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TOPIC: Fuse blowing, spark plugs overheating after valve re-shim

Fuse blowing, spark plugs overheating after valve re-shim 05 May 2020 14:40 #825071

  • limegreenlemon
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Hello all,

Long time reader on this forum and was digging through the forum looking for some help but it seems when I go to fix something it creates 5 more problems.

The bike in question is a '77 KZ650-B. I've had it for about a year now and it ran pretty good when purchased. The main issue was it would take a very, very long time to start in moderately cold weather, more than 20-30 seconds, and was making clicking and knocking sounds in the engine, so being a complete noob with fixing old bikes I went and bought a brand new battery, hoping all problems would go away. Same starting issues persisted.

I finally decided to take it to a shop and they said the valve clearance may be too tight, among other things, and quoted about $500 to re-shim the valves and look at what else is going on.

Anyway I ended up replacing the shims myself with a shim kit ordered off ebay, replaced the head gasket as well. Clearances were way out of spec but now they're in spec but this seems to have created more problems. The plugs were already carbon/oil fouled (another reason to re-shim the valves) so I swapped them with brand new plugs (NGK BR7ES) before my 1st ride after re-shim, only to have the bike die after 5 mins of riding. It blew the 20a main fuse and after replacing the fuse it blew instantly again, something somewhere is overheating?

The left coil connects plugs 1 & 4, right coil connects 2 & 3. Plugs 2 & 3 are light grey on the tip in addition to the instant carbon buildup and plugs 1 & 4 are completely black.

As for the ignition, it was replaced with a Dyna ignition and I tested the coils this morning and they seem to be good. Tested spark in cylinder 4 and was looking pretty weak. Other people have posted topics about plugs fouling and it usually points to the carbs. But how would that explain the fuse blowing when the bike gets hot? I never had that problem until the valve adjustment. I was hoping to just adjust the air screw slightly to reduce richness but not sure how much that would help.

I will be bald soon from all the hair pulling so any info helps, thanks!
1977 KZ650-B
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Fuse blowing, spark plugs overheating after valve re-shim 05 May 2020 16:22 #825075

  • Greybeard
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Spark plugs overheating after valve shim. Hmmm. Check the polarity on the leads going into the coils.
Might be more than one problem
1982 KZ1100 D-1

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Fuse blowing, spark plugs overheating after valve re-shim 05 May 2020 18:07 #825081

  • F64
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did your coil wires short out?
Make sure none of your wiring is pinched.
81-KZ440-D2. Louis Dudzik's GM HEI ignition module converted 2015--no issues, Motogadget m-unit blue.

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Fuse blowing, spark plugs overheating after valve re-shim 05 May 2020 18:51 #825083

  • 650ed
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Obviously you do not own a Kawasaki Service Manual - I would urge you to buy one. It may not be the source of your problem, but there is no reason to run the wrong spark plugs (NGK BR7ES) when it would make better sense to run the correct spark plugs (NGK B7ES or even better (Denso) ND-W22ES-U). Ed
1977 KZ650-C1 Original Owner - Stock (with additional invisible FIAMM horn)

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