Carb Jetting 101: Terms, Tips and Jetting Theory

**Just-Tri-It** · 05-30-2008, 11:23 PM

I have a 85 Tri-z. It came with aftermarket pipes and performance piston and head and standard foam air filter. It has a 500 main jet and idles and revs pretty good. When I take off she goes fairly good but as I speed up and accelerate half way to 3/4, its starts sputtering real bad. I go into 2nd and easy accel. its good but as I get on it and it gets close to changing to third it sputters bad again. The needle is in middle position and air screw out about 3 turns. I have adjusted the screw some back and forth but it still doesnt take the sputtering out. Actually it makes it worse sometimes.
It had a 450 jet and at idle would sputtered hard when rev it. Couldn't ride at all. And no adjustment on screw or needle clip helped except worsened it.
The 500 made it idle a lots better but still if if take off and get on it good it will sputter bad.
Will changing the clip up or down help ar do I need to change to a different jet?
Are spark enhancer any help?

**Kintore** · 06-01-2008, 05:31 PM

Got it guys

178 main, and all the way lean needle clip, Runs like a raped ape now!

**oscarmayer** · 07-01-2008, 10:14 PM

if it's ok, i would liek to add 1 thing.
Learn to read your plugs. that is the single most important thing you can do. it will help you determine where you are int he tune and let you know if you need to ho bigger or smaller on jet sizes or even if your needle is in the wrong position.

but that part only comes in handy once you have learned how to jet and needle the carb.

**oscarmayer** · 07-01-2008, 10:19 PM

Originally Posted by sheeptender

I have a 85 Tri-z. It came with aftermarket pipes and performance piston and head and standard foam air filter. It has a 500 main jet and idles and revs pretty good. When I take off she goes fairly good but as I speed up and accelerate half way to 3/4, its starts sputtering real bad. I go into 2nd and easy accel. its good but as I get on it and it gets close to changing to third it sputters bad again. The needle is in middle position and air screw out about 3 turns. I have adjusted the screw some back and forth but it still doesnt take the sputtering out. Actually it makes it worse sometimes.
It had a 450 jet and at idle would sputtered hard when rev it. Couldn't ride at all. And no adjustment on screw or needle clip helped except worsened it.
The 500 made it idle a lots better but still if if take off and get on it good it will sputter bad.
Will changing the clip up or down help ar do I need to change to a different jet?
Are spark enhancer any help?

still sounds like it's breakign up at the top end. have you checked your plug gap or even change the plug?
you still may beed to change the jet to a bigger jet. what doe the plug look like ( use a new plug to test and check)

you can change the a/c on the idle and lower end by changing the needle clip. the lower the clip the richer it runs. the closer to the top edge the leaner it runs. so if your at the bottom, you may want to move it to the middle and then chagne jetting sizes to like a 525 jet (or something clsoe to that). once you get the top end settled down, then it's easier to set the idel area. the top end area is what will most certianly damage the bike motor, not the idle area.
also is this a 2 or 4 stroker? i am not that fimular withthe Z bikes. (i know tuning, but 2 and 4 have slight tweaks to help)
if it's a 2, make sure your running 35:1-40:1 fuel to oil.

**Hoosier_Daddy** · 07-23-2008, 01:19 AM

I've seen a few conflicting opinions in this thread. (maybe it was typos) So let me get it straight. If it bogs in the bottom end then pulls out of it when you get on the gas, it's lean right?

**tecat-z** · 07-23-2008, 01:35 AM

A bog right off of idle, or when the throttle is stabbed at low rpm's is almost always a lean condition. Raise needle one clip at a time. Remember, to raise the needle, lower the clip.

**Dammit!** · 07-23-2008, 10:14 AM

You have to adjust it too far in each diretion to hear the difference. It's really hard to describe the way these things sound in text. Being way too rich can make it stumble off idle. Being too lean it will bog and sound like it does when you forget to turn the gas on. I edited the original post a little bit to make it less confusing.

The name of the game is experimentation. Don't be afraid to mess with these things. Going too lean or too rich just long enough to hear it won't hurt anything.

**Hoosier_Daddy** · 07-23-2008, 03:19 PM

Ok, thanks guys.

**jims72** · 10-14-2008, 03:13 AM

I just did the top end on my 200x and noticed when it is first started it smokes a bit then once warmed up stops is this a sign of being too rich?I know briggs motors will smoke if too rich.

**Just-Tri-It** · 10-25-2008, 03:40 PM

I have a 85 Tri-z with after market pipe and oem muffler. I believe a Weisco piston is in it but not for sure as it came this way. It runs decent if you play with the throttle but taking off fast and then changing gears and stabbing it will cause major sputtering through all gears unless you ease off the throttle, and it clears up alot. It had a 500 main jet and I had a spare 450 so I placed it in it. It revs and idle better with the 450 but the wot and running thru gears with 1/2 or 3/4 to full makes its sputter badly. I have the clip all the way up allowing it to go down further in the carb and the idle screw is around 1/2 trun out for best performance . I thought the 450 would have made it bog at wot but basically its the same thing.
Any thoughts would be helpful.
Thanks

**Brad200X** · 11-02-2008, 12:59 PM

Somebody on this thread said this already I think: don't always assume that your
jetting is the problem. My bro messed with his carb for weeks to no avail. Turned
out that he bought two brand new plugs and they were both bad!

**Just-Tri-It** · 11-02-2008, 08:47 PM

Originally Posted by Brad200X

Somebody on this thread said this already I think: don't always assume that your
jetting is the problem. My bro messed with his carb for weeks to no avail. Turned
out that he bought two brand new plugs and they were both bad!

This is true. I went through 8 different jets before changing the coil and finding out that it was breaking down esp. after it warmed up. It has a 500 jet in it with after market piping and bored 40 over. Yet it kept acting like it was getting to much fuel. I worked my way down to a 400 to no avail. On a hunch and desperation I started looking at the electrical and changed the coil, went back to the 500 jet and now I have to grip the sides with my legs like I'm holding on to a bull to stay on the thang. If I'm not careful it will give a new meaning to bring a tree hugger. I took it for a test run and came back, got off and stayed off for a while til my nerves calmed down... and I own 3 of em!
But that article on checking the electrical came to mind and whaala...ZZZZZZZZZZZZZZZZZ's too dang fast.

So go on and

Just
TRI- IT!!!!

**Autophysn** · 12-03-2008, 03:11 AM

Hey

, just wanted to thank you for this thread bro, It has helped me tremendously

**3Razors** · 12-07-2008, 12:55 PM

Here is a link for 2 stroke plug chops:

http://www.dfn.com/benkaren/plugchop.html

**yooper1** · 01-06-2009, 12:38 AM

i have a 84 honda big red 200ES i had new rings and crank seals put in and ever since got it back going fouls plugs left and right. i cleaning the carb and i mean a good cleaning. i put the pilot screw back to 1 7/8 turns out and tried it still fouled plug jst not as fast so i tried moving the jet needle clip down one notch and fouled it so i moved it up on instead and fould seems like fouls faster after moving needle clip i am at a stand still because i i dont understand it because before i had the repairs done it ran like a top never had no probs and only had to change plugs on it maybe twice in many years if any one has any info for me that can help me i would greatly appreciate it wanna get the ol girl running again had to see her at the junk yard thanks

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