1.5 turns out. All this, of course, along with setting fuel levels and balancing carbs. If the screws are more than a half a turn different from each other, then you need to find out why.

On my website:
www.geocities.com/loudgpz
you'll find a mod for the choke to make it more controllable.
You'll also find a program that compares the three needles available for these carbs (stock single-groove Kawasaki, adjustable 5-groove Kawasaki, and the Dynojet). There's also a lot of ignition and charging system stuff.

Post edited by: loudhvx, at: 2006/03/02 00:20