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Uneven cylinder temps. Need Insight

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02 Oct 2024 17:05 #904819 by 84_GPz750
Replied by 84_GPz750 on topic Uneven cylinder temps. Need Insight
 Thanks @Warren3200gt and @Wookie58. I let the bike run for a minute or two and cylinder 2 was still cold. Pulled the plug and the earth strap was not bent. Purchased a cheap borescope and looked inside the spark plug hole and saw no foreign objects, just some carbon build up on the piston. 



I swapped plugs from no1 to no2 with no change. Checked the resistance on those two plugs and got 5.48k on no1 plug and 5.84k on no2 plug so they seem to be okay. 

Time to pull the carbs and check for a fueling issue next?

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02 Oct 2024 21:05 #904820 by F64
Replied by F64 on topic Uneven cylinder temps. Need Insight
Spray a bit of starting fluid into cylinder 2 once the engine is warm to see #2 fires up.

81-KZ440-D2.
Louis Dudzik's GM HEI ignitor conversion installed 2015 s3.amazonaws.com/gpzweb/Ignition/GPZgmHEImod.html
Motogadget m-unit blue installed 2017.
LIC, NY

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  • howardhb
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  • Sustaining Member
  • God, I trust
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03 Oct 2024 04:17 - 03 Oct 2024 05:06 #904822 by howardhb
Replied by howardhb on topic Uneven cylinder temps. Need Insight
Have you checked if cylinder #2 plug is sparking?

Remove cylinder #2 plug from the head, and plug it into it's (#2) plug cap, and earth the plug (contact the threaded part onto the cylinder-head), and start the engine.
You should see bright blue sparks at the plugs centre electrode.
If you do see sparks, then you problem is most likely to be fuel supply (carb issue) or compression related. (valve clearance / rings)
Have you checked if there is fuel in #2 carbs float bowl?

H.

'81 GPz 550 D1
'81 GPz 1100 B1 ELR "Tribute" www.kzrider.com/11-projects/617040-1981-...-rstomod-elr-tribute
'82 Yamaha YB100 Fizzie
'79 Suzuki GT200 X5 TWO STROKE TWIN - SMOKER!
Last edit: 03 Oct 2024 05:06 by howardhb.

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04 Oct 2024 01:54 #904845 by 84_GPz750
Replied by 84_GPz750 on topic Uneven cylinder temps. Need Insight
With the ball valve closed on my auxiliary tank, I drained the float bowl on #2 carb and got maybe 3oz of fuel out. I tightened the drain screw up and opened the ball valve on the tank line and let the fuel flow into the carbs for a few minutes. I then closed the ball valve again and opened the drain screw on #2 and got no fuel. Am I correct in remembering the engine doesn’t need to be running or producing vacuum to fill the float bowls? 

@howardhb I did the same process you describe about a week ago. I had (and felt) the spark on #2 with it arcing to the head. Now this was done during the day so it was bright out and I cannot say how bright the spark was. I will try it again at dusk and with a better insulated pair of pliars to see how strong the spark is. 

@F64 I did what you suggested by spraying starting fluid into the intake rubber on #2 and the idle smoothed out then rose quickly. I had adjusted my idle screw so maybe with all cylinders having fuel, it’s too high. I did feel the #2 header pipe once I shut it down and it was warm unlike prior to trying the starting fluid.

I really appreciate the tips from everyone. 

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04 Oct 2024 20:21 #904860 by TexasKZ
Replied by TexasKZ on topic Uneven cylinder temps. Need Insight
You are correct about the fuel flow. Gravity does it, even with the regular fuel tank and petcock in place. The vacuum hose to the petcock merely operates the valve. When vacuum opens the valve, gravity pulls the fuel out of the tank and into the carburetors.

 

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

www.kzrider.com/11-projects/620336-anoth...uild-thread?start=24

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  • FaultedGeologist
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05 Oct 2024 11:03 #904874 by FaultedGeologist
Replied by FaultedGeologist on topic Uneven cylinder temps. Need Insight
Same issue for a while, think compression here but bewildered. 

On mine there is Res Pri On... if Res or On with a good petcock, no.fuel gets thru without vac.  On Pri Prime it will fill the bowls bypassing the vac.  If u don't have a prime on your petcock, the real experts here should answer.

This got me thinking - I just drained all 4 carbs after prime and got just under 50cc except the rightmost sitting on bike, meaning everything is good there or the one is overfilling and fills the cold pipe bowl from the common fuel rail... I think it is good, but Ill adjust that last float to make sure and do it again.

Clint
1980 KZ750 LTD H4
FSMaunual: kz.bike-night.com/media/GPz750-full.pdf
Stock except for:
New chain and sprocket (530?).
Dynatek Ignition
Manual tensioner on the way.

Buy JIS screwdrivers.
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