108 overheat? smoking from breather cover.
 

I restored this 108 last winter and paid the local Case/IH dealer to overhaul the engine. Piston, rings, rod, valves. Cylinder was in spec (they said) so standard piston and rings were installed.

I put it all back together and have been using it all summer, cutting an acre or so every week. Engine seems stronger than it used to be, so I've been happy.

Until last week. After cutting for half an hour (heavy grass, working hard) the engine started to lose power and blowing lots of smoke out of the breather cover. Seems like the engine was working hard, but going nowhere, slowing down, but at full throttle. Barely finished cutting the grass, and put it away, not sure what was going on with it.

Today (a week later), it started fine, ran great for about a half hour (again, thick grass, but cutting it fine) and it started doing it again--losing power and smoking from the breather cover. So I shut it down. Went to go get the 1650 from the other house a few hours later to finish cutting the grass. Went to put the 108 on the trailer to bring home to fix. It started fine, no smoking, so I put it on the trailer. Now I have it home, so looking for ideas on where to start. Is it overheating? Or something else.

Sounds like it's happening when the pto's engaged and you're mowing? Does it still bog down and smoke after you disengage the blades? Grasping at straws, but maybe a pto, mule drive, or deck issue after warming up causing power loss. Of course, not so much if it still happens after shutting the deck down.........:bigthink:

Mouse nest? Grass clippings? Sounds like the engine is getting hot, :bigthink:

When it started doing this, my first thought was that the belt had come off a mule drive pulley causing excessive load on the engine. Or the deck was clogged up. But the smoking continues with the load removed (PTO clutch disengaged) when it does this.

The smoke out of the breather cover indicates excessive blowby, right? Why would this happen after using the tractor for a half hour?

Sawdust. Kind of sounds like the same problem I had with my 1200 after I refreshed it. Here is what I found out to be "my" problem. Maybe not yours. I had smoke and oil spewing out of my breather. I pulled the head and found it had "melted" and blew out the head gasket. I was running WAY lean because I did not adjust the carb correctly. Maybe take a look by pulling the head and seeing if you are burnt/melted and/or blown out gasket. I replaced the head and gasket, breather cover gasket, rubber grommit and filter, readjusted the carb to run a little/alot richer and have not had any problems.
Like I said this may not be your "fix" but a possible check.
Hope it goes well for you.
John

Sawdustdad, not saying this is the problem, but you could check the valve to tappet clearance. Something else to rule out. Just my :TwoCents:

So I spent some time today working on the 108. It started and ran fine. So I cut some grass, had to go out to the pasture to get some heavy grass to duplicate the conditions that caused the problem yesterday. After about half an hour it seemed to lose power again and smoking out of the breather again, so I opened the high speed jet to enrich the mixture and it regained power. So I think that might be the problem--running too lean, so when it's really hot, under heavy load it starts losing power. That seems to have solved the problem of power loss, but it's still smoking out the breather a lot.

The only way you get smoke out the breather is piston ring blowby, right?

you may want to put a cyl leak down tester on it. once you start getting smoke out the breather and losing power there's something wrong. if you don't have access to a leak down tester take the head off and check the bore. you will also get smoke out the breather if the rod starts to go tight on the crank. do you check the oil?

Yes. Even if the rod is getting hot and smoking it won't move more air, just make more smoke. The ONLY way it can have more air exiting out the breather is if there is more piston blow by. If the motor already got too hot from a lean condition, the damage is already done. Sorry man, it probably won't get any better on it's own. If it didn't score it too bad, it might go ahead and run, but if it was losing power, it was swelling the piston in the bore. If you want to, pull the head and look, but it has been my experience with engines that you probably won't see anything till you pull the piston out. Then you'll be like, "oh, there's the problem". It might make it worse to keep using it.... It may be fine. Your choice. But one thing is for sure, it got hot.

J-Mech ; everytime the piston travels downward you displace whatever cubic inchs of air the bore take's up in the crankcase. in the case of a K241 its 24 cubic inchs so your statement is incorrect. that's why there's a breather if it didn't your oil seals would start blowing oil out.