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Old 06-11-2019, 08:15 PM   #1
jacobsond
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Default engine diagnosis

I figured I would start a new thread on my engine diagnosis. Just to catch anyone up 94 G9 original engine. I changed oil put in 5w30 synthetic. The cart never took any oil so I did not check for 3-4 weeks. It was just about bone dry. Added 10w40 conventional. Smokes like crazy now at startup and you notice a drop in oil level in 5 miles. Tonight some quick tests. I took the valve cover off and spark plug out. Plug oil soaked. At top dead center you could see oil on the piston. Valve lash was less than 0. I mean the both exhaust and intake valve were open slightly at top dead center. Leak down test 100% fail.I loosened the valves up spun it a few times now only 10% leak when cold. Valve lash not set yet so they are pretty loose. Compression test 160 cold. Going to set the lash tomorrow and start it up and see what happens. Hope a valve didn't burn. Wonder why the lash changed so much? I always set the lash on the loose side and I did that last fall.
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Old 06-11-2019, 08:57 PM   #2
CP241
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Default Re: engine diagnosis

Just an educated guess, but I'd say the valves have absolutely nothing to do with the smoke. Valves cause compression loss, power loss, etc but not smoke. Valve seals can cause a little smoke but not like you're describing.

I'm gonna say you either broke an oil control ring, or when it ran low whatever oil was in there coked up and now its stuck.

You can get a bottle of the engine oil flush stuff and try it. You basically add it to the oil, run it around (low RPM) for about 15 minutes and then drain the oil and change it. I have used this stuff to loosen insane amounts if sludge and stuff. If the oil.control rings are stuck, and it's a recent occurrence then it may free them up and cure the issue. If not, there really isnt much alternative to tearing it down and rebuilding.

Since your compression is pretty much perfect, there shouldn't be any significant scoring to the cylinder walls requiring an overbore. You may be able to get away with a "light rebuild" which is basically new rod/crank bearings, rings, and a quick hone of the cylinder just to deglaze it.

While its apart changing a valve is easy. I'd replace the valve seal anyway (and I always install seals on both valves, from the factory only the intake valve has a seal on it).
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Old 06-12-2019, 06:40 AM   #3
jacobsond
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Default Re: engine diagnosis

I will do a "Mystery oil" soak on the piston then and add a little to the crankcase then change oil right away. Since I have 10W40 in there now oil dilution should not be an issue. I noticed that there was only a valve guide seal for the intake in parts list which I thought was odd. The I will go from there depending on the results. If It only needs a light rebuild that will be ok. I think the rod bearings are making a little knock anyway so replacing is not a bad thing.
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Old 06-12-2019, 06:50 AM   #4
trig123
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Default Re: engine diagnosis

You are saying the cart never once smoked until you changed the oil ? with Millennial oil , whoops mean synthetic
You didn't overfill it did you ?
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Old 06-12-2019, 06:51 AM   #5
CP241
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Default Re: engine diagnosis

Not a marvel mystery oil, it's not the same thing. You can try that but it's not as aggressive and you're burning a lot of oil. I was referring to something like this. https://shop.advanceautoparts.com/p/...YaApNzEALw_wcB
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Old 06-12-2019, 05:39 PM   #6
jacobsond
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Default Re: engine diagnosis

It never smoked before it ran almost out. It never used any oil either. I had put the synthetic in about 3 or 4 weeks ago 5w30. We cruise around the little town a lot so probably put 50-60 miles on it. I had to put about 3/4 qt in it and all I had on the shelf at home was 10w40 or 0w20. I put the 10w40 in. Now it really smokes and you can notice a decline in oil on the dipstick after 5 miles. The smoke is mostly for the first 1/2 block. It is starting good sounds pretty good.
The only thing I have on the shelf for engine clean is the Marvel. I will try that 1st. Overnight soak. I will get some better stuff depending on the results.
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Old 06-12-2019, 06:11 PM   #7
CP241
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Default Re: engine diagnosis

The problem with marvel in a situation like this is marvel is designed to leave in long term. It's not an aggressive detergent so it's not going to do what you need. If anything at all ia going to work it will be that motor flush stuff. Even then, it's a long shot and probably wont work, but for leas than 5 bucks it's worth a try and wont hurt anything.

I still think something else is going on though. I've never seen an engine burn so much oil that you notice it lower on the dipstick in only 5 miles. That's a LOT of consumption. You either would have to have completely broken oil rings. Or its leaking somewhere, maybe when it's running only (oil feed line to the head, crank seal, etc). Something just isn't adding up here. Simply changing the oil, it ran out of oil, and now burns and smokes like crazy. I have to believe that something was loose, it leaked out, ran low on oil and as a result you now have damage inside the motor. Synthetic CAN cause seals to leak if they are bad to begin with, and only "sealing" due to the amount of sludge and buildup. But that seems a little far fetched based on the amount of oil you are using and how quickly it ran low to begin with.
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Old 06-12-2019, 06:13 PM   #8
mikeasis
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Default Re: engine diagnosis

I could be wrong here but 5w30 seems awful thin for an air cooled engine. I once changed the oil in my xr200 and put dads Pennzoil 5w30 in it. Smoked like a freight train. Changed the oil with Honda GN4 20w50 and problem solved, no more smoke. Ive never run anything but 20w50 in an air cooled engine, This was 20 years ago so things may have changed.

Wondering too if it was over filled.
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Old 06-12-2019, 10:06 PM   #9
cgtech
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Default Re: engine diagnosis

Quote:
Originally Posted by mikeasis View Post
I could be wrong here but 5w30 seems awful thin for an air cooled engine. I once changed the oil in my xr200 and put dads Pennzoil 5w30 in it. Smoked like a freight train. Changed the oil with Honda GN4 20w50 and problem solved, no more smoke. Ive never run anything but 20w50 in an air cooled engine, This was 20 years ago so things may have changed.

Wondering too if it was over filled.
Were the air cooled engines you are referring to "splash oiled" like a Yamaha, or did they have an oil pump. Splash oiled motors are more critical that they get the correct viscosity. Too thick, and it won't get splashed into the passages adequately.
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Old 06-12-2019, 10:30 PM   #10
trig123
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Default Re: engine diagnosis

Is the oil staying up top and not running down in the crankcase ? I am with CP241. I don't see how just changing to synthetic would have caused anything like this to happen.

I do know if the oil stays up top and don't go down it will leak around valve guides in an auto engine. I have removed valve covers on 350 Chevy engines after a customer complained about the engine being low on oil and smoking. Oil would run out as soon as you removed the valve cover because return holes were stopped up.

I am not an expert on these engines though.
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