ZRX 1100 idling. - Kawasaki Motorcycle Forums
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post #1 of 4 (permalink) Old 07-07-2019, 06:54 AM Thread Starter
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Question ZRX 1100 idling.

Carb balance OK, coils checked OK, engine won't idle cleanly. Main thing I've found is all compressions are 100lbs? Should be 140+ at least. Engine revs slow to return?
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post #2 of 4 (permalink) Old 07-07-2019, 09:28 AM
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The compression tests on my ZN700 when I first got it with only 1,054 miles on it was 178 in 3 cylinders and 180 in the 1. So, I would say 100 is way too low. Did you squirt some oil into the spark plug holes to see if had an effect on the compression? If it goes up with oil, it indicates the piston rings are worn. If the oil has no effect, the valves need attention.

1985 Kawasaki ZN700 Shaft, 4cyl
1989 Yamaha Venture Royale
2007 Yamaha Royal Star Venture
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post #3 of 4 (permalink) Old 07-08-2019, 02:20 PM Thread Starter
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Refitted the carbs yesterday. Started up but still the engine races with the throttle shut and slow return to idle. This would usually point to an air leak or something with the vacuum carbs. Went through everything, if its there I can't see it. Manual actually has comp as 160- 200psi so definitely low. He had the fuel tap problem with the tank dumped into the sump and tried to start it without knowing. I can only assume the rings are busted. (But it doesnt smoke) Will try the oil down the plug holes but its a deep hole so not easy. An old school fix for stuck rings was to pour an additive called REDEX down the bores and leave for a week or so. I think its more than that. I've had a selection of 4 cyl incl CBX and never encountered the slow revs return as a vacuum problem. I'm sort of hoping someone will see this. I don't see the low comp as causing that. Its only done 36k.
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post #4 of 4 (permalink) Old 07-11-2019, 04:17 AM Thread Starter
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Put the tank back on and its idling sweet, revs are pretty quick to drop back. I've no idea whats happened other than the carbs cleaned again, but there is a slight misfire just off idle as you pull away on light throttle. So more poking about, another set of plugs to fit because above idle it steams away with no problems. As it falls off onto 3 I can't see it being the coil because it fires 2 plugs so 2 cyl would drop off, easy job first, try another plug. More later.
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