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76 KZ900 Plug Fouling 20 Nov 2022 14:44 #877008

  • Wookie58
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Compression numbers.
1- 125
2-120
3-120
4-125
Dyna S ignition, and 3 ohm coils . timing is dead on , and a good strong visual spark. Charging system functioning well ( I have a volt meter under the seat to be able to monitor it periodicly)
Are these compression readings on a warm engine with the throttle wide open, if so they aren't great. If you have the facilities try a "leak test" if not put a SMALL squirt of light oil down the plug hole and re-test (too much oil will fill your tester with oil and could hydraulic the engine) if the readings improve the bores or rings are worn. Should be around 130-160 so you are under the lower figure. Not catastrophic but enough to cause issues with combustion. Nice and even though so just wear as opposed to a deeper issue
1982 KZ1000 Ltd

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76 KZ900 Plug Fouling 21 Nov 2022 05:07 #877027

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Compression numbers.
1- 125
2-120
3-120
4-125
Dyna S ignition, and 3 ohm coils . timing is dead on , and a good strong visual spark. Charging system functioning well ( I have a volt meter under the seat to be able to monitor it periodicly)
Are these compression readings on a warm engine with the throttle wide open, if so they aren't great. If you have the facilities try a "leak test" if not put a SMALL squirt of light oil down the plug hole and re-test (too much oil will fill your tester with oil and could hydraulic the engine) if the readings improve the bores or rings are worn. Should be around 130-160 so you are under the lower figure. Not catastrophic but enough to cause issues with combustion. Nice and even though so just wear as opposed to a deeper issue
I think they are fine.  Compression ratio on a Z1 engine is 8.5 to 1.  Multiply 14.7 (atmospheric pressure) times 8.5 gives you 125 psi.  Kawasaki also recommends the four readings should be within 15 lbs of each other.

I suspect we are being teased here.
I have several restored bikes along with a 2006 Goldwing with a sidecar. My wife has a 2019 Suzuki DR 650 for on and off road.
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76 KZ900 Plug Fouling 21 Nov 2022 05:54 #877029

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I could not find my original results from when I bought the bike but remember the results being decent. 
So yesterday I did the compression test again, cold, wide open throttle and got the results noted.

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76 KZ900 Plug Fouling 21 Nov 2022 06:00 #877030

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Not sure of exact spec for yours, quick skim of the manuals say 126-158 for a KZ1000 and 125 for a Z1 as HRM pointed out
1982 KZ1000 Ltd
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76 KZ900 Plug Fouling 21 Nov 2022 06:51 #877031

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You might want to try an experiment and run the bike without the air filter. If it's running rich because of wear on the needle jet, and jet needle parts, that test should add some data points to the discussion.
Ed

Carburetor O-ring Kits For Sale: Mikuni VM & BS/CV, and Keihin CV34 (as used on KZ750E/H/N/Spectre, 400)

www.kzrider.com/forum/forum-index/faq-wi...owner-things-to-know

1981 KZ750E2
www.kzrider.com/forum/11-projects/604901...z750e-project-thread
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76 KZ900 Plug Fouling 29 Nov 2022 13:02 #877314

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Changed out 115 main jets to 112.5 , and lowered the needles one slot, 17.5 pilots . Weighed the floats to see if any differed, but all measured the same 10 grams. Checked float height with clear tube method . Reinstalled carbs, set idle mixture, and double checked timing to be on. New plugs. After a 30 minute test drive , plugs 3 and 4 look great, however 1 and 2 again totally soot fouled. Black non oily soot. Tried  removing the air cleaner element to remove any restriction, made no difference. Grabbing at straws at this point. The bike has Dyna green coils, perhaps these once warm are not producing a hot enough spark , but with the left coil firing 1 and 4 , the right  2and 3 , it does not line up with my 1 and 2 fouling..

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76 KZ900 Plug Fouling 29 Nov 2022 17:47 #877325

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It seems like attempts to lean things out are partially successful but you still have an apparent fuel problem.

This may seem like a silly question but do you have needle jets in these carbs?  Is it possible someone removed them and never replaced them?  You should be able to see them poking up through the center of the main body into the airstream.

Also wondering about your new choke plunger seals.  Who did them?  Are they depressed too far into the plunger to stop leakage?
I have several restored bikes along with a 2006 Goldwing with a sidecar. My wife has a 2019 Suzuki DR 650 for on and off road.

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76 KZ900 Plug Fouling 30 Nov 2022 00:11 #877331

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Also wondering about your new choke plunger seals.  Who did them?  Are they depressed too far into the plunger to stop leakage?
The seals won't be leaking .
I produce them to original dimensions in superior 75 shore Viton.

AIR CORRECTOR JETS FOR VM CARBS AND ETHANOL RESISTANT VITON CHOKE PLUNGER SEAL REPLACMENT FOR ALL MIKUNI CARBURETTORS
kzrider.com/forum/23-for-sale/611992-air-corrector-jets-





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76 KZ900 Plug Fouling 30 Nov 2022 04:51 #877336

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Also wondering about your new choke plunger seals.  Who did them?  Are they depressed too far into the plunger to stop leakage?
The seals won't be leaking .
I produce them to original dimensions in superior 75 shore Viton.
I guess we know who did them then!  I know there are multiple people doing them these days, and some may not be doing them correctly.

If the choke plungers are eliminated as a possible fuel source it leaves only the pilot and main circuits, plus the bowl fuel setting.  I would be inclined to replace the needles and needle jets, as they will wear over the years as the slides move up and down.
I have several restored bikes along with a 2006 Goldwing with a sidecar. My wife has a 2019 Suzuki DR 650 for on and off road.

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76 KZ900 Plug Fouling 30 Nov 2022 07:47 #877341

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This won’t explain why one plug on a coil is good and the other is fouled example 4 good 1 fouled. Dyna coils are Notorious for shorting out between the coil negative and the frame. The terminal is close to the mounting post and they will short to the frame, I have personally experienced this. The fix is to shrink Wrap the metal stand-off post or replace it with plastic. It’s just one more thing to do to rule out possible causes. 

To add to HRM, not only check the needle jet is in place but you need to verify the are all the same size. Should be O-6 with 5DL31-3 needles. Make sure all slides are 1.5 cutaway. 
1976 KZ 900 A4 kzrider.com/forum/11-projects/613548-1976-kz-900-a4
1976 KZ 900 B1 LTD
1978 KZ 1000 B2 LTD
1980 KZ 750 E1
Kowledge Speaks, But Wisdom Listens.
Jimi Hendrix.

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76 KZ900 Plug Fouling 30 Nov 2022 11:00 #877351

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To add to HRM, not only check the needle jet is in place but you need to verify the are all the same size. Should be O-6 with 5DL31-3 needles. Make sure all slides are 1.5 cutaway. 
The 900 seems to be set up rich.  The 0-6 Needle Jet is rich, and that needle is medium skinny.  Maybe between a somewhat weak spark, rich carburation that's even richer after wear on the parts, plus compression on the low side, is all conspiring.
Ed

Carburetor O-ring Kits For Sale: Mikuni VM & BS/CV, and Keihin CV34 (as used on KZ750E/H/N/Spectre, 400)

www.kzrider.com/forum/forum-index/faq-wi...owner-things-to-know

1981 KZ750E2
www.kzrider.com/forum/11-projects/604901...z750e-project-thread

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76 KZ900 Plug Fouling 30 Nov 2022 12:20 #877358

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To add to HRM, not only check the needle jet is in place but you need to verify the are all the same size. Should be O-6 with 5DL31-3 needles. Make sure all slides are 1.5 cutaway. 
The 900 seems to be set up rich.  The 0-6 Needle Jet is rich, and that needle is medium skinny.  Maybe between a somewhat weak spark, rich carburation that's even richer after wear on the parts, plus compression on the low side, is all conspiring.
All from the FSM. I pulled out my ‘77 Kz1000 A1 model that used the same carb and it shows a O-6 needle jet, changed the needle to a 5CN08 needle and a 107.5 main, with the same 1.5 cutaway. Maybe that might be a better setup

EDIT. The 5CN is two steps leaner than the 5DL. I’d make one change at a time. After confirming the components are correct and all carbs have the same parts, the jet drop is the easiest. But also a very crude adjustment. The needle change would be a finer adjustment. 
1976 KZ 900 A4 kzrider.com/forum/11-projects/613548-1976-kz-900-a4
1976 KZ 900 B1 LTD
1978 KZ 1000 B2 LTD
1980 KZ 750 E1
Kowledge Speaks, But Wisdom Listens.
Jimi Hendrix.

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Last edit: by Mikaw.
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