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‘80 KZ650: cyl 1-4 not firing but have great spark 24 Sep 2020 20:34 #835619

  • jekyllman
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Cleaned out the carbs recently and the bike was running great. Had a hard time starting yesterday on the way back from work which has never happened but eventually warmed up and did fine. Went to go to work today and it sputtered but wouldn’t stay running. I kept it sputtering for a minute and felt the exhaust. 1-4 are freezing, 2-3 are warm. Tested spark on all 4 and all four looked great. Compression between 145-150 on all 4 cylinders. Not sure why it suddenly decided to not run on those two cylinders, simultaneously. I can’t help but look at the ignition coil since it’s both 1 and 4 but the spark looked good on both so who knows. I know I should consider carbs but how did 2 cylinders stop working at the same time?

Note: I swapped some valve shims last week but it ran just fine for a few days afterwards.
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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‘80 KZ650: cyl 1-4 not firing but have great spark 24 Sep 2020 22:19 #835622

  • jekyllman
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Figured it out but don’t know how to delete thread. Just ignore.
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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‘80 KZ650: cyl 1-4 not firing but have great spark 25 Sep 2020 06:13 #835629

  • TexasKZ
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What was the problem?
1982 KZ1000 LTD parts donor
1981 KZ1000 LTD awaiting resurrection
2000 ZRX1100 not ridden enough

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‘80 KZ650: cyl 1-4 not firing but have great spark 25 Sep 2020 21:56 #835668

  • KZQ
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jekyllman wrote: Figured it out but don’t know how to delete thread. Just ignore.


Sorry jekyllman that's not how KZR works!

KZR is a community of enthusiasts who share and learn. You asked a question and then apparently learned the answer on your own. I'm sure that there are others who would benefit from your lesson.
If you're interested in this community, please let us in on the "Rest of the Story"
Bill
www.KZ1300.com
Riders:
1968 BSA 441 Shooting Star, 1970 BSA 650 Lightning, 1974 W3, 1976 KZ900, 1979 KZ750 Twin, 1979 KZ750 Twin Trike, 1981 KZ1300, 1982 KZ1100 Spectre, 2000 Valkyrie, 2009 Yamaha Roadliner S. 1983 GL 1100
Projects:
1985 ZN1300

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‘80 KZ650: cyl 1-4 not firing but have great spark 02 Oct 2020 08:49 #836021

  • jekyllman
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Been trying to post a response to this for days but this forum constantly gives me errors when I try to post.

Well the solution is somewhat "unrelated" to the issue brought up but here's what happened:

Decided to remove the carbs to see if there was something blocking the jets on the cylinders that weren't warm. When I opened the drain plug nothing came out. I gave the #4 a few good taps with a wrench and voila! Carb float unstuck and the bike has ran great since! Stupid solution for a stupid problem.
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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‘80 KZ650: cyl 1-4 not firing but have great spark 02 Oct 2020 10:12 #836024

  • Mikaw
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Thanks for the update. It’s common. I had it happen on a fresh rebuilt rack. They preformed flawless then one afternoon during my pre ride inspection i smell gas. Pulled that bowl and everything seemed normal. Put it back together and haven’t had another incident yet to date.
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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‘80 KZ650: cyl 1-4 not firing but have great spark 02 Oct 2020 23:10 #836082

  • azman857
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Usually the floats stick down and the gas won't shut off! It happens.
I don't have a plan and I'm sticken' to it! '77 KZ 650 / 750 GPz custom project in progress

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‘80 KZ650: cyl 1-4 not firing but have great spark 03 Oct 2020 05:45 #836090

  • TexasKZ
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Sometimes it is the simplest of things.
1982 KZ1000 LTD parts donor
1981 KZ1000 LTD awaiting resurrection
2000 ZRX1100 not ridden enough

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