Jetting-couple questions and a guesstimate

[ridin434]

After reading through the jetting database, I think I have figured a few things out. From what I read, the stock main jet on 03-04 is 150, and 05-08 stock main is 130?

Ok, where I am standing right now I am unsure of where to start with new jets. Heres what I have:

2004 z434
cylinderworks big bore kit (nothing else done to compression ratio)
uni air filter
400ex intake boot to install tomorrow
dyno-jet kit, also install after the ex boot
hoping to remove the lid along with the boot install, and have jetting to match
stock carb-stock jets (150 main jet?)
stock exhaust

Now from what I have been reading, I should be starting my jetting at:

155 or 160 main jet
25 pilot
fuel screw, as talked about in the thread about the fuel screw
needle-This I know nothing about..

I have rebuilt engines, but never really taken apart a carb before, but this sounds like it is doable. Anybody else have some input on this?

Edit: where I stand now it runs pretty well, the plug is a nice brownish color. When I'm trail riding, and get down into the lower RPM's, in say 3rd gear, then punch it, it kinda stumbles before taking off. Other than that all kinds of power up top.

edit 2: It had NO stumble before the bore kit

[spize909]

If it dyno jet then go 160-165
25 pilot
Start at about 2.5 on the fuel.
The kit should have a needle and you should probably be on the 3rd clip.

This is where I was at with my stock carb before the FCR with similar mods but I had full exhaust and I just notice you are stock. Might want to start with 155 on the main...

This is assuming low elevation....you didn't include that info.

[grnenvy]

Do what he says and then put a full header a muffler on that bike. Made a huge diff on my bike. I would go with yoshi.

Originally Posted by spize909

If it dyno jet then go 160-165
25 pilot
Start at about 2.5 on the fuel.
The kit should have a needle and you should probably be on the 3rd clip.

This is where I was at with my stock carb before the FCR with similar mods but I had full exhaust and I just notice you are stock. Might want to start with 155 on the main...

This is assuming low elevation....you didn't include that info.

[ridin434]

Well I am in Central MN, elevation map I just looked at say about 1300 feet. It is in my plan to put a full system on the z, but I ended up spending all my money on rebuilding it and a few other goodies. Thanks for the input already. I would love to get a yoshi system, but I bought this wheeler for 1500 and already have almost 1000 more into it, so I am trying to pace myself with buying aftermarket stuff. Another reason I am hesitant on getting a pipe is noise-MN isn't too ATV friendly, and some places such as the Gilbert Rec Area in Northern MN check for dB. Some people have some pipes and say they are too quiet and some have some and say they are loud-and I have never even heard a pipe on a z haha even though I have owned two of them.

[ridin434]

Post from Crazie:

"Mikuni / Dynojet Size Comparison Chart

Mikuni--Dynojet
140-----149.3
150
142.5---152.0
145-----154.7
155
147.5---157.3
150-----160
152.5---162.7
165
155-----165.3
157.5---168.0
170
160-----170.7
162.5---173.3
175
165-----176.0
167.5---178.7
180
170-----181.3
172.5---184.0
185
175-----186.7
177.5---189.3
190
180-----192.0
182.5---194.7
195
185-----197.3
187.5---200
190-----202.7

A 140 Dynojet is going to leaner than your stock mikuni jet. I would go to the dealer and get a 147.5 or 150 Mikuni main. "

So with my stock Mikuni carb, I would have a Mikuni 150 jet, correct? Putting a Dyno Jet 160 in would be equal to that, so if I wanted to go richer on my fuel mixture, I would use a dynojet 160 or 165? I'm starting to figure carbs out I think

[spize909]

thought you already had the dynojet kit..........my main jet suggestions were dyno jets.

[ridin434]

Just put in the dynojet kit-haven't got the 400ex boot on yet because it seems like its really gonna be a tight fit, and I can't find a razor blade hahah. I put the dynojet 155 main in, and am messing with the fuel screw at the time. It is running really rich it seems, even with the air box lid off. Hoping that getting the new boot in will help lean it out some.

[spize909]

try the 150

[ridin434]

Alright I put a 150 in and it still feels weak and revs slow, feels like a big heavy 4x4 wheeler haha. I adjust the fuel screw, doesn't seem to really do anything different... Guess I should now try a 145 huh

[ridin434]

Ok, you guys have info about pilot jets... None came withy my dynojet kit..

I would advise anyone who is going to do any carb work to buy an adjustable fuel screw so you don't need to spin the carb a million times. So by turning the fuel screw in further, you are allowing less gas correct? I may have to put a 145 in....

[ridin434]

Ok, you guys have info about pilot jets... None came withy my dynojet kit..

I would advise anyone who is going to do any carb work to buy an adjustable fuel screw so you don't need to spin the carb a million times. So by turning the fuel screw in further, you are allowing less gas correct? I may have to put a 145 main in.... Starting to get sick of taking the carb apart

[ridin434]

Alright, I'm in need of some help here. I have the DJ 150 jet in, the needle is set to the third clip, and the fuel screw is turned out 2.5 turns, have a pretty big lack in power-its about 65 degrees here and dry at 1300ft elevation.

It seems if I went down to a DJ 145 that it would be around the same size as stock? I am just trying to tune this so I can run without a box lid now and my uni filter. Any suggestions?

[spize909]

Should run pretty good with the 150.......what does the dynojet instructions say to use with our mods?
Pilot jet shouldn't be an issue, going to a 25 just means less turns out on the screw and you'll need it the more you mod it anyway. I am by no means a jetting expert, just know what has worked for me on both Z's I own.

As for the fuel screw, I use a long screw gun tip. One of the one's that is 2" long. I had to grind it a little to get it narrow enough to fit but you can barely get your fingers in there and turn the screw with it.
I put some grip tape on the bottom half of it and marked it with a yellow paint pen to monitor turns.

[spize909]

or you can do this for the fuel screw
LTZ400 Adjustable Fuel Screw - Advantage Cycle LC - Indianola, Iowa

[ridin434]

I sat and stared at mine trying to figure out what tool to use, and was almost ready to cut a screwdriver in half. A screw-tip is a great idea. Now I won't have to loosen the boots and twist the carb over. The DJ instructions say to use a 146 for stage two. This is different then most people use it sounds, but I could give it a try. The jet kit I got starts at like 125 and goes up to 165 in increments of 5. It also says "for 03-04 suzuki ltz400"