Stubborn cylinder #2 - Can't figure it out!

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21 Aug 2021 22:09 #854167 by jekyllman
I'll try to keep this brief (unlikely). I've completely customize a 1980 KZ650 F1 into what you see as my avatar image. I've gone through everything, short of a total engine rebuild. I drove it all year last year and the first half of this year with little issue. However, one persistent issue I had was the exhaust header on cylinder #2 being at the same temp as the other 3. It didn't really bother me but now I'm obsessed with it and NEED to figure out why. This is mostly the case now as I'm trying to re-tune the carbs and the plug on #2 is wet, black, and oily. In fact today there was oily gas dripping from the exhaust drain hole. The other 3 are completely clean and/or slightly white. 

Current setup:
-K&N pod filters (I know, I know...)
-Rejetted (115 mains, 15 idle?)
-Aftermarket muffler welded to original 4-into-2 headers. Lightly baffled mufflers (cheap shorty ebay ones)

What I've done:
-New ignition coils
-New NGK plugs
-New timing condensers
-Timing calibrated carefully
-Carbs balanced to around 200mmHg
-Floats dry calibrated (not wet, don't have the little connector thing)
-Biggest thing: ALL 4 cylinders test right about 150psi consistently!

Last piece of info: after a ride home from work, headers on 1-3-4 are around 250-350 deg F. The header on #2 is around 150 F. So not totally cold. It seems to fire occasionally but not consistently? It also seems to fire only when getting beyond idle circuits and getting into the main jet throttle level. So my final thoughts here are to rejet the pilot jets with something bigger. 1-3-4 plugs are very white/clean at idle despite air screw basically being all the way in.

Thanks to those who read through all of this and have any thoughts for me!! I really hope this is a carburetor issue and not an engine issue! 

 

1980 KZ650F1 - 10k miles (see photo)
1981 KZ305 CSR - 10k miles (didn't have the heart to customize this one, will stay original)

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22 Aug 2021 04:19 #854172 by 73z1
Check compression on all cylinders.
Replace spark plug.
Swap plug wires between #2 and #3
 

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  • bluej58
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22 Aug 2021 04:56 #854174 by bluej58
Replied by bluej58 on topic Stubborn cylinder #2 - Can't figure it out!
Sounds like a bad valve seal is fouling your plug with oil

78 KZ1000 A2A

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  • hugo
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22 Aug 2021 07:35 #854176 by hugo
........and that is where the extra cooling would be coming................but if so, he would notice oil level drop.

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  • gd4now
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22 Aug 2021 11:45 #854190 by gd4now
Replied by gd4now on topic Stubborn cylinder #2 - Can't figure it out!
Since it is an 80 I would assume you have a vacuum operated petcock which runs off of the number 2 carb.  If there is a hole in the diaphram in the petcock it can pass more fuel into carb/cylinder number 2 which would make it rich and run cooler. 

1977 KZ650 B1
Pods and Denco header


OLD KAW OWNERS SMILE ALOT

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22 Aug 2021 18:18 #854204 by jekyllman
Replied by jekyllman on topic Stubborn cylinder #2 - Can't figure it out!
Compression checks out across all 4. Would that rule out valve seal?

New plugs on all 4 and have swapped numerous times to be sure (incl wires)

Oil level seems steady but I can keep an eye on it

I did have a vacuum petcock but it became leaky so I got a different one. I run it on prime quite often. I did notice as I was balancing the carbs that the vacuum ports, the ones located under the couplings, had some gas in it when I took them off. 

1980 KZ650F1 - 10k miles (see photo)
1981 KZ305 CSR - 10k miles (didn't have the heart to customize this one, will stay original)

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22 Aug 2021 18:45 - 22 Aug 2021 18:45 #854206 by Mikaw
Fuel in the vacuum caps is ok. I learned that from Swest. I had the same question.

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.
Last edit: 22 Aug 2021 18:45 by Mikaw.
The following user(s) said Thank You: SWest

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22 Aug 2021 18:49 #854207 by TexasKZ
Replied by TexasKZ on topic Stubborn cylinder #2 - Can't figure it out!
A compression test will not tell you anything about the valve stem seals. All they do is prevent oil from running down the stems into the combustion chamber. Even if you left all of them out of the engine, the oil level would drop so slowly it would take a bunch of miles to see a difference. It does not take much oil to foul a plug or smoke up the neighborhood. A drop or two of fuel in those bottom vacuum tubes is normal. 

1982 KZ1000 LTD parts donor
1981 KZ1000 LTD awaiting resurrection
2000 ZRX1100 not ridden enough

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22 Aug 2021 19:59 #854210 by woodyvale
Replied by woodyvale on topic Stubborn cylinder #2 - Can't figure it out!
Different bike with a DFI setup I know but...

Had a similar problem with my GPZ Uni. Was getting lean/sooty plugs and wildly out of sync header temps and uneven tickover/running

Turned out to be very slight cracking inside the rubber head carb boots. They weren't visible until they were tightened and opened up which was causing an air leak as they weren't sealing properly against the head.

Drove me mad at the time trying to find the problem.

Anyways just a thought for something else to check!

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  • howardhb
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23 Aug 2021 08:46 - 23 Aug 2021 09:00 #854220 by howardhb
Replied by howardhb on topic Stubborn cylinder #2 - Can't figure it out!
I see you changed coils and plugs.
What about plug caps and HT leads?

Swop cyl. 2 plug wire with 3 and 3 with 2... you can do that and have the engine run just fine because it fires on the power and exhaust strokes. (You may have to un-mount the coil due to HT lead length)
 
If the problem persists, at least you will have ruled out the ignition system as culprit.

'81 GPz 550 D1
'81 GPz 1100 B1 ELR "Tribute" www.kzrider.com/our-forum/11-projects/61...-elr-tribute?start=0
'82 Yamaha YB100 Fizzie
'79 Suzuki GT200 X5 TWO STROKE TWIN - SMOKER!
Last edit: 23 Aug 2021 09:00 by howardhb.

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24 Aug 2021 16:17 #854296 by jekyllman
Replied by jekyllman on topic Stubborn cylinder #2 - Can't figure it out!
Has anybody tried using an overhead valve spring compressor on one of these engines?
 

1980 KZ650F1 - 10k miles (see photo)
1981 KZ305 CSR - 10k miles (didn't have the heart to customize this one, will stay original)

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  • bluej58
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24 Aug 2021 18:14 #854300 by bluej58
Replied by bluej58 on topic Stubborn cylinder #2 - Can't figure it out!
Yes,
here's a vid I found that is obviously (not ) a kz650 but it has similar parts  that a 650 has and will give you an idea on how to use a valve compressor 

  (76) Valve Removal & Installation Method 1 : Valve Spring Compressor - YouTube

78 KZ1000 A2A

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