All 4 plugs indicate lean. What to adjust?

I pulled my plugs last night, and all four had clean white insulators, and black soot around the outside ring. From what I've read, this indicates a lean condition.

So my question is, what do I adjust? The fuel screws? Jet Needle? Both?

Details:

Stock VM26 carbs with fuel mixture screws on the bottom, 1.5 turns from lightly seated.

Jets: 107.5/17.5.

Needle clipped at #3.

Stock air/exhaust.

Post edited by: Skyman, at: 2007/05/29 17:06

Do you have any way to sync the carbs? How is the bike running? I would only adjust one thing at a time. First try the mixture screws. Did you ever mess with the jet needles? My 650 stock is on 4 according to my manual. Though I've heard people around here put them on 3, but they have always been on 4 and running strong. If you have everything stock I would say the mixture screws because everything else is the way it's supposed to be.

Carbs are sync'd. Seems to be running well.

I changed the needle position from 4 to 3 a while back based on WG's suggestion--at the same time I went from stock 102.5/15 jets to 107.5/17.5.

I've heard about the 3 setting here even for my 650.. Though the manual says 4 and when I just rebuilt the carbs they were on 4. So... If I were you, I would check your manual and see what it say's.. From 4 to 3 will lean the bike out. If it was stock at 4 and you never messed with it before, I would put it back to 4 and see how your plugs react. All your going to do is richen it up and burn a bit more gas. It won't hurt anything.. Check your manual first though and see what it say's..

I didn't read the part about the jet upgrade. I'm not sure why you changed jets and the clip when everything else is still stock.. The only reason you might move the clip and go up or down on the main when things are all stock is maybe an altitude adjustment. If you make header mods or pods. You might adjust the jet needle. Most likely you will go up about 3 mains and a pilot. If you have no mods I would put it all back to stock, that's how it's suposed to be.
0 to 1/8 throttle=pilot screw
1/8 to 1/4= throttle valve cutaway or air or pilot screw
1/4 to 3/4=jet needle position
3/4 to full=main

Post edited by: vach, at: 2007/05/29 20:52

vach wrote:

I've heard about the 3 setting here even for my 650.. Though the manual says 4 and when I just rebuilt the carbs they were on 4. So... If I were you, I would check your manual and see what it say's.. From 4 to 3 will lean the bike out. If it was stock at 4 and you never messed with it before, I would put it back to 4 and see how your plugs react. All your going to do is richen it up and burn a bit more gas. It won't hurt anything.. Check your manual first though and see what it say's..

I didn't read the part about the jet upgrade. I'm not sure why you changed jets and the clip when everything else is still stock.. The only reason you might move the clip and go up or down on the main when things are all stock is maybe an altitude adjustment. If you make header mods or pods. You might adjust the jet needle. Most likely you will go up about 3 mains and a pilot. If you have no mods I would put it all back to stock, that's how it's suposed to be.
0 to 1/8 throttle=pilot screw
1/8 to 1/4= throttle valve cutaway or air or pilot screw
1/4 to 3/4=jet needle position
3/4 to full=main<br><br>Post edited by: vach, at: 2007/05/29 20:52

I changed the jets based on a recommendation from WiredGeorge who wrote that the stock jetting on the '78 B2 was quite lean. He recommended that I go up two on the mains and one on the pilot. He also suggested clipping the needle at 3.

I looked in my factory manual and it did say "4". Maybe I'll put it back to 4 and see what happens.

Thanks.

Hey, Vach, which manual? I'm curious because my KZ650 factory service manual specifies groove 3 (the middle groove) in several places.

Actually, they should be where the bike runs the best.

It's a big huge book called the Kawasaki KZ650 motocylce sercvice manual. Made by Kawasaki Heavy Industries LTD. 1976, 77, 79. I believe it's actualy Kawasaki. I 've seen photo's around here from the same book.. Pgs. 135, 248 and 269 all say clip it on 4. Yes you should put the clip where ever it runs best but leaning a lean setup is not going to help you.

As far as putting the clip to 3, that will lean your bike aout from1/4 to 3/4 throttle, the mains only kick in at 3/4 to full throttle, unless your running around at full or almost full throttle all the time. You have just leaned your bike out considerably. I say put it back to stock and check your plugs. If they are lean, find out where. Then adjust accordingly. If anything to richen the bike up Most operating levels (1/4 to 3/4 throttle, you would put the clip on 5. to richen a lean condition. I would go back to stock and put new plugs in. run the bike, not wide open, say at 4000, rpm's on a straightaway and then shut the bike off, let it coast to a stop and pull a plug. Then run it wide open and shut it down the same way, pull a plug. This process will tell you if the bike is running lean, rich or whatever. If it's the jet needle, bump it up a notch, if it's the mains go up one jet at a time and see.


0 to 1/8 throttle=pilot jet

1/8 to 1/4= throttle valve cutaway or air or pilot screw

1/4 to 3/4=jet needle position

3/4 to full=main

Sounds like the same book as mine, but an earlier edition. Mine has a PN of 99924-1007-03 and covers the KZ650 B2A, B3, B4. C3, C4, D1A, D2, D3, E1, and F1. I wonder if by the time my manual was printed the EPA regulations forced them to rewrite clip positions to groove 3?

Interesting difference.

Yeah, same book only mine is 99924-1001-03. Weird..All of those pages I refernced say clip 4. Hmmmm. Not sure. I do know that Iv'e never messed with the clips before and I just rebuilt the carbs and they were on 4.. They guy I bought the bike from 17 yrs ago never messed with them either. It was completely stock. When it's running,(not right now, soon) it ran great. Mine does have emissions though. I don't know.. I was wondering why everyone was saying to put the clip on 3 though. I'm going to keep mine on 4, just because it was always like that. Did you move yours or was it always on 3? Very interesting....

Skyman wrote:

I pulled my plugs last night, and all four had clean white insulators, and black soot around the outside ring. From what I've read, this indicates a lean condition.

What is the plug and heat range?

What was your riding state just prior to the inspection?
In other words, what RPM / throttle range were you operating in. And for how long?

vach wrote:

Mine does have emissions though. I don't know.. I was wondering why everyone was saying to put the clip on 3 though. I'm going to keep mine on 4, just because it was always like that. Did you move yours or was it always on 3? Very interesting....

My SR has emissions air injection in place and the plugs look great on groove 3. It has VM24SS carbs with the air screws and accelerator pump.

Where the clip was from the factory, I don't know. The PO was trying to get it working with pod filters and what position he had them in, I forget. I did move them to #3 myself in 2004.

KaZooCruiser wrote:

What is the plug and heat range?

Stock--B8ES

KaZooCruiser wrote:

What was your riding state just prior to the inspection?
In other words, what RPM / throttle range were you operating in. And for how long?

I just returned from a long ride. Didn't do a plug chop or anything like that. Just pulled into my driveway and shut it down. I wanted to check my compression, so I removed my plugs. That's when I noticed they were clean white.

I did some more work on the bike tonight, and while I was in there, I moved the needle clips to #4. We'll see how it rides tomorrow. I know I need to be more scientific about this and do it right. When I have time, I'll do a full plug chop work-up.