CH20S

[comet66]

I was mowing with my Ultima on Sunday when it started to miss some then got worse to the point where I had full choke to get it back to the shop. Acting like it was fuel starved. Since I had a spare pump and filter on hand it only took 5 minutes to swap them out. It seemed to run better for about 20 minutes then started missing again. Pulling the plug wires one at a time made no noticeable change. Did find a fouled plug, so I changed them out. It started hard but did restart. Idled for a couple of minutes and then commenced to spouting a real heavy cloud of blue/gray smoke out of the exhaust. In a matter of a couple of seconds it was almost impossible to breath in the open shop.

It continued to run (actually seemed to smooth out) until I got to the switch. A couple of seconds. When I crank it over now it will not try to start but spews smoke out of the exhaust. Now there are a number of things that would cause this to happen, but what confuses me is that it still has 150# compression on both sides. When cranked over with out plugs it sprays oil out of one cylinder. So I know where the problem is, just don't know yet what it is. Anybody have a guess?

[BLT]

Sounds like a breather problem. I just had a similar problem with a Briggs 16 HP on my repowered 917. Disc inside breather was 'frozen' in place taking away the balance of crankcase pressure. CH 20 has has its breather under intake manifold and has a reed valve do its work. I was there when I first bought my Sunstar.

[RayS]

Kind of sounds like the same situation when the head gasket blown on my CV 20 Kohler. Bob is probably right.

[comet66]

quote:

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Originally posted by BLT
Sounds like a breather problem. I just had a similar problem with a Briggs 16 HP on my repowered 917. Disc inside breather was 'frozen' in place taking away the balance of crankcase pressure. CH 20 has has its breather under intake manifold and has a reed valve do its work. I was there when I first bought my Sunstar.

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I know dat!!:O I have had to replace the reed valve before. Different symptoms, caused too much pressure in crank case and blew out the main seal. But why didn't I remember that?...CRSdz Thanks guys, appreciate the help!!

[comet66]

Well that didn't do it. She's still spraying oil right into the carb. Can you think of anything else I've forgotten?

[CarlH]

Not experience but logic. Oil into carb means positive crankcase pressure. One cylinder pumping oil. How about broken ring??? Might explain both.

[acfarmer]

If you have compression on both cylinders that rules out alot of things.I'd pull the valve covers if a rocker has worked loose.

[BLT]

Where is the pressure sender for the dash light?

[comet66]

160# compression on both sides. Sending unit is in the valley cover that also covers the reed valve. I wonder if this oil pump has a pressure relief valve that may have gone slinky. I can't find any information on it.

[bluecap24]

There is a pressure relief on the pump. It is just a spring and plunger that lets the pressure blow back into the crankcase. Possibly a valve stem seal letting oil back into the intake? My sunstar's CH20 went out last week too. Oil pressure dropped for a split second to turn the light on and it was too late. I would suggest finding out what it is before you run it much. The command doesn't put up with a whole lot of abuse. Just dropped $1800 in mine for a new 27hp command. That hurt.

[Al]

Hi, My first guess would be a broken expander in the oil ring. I have seen this several times. Once in 1959 my 58 315hp 348 Chevy. It would run fine, but would foul the #5 plug. Compression was within 2lbs on all cylinders. Would still pull good to 6200 and get in the high 13s in the quarter. I ended up pulling the piston and the oil ring expander was broken. Oil will wash past compression rings with almost no resistance. The oil than washes past the first rail is dumped back in the crankcase through the oil passages in the piston in oil ring groove. Any oil that passes the upper oil ring rail has no place to go and the compression rings sort of slide over it. I have seen this in several engines. About a month ago I got a call about this from a person about a garden tractor pulling engine doing this on the dyno, but power was falling off at high rpm. Problem turned out to be the camshaft was failing and the metal particles were getting embedded in the piston and the cylinder from the oil ring down was severely scored, the oil was going past the oil ring on the way down, but the cylinder was smooth above the oil ring with the piston up, so the compression remained good. Power was way off in this one especially from about 3 to 7000 rpm due to cam lift being low etc. If this were a Command or Vangard, my next area to look at is head gaskets. We have seen a lot of Vangards (and some Commands) that run fine and when you get in tall grass, all of a sudden clouds of blue smoke. Get through the heavy stuff and it runs good again. Compression and leak down and crankcase vacuum tests are normal. If you keep running it, it will run very rich and have a lot black smoke. Checking the air cleaner will reveal oil and vapor have been blowing up the breather tube into the air cleaner cover. The air cleaner get soaked and then chokes the engine. The problem is caused by a bad head gasket. The gasket isn't blown and everything including compression checks normal. What happens is the head gets warped and when the engine is running normal all is fine. When a heavy load is applied the combustion pressures soar and some of the compression leaks past the gasket into the push rod passage cut out or the oil return hole in the block. This leakage reduces the crankcase vacuum and the gasses that leak into the crankcase get expelled through the crankcase breather into the air cleaner where it is sucked into the carb. and burned resulting in smoke. It was very common in the 14 and 16 hp Vangard single cyls and the earlier Vangard V twins with the steel head gaskets. If you monitor the crankcase vacuum with a manometer and put a heavy load on the engine you will see the crankcase vacuum go from a vacuum of greater than 12"hg to actually positive pressure. Removing the head will reveal the path where the leakage is. Checking the head surface will reveal over .003" of "bow" in the head surface between the bolts. Resurfacing the head, getting it flat again fixes the problem. Once the heads have distorted and are resurfaced it seems to fix them forever. One other thing OD NOT USE THE EARLY STYLE STEEL GASKETS, use the new Graphoil gaskets and the problem will be cured. If this had been an early series unrepowered Ultima, I would expect it to be a Magnum. The OHV problems would not be applicable. I would bet on an oil ring expander, unless the breather is blowing oil into the air cleaner. If so look for a crankcase air leak. Most common is the dipstick not being pushed completely down? This and $2.00 may buy you a cup of coffee. It's free value accordingly. Al Eden

[comet66]

This a 900 hr command I bought new. I did notice over the winter that under a heavy load it seemed to consume a little more oil than normal. Just barely enough to be noticeable, and never any smoke. So I just passed it off as being a 900 hr engine. I'm leaning toward head gaskets my self and ordered a set yesterday morning. Thanks guys, I appreciate your input!!

[colincox1]

Please , this is very interesting, please post the final diagnosis and fix

[comet66]

Turned out to be a headgasket. Running like new again.

[RayS]

Glad to hear you got it fixed. Mine was doing the same as well when it blew the gasket. It would use about 1/2pt. of oil to mow 3/4 of an acre.

[cheken]

Sirs, My Sunstar (CH18) will hardly idle at low RPM's. Other than the oil vapors in the air cleaner, she functions as expected. Cold blooded, yes. Needs choke to start, as typical. Can anyone comment on low RPM idling issues? I will be ordering new head gaskets soon to see it that takes care of the oil venting issue. Gas filter? Thank you.

[BLT]

Do you have an oil consumption problem? I don't think head gasket replacement will reduce oil mist venting into carb. Also, if I remember, 1800 RPM is correct engine idle speed. As low speed might cause it to die from time to time.

[cheken]

Thanks BLT for your reply. Because my memory fails me, I cannot recall if there is an oil consumption problem. The Sunstar is currently on sick leave due to a starter (gear) issue. Soon to be resolved so I will check soon. Here is what Al (above) says about the head gaskets: "Checking the air cleaner will reveal oil and vapor have been blowing up the breather tube into the air cleaner cover. The air cleaner get soaked and then chokes the engine. The problem is caused by a bad head gasket". This is the reason for my head gasket pursuit.