My 00 Trailblazer spark plug is black with build up on it. Does this mean its running rich? Will leaning it out with the carb needle help? It has a 140 jet and the needle is set on the 4th notch from the top. It has NO low end power at all. Thanks.
PD

 

How old is the plug? Is it a brand new one that you put in just for checking the readings? Is it black on the tip of it or just near the threads?

If it is an old plug put a new one in it and take a full throttle run and shut it off then do another reading.

You can check out www.ngksparkplugs.com for plug reading tips...They have some pictures on the site which are very helpful.

As for the no low end power, yes that could be a jetting issue, but since the quad isn't brand new it's suspicious that this problem would suddenly appear. Did it appear after you modded it? If I remember right, stock jetting on those is a 130 main so upping it to a 140 with your pipes shouldn't make it too rich...did you drill any holes in your airbox or add a new high flow filter? If you did then 140 should be lean if anything, but I guess it depends on your elevation and weather.

Have you cleaned your carbs and your air filter lately? That can really make a difference.

Hope you figure out the problem.

-Josh

 

Before I would get into the carburetor , I think I would have a look at the secondary clutch , I suspect it may not be wound tight enough . I would check this first before getting into playing with the jets .

The jetting seems close , (maybe a notch off on needle and main size) .

A check of your compression would also be a wise idea . It should be around 120 lbs. With the mods you have listed , your machine should run great , there is something wrong other than jetting that is giving you grief .

Rick

 

Thanks for the advice. The plug only has a few hours on it, the carb is spotless, and the K/N is clean but the airbox is very modded so this thing is getting tons of air. Im at 4000ft elevation. Moved the needle clip to the second from the top of the needle, I have new plugs and will put one in it and do the reading. The jet thats in it is a 140. I have the HPD clutch, pipe and a K/N on it. After moving the clip the bike seemed more responsive but havent had a chance to ride it yet. Thanks for the help, tuning these carbs is tricky.
PD

 

Rick,
On the HPD clutch, I messed around with the weights. Thinking putting on lighter weigths, 55g, would help it wind up quicker. Well I put 58s back on it but have not ridden it yet. I think your right about the clutch, I didnt think about it. Any suggestions on the secondary spring would be great, this bike has NO bottom end whatsoever. Also, I will take a compression reading. Thanks.
PD