16 Tooth Sprocket + Needle Shim Combo = spark plug fouler?

[Canuck]

In reference too... (16 Tooth Sprocket + Needle Shim Combo)

Hey I was just curious if anyone else who has these 2 specific mods done to their GZ.

And if so...did you find that it seems to go through the spark plug quicker and if there is a rational explanation behind all this?

Also with these two mods should I also adjust the lower screw on the GZ's Carburator( some owners have a brass plug preventing direct access to this adjustment)
In addition to this once access is gained should you increase the numbers of turns or decrease and by how much ?

Thanks everyone

[Canuck]

by go through the spark plug i mean quickly fouling....smokey grey film/deposit covering the plug and also seemingly increased clearance from the normal space between the plugs end

[mr. softie]

I have the 16 tooth sprocket and I have done the needle shim mod, and I have had no problem with the plug that I know of. The bike is running so well I have not checked the plug since I installed it about 2000 miles ago.

I have adjusted the screw on the bottom of the carb to give the best idle. It is called the Pilot Screw or Fuel Screw. It controls the amount of fuel entering the intake at idle to about 1/4 throttle. Mine seems to run best at 2-1/4 turns out, but each bike is different. Turning it in decreases the amount of fuel, out increases the amount of fuel.

Here is one procedure that works:

1) Warm up the engine to full operating temp.
2) Turn up your idle a few hundred RPM using the throttle stop screw (basically you want a fast idle). This will make it easier to hear small changes in RPM.

Each time you change the screw setting 1/4 or 1/2 turn or so, wait about 5 seconds to let the idle speed normalize. It usually take the carb and engine a moment to react to the change.

3) Turn the fuel screw IN until the idle starts to drop and miss.

4) Then begin turning the fuel screw OUT. The idle should peak and become smooth. Keep going and look for the idle to begin to drop/miss again.

5) The goal is to find the setting that provides the highest and smoothest idle. If it's unclear exactly were that point is then set to the midpoint between step #3 and step #4. For example, if the idle starts to smooth out at 1 1/2 turns out and starts to get rough at 3 turns out then 2 1/4 turns out should be the correct setting.
When the combination of adjusting the pilot screw and reducing the idle speed (with the throttle stop screw) gives you the best and smoothest idle, the adjustment is set.
Typical fuel screw settings on the GZ are in the 2 to 3 range.

Try riding (putting) around in first or second with the idle turned up. Don't use any throttle. After a couple of minutes just push in the kill switch and then pull the plug. Black is rich in the pilot circuit, white is lean and a nice light brown is just right. Do the same for 1/2, 3/4 and full throttle. This will tell you where you stand for the main jet and needle.

Not a GZ carb but this pic shows the Pilot Screw: 5 is the pilot screw and 6 is the pilot jet. 3 is the pilot orifice and the green shows the fuel/air mixture as it heads for the intake.

[JWR]

needle shim mod

mr. softie

Could you really tell and difference before and after with this mod??

[mr. softie]

No, maybe a bit less fuel economy.

[JWR]

Were your exhaust pipe very blue?

Mine are very blue but my riding buddy Ed's do not have any color at all.

Mine does out pull his, even with the 16 tooth sprocket.

Just thoughts ....

[mr. softie]

JRW...Yes my pipes do blue, but only when I'm pushing hard. They used to blue worse before I adjusted the valves. I clean the bluing off by rubbing with Dursol Simichrome Polish.

My GZ really pulls very well. I have no problem cruising at 70. Had it out today for 3 hours and was hitting 65 in 4th easily up hills and against a stiff headwind, and maintaining 70 on the level in 5th. With no wind or a tailwind I can maintain 75 in 5th. I really like the 16 tooth a lot.

I used to live right over the mountain from you in Asheville, that's some great riding country there.

[JWR]

Yes, we rode the Dragon, Joyce Killmer, and the Skyway yesterday.

About 5 miles of the skyway was so foggy you could barley make out the road.

I don't have any problem pulling the 16t, just have not done the shim yet.



Jerry

[Canuck]

I found the Shim Mod to be a great addition to the 16t...

when I did the needle shim i found all of the "flat spots" with gearing seemed to level out and I cant say enough how well the GZ runs now..

Still loving this bike after 1.5 years and looking back if i knew about it I would have done the 16t and needle shim right from the start...

A little less fuel economy but with already incredible fuel economy why not smooth out those flat spots and see how it fits ya !

Thanks for the responses guys..
Cheers

[Easy Rider]

Originally Posted by Canuck

when I did the needle shim i found all of the "flat spots" with gearing seemed to level out and I cant say enough how well the GZ runs now..

I found that to be the case with only the 16T and no other changes. I have never noticed any flat spots in the performance curve; not saying they are not there, just I don't notice it.

I DID notice, however, that the engine seemed to run a bit better after it passed the 4K mile mark or so........and had a few multi-hour runs on the highway.