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Need Help with Antique Tecumseh, Long

12K views 24 replies 5 participants last post by  MBDiagMan 
#1 ·
I haven't been on this forum in a long time, but I remember the great amount of small engine savvy on here so I would like to ask for help. Although I am working on a Tecumseh OH160, many of my questions are more related to general small engine knowledge as opposed to model specific information.

I am trying to fix up a Miller BlueStar welder that's probably a little over 20 years old. It came with a Tecumseh OH160, but the owner had someone put a different OH 160 on it after the first one trashed. The reason I point this out is that I have very little history and suspect that the correct carburetor might not be installed, or other parts mismatches.

It has sat for probably about a year, and evidently outside for part of that time although it was inside when I picked it up.

Owner complaint:

He said the engine would not make enough power to weld with and that the engine was smoking badly. He had gotten governor instructions and tried to speed it up so he could weld with it so the governor will need to be sorted out after I get the engine running correctly.

Note that I realize that there can be electrical problems causing it not to weld and I am capable of dealing with that part of it when I get that far along with the project.

Initial Examination:

When I brought it to my shop and looked it over, I found oil in the crankcase that looked like grey paint. I managed to start the engine and run it and it indeed is basically a "mosquito sprayer." The smoke looks white under the Metal Halide lights in my shop, but I believe it is actually blue. I left it in the bed of my pickup for now and it soaked the side of the pick up bed with oil from the exhaust while running.

Although I have yet to load the engine, it sounded and ran pretty well. When I pulled the spark plug it looked oily, but not oil fouled as I expected it would be. In fact what looked like oil might have been gas instead.

When I pulled the plug to drain the oil, a few tablespoons or so of water came out before the grey paint looking oil. I let it drain overnight and filled it with some Delo thinking that the extra detergents in this type oil might help to clean it out. The new oil turned grey right away.

I removed the oil breather connector on the valve cover and it was pulsing pressure out of the valve cover vent. It did not seem to make any difference in how much oil it was blowing.

Further Examination:

When I changed the oil I pulled the plug and put some Marvel Mystery Oil in the cylinder thinking there is a small possibility that the rings are stuck. After it setting overnight, I turned it over to blow out the MMO and put the spark plug back in. I started it up and ran it for awhile. Once it warmed up it mysteriously started losing speed and died. With the ignition parts being rare and expensive, I was worried about that, so I sprayed a little carb cleaner in the carb and it would bust off and run a little proving the igniton okay. There was fuel in the fuel bowl and plenty at the fuel line where it enters the fuel bowl.

I left it and ran some errands. After coming back to it being cooled off, it started and ran fine, making me think that it had possibly been trying to sieze up although when it wouldn't run before, the starter would spin it over easily.

After pulling the plug and soaking the piston overnight with MMO again, I spun it over to blow out the MMO and put a compression gauge on. It made 95PSI compression while spinning it over with the starter.

I then replaced the spark plug and ran it some more before doing what I thought would be a dry compression test. It then made 115PSI compression. I thought this was puzzling. I expected the dry test to give a lower number. Also, with it blowing smoke I didn't expect it to make this much compression in any situation thinking 1.) it's probably worn out and 2.) this engine has a compression release to make it easier to start.

After pulling the compression gauge the last time, I looked in the cylinder and could see liquid on top of the piston. I turned it by hand and the liquid remained. I then turned it with the starter to blow it out and ran the piston to the top where it looked pretty dry. I then walked away to let the cylinder dry out as much as possible so I can check compression again tonight.

Questions:

It seemed like the liquid on top of the piston, in the last paragraph above, was gasoline. Is this possible? Could there be so much gasoline in the cylinder that it would stand there as liquid? Could it be running this ridiculously rich and not blow BLACK smoke?

I assumed from the beginning that I would have to take it apart and see to the rings and maybe even bore it and replace the piston. With this kind of compression, could it still be blowing that much oil past the rings?

Since I have no history on what has been done and what parts were used, I suspect that this is not the correct carb for this engine. In the Tecumseh manual it shows several ones and most of them have an adjustable main jet, while this one does not. It is fixed. I am curious if it could be so rich so as to be causing the smoke and the liquid on the piston?

I don't mind taking it apart and putting in rings, or boring it or whatever needs to be done, but I don't want to do this only to get it back together and find that I still have a carburetor problem or some other ill that is causing the smoke and reported lack of power.


Thanks very much for your thoughts. If I do get to the disassembly stage I will be asking some questions specific to this particular animal.
 
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#2 ·
I'm not familiar with this engine. Is it by any chance water cooled? The reason I ask is the "oil" looking like grey paint sounds exactly like you have a substantial amount of water mixed in the oil. The statement that a few tablespoons of water came out before the grey colored oil, also sounds like water in the crankcase.
Sounds like you have water in your oil and you need to find out where it is coming from before you do anything else.
 
#4 ·
Thanks for the great information and links.

I managed to finish a wet/dry compression test last night. I got 110 PSI dry and 120 after putting a little oil in the cylinder. I think it's coming down to cleaning the crankcase of the "grey paint" while I have it apart for overhaul.
 
#6 ·
Thanks Piston Slapper!

Evidently the grey paint did not happen until the owner put it away without running it. I have run it very little, so hopefully no significant damage has been done. I think I will need to put some solvent in my parts washer for this job.
 
#8 ·
I rebuilt an OH160 for a customer with an old skid steer last winter It was also smoking like crazy. The source of the smoke was extremely worn vavle guides. Pull your muffler off and look inside. I would bet you wil find that the stem and back of the vavle are covered in oil and buildup. Parts are getting expensive and tough to find for these things. Looking back at that invoice, I see that the exhaust valve 730218 alone was about $80. Another $20 for the guide kit. I also remember it being kind of a PIA to get the valves out.

Q
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#9 ·
I rebuilt an OH160 for a customer with an old skid steer last winter It was also smoking like crazy. The source of the smoke was extremely worn vavle guides. Pull your muffler off and look inside. I would bet you wil find that the stem and back of the vavle are covered in oil and buildup. Parts are getting expensive and tough to find for these things. Looking back at that invoice, I see that the exhaust valve 730218 alone was about $80. Another $20 for the guide kit. I also remember it being kind of a PIA to get the valves out.

Q
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Thanks Jim!

In reading through various material I have seen mention of replacing the valve guides and have also seen mention of using valves with 1/32" oversize stems and then reaming the guides to fit. In your description it sounds as if the valves and guides BOTH were severely worn.

It sounds like it might be worth pulling the head and examining the guides before going ahead and taking the whole engine apart. The head will have to come off any way.

Thanks again.
 
#10 ·
Thanks Jim!

In reading through various material I have seen mention of replacing the valve guides and have also seen mention of using valves with 1/32" oversize stems and then reaming the guides to fit. In your description it sounds as if the valves and guides BOTH were severely worn.

It sounds like it might be worth pulling the head and examining the guides before going ahead and taking the whole engine apart. The head will have to come off any way.

Thanks again.
If memory serves me, the valves with oversized stems were NLA. Yes, the valve stems were also worn. I remember needing to get creative to compress the valve springs and get the keepers out. Replacing the guides wasn't too bad. I slowly heated the head with a rosebud and used a press to pop them out. The recommend method calls for immersion in hot oil. That sounded like a PIA to me. Probably safer but...

Q
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#11 ·
You're right Jim, I looked and the o/s valves are no longer available. I don't have a press. I wonder if I could drive the guides out with a drift and hammer once I warm up the head with a rosebud?

After thinking about this, since it's making what appears to be decent compression at 110PSI dry, I'm thinking that once the head is off, if the valves and guides are seriously worn as you describe and if the bore looks good, I might just redo the head and slip it back on without doing the bottom of the motor.

That said, you never know what you're going to find until it's apart.

Thanks again!
 
#12 ·
Im sure that would work to get them out. Then maybe a piece of wood or nylon to get them back in. I would give it a shot. I went through the bottom end (bored .020" over) but that was because it was getting so sloppy, you could hear the piston slap. It had 1600+ hours on it running at 3750 RPM. It was cranked WAY up.

Q
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#13 ·
Im sure that would work to get them out. Then maybe a piece of wood or nylon to get them back in. I would give it a shot. I went through the bottom end (bored .020" over) but that was because it was getting so sloppy, you could hear the piston slap. It had 1600+ hours on it running at 3750 RPM. It was cranked WAY up.

Q
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Piston Slap....?????
I should know something about that....good thing they don't knurl pistons anymore..
They were so abrasive...they hogged out the bores...
When checking the welder..find and check the connections on the square fullwave rectifier...wires like to melt and make it not weld so good....
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#14 ·
Got the head off last night & yes the valves are a pita.

The exhaust valve/guide is loose. Rattles probably four thousandths or so. Oil had clearly been running down the exhaust valve. Intake good &tight though. Both valve faces & seats look good & are sealing well.

The piston top was clean as a whistle & no ridge at top of bore. Miced cylinder with piston at bottom. About .006 or .007 wear across thrust dimension above lowered piston.
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#15 ·
Get a new set of rings.....insert the new top ring at the top ...middle..and bottom of the bore.
Using a feeler gauge...measure the ring gap...Anything more than .020 - .025 is bad...
while it may run..it would probably use oil....and maybe even piston slap.....
 
#16 ·
Thanks Slapper!

I used to measure cylinders with the method you describe and it works quite well. Since I now have a set of inside mics, I come up with a cylinder that is very close to the limits your method indicates.

With .006 added to bore dia X Pi, you get ALMOST .019 additional bore gap. Add that to the .0035 or so that the gap would be in a new cylinder and you are right in there at .0225 gap, which is smack dab in the middle of your limits. In the real world, a new ring squared up in the bore might be something less, since the sides of the cylinder adjacent to the piston pin are probably not worn so much.

All that said, it would seem that it would be marginally acceptable for working out with new rings.

At this point, considering that it's making decent compression and the oil usage is probably due to the worn exhaust valve and guide, and since the engine was actually running pretty good, I'm thinking I'll fix that and see how it does.
 
#17 ·
Well I've been buried with other things to do and also took awhile to get the parts. I got in the new guide and valve with a fresh valve job. Good news... it seems to run a little better and smokes a little less. Bad news.... that's not good enough.

I ordered an overhaul kit including piston, rings, gaskets and seals for a good price, less than a gasket set and rings from other suppliers. I should get the parts next week and tackle it that weekend.

I'll keep everyone posted.

Doc
 
#20 ·
Thanks slapper!

I got my overhaul kit Saturday. I had the welder in the back of my pickup backed in the shop. The light engine work I've done so far, I just sat in the truck while working. Now that I'm going farther into it, I lifted it up and drove the truck out from under it. It's a four wheel drive, so it was a pain getting in and out of to fetch tools. Working on it while in the bed of the truck was a good plan that didn't turn out so good.

When I set it on the floor yesterday, I pulled the plug to drain the oil. The oil came out nice and clean FINALLY. The soaking the innards in diesel fuel finally cleaned it out.

I fell Saturday on my tailbone and I'm sore. I have a roll around chair I was planning on using to work on it while it's on the floor, but with my tailbone like it is, I might be walking around on my knees instead.

Looks as if I'm FINALLY getting down to the meat of the project.

I'll post progress as I go.

Thanks for all the help.
Doc
 
#22 ·
Got it pretty much done. I did not find stuck rings as I suspected. The rings didn't look bad. The new ring had about .024 gap. Honed the cylinder and got all the rings in by the book. Found the rod in backwards according to the book. Found two rod nuts, their washers and a screw in the crankcase.

I didn't find anything that looks like it would have been causing the blue smoke. I'm wondering if the dipstick is not reading correct making for too much oil.

How much oil do you guys put in one of these engines at oil change time?

I have to get some fuel line and plug off a connector on the fuel pump. It has the wrong one with an extra input that needs plugging. After that I'll add oil and start it up. I expect that it will still be a mosquito sprayer though.

Thanks for all the help.
 
#23 ·
Get a new set of rings.....insert the new top ring at the top ...middle..and bottom of the bore.
Using a feeler gauge...measure the ring gap...Anything more than .020 - .025 is bad...
while it may run..it would probably use oil....and maybe even piston slap.....
Its a crapshoot....good crosshatching may help....
Did you check the ringgaps on the rings you took out...I'm guessing they were about .050...
 
#24 ·
No slapper, I didn't think to check the old rings while I had it apart. All's well that ends well though, because it doesn't smoke any more.

I put one quart of oil in for frear of the dipstick not reading correctly. I read so many situations in the troubleshooting section of the manual that were due to overfilling with oil, I want to know exactly how much oil I should put in. I think the dipstick is not right.

How much oil should be pourted into an empty crankcase of a Tecumseh OH160?

Thanks to all for the help.
 
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