My Tractor Forum banner

1 - 18 of 18 Posts

·
Registered
Joined
·
323 Posts
Discussion Starter · #1 ·
Alright, so I've had this Craftsman LT2000 for about a year now, and I absolutely love the thing. It runs fantastic, can't hear a single miss in it anywhere in the rev range.

Last year, I rebuilt it. Everything went pretty well, except for one Achilles heel of a problem. The carburetor. At first the engine ran way to rich. It was a chinese carb that had an adjustment, so I turned it down some. Then upon inspecting the spark plug, I found it was running too lean. I readjusted it towards the richer side, and it may have been too rich. So I went back and fourth with it almost until the end of last season until I decided to replace it with another that did not have an adjustment. After doing so, the tractor appears to be running just fine. Upon inspecting the spark plug, it is not too rich nor too lean in my opinion, but I'm keeping a close eye on it. It's an acceptable brown slightly on the richer side.

Anyways, I got curious and decided to run a compression test on it. At first, I put it on cold. I don't even know what the point of that was but I did it anyways. I was pretty spooked when I cranked and reset the tester twice only to get up to 90 something. I had no idea how it could be running the way it was, yet put out 90. Then I remembered that it had ACR and that I just don't remember anything for some reason. After running it for a few minutes, the tractor did the same thing for the first couple of seconds, just 90 something, and then you could hear a click (from the ACR disengaging) and the tester flew up to 195 PSI. I didn't believe this, so I did it again, same result. I then took the tractor over too my neighbor's place, a mechanic for many years. He said that there was no way that was right and that it was because I had gas going into it while testing.

So I took it back home to try again. This time, I unplugged the fuel solenoid so it would stay closed while I cranked it and would cut off fuel. By now it was fully warmed up from me driving it around, so it first went to 90 for about 2 seconds, then jumped up to almost 210 PSI on the tester. Took it back over to my neighbor's place and he said no way again, he suggested that it could still get gas even if it was a small bit with the solenoid closed. I took his word for it, so this is what I did. Disconnected the fuel line from the carb and put it in a seperate container. Started it up until it ran all the gas out of the carb and then ran on choke to make sure it was fully gone followed by a few cranks afterwards. Then I pulled the wire from the solenoid at the bottom of the carb again just in case. I then also pulled the plug and cranked it over a few times before I put the tester on.

Cranked it over and it shot right back up to 210. I figured maybe the throttle was messing with it so I moved it from where it was at idle to full throttle no choke. Exact same result of 210. My question is, is this normal? I don't know what these engines are supposed to put out in terms of PSI, but I figured it was less than that. It has an 8:7:1 compression ratio. My Honda powered DLT 3000 put out 120 PSI fully warmed up. That is supposed to be an 8:0:1 engine I'm pretty sure. So my question is, can anyone on here confirm this is normal or at least ok? Or do I have to worry about something. Thanks in advance.

IMG_2348.JPG
 

·
Administrator
Joined
·
12,664 Posts
that’s very high compression for a lawn mower engine, I doubt it would turn over with that high pressure in the cylinder. Maybe a bad compression gage?

The Kohler Command is one of the greatest line of engines out there, long lasting and reliable. Only real issue is they are a bit noisy. My JD LT133 has a 13hp Command and is a great riding mower.
 

·
Registered
Joined
·
323 Posts
Discussion Starter · #3 ·
that’s very high compression for a lawn mower engine, I doubt it would turn over with that high pressure in the cylinder. Maybe a bad compression gage?

The Kohler Command is one of the greatest line of engines out there, long lasting and reliable. Only real issue is they are a bit noisy. My JD LT133 has a 13hp Command and is a great riding mower.
Well it normally fires up with ACR first when it gets going then kicks off and fires. I guess that's the only reason it's still turning over. The compression gauge is possible, I just bought another one so I'll put it on again tomorrow morning with a photo this time. I'm reading posts about carbon caking up in the cylinders and causing a problem leading to higher compression. If that's the case I guess I'll just have to crack it open and get to work all over again. That'll be just great...
 

·
Administrator
Joined
·
12,664 Posts
I’ll be interested to see what the new gage reads. Keep us posted.👍
 

·
Super Moderator
Joined
·
5,869 Posts
Ya something's not right with the gauge I think... compression is dictated primarily by the travel of the piston, so unless you got an abnormally long connecting rod in there 200 PSI is unlikely. Approaching diesel compression there...
 

·
Registered
Joined
·
323 Posts
Discussion Starter · #6 ·
Ya something's not right with the gauge I think... compression is dictated primarily by the travel of the piston, so unless you got an abnormally long connecting rod in there 200 PSI is unlikely. Approaching diesel compression there...
I looked it up and it said that 210 PSI was basically 13:9 type of engine compression. I feel like for the amount of time it's been used like that, it should've just blown a hole in the head by now. I'll see what she does tomorrow for sure... This gauge issue has me wondering. Then again I'm trying it again with a $20 amazon gauge, not sure how much better that'll be, but at least if there's a difference, I'll know. The only thing that worries me is that the gauge showed an almost exact 120 for my Honda in both cylinders. So I'm definitely wondering whether or not this really is a gauge problem, even though it seems to be accurate on the other one.
 

·
Registered
Joined
·
1,819 Posts
Assuming you used the same valve train parts to preserve the correct geometry in your rebuild, that is high compression for this type of engine.

As I recall, small engines should come in somewhere around 110 -120 lbs. Someone with an engine manual with specs can maybe confirm that. Sounds like it could be a valve issue, although even with an exhaust valve closing before the designed scavenge effect, that still sounds like a lot of pressure.
 

·
Premium Member
Joined
·
949 Posts
To begin with, I have trouble believing you can spin a Kohler fast enough with a starter to overcome the ACR. ESPECIALLY, if the motor has 200 PSI. Are you using a 10 horse as a starter? I have a 7 hp Tecumseh. If I REALLY work at it, I can start it with the recoil starter. A 17 HP???? I gotta wonder. I may be all wrong about this, as I am FAR from being an expert.
 

·
Registered
Joined
·
1,819 Posts
BoWoggie's info shows 8.5:1 compression ratio. This should work out somewhere around 120 to 125 lbs on a compression tester. Someone check my math please..
 

·
Super Moderator
Joined
·
9,390 Posts
Can you get your hands on a leak down tester?...or disconnect the spark plugs and battery and try turning the engine by hand..other guys chime in, but I don't think you would be able to at that pressure
 

·
Premium Member
Joined
·
949 Posts
BoWoggie's info shows 8.5:1 compression ratio. This should work out somewhere around 120 to 125 lbs on a compression tester. Someone check my math please..
Depending on the prevailing atmospheric pressure, you are correct
 

·
Premium Member
Joined
·
949 Posts
Can you get your hands on a leak down tester?...or disconnect the spark plugs and battery and try turning the engine by hand..other guys chime in, but I don't think you would be able to at that pressure
Not without a crowbar.
 

·
Registered
Joined
·
1,819 Posts
Crowbar? No way!
I wouldn't risk damaging one of my finer instruments like that. 😁
 

·
Super Moderator
Joined
·
9,390 Posts
I would be afraid of breaking something on the engine with a bar...but if you can move it by hand, that would tell you that it cannot be an accurate reading on the gauge
 

·
Registered
Joined
·
323 Posts
Discussion Starter · #16 · (Edited)
Wow! A lot of responses! So I did make my way out to the engine today and found out some things.
Assuming you used the same valve train parts to preserve the correct geometry in your rebuild, that is high compression for this type of engine.

As I recall, small engines should come in somewhere around 110 -120 lbs. Someone with an engine manual with specs can maybe confirm that. Sounds like it could be a valve issue, although even with an exhaust valve closing before the designed scavenge effect, that still sounds like a lot of pressure.
Right, it is too much compression. I figured it should be about 120 like my Honda.
To begin with, I have trouble believing you can spin a Kohler fast enough with a starter to overcome the ACR. ESPECIALLY, if the motor has 200 PSI. Are you using a 10 horse as a starter? I have a 7 hp Tecumseh. If I REALLY work at it, I can start it with the recoil starter. A 17 HP???? I gotta wonder. I may be all wrong about this, as I am FAR from being an expert.
Yeah that's what I figured, there shouldn't be any way it's turning over like that. But also I had the spark plug out and it was warmed up so that's why it clicks off the ACR. You can tell because it'll do this (crank crank crank cranck click whoosh whoosh whoosh etc.) So it can click off the ACR, but it only does it when warmed up anyways.
BoWoggie's info shows 8.5:1 compression ratio. This should work out somewhere around 120 to 125 lbs on a compression tester. Someone check my math please..
It's a CV490 with the higher but not the highest output which is the CV495. Even still, they both do 8:7:1 as I confirmed in the manual. Either the service or the owner's manual I don't remember but I know it's 8:7:1
Can you get your hands on a leak down tester?...or disconnect the spark plugs and battery and try turning the engine by hand..other guys chime in, but I don't think you would be able to at that pressure
I wish, but I usually don't use tools like that. So it'd be something else to buy in addition to the compression tester I bought. I'm curious though, what does turning it by hand do? Just to add to that, the engine is very hard to turn by hand. It may be because of the plastic flywheel screen, but sometimes I just can't even turn it!

Anyways, got her out this morning after the new compression tester came in last night. Decided to warm it up first and let it run for a bit of course. Put the new compression tester on. Crank crank crank clicks off ACR whoosh whoosh whoosh. Came out with a little under 150. I also will note that I think I misjudged the spark plug the other day, a little darker than I remembered. Anyways, I started it up and ran a can of decarbonizer through. Put the tester back on in the second photo and it made the same PSI. So I figure the gauge I had originally was just off. Only thing to do now is figure out why it's so rich :) I also uploaded a video of it running. As you can hear, it runs very well.

IMG_3099.JPEG IMG_3100.JPEG IMG_3098.JPEG
 

·
Registered
Joined
·
9 Posts
I got 80 psi on opposed twin briggs i rebuilt!!!!! of course the .015" feeler gauge that i slid down the side of piston skirt might have something to do with that? .010" oversize rings were file fit with ~.016" end gap... might have been a little much since i seen u tube vid that they guy said he had .010" ring end gap. oh well it runs... seems to KNOCK even with new top rod as the old top rod was egg shaped and wud hang as i twirled it on the crankshaft where the new rod did not hang on its way around the crankshaft. i wud have been much happier with 110-130 PSI like is recommended on atv 350cc engine. 80 PSI should be able to run LOW octane fuel and not knock. ... besides the (sigh) knock it has in the engine... from rod? or piston slap? oh well, more STP oil treatment...20% by volume might quiet it down some. 20% of 48 oz is...??? 10 oz rounded up, right?
 
1 - 18 of 18 Posts
Top