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post #1 of 12 Old 09-10-2019, 09:09 PM Thread Starter
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Rebuilt vanguard smokes after getting warm

Looking for some thoughts. Recently got a 20hp vanguard that had a broken rod. It looked very clean as though it had very low hours. Found out the cam broke as well, and likely went first, taking out the rod. Cylinders were clean as was pretty much everything else. Got replacement parts and buttoned everything up and it fired right up. After about a minute of running, it starts to smoke. Most rebuilds smoke a little, but this seemed more than what I usually encounter. Full disclosure, I didn't measure end gaps on rings, but I've also never had to adjust any either so it seemed low risk.

I put some oil on the Pistons and rings, and i put some assembly lube on the cylinder walls, valves, etc. Could the smoke be from burning off the assembly lube or is it more likely that the oil rings got goofed up in the assembly?

The engine seems to run good, but I live in the city and my neighbor is a real pita, so I didn't run it for more than a couple min. Let it cool and tried it again with the same result. After a minute, it slowly starts smoking heavier.

I plan to take it to our farm in a few weeks to just let it run for a while and see if it clears up, but thought I'd quiz you guys first.

Thanks
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post #2 of 12 Old 09-10-2019, 09:39 PM
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Re: Rebuilt vanguard smokes after getting warm

Sounds like you got it without ever seeing it run...sounds like it was possibly run low on oil which caused the cam and rod failures...could the rings have needed replacement also?
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post #3 of 12 Old 09-10-2019, 09:59 PM Thread Starter
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Yes, I got it without hearing run.

Rings could have been bad I guess, but they looked ok and it looked like the engine had such few hours. There were no marks on the crank or Pistons like they overheated, but there was a large buildup of scaley carbon on the piston tops which seemed like more than normal.

The valves and guides all looked good and seemed tight. I'm now paranoid that the rings were somehow very worn and I now have a massive end gap - but the delayed smoke still doesn't work add up. Was thinking maybe the lube on the exhaust valve stem is burning off once it gets hot?
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post #4 of 12 Old Yesterday, 12:02 AM
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Re: Rebuilt vanguard smokes after getting warm

How long has it run in total since the rebuild? It does usually take a while to burn everything clean, especially if some oil and stuff got into the muffler.

How do the plugs look?

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post #5 of 12 Old Yesterday, 08:01 AM Thread Starter
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It's only got about 3-4 minutes on it. Like I said, didn't want to smoke out my neighbors. It wasn't smoking so bad you couldn't see through it, but enough to fill the garage up.

How much air should be going in and out of the crankcase breather? Seems like there is a big hiss each time I turn it over by hand, and the previous owner had the tube disconnected and plugged. Thought it was odd
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post #6 of 12 Old Yesterday, 10:18 AM
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Re: Rebuilt vanguard smokes after getting warm

I'd mic the cylinder with a bore gauge if you have one; failing that, a set of telescoping gauges and a micrometer or good caliper, failing that I'd take it to a shop that has a bore gauge. If you just want to get a fair estimate, check the ring end gap. If the bore is worn out of spec, the gap will be beyond spec and will leak in much the manner you are describing. The amount of slop required to cause problems can be quite small and not really noticeable with the naked eye. It sounds to me that at this point you're throwing parts at an engine without knowing what condition it's really in, at that point it's upto chance.

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post #7 of 12 Old Yesterday, 10:48 AM
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Re: Rebuilt vanguard smokes after getting warm

It can take awhile for oil to burn off completely..some engines I have gotten that sat a long time took an hour to finally stop smoking,the rings were probably stuck in the grooves..


A car a friend had that we replaced the blown engine in smoked for 2 days after we got the supposedly good used salvage yard engine in it and running..

He was about to drive it to the place he bought the engine from and demand a replacement or refund,but it finally stopped smoking after the second day,when he drove it about 20 miles on the highway...evidently the muffler and whole exhaust system had been "oiled" by the dying first engine--must have been a quart or two in the muffler..
Weird thing was it didn't start smoking till it had been run a good 10-15 minutes,I guess it took that long for the muffler to get hot enough ?..


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post #8 of 12 Old Yesterday, 10:50 PM
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Re: Rebuilt vanguard smokes after getting warm

It's going to need to run at least 30-45 minutes before you make any decisions.
If the breather was plugged up I bet it was sucking oil out and into carb. I had a vanguard do that. They are more picky than other engines but great!
The dipstick tube on mine was the culprit. Put a new one that sealed 100% and no more oil coating inside of air filter housing in middle of filter.
Head gaskets will cause a lot of smoking too. The vanguards have old style with is thin metal and new style with is graphoil.
They usually have an intake valve stem seals too.
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post #9 of 12 Old Yesterday, 11:13 PM
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Re: Rebuilt vanguard smokes after getting warm

Quote:
Originally Posted by baconK5 View Post
It's only got about 3-4 minutes on it. Like I said, didn't want to smoke out my neighbors. It wasn't smoking so bad you couldn't see through it, but enough to fill the garage up.
I'd say drive it for an hour like you stole it and see what happens. Probably the worst that will happen is you kill a bunch of mosquitoes.

If it hasn't cleared up by then it'd be time to maybe dig deeper.

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post #10 of 12 Old Yesterday, 11:37 PM
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Re: Rebuilt vanguard smokes after getting warm

Quote:
Originally Posted by baconK5 View Post
Looking for some thoughts. Recently got a 20hp vanguard that had a broken rod. It looked very clean as though it had very low hours. Found out the cam broke as well, and likely went first, taking out the rod. Cylinders were clean as was pretty much everything else. Got replacement parts and buttoned everything up and it fired right up. After about a minute of running, it starts to smoke. Most rebuilds smoke a little, but this seemed more than what I usually encounter. Full disclosure, I didn't measure end gaps on rings, but I've also never had to adjust any either so it seemed low risk.

I put some oil on the Pistons and rings, and i put some assembly lube on the cylinder walls, valves, etc. Could the smoke be from burning off the assembly lube or is it more likely that the oil rings got goofed up in the assembly?

The engine seems to run good, but I live in the city and my neighbor is a real pita, so I didn't run it for more than a couple min. Let it cool and tried it again with the same result. After a minute, it slowly starts smoking heavier.

I plan to take it to our farm in a few weeks to just let it run for a while and see if it clears up, but thought I'd quiz you guys first.

Thanks
I've not much smoke on a rebuild. Maybe I have been lucky. Any chance you put a ring or two in upside down? The plugs should tell you after some run time if the breather checks out.

BTW - I would think the failure was most likely the other way around, rod failed and took out the camshaft. As someone else pointed out, perhaps it was low on oil albeit I would expect the crankshaft journals to answer that question.
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post #11 of 12 Old Today, 10:58 AM Thread Starter
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Did a little inspection last night...I know compression values aren't particularly meaningful with compression release, but I did have about 23% difference between cylinders 1 and 2 which is high (but still in spec). I don't have a real leak down gauge, but with the homemade job I've got, I can clearly tell that cylinder 2 has got a significant leak to the crank case. Valves seem to be sealing as do the head gaskets, so I guess I get to tear it down again. At least everything is already cleaned....

I leave for a work trip tomorrow so I won't be able to get to it for a couple weeks, but I'll post back what I find.

Thanks for the responses. Fun and helpful to read
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post #12 of 12 Old Today, 11:23 AM
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Re: Rebuilt vanguard smokes after getting warm

I'm guessing that since it was apart and disturbed maybe the rings just haven't seated properly yet... but that's just guessing.

Let us know how it goes, and have a safe trip.

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