Kohler 20.5 V-Twin stumbles

I bought a used but extremely well cared for riding mower with a Kohler 20.5 V-Twin engine.

It needed a new fuel pump, which I installed easily myself. It's a simple pulse pump.

It runs fine, does not burn oil at all, but the engine stumbles a bit whenever I go downhill. It seems to flood out briefly, or misfire, or lack fuel or air for a second. Then it recovers.

What should I look at to diagnose this issue? Fuel filter? Plugs? Carburetor? Or is this normal?

Any advice?

Thanks,

Antifa

 

Does it do it just one time, or repeatedly while going downhill. Does applying partial choke help stop it or keep it from happening? There may be a little water in the carb bowl and the angle might be just right for the engine to pick it up some.

 

Hi, Cheese;

It does it once, right as I head down a steep grade. Then it recovers right away and runs steady after that.

Sometimes it does the same thing on level ground, not mowing or towing anything.

At first I thought it might be some water condensation in the gas tank, but I've run through a couple tankfuls of fresh gas now, so it's something else.

I will try setting the choke lever out a bit to see if that helps, and report back.

Thanks

 

Don't completely rule out water in the fuel SYSTEM yet; the most likely place to find water will be in the bowl of the carburetor. Whether water or otherwise, I say you have a carburetor that needs to be flushed, cleaned and reconditioned.

 

Well, yesterday was the first time since I bought this used tractor a couple weeks ago to really run it a bit. I loaded ten little utility trailer-fuls of firewood one after another, and brought them down the hill to the house.

Ten trips. My property is hilly, so what the tractor had to deal with was 1/8th mile uphill towing an empty trailer, and then 1/8th back downhill with about 400 lbs of firewood in the little trailer. No real load there.

Three things -- the stumbling problem on hills has gone away. Must have been some water or bad gas. I'm still going to get a new air filter and fuel filter, since I do not know the age of the ones on there now.

Second issue -- late in the afternoon, after 7 of the 10 trips, the exhaust suddenly blew a big puff of blue oil smoke, a sure indication that the last bit of oil was burning off. I shut it off instantly, and checked. Sure enough, there was no oil on the dipstick. I added fresh oil on the spot and started up again. It smoked for a couple seconds, then settled down sweetly, and ran fine for the remaining trips, and runs nice again today. It does not produce any smoke at all, but this engine obviously burns some oil.

What typically causes this, and what repairs are needed? Any advice or experience on this would be much appreciated. It's a Kohler 20.5 V-Twin, Model CV20S.

Third thing that came up is the drive belt overheats and smells of burning rubber. This started on about the 7th of ten trips as well. This is a Craftsman Model 917.251510 Serial# 111695C 001287. It has a 6-speed manual transmission. The drive belt is old, but not cracked. I guess it is slipping on its pulleys, and needs replacing and adjusting, which I'm happy to do.

Just to be careful, I looked through the Owner's Manual to see if perhaps I had the option of checking the transmission oil level, thinking perhaps the fluid there was low, too. My old Wheel Horse tractor had a transmission fluid reservoir to check on. I was thinking the belt was heating and slipping because the transmission was getting hard to turn or something.

Nope, there is nothing in the manual on this tractor to indicate I can check or monitor the transmission fluid level. It's apparently factory sealed. That seems odd to me, since a leaking axle seal could slowly drain the tranny and you'd never know it. Does anyone have experience with this model?

Thanks for any advice on what to do for this beast. It sure is strong, and the previous owner took excellent care of it, so I want to give it what it needs now.

Antifa

 

The oil burning is likely rings or a head gasket. The oil puff sounds like a head gasket unless it was at an angle when it did it. An oil puff isn't a sign of the last oil burning up. It will be too late when you get a sign of the last bit of oil burning up.

The drive belt burning may be as you suspect, and it may need tightening, or there may be a pulley with bad bearings going bad, or it could be because of the fact that it drove 2 1/2 miles up and down hill (downhill puts stress on it too, the belt is keeping the mower and the load behind it from rolling freely away down the hill).

The transmission on most all models is not serviceable.

 

Hi, Cheese;

Thanks for the advice. If it's the head gasket, would I be able to see any oil leakage? Would I see or smell oil burning?

I did find one website that indicated these older AYP transaxles commonly need their pulley and shaft replaced.
For what it's worth:

Manual Transmission Fluid Change - TractorByNet.com

Thanks,

Antifa

 

What Cheese is getting at with the head gasket is a possible breach between the combustion chamber and the valve chamber. The head gasket it relatively narrow between these two points and commonly breaks through thereby allowing oil that will be in the valve chamber to flow through into the combustion chamber. The other thing I'd like to bring up is that this is a 16-year old tractor and you may indeed have some wear in the piston/cylinder/rings area and blowing oil past the rings...in addition to the possible breached head gasket - which I believe you will find a problem with. Like Cheese, I'll bet you're just overworking the tranny belt with all the loads of wood and as a result it is now spent and burning, especially after heating up well after several heavy loads.

 

I took the tractor to the repair shop this morning. I had to drive gently it a couple hundred feet to load it in the truck, and I noticed within 30 seconds of starting up a very strong burning rubber smell, before I ever engaged the clutch. This makes me think the burning smell is the engine, not the belt.

We'll see. The Kohler mechanics said this engine was manufactured in 1995, so it would have seen use from around then until 2006. About time for it to be reconditioned.

I'll let you know what they find, and what repairs they do.

Antifa