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sfw1977

Agco Allis 918H

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sfw1977

Hi folks,

I don't post often, but read often enough when having trouble.  This time, I can't seem to find an answer.

I have an Agco-Allis 918H.  Simplicity M/N:1692452.  I has a Kohler Command 18. Model CH18S Spec No. 62513.

I have been running this thing for 3-4 years, since i took ownership from a relative who had passed away.  I haven't had to do anything to it other than change a worn belt, change the oil, and sharpen the blades on the mower deck.  The deceased family member was a very good mechanic and it is very well maintained otherwise.

Here is the issue:  This spring, I went to start her up after about 5-6 months, last moved her in late November.  She fires up pretty quick but starts smoking rapidly.  I mean dumping out fumes.  So much i had to shut her off and run out of the little garage I  keep her in or I would have been in trouble.  I then also notice there was a small puddle of oil below the front of the mower deck.  Not a ton, but the floor was wet.

Today I finally got to look at it.  I looked underneath and couldn't see any obvious point of leakage, but it was wet all around the tray below the motor.  I checked the oil filter, checked the plug, checked that she hadn't lost too much oil etc.  All seemed fine and snug.  No leaks.  So I did a little reading in the service manual, and a couple articles that I did fine mentioned a plugged breather hose or bad breather needle.  So I decided to take off the air cleaner and have a look.  Low and behold, just inside the air filter, i could see it was wet with oil.  And the source was the breather hose.  So I took the air cleaner plate off, and took off the breather hose, it does have one crack in it under the clamp.  The hose is old, but seems to be ok otherwise.  I cleaned every thing up, put it all back together.  Fired up, and no smoke.  Ran for about a minute, then slowly started smoking and then it was right back to smoking like it had the first time it started this spring.

So I guess my question is, if the oil seems to be coming from the breather hose, is it likely that i need to replace just the hose, is the needle stuck, the whole breather assembly?  Or is there something worse like a ring broken or something along those lines?  It just seems to me like maybe the breather isn't doing its job.  Is it normal for this to cause leaking?  Or could it be some low end seal has gone bad and is maybe not creating enough pressure in the case and the oil is just getting up there?

You might be able to tell i understand how these things work. But i get a little out of my league when trying to troubleshoot them...

Any comments or suggestions are appreciated.  You folks have helped me through a couple other issues so I have faith someone will catch this.  

Thanks!

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RAC

Probably (ok, maybe, hard to tell from here) a head gasket. Is there a lot of blow-by out the breather hose after warmed up? They tend to go bad near the oil return passage and the escaping cylinder pressure blows oil vapor out the breather. That gets sucked into the carb and becomes smoke. If it is a freshly blown gasket it may run fair but it'll eventually foul the plug on that side. Have had the same thing happen on both Command twins I have, a CH18 and a CH25.

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sfw1977

Thanks RAC for the reply.

It wasn't a terrible amount in the carb.  But it was obviously wet... looked sort of like someone rubbed it down with oil...

It doesn't want to stay running.  It starts up, and runs, but once the smoke really starts pouring out, its like it suffocates itself and shuts down.  I thought it could be a head gasket, but I don't see any external leaks up that high.  I guess the leak could be internal.  Still unsure why I have what seems to be an oil leak, this is what led me to the breather hose and case pressure.  I guess ill have to really pull it apart to tell though... I will check the plugs as well see if one is fouled up.

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RAC

The CH25 in my Legacy was blowing out the breather so bad I considered not buying it. The hose was also cracked a little which was oozing oil out over the top of the crankcase.

 

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dhoadley

The cheaper and easier option would be to replace the breather. I would start there. I've never had this issue, so take my advise for what its worth, but I've read enough on here that this is not an uncommon occurrence. Good luck, Dave

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sfw1977

Since the breather hose was a little rough, and that area of the engine was a little dirty, I decided to start there.  Either way I'll need to replace the hose.  The whole breather assembly, gaskets, needle, filter and hose was only $33.  So... I will look at the plugs, and see if I can tell if its cylinder specific etc.  Worst case I have those parts on hand.  I will follow up with my findings.

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sfw1977

Well I went through and changed the whole breather assembly.  New Filter, new needle, new plate and gasket, etc.  Fired right up, and raced... realized I had forgotten to re-adjust the governor... whoops!  Adjusted that, and it ran clean again for about a minute.  Ran strong like it always has, then smoke again.  So I guess i it must be a head gasket.  I pulled both plugs, neither of them are clean, but one is obviously more fouled than the other.  So I guess I need to do the head gaskets on both just to be sure. 

I am still confused about the leak though.  There isn't enough leaking through the breather hose the little I have run it to cause the wet spot I have on the ground.  Are there any other symptoms I can look for to help be sure its a head gasket before I pull it all apart?

Again, thanks for all the comments an help thus far.

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B10Dave

Just a thought. Did you check the oil level. If it is high and smells like gas you may have a leaky float and gas in the crankcase. This would cause engine to smoke badly if it starts without hydrolocking.

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ShaunE

A compression test followed by a cylinder leak-down test should reveal your problem.  My Command was nothing but problems for 3 years & hundreds of $$$.

 

 

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RAC
7 hours ago, ShaunE said:

A compression test followed by a cylinder leak-down test should reveal your problem.  My Command was nothing but problems for 3 years & hundreds of $$$.

 

 

I've two Command motors, an 18 in a 1864 Cub and a 25 in the Legacy. Other than head gaskets no real issues. Head gaskets a cheap fix if you're handy. The 25 required the Kohler ignition conversion but it wasn't the fault of the motor. Mice chewed insulation off the wires and shorted out the ASAM module.

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ShaunE
57 minutes ago, RAC said:

I've two Command motors, an 18 in a 1864 Cub and a 25 in the Legacy. Other than head gaskets no real issues. Head gaskets a cheap fix if you're handy. The 25 required the Kohler ignition conversion but it wasn't the fault of the motor. Mice chewed insulation off the wires and shorted out the ASAM module.

What can I say?  I'm the odd guy out.  Warped heads (.009"), Valve seats, Valve seals, leaky valve covers (all three kinds with correct gaskets), Coils, Magnets off the flywheel etc.  I've had fewer problems with my Triad & both tractors are used equally.

But like I stated above, if it's not electronic or carburetor related, a compression test followed by a cylinder leak-down test should reveal the problem.

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