85 ZN700 LTD smoking like a banshee

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11 Aug 2016 05:40 - 11 Aug 2016 05:41 #738232 by Patton
Replied by Patton on topic 85 ZN700 LTD smoking like a banshee

lemonyguy wrote: . . . oil dripping . . . leaking is somewhere in front of the back tire, haven't pinpointed it yet. . . .


Is the crankcase vent routed to exit underneath the bike in front of the back tire (would likely be via a length of non-stock hose connected to the crankcase vent)?

Excessive crankcase pressure (due to worn compression rings and/or worn cylinders or whatever reason) may result in oil being discharged from the crankcase vent.





Good Fortune! :)
1973 Z1
KZ900 LTD
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Last edit: 11 Aug 2016 05:41 by Patton.

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11 Aug 2016 06:04 - 11 Aug 2016 06:10 #738237 by Patton
Replied by Patton on topic 85 ZN700 LTD smoking like a banshee
Examples of crankcase breather vent hose ---





Or otherwise routed - - -




A "catch-can" is often fitted incident to racing applications in order to collect oil from the breather vent (purpose being to keep oil off the track).

The stock set-up may be a tube from the crankcase breather vent which exits into the air breather box (such as on the stock Z1 for re-ingestion through the carbs into the engine).

The air-box may also include a drain whereby the oil may discharge from the air box (sometimes into some form of catch system to prevent oil from draining underneath the bike).

Here's the "catch" system arrangement on Honda's GB500:





Good Fortune! :)
1973 Z1
KZ900 LTD
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Last edit: 11 Aug 2016 06:10 by Patton.

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11 Aug 2016 09:36 #738267 by lemonyguy
Replied by lemonyguy on topic 85 ZN700 LTD smoking like a banshee
Crankcase breather is routed into the airbox it seems. As for testing everything, even if I find what's wrong I can't find parts, no piston rings, no valve stem seals, did find a cylinder head gasket but it seems no one makes the big parts for a rebuild.

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  • SWest
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11 Aug 2016 17:53 - 11 Aug 2016 17:54 #738325 by SWest
Replied by SWest on topic 85 ZN700 LTD smoking like a banshee

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11 Aug 2016 19:34 #738346 by lemonyguy
Replied by lemonyguy on topic 85 ZN700 LTD smoking like a banshee
So swap motors? If I'm doing that would be easier to throw the more common 750 in because to my knowledge the 750 and 700 are near identical besides different carb jets. Could swap motors, rebuild the original and put it back in and then I could have a spare for a custom project if I want.

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12 Aug 2016 06:37 #738379 by Nessism
Replied by Nessism on topic 85 ZN700 LTD smoking like a banshee
Humm, just checked and the rings have been discontinued. That could be a problem. You best do that compression check and see where you are at. How many miles on the engine? You may be okay to replace the gaskets and run the old rings, assuming they measure up decently.
Ed
Carb O-ring Kits : www.kzrider.com/forum/3-carburetor/61807...-o-ring-kits?start=0

www.kzrider.com/forum/faq-wiki/618026-new-owner-things-to-know

1981 KZ750E2
www.kzrider.com/forum/11-projects/604901...z750e-project-thread

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12 Aug 2016 09:45 #738392 by lemonyguy
Replied by lemonyguy on topic 85 ZN700 LTD smoking like a banshee
Motor has 15k on it, that's what I found too. Looks like if anything in the bottom end of motor is gone the whole thing is gone. Time to pray for good results from the leak down tests, I found someone with one and he is ganna let me use it on Sunday. Hopefully I just have top end problems.

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12 Aug 2016 15:51 #738426 by lemonyguy
Replied by lemonyguy on topic 85 ZN700 LTD smoking like a banshee
I tested compression and found all cylinders were good, 140-50. I don't have access to a leak down tester though, anyone know a good one to get for cheap?

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12 Aug 2016 16:05 #738427 by Patton
Replied by Patton on topic 85 ZN700 LTD smoking like a banshee

lemonyguy wrote: I tested compression and found all cylinders were good, 140-50. I don't have access to a leak down tester though, anyone know a good one to get for cheap?


Would assure that each and every valve clearance is within specs, and then consider compression rings and cylinders okay, and look for another cause of excessive exhaust smoke, such as perhaps faulty oil ring(s), clogged crankcase breather, faulty valve stem seals, or something else.

Seems unusual that a motor with such low mileage and good compression would have such an extreme oil burning issue.

Good Fortune! :)
1973 Z1
KZ900 LTD

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13 Aug 2016 09:41 #738522 by lemonyguy
Replied by lemonyguy on topic 85 ZN700 LTD smoking like a banshee
I cleaned my airbox, air filter and the tubes. Lots of oil in the box. Guess I need a new crankcase breather filter. Could that be the cause? Once all that was done the smoke Waa reduced. I still need to adjust the valves to be safe but there isn't a tick. Spitballing here so don't laugh if I'm an idiot.

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13 Aug 2016 09:46 #738523 by SWest
Replied by SWest on topic 85 ZN700 LTD smoking like a banshee
Breather filter? Pods? There should be no restriction. Running pods not jetted correctly will make it run lean and can destroy the engine. I'd rout the breather down to the chain if there's no air box.
Steve
Z1b1000 1975 Z1b
kzrider.com/forum/11-projects/598262-kz-...-will-it-live#672882
kzrider.com/forum/2-engine/597654-poser?start=240#704229

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13 Aug 2016 09:58 #738525 by lemonyguy
Replied by lemonyguy on topic 85 ZN700 LTD smoking like a banshee
I run the stock airbox still, the breather has cover where a hose goes that leads back towards the valve covers. It goes through the box. I was guessing it was leaking oil into the box and that could be a cause of some of the smoke. It looked like there was a spot under the breather cover for a filter

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