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Tecumseh H60 - broken rod, gunked up crankshaft


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Old 04-14-2006, 10:48:03 AM
AlanCorey AlanCorey is offline
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Default Tecumseh H60 - broken rod, gunked up crankshaft

I bought this for $5, knowing it had a broken connecting rod, because it's close the original engine that's supposed to be in my Wheel Horse 603. It's my first Tecumseh, but I've got a dozen or so Briggs.

I opened it up and sure enough, the bottom of the rod was broken about an inch from the lower end, and the whole clamp arrangement where it goes around the crankshaft was smashed into about 6 pieces.

There doesn't seem to be any damage to the rest of the engine other than what looks like aluminum spun onto this crankshaft bearing. In at least one place I can feel a ridge with my thumbnail.

Is there any cheap way to clean this up? I'm not sure if this is one of their "extended life" engines with a harder crank or not, but I think so because it has staked-in bearings. Could I try scraping with soft steel like a nail, or using crocus cloth or emery paper? Or should I just not worry about it? The connecting rods are only $25, but the crankshaft is about $110.

Thanks,

Alan
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Old 04-14-2006, 12:15:52 PM
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John Newman, Jr. John Newman, Jr. is offline
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Default Re: Tecumseh H60 - broken rod, gunked up crankshaft

I think I would see how much of the galled up aluminum will come off with a wire wheel. It won't eat into the crank, but should take off the aluminum. I've had cranks the looked worse than yours that cleaned up nicely.
Patience & persistance. Go slow - take your time.
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Old 04-14-2006, 03:17:57 PM
AlanCorey AlanCorey is offline
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Default Re: Tecumseh H60 - broken rod, gunked up crankshaft

Thank you, I was hoping there was some solution like that. I had thought of a wire wheel but dismissed it because I didn't know for sure the wire was softer than the crankshaft. I'll give it a try tonight.

Alan
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Old 04-14-2006, 04:36:33 PM
Andrew Mackey Andrew Mackey is offline
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Exclamation Re: Tecumseh H60 - broken rod, gunked up crankshaft

Use a fine wire brush. For the heavy stuff, use a jewlers file to remove the aluminum. Before you go thru all the hassle though - thoroughly inspect the block and everything inside it! When a Tech throws a rod, it usually busts a hole in the block, behind the starter if it has one, or the side opposite the carb and exhaust. Look for cracks, or a hole the size of a quarter Look at the camshaft (is it bent, or do the lobes look like they were hit?) Look at the cam bearings in the sump cover, and the block. These surfaces are thin, and if the cam took a hit, they will be egged out, or cracked. Look at the crank bearings. Tech's are usually very reliable, and strong, but they won't tolerate being run low on oil. What you have bought is a low oil special. A lot of times we would get these into the shop with pristine oil in the crankcase! The owners would give us hell for not honoring the warrenty (But it does have oil!) It's tough to look at a blued crank, and say it was oiled! By the way, is the crank blued? If so, it probably will have metal fatigue problems later on. When you are done cleaning the crank, sand with super fine emery (#1,000), and then check with a Michrometer. It should be close to Specs. Techempseh engines are more sensative then B&S for clearances, if there is too much, the crank and or rod won't last too long.
Andrew
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Old 04-14-2006, 05:08:18 PM
Ed Radtke Ed Radtke is offline
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Default Re: Tecumseh H60 - broken rod, gunked up crankshaft

soak the journal in muratic acid for about 1/2 hr. then polish with fine emery paper. do the soaking outside at least 20ft from everything.FYI,it works faster if you clean off the oil first.
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Old 04-15-2006, 12:03:42 AM
AlanCorey AlanCorey is offline
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Default Re: Tecumseh H60 - broken rod, gunked up crankshaft

I've been checking the areas Andrew suggested to look for problems. I don't see any sign of anything hitting the camshaft, it doesn't seem to be bent, and its bearings in the aluminum seem OK. I don't have a way to mount it in a lathe and check for straightness with a dial indicator. The crankshaft isn't bluish anywhere like it got overheated. The bearings for it look OK, but what I find odd is that there's a staked-in bronze bearing on the PTO side, but not on the flywheel side. I'm still trying to figure out if this is one of the extended life engines or not. It's model H60-75210H, serial 8142 16790. Is that 8142 a date code meaning the 42nd week of 1981?

So far I've gone around the connecting rod bearing twice with a hand (manual) wire brush, because the rotary ones I've got aren't fine wire. In the first picture below at the far side of the bearing is the main ridge of aluminum that got deposited. It's somewhere around 0.005" thick. This bearing measures 1.062", round to within a thousandth, but I don't know what it should measure. I've got a CD of Tecumseh data ordered but it hasn't gotten here yet. I've just got a PDF parts list.

In the second picture is the spot where it looks like the bottom part of the rod hit. It's below the cylinder, which is at the right, and on the side opposite the carb and exhaust as expected. That's a AA battery I stuck in there for size comparison.

I had suspected it ran out of oil or had something in the oil. It seems like the bearing seizing might have caused the rod to break. This is the first broken rod I've seen and I was surprised to find the bearing parts also broken.

Once I do a little work on that ridge with a tiny file and get some 1000 grit emery paper and use that on it, I think I'm ready to order a connecting rod and a couple of gaskets for putting it back together. There's hope for it, I guess.

Alan
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Old 04-15-2006, 10:14:46 AM
Andrew Mackey Andrew Mackey is offline
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Thumbs up Re: Tecumseh H60 - broken rod, gunked up crankshaft

In no oil engines, the con rod bearing is the one doing the most severe service, All the pressure of the gasses above the piston pushing on the rod, and the crank throw, geterate the most friction at the point of contact. When the engine runs low on oil, the film of oil needed to provide the slippery surface, is lost, allowing direct metal to metal contact the friction generated, heats up the surfaces enough to allow the aluminum rod to begin to melt. As it melts on the loaded surfaces, it also cools on the back side of the load areas, thus depositing metal on the cooler surfaces. Eventually the re-deposited begins to stick to the steel of the crank, and thet is when the real trouble begin The metal now besides melting, begins to weld to the crank surface, and begins to gouge even more aluminum into the bearing surface, creating even more heat, melting more aluminum, getting hotter - a vicious circle you see. Eventually the bearing on the rod gets so hot, it begins to suffer metal fatigue. At this point, there is also so much friction and heat at the bearing surface, that the rod cannot take the stress any more, and it snaps off. Nearly instantly, the melted aluminum on the journal solidifies, locking the big end bearing in place. The metal is still a little soft though from the heat, and when whats left contacts an obstruction (usually the block, or camshaft)It will break to bits, and punch a hole in the offending hit object If your block is not damaged, you are one of the lucky ones! If the cam looks OK, and the bearings look good, chances are the cam was not hit. Bronze bearing on the sump plate does provide an extra long wearing surface, than on the standard aluminum bearung. As the belts and or load pull against the sump plate, you need a stronger wearing surface. The next step up would be ball bearings. As long as the steel surface of the crank is smooth, and close to spec, you should be fine just replacing the rod, gaskets, and as a safty, I would also replace the rings. With a valve job, you will basicly have a new engine.
Andrew
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Old 04-15-2006, 10:36:53 AM
Bill Sherlock Bill Sherlock is offline
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Default Re: Tecumseh H60 - broken rod, gunked up crankshaft

Quite a few years ago I had a 6 HP Craftsman (Tecumseh) throw a rod and punch a hole in the side of the crankcase. When I checked the oil, there was very little. I had recently changed oil and lent the rototiller it was on to someone else before using it myself. It had never used oil before that point so I didn't check the oil before I began using it. Maybe I forgot to put oil in it?? Don't think so though.

Anyway after taking it apart, other than the broken rod and hole in the crankcase, things still looked pretty good. There was some aluminum on the crank throw so took the crankshaft to an engine rebuilder and had them polish it up. Had a friend weld the hole shut and installed a new rod. I don't remember if I replaced the rings.

The engine is 32 years old and I still use it a couple times a year to rototill a garden spot to keep the weeds down.

Bill
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Old 04-16-2006, 11:55:08 PM
Andrew Mackey Andrew Mackey is offline
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Exclamation Re: Tecumseh H60 - broken rod, gunked up crankshaft

I have seen many 'no oil specials' in the 47 years of working on small engines. 2 stand out. #1 was a HS60 Techempseh, belonging to a neighbor, down the street from me (no not the wing nut next door with the chainsaw ). This fellow was running this poor engine flat out, with the governor disconnected, on a MTD snow blower. For those who do not know, the HS50 and the HS60 model engine have a designed failure point within the engine. It is the exhaust valve keeper. It is designed to fail, if the engine exceeds approximately 42 to 45 hundred RPM. This part fails due to a resonant valve spring action, at that speed, that causes the valve to float. The float (un-sprung valve action) creats a condition that makes the valve slap against the spring with enough force to break the keeper in half. When this happens, the engine most often just quits, with a loss of compression out the exhaust, as the spring is no longer attached to the exhaust valve. I have seen this breakage in about 30 engines, over the years. A couple of them would start at idle, but once the throttle was opened, would die nearly instantly. (this drove my shop forman nuts for 3 days, until I asked him what was wrong with the engine, and told him what to look for) This designed failure saved these engines from more traumatic rod failures, due to excessive engine speed. It Was a cheap fix too - 35 cents for a new keeper, and a quarter for the breather gasket! I Digress - Any way, I installed a new keeper, and repaired the governor several times the year before (he kept re-adjusting{"It runs too slow"}) I had also warned him to check the oil often, as the 60's acted like the B&S 5 HP's, they burn oil, without smoking, and you should check oil lever every time you put gas in the machine (A good practice on any air cooled engine). This particular time was during the bliddard several years ago. The engine was screaming, as usual, when I detected a strange squealing noise coming from the machine. I was blowing off another neighbor's drive, and he heard the strange noise too. "what is that?" he asked. "Low oil warning - iminant self desrtuct" I answered. He looked puzzled for a moment, and I said to him "Listen and learn!". I went toward the idiot running the machine, and yelled over the din of the screaming engine, that he had better check the oil, if nothing else. He gave me the finger, turned his back, and went back down the drive, into a heavy snow drift (about 4" deep). As I was returning to my friend's drive, he asked what all that was about. I told him what I told his neighbor, and he then said "Now What" He didn't finish the word 'what', when a loud CRACK was heard, amd then near silence, as the engine crank lost inertia, and spun to a stop, in total silence. "Peace at last" I said. A couple of minutes, the Idiot comes out of the snow drift, draging the profusely smoking machine. He hooked up his electric starter, but only got w whine and a repidly spinning crank. He looked at me and says "What do you think it is?". I replied" I know, but you told me to F%#@ off. So go figure." "Aww cumon, I didn't mean it, Gimee a break!" he says. At this point my neighbor is looking at the still smoking engine. I asked him "Do you see the starter?" "yeah?" Is there a hole behind it, about the size of a quarter?" Yeah, and a piece of shiny metal too" "$285 plus labor I said, and turned my back, to go back to work. "What?" the guy says, I turned around and told him "there probably isn't a tablespoon of oil in the case. The engine was screaming because the journal was overheating, and when I told you to check the oil, you blew me off. Now you have blown the engine, You need a short block. You need to transfer all the external parts to a new block, because I can see from here that not only has the rod punched the block, but it also took out the camshaft,as well, and they have both ripped the starter off its mounts. If you are lucky, the starter bolts sheared, and I can re-use the starter. If the starter broke, it's another $110.". "Gee, that seems like a lot" he says. "Try about 750 for a brand new engine" I told him. I got the job 2 days later. #2 was the same type engine, a HS60, this time on a Snowbird snow thrower. It was my own My son had changed the oil, as a favor, and I had used the machine several times, after the change. The only difference was, it was -15 degrees F out, and all the other times it was about +35 F or more, when I had used it. I started the engine, as usual, and let it idle, to allow the oil to warm up, befor putting a load on it. My wife had called me inside, to answer an emergency call, and when I returned outside I was just in time to hear SQUEEK-SQUEEK-SQUEEK-SNAP-CLUNK, and then dead silence. I immediately knew the engine broke the rod, and looked behind the starter. I got lucky - no cracks (thankfully, ther engine was just idling! I pulled the oil stick, and the engine read full oil. I re checked it, the sump was full. I took the engine into the shop, pulled it off the machine, and then removed the engine sump I had forgotten to remove the oil! As thwe sump came off, the oil appeared to be as thick as gear oil. The block interior was nearly dry, and the rod had snapped cleanly off at its thinnest point - about 1 inch from the crank journal. The rod journal itself had broken in two, and had fallen into the oil, in the sump, and the piston had stopped 1/2 way up the bore. There was just a bit of transfer onto the crank, and it was cleaned off in a hurry. Luckily for me, I had a spare rod for the engine, and it was installed in short order. I had the engine back on and running in less than 2 hours! I later found out that my son had put SAE 40 oil in the engine, instead of the 10w30 I had asked him to put in. Thank heaven I was not running the engine hard, when it blew. The SAE 40 looked like honey when it was at the 15 below temp. At that low temp, the oil did not splash, therefore the engine starved for oil, just as if the case was empty. Now, if it gets below 0 F, I use my jacobsen 2 cycle mackines to blow off the drive. (No heavy oil worries, no matter what the temperature is!
Andrew
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Old 07-02-2010, 12:04:44 PM
a.beam.reach a.beam.reach is offline
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Default Re: Tecumseh H60 - broken rod, gunked up crankshaft

Andrew-

First. . . I am very new to any type of small engine repair.

I have an H60 75488N motor that I stole off a Lawn Vacuum for a Go Kart project. . . . It ran fine when I started the project and now it will idle but instantly dies when you get a little past 2000 rpm. . . .. I know the rpm because it will just barely engage the centrifugal clutch. I suspected the carb since the fuel line was old and really in rough shape. . . . so I rebuilt the carb and it runs better than ever at idle but still dies once you add throttle. I have taken the carb apart again (it is soaking in carb cleaner) thinking perhaps I did not do a good job. . .

This takes us to now. . . . where I stumbled across this thread. After reading your post I think I may have broke the exhaust valve keeper. Before I had installed the clutch (no resistance attached) I was testing my throttle mod for the kart and it went to full throttle for a few moments until I could get her shut down. I heard nothing that indicated a problem and it even started right back up. I did not recall it only running at idle though everything is fuzzy now.

Anyway. . . because you indicated that the fix was cheap.. .. just a breather gasket and a keeper. . . . Is it fair for me to assume if I have this problem that I can go at it from behind the breather housing? I don't need to come from the top of the head? Is this really as easy as it sound to fix? I sthere anything I should know before opening it up?

Thanks in advance!
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Old 07-02-2010, 11:37:40 PM
Andrew Mackey Andrew Mackey is offline
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Exclamation Re: Tecumseh H60 - broken rod, gunked up crankshaft

First, I don't think it's the keeper. If it has broken, the engine won't get to 2000 RPM. In case it did though, you will have to remove the head in order to remove the valve and the spring, as well as the pieces. Your best bet is to remove the carb and muffler. Then the valve chamber cover, and have a look. Turn the engine until it is at TDC compression. Watch the springs. If the keeper broke, the keeper and spring will be resting on the floor of the valve chamber. If the keeper is OK (spring about 1/4" above the floor of the chamber), check valve clearances while you are there. You should have a minimum of .004", each side, I usually set mine at .006" intake and .008" exhaust. To set clearances, the head must be removed, and the valves removed. The stems have to be ground to make clearance. Do a little at a time, making sure the grind work is even across the surface. ONLY DO A LITTLE AT A TIME, and check often. If you remove too much material, the valve has to be replaced! Check the valve stems for wear also. If the valve head moves more than about a 16th of an inch, the guide needs to be replaced. Stem clearance only about .003". After replacing all the parts, start the engine. Still quits after low speed? Remove the jet at the bottom of the carb, and the fuel bowl. Clean out the bowl, clean the jet with carb cleaner. Make sure the central hole is clean and clear, as well as is the guide tube to the main venturi in the carb. There is also several ports into the main jet - one upper drilled at an angle, about .006 or .008 in diameter, and a larger lower one near the base, about .030. If this jet is obstructed, your engine will starve for fuel. Check float level. The soldered float joint should be parallel to the fuel bowl mount surface with the fuel valve closed. Bend the fuel valve tang to set the level. Re-assemble the carb. Check the throttle shaft for play, there should be virtually no play, front to back or side to side. Tighten the bottom fuel adjusting screw lightly, and back out 11/2 turns. Set the idle mixture screw at 1 turn out. adjust from there. High speed - open throttle to maximum governed speed (around 4000 RPM), turn out mixture screw counter clockwise until engine double strokes or exhaust gives off black smoke - whichever comes first. Turn in clockwise until smoke just clears or until engine just runs smoothly. Idle engine, and adjust idle mixture until engine runs best. Re-set high speed mixture, and you should be good.

One other thing to check is engine still does not speed up. Pull coil wire off plug, and hold about 1/8" to 3/16" from the plug, and start the engine. Open throttle, and watch spark. If it gets intermittant, as the engine accellerates, either bad points or coil. Also check for play in the engine top bearing - try to move the flywheel and crank in different directions. If there is play in the bearing, points setting will change, possible contact between the mag and flywheel = BAD!

Let us know how you make out!
Andrew
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