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.

http://www.postimage.org/Pqoaqn9.jpg (http://www.postimage.org/image.php?v=Pqoaqn9)

[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]

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.

[Easy Rider]

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.


Good writeup. :tup:

I have usually found that the final, fine adjustment is easier if you decrease the idle speed back to normal.....or slightly below.

I don't think this is going to be a factor for Canuck though. I believe something is amiss with his needle adjustment. Either he went too many notches or didn't get something back together exactly right.

The other posssibility is that the Canadian carb. is jetted different and he really didn't need to do the mod in the first place. I don't think we have heard from anybody else having a similar problem caused by the needle mod. Might be something else causing it too.....like the choke not going completely off or a clogged air cleaner...........?????

[alantf]

The other posssibility is that the Canadian carb. is jetted different and he really didn't need to do the mod in the first place.

According to my owner's handbook (Spanish bike) the Canadian spec is the same as the Spanish.
The only difference is the lighting (to comply with Canadian regulations), therefore it is HIGHLY likely that he didn't need to mess with the carb. If it is the same as mine, he certainly didn't. It seems like he was reading about the mods to the American carb, & just assumed that his was the same. As you, yourself, pointed out, the European carb is slightly richer.

[Canuck]

If the choke doesnt go completely off while your riding can this cause extensive damage in the future ... or also cause the spark plug to foul ?

how does this happen ....an old spring mechanism inside the carburator from the choke cable warped and not returning fully??

In this case would you replace or use something to clamp the spring tighter and put it the needle then screw back into the carb ? or need a whole new choke cable altogether?

[Canuck]

I had posted LONG ago about my Carburator issues so i got one off Ebay from a guy in Illinois

Works beautiful and the bronze cap is covering the main jet screw from the bottom?

I'm wondering if i should take that off and check its adjustment before i REVERSE the washer from its current position back to the original on the main needle.

[Easy Rider]

If the choke doesnt go completely off while your riding can this cause extensive damage in the future ... or also cause the spark plug to foul ?


No and yes, in that order. It will only affect the mixture at idle AND would pull up the idle speed too, likely making it impossible to set the idle speed with the throttle stop.

[Easy Rider]

Works beautiful and the bronze cap is covering the main jet screw from the bottom?


No that covers the IDLE jet. Probably not worth messing with unless you are having trouble getting it to idle smoothly (when hot). OTOH, the plug is about impossible to remove when the carb is ON the bike so if you have it off, that would be a good time to pop it out.

At this point, I think I would advise putting in a new plug and inspecting it again after a few hundred miles. Always the chance of screwing something up big time whenever you take something apart so I wouldn't go back into the carb unless I was pretty sure I needed to.

[Canuck]

So after i thought about it, Im considering putting the washer back on top of the needle.

doesnt take much to reverse, Take the screws out of the top of the carb take off the black cap and gently remove the needle and put the washer from underneath to on-top of the needle.

Might be why my spark plug is getting fouled. Ill check the color of the plug again as well but im guess im running to rich with the needle shim mod.

Dont know why or how cause i did like the mod at first. In the end i think it does more harm then good.. IE Lower mileage and a mix too rich.

Oh well.