question on the 108

[Jim H.]

Last couple times while mowing I seem to notice the engine more.

When I start mowing it seems to have normal loud exhaust the more I mow,the quieter it seems to get., Now this probably sounds like{ I'm just getting used to it symptom}

Anyway yesterday I mowed my yard and as usual it got the quieter sound, I finished my yard, then without stopping I went to the school yard beside me .

the grass was cut two weeks ago over there 'but has some real tough places even with my new blades, I cut mine every week.

While in the heavy cutting grass the engine would start to smoke a little from the breather side and if left to cutting for a short period of time say 20 feet engine would act like it was going to bind and the valves would rattle like crazy. I would try to take lesser width cuts same thing.

So I left it cool off and now seems top run normal. I even finished the heavy grass last night without a glitch.

Just wondering , Is this a sign of carbon build up you guys talk about ?

I noticed the engine started to smoke a little in the spring on especially down hill right turns out the breather, but went away on the level. no it wasn't over full unless dip stick may be messed up. Metal above rubber grommet is not fastened to the stick so when in crankcase it does go to bottom. I may be overfilling it a little???

[Matt G.]

Overfilling it with oil isn't going to make it "bind up" and the "valves rattle like crazy". My 124 loader tractor was 1/2 quart over filled, and it smoked like a chimney. Is the carb set too lean? That's usually a cause of power loss/overheating/sticking valve.

[Jim H.]

Don't seem to run too lean starts fine, runs as good as can be as expected I guess. Did notice last couple times it was run hard the carb drips after parking tractor ,{telling me float needs adjusted. if I park on a little up grade it quits dripping.

I've had it off twice now afraid to adjust it too tight, Guess I'll have to do it again.

I need to figure out how to incorporate Velcro fasteners , cause with clubs for fingers that right nut is hard for me to remove on carb, Even harder to put on if the left one is too far turned on the stud.

Never knew frustration could be so much fun ! ~~LOL

[punkid]

Well I don't know too much about these tractors yet, but if this was a car I would say you are running it real hot and your starting to experice detonation. I would try running a tank of premium fuel and see if it goes away. if so it might be time to remove some carbon, and or clean the outside of the engine to make sure your getting full cooling.

[Merk]

When was the last time the crankcase breather was cleaned?
I would double check to make sure it was installed the correct way.
Page 12.16 and page 12.17 shows how to install the breather conponents the correct way.
Make sure the breather plate has the drain hole towards the bottom.

[Matt G.]

"Doesn't seem to lean"

Ok, I'd make sure it's not too lean. Every carb has it's own sweet spot, but 2 1/8 to 2 1/4 turns out on the main needle is pretty close for most tractors. Here's how I adjust mine:

Start the engine, let it warm up to operating temp. Advance throttle to wide open. Now, you can start playing with the mixture screw. Turn the needle out 1/4 turn at a time until you get black smoke, galloping, etc. and then back in until it just smooths out. Now, idle it down and ram the throttle back to WOT. It's too rich if it stumbles and there's black, sooty smoke. If you get stumbling and black smoke, lean it 1/8 to 1/4 turn and try again. Repeat until it'll go from idle to WOT without black smoke and it should be just about right. It wouldn't hurt to turn it out 1/8 turn after that. Air-cooled engines should run a little rich. NOTE: that method only works well if your engine is in relatively good condition. If it's not in good condition or it smokes such that you can't see the black smoke, you can use a leaning method similar to what we use is small airplanes that don't have a cylinder head temp gauge.

For this method, it's real helpful to wear earplugs to deaden PTO clutch noise and hydro whine (if applicable) to make this a bit easier. Start the same way by warming the engine up. Run it at WOT, and SLOWLY lean the mixture until it really bogs down, then turn it out again until you get an rpm rise and then a drop. After it drops again, turn it back in to where the engine runs the fastest. That should also be correctly set.

If you've got a leaky carb, take care of that first. Adjust the float or put in a carb kit as necessary.

You can also put a capful or two of seafoam in the gas tank to clear out the carbon. Similarly, you could fill a spray bottle with water and spray it into the carb with the engine running. Either method should decarbon the combustion chamber.

One last thing....sounds like your carb is held on with the wrong fasteners. All of mine are hex bolts with a screwdriver slot in them. They are relatively easy to remove and reinstall.

[Jim H.]

Originally Posted by Merk

When was the last time the crankcase breather was cleaned?
I would double check to make sure it was installed the correct way.
Page 12.16 and page 12.17 shows how to install the breather conponents the correct way.
Make sure the breather plate has the drain hole towards the bottom.

Thanks Merk ,
I was just assuming it was working as the smoke comes out of it .

I'm guessing this would be the first time in 38 years that it was serviced.. gotta get my work pants on> :>)


Matt,
Tried your suggestion setting seems to be OK,

I do since my old 52 chevy experience give mine a "drink of water" once in awhile, that does work!!
Softens the carbon by steam cleaning. no way to tell if it is all gone but seems to show improvement in the running power.

I have seen here thanks to these guys, the correct most sure way is to pull the head and wire brush it off. unlike an automobile they are simple to do .

For the price of a head gasket cant beat the cost either.

[RPalmer]

Jim H.

I have seen here thanks to these guys, the correct most sure way is to pull the head and wire brush it off. unlike an automobile they are simple to do .

For the price of a head gasket cant beat the cost either.

Compared to automotive heads a Cub Cadet is a cake walk! No kidding. That carbon build up might be more. I have seen on two out of two build up that was more like a "clinker" from a coal furnace. But instead of the blue - purple colors it was orange - yellow. The guys that know said that was most likely from fuel additives. But the stuff is rock hard and not what you think of as carbon build up. I just found an otherwise good piston that had about two inches of it's edge taken out from this stuff. Also before you finish take 10 minuets and adjust your valves. This sounds like a lot of work to a novice wrench. But if you have done top end work on cars this is just so much easier with the end result being the same. Good luck and let us know what kind of crap you find under the head.