Oil in carb and air box, easy fix?? - ZX Forums
 
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post #1 of 12 (permalink) Old 03-31-2015, 05:02 PM Thread Starter
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Oil in carb and air box, easy fix??

Hello!

I have a 93 ZX-7 with 33,000 miles on it. Last riding season, the guy was fun to ride but was definitely running rich, would miss occasionally, got poor mileage, and the idle was all over the place. I said to myself I just need to rebuild the carb and we're good.

Fast forward to this season. I get the bike running but it just WILL NOT idle. I have to keep revving it to keep it alive. I notice an oil leak out of the left side of the bike where there should be absolutely no oil.

So today I take the fuel tank off and inspect the carbs and there is oil all up in there where the idle screws are. There is a bunch of oil too in the airbox right where it fits on the carbs. So I start the bike up with the airbox off, and it starts right away too without choke which is surprising, and then a fuel/oil mixture comes gushing out of a hose that used to go to into the rear of the airbox right above the #3 carb. It's a thick hose that comes straight out of the top of the clutch/transmission assembly right under the seat.

http://imgur.com/HWopKdC

Is this the crankcase breather hose?? If so, what is causing this to shoot oil/fuel out? Can I just seal this hose and call it good? This is surely flooding the engine and clogging the idle screws.

Eager to get riding again,
-Captconan
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post #2 of 12 (permalink) Old 04-01-2015, 02:58 AM
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There's a lot going on ! yes its the breather hose for the crankcase going into the bottom of the air box...if it was kinked it would give you problems, being kinked may also have caused surges of oil to enter the air box at high revs...in that crank case pressure would have over come the restriction caused by the kink and spurted oil and petrol into the air box.....one other reason for having fuel (only fuel) in the air box is knackered float needle valves...this would cause poor starting if the bike had been stood for a while..overnight..allowing fuel to flood the crankcase and causing vapor/fuel lock..the piston cant go down owing to the fuel below it in the crankcase...if the carbs are flooding you are looking to do a oil change once things are sorted...petrol getting into the crankcase will contaminate the engine oil inso breaking down the protection the oil provides....post up your most recent findings.
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post #3 of 12 (permalink) Old 04-01-2015, 04:58 AM
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You need to have a leakdown test done on your engine to determine if blowby past the piston rings is over-pressurizing the crankcase causing the engine to pump excessive oil into the breather. This will determine if you need a top-end rebuild or the problem is something easier and cheaper to fix. A regular compression test may not show worn piston rings due to the oil present. Pull the spark plugs also to check for the presence of excess oil.

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post #4 of 12 (permalink) Old 04-02-2015, 08:57 AM Thread Starter
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Sounds like I'm going to spend the whole weekend doing a major overhaul. It seems fuel has gotten into the oil. I plugged this crankcase breather hose with a rubber stopper and then ran the bike for a bit, which then caused an oil/gas mixture to come spilling from some other new place underneath the bike.

When I did pull it from the shed initially, there was fuel/oil in the plywood underneath the bike. Seems some seal decided to fail over the winter. In any case, yeah, excessive crankcase pressure caused by.... blowby? Worn rings? Compression test to follow...
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post #5 of 12 (permalink) Old 04-02-2015, 10:14 AM
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Originally Posted by Captconan View Post
Sounds like I'm going to spend the whole weekend doing a major overhaul. It seems fuel has gotten into the oil. I plugged this crankcase breather hose with a rubber stopper and then ran the bike for a bit, which then caused an oil/gas mixture to come spilling from some other new place underneath the bike.

When I did pull it from the shed initially, there was fuel/oil in the plywood underneath the bike. Seems some seal decided to fail over the winter. In any case, yeah, excessive crankcase pressure caused by.... blowby? Worn rings? Compression test to follow...
Your issue is oil volume, not bad anything.
Change the oil and clean your carbs. The float needles ( one or more) are stuck open and allowing the fuel to fill the carbs. You don't have to have bad rings for it to get into the crank case. Clean the hell out of the carbs and try again. If you're set on testing compression then let the bike warm up first. It'll have better numbers that way. Doing it on a cold engine that sat all winter is a recipe for failing numbers. And all that means is the bike sat for a long time and you're taking it that the rings are worn out and you're not giving the engine a chance to pass.

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post #6 of 12 (permalink) Old 04-02-2015, 11:10 AM Thread Starter
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I will work on that this weekend and report the results after I tear the carbs apart. Thank you for the insight!
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post #7 of 12 (permalink) Old 04-05-2015, 02:57 PM Thread Starter
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Just took the carb off and drained the "oil". By "oil" I mean it was about 99% gasoline in the oil pan and clutch housing, like, completely full over the eye on the clutch cover.

I suppose my next question is what damage could have been done to the engine and all associated gaskets and pumps when there was premium fuel being pumped as lubricant instead of oil. What should I look at replacing at this point?
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post #8 of 12 (permalink) Old 04-05-2015, 04:15 PM
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Originally Posted by Captconan View Post
Just took the carb off and drained the "oil". By "oil" I mean it was about 99% gasoline in the oil pan and clutch housing, like, completely full over the eye on the clutch cover.

I suppose my next question is what damage could have been done to the engine and all associated gaskets and pumps when there was premium fuel being pumped as lubricant instead of oil. What should I look at replacing at this point?
Change the oil & filter and check it out for strange sounds. The gas thins the oil and prolonged use this way could eat your bearings. If you haven't heard any knocking I would think you're good to go.

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post #9 of 12 (permalink) Old 04-05-2015, 04:17 PM
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If it hasn't been run for a long period of time with the diluted oil, I wouldn't expect any damage. As said above, fix your carbs, most likely the float valves(needle and seat). Then put cheap engine oil in, run for a while then change the oil again
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post #10 of 12 (permalink) Old 04-12-2015, 02:32 PM Thread Starter
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`

So I took the carb apart and cleaned it and put it back on, completely cleaned out the oil system and changed the filter, flushed it, and changed it again. The bike now starts and idles and revs and the crankcase isn't positively charged anymore.... however...

after the bike warms up it starts to produce a cloud of exhaust, seems like burning oil. It's pretty bad. But when it first starts when cold it's fine, purring like a kitten with no exhaust cloud of death. Revving it though when it is warm though produces a mighty cloud of oil smoke.

Are my valve seals shot from running gas through the lubrication system?
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post #11 of 12 (permalink) Old 04-12-2015, 03:43 PM
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Run it for awhile. Don't venture to far. May just be burning off whats left. I know these have a fuel pump . But is a leaky petcock possible to fill crankcase?
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post #12 of 12 (permalink) Old 04-12-2015, 05:01 PM
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Quote:
Originally Posted by Captconan View Post
So I took the carb apart and cleaned it and put it back on, completely cleaned out the oil system and changed the filter, flushed it, and changed it again. The bike now starts and idles and revs and the crankcase isn't positively charged anymore.... however...

after the bike warms up it starts to produce a cloud of exhaust, seems like burning oil. It's pretty bad. But when it first starts when cold it's fine, purring like a kitten with no exhaust cloud of death. Revving it though when it is warm though produces a mighty cloud of oil smoke.

Are my valve seals shot from running gas through the lubrication system?
Its the bearings that suffer from petrol in the oil...and thats when you leave contaminated oil in the engine then put several k miles on...so you did the right thing...black smoke when the engine is warm ? take the bike out for a run as suggested...see what she pulls like on a steep hill..dont rag her ..its better to take her out for a run than to run the engine whilst on the paddock stand....i'm optimistic things will settle down.
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