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Discussion Starter #1
I have a 1984 Ariens snowblower with a Tecumseh 5hp motor.

In 2014 the motor finally broke.

I replaced the piston, ring, crank and rod and had the block bored.

The local CTC shop put everything back together and it fired up but since it was in June, I didn't have the need to use it.

Just this year, I used it for the first time and the motor locked up.

I took it back to the shop and they told me nothing broke, but the rod locked up on the crank.

What could have caused this?

My concern is, what damaged was done on the journal or rod, and is it safe to have them put it back together and run it as is or should parts be replaced?

If it matters, all parts were Tecumseh brand.

Thank you.
 

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The most important thing is to be able to determine the cause, otherwise it may very well happen again.

The only two possibilities I can think of (although are related) are:
1. Lack of lubrication.
2. Tolerances too tight.
 

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Asuming your 5 HP only has 1 shaft coming out the front of it I would just stick one of the 212cc Predator engines on there.

As to why your rebuild failed, no idea. Was there any assembly lube used? Maybe it was put back together dry and the rod started to weld itself to the new crank right away? I think the rods and cranks come with different journal sizes, so maybe you got the wrong parts?
 

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Discussion Starter #4
I didn't know what to think when this first happened. I cleaned the driveway off and then later that night went back out and after it started, it puffed and shut down. I went to restart it and it was locked up.
I thought the rod bolts let loose.
I ordered all new parts from Tecumseh, but now thinking about it, the only part I had to order with a tolerance was the piston.
I don't know if the crank and rod journal were checked?
But now knowing what happened, I'm worried if there is some rod or crank damaged possibly due to lack of oil?
I'm going up to see it today and see what my options are.
This motor has the two shafts.
Thanks
 

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Either someone put it together dry (you don't need assembly lube, but you do need at least some motor oil on the crank journal before putting the rod and cap on) or someone over-torqued the cap bolts on the rod.

At this point it will need a new rod, and the crank will have to be cleaned up.
 

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I will toss my .02 cents in.
Possibly the con rod was installed backwards, then the cap/oil slinger installed correctly from the side view. This would result in the rod/cap not matching to the machined ID.
Or a stack up of tolerances. Outer limits for crank OD and smaller ID for con rod.
At this point see whats damaged. Hopefully all you will need is a new con rod. Simple enough to check the NEW bearing clearance with plastigage.
 

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I will toss my .02 cents in.
Possibly the con rod was installed backwards, then the cap/oil slinger installed correctly from the side view. This would result in the rod/cap not matching to the machined ID.
It's been a while since I had one apart but I'm almost positive you can't get the rod on backwards, you can get the cap on backwards though and that can potentially cause some clearance issues.

At this point see whats damaged. Hopefully all you will need is a new con rod. Simple enough to check the NEW bearing clearance with plastigage.
It's not normally something you check, there's no bearing, and no different sized rods or cranks, yes you can check it, but you can't really change it if it's wrong so no one ever does.
 

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It's been a while since I had one apart but I'm almost positive you can't get the rod on backwards, you can get the cap on backwards though and that can potentially cause some clearance issues.



It's not normally something you check, there's no bearing, and no different sized rods or cranks, yes you can check it, but you can't really change it if it's wrong so no one ever does.
Yes agree. If the clearance is wrong, something is wrong, or run it until the problem shows. For the 5 mins it takes check it.

Not starting an argument. Something was wrong with the assembly of parts.
 

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Discussion Starter #9
Here is an update. There is rod and crank damage. I'm hoping both can be cleaned up. The slinger and rod cap were installed in the correct location, BUT he told me he did not have a torque spec, so he just tightened it up. In fact he told me he didn't check any tolerances, since all the parts were new.
So I got a crank with a small gouge and the rod has score marks on it, which I'm hoping will clean up but my question is, the gouge on the journal will grab your fingernail, if this has to be turned, do they make a spacer or can one be made to fit between the rod and crank? I'm used to working on big block chevy's, and don't know much about these small engines.
Also, when you put the rod on the crank, it does not spin freely, without help. It feels egg shaped and gets tight on the one side.
To me, since the cap was not torqued correctly, and from the marks on both the rod and crank, I think it was oil starved and locked up.
I'm surprised it lasted an hour!
What options do I have at this point?
 

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Here is an update. There is rod and crank damage. I'm hoping both can be cleaned up. The slinger and rod cap were installed in the correct location, BUT he told me he did not have a torque spec, so he just tightened it up. In fact he told me he didn't check any tolerances, since all the parts were new.
So I got a crank with a small gouge and the rod has score marks on it, which I'm hoping will clean up but my question is, the gouge on the journal will grab your fingernail, if this has to be turned, do they make a spacer or can one be made to fit between the rod and crank? I'm used to working on big block chevy's, and don't know much about these small engines.
Also, when you put the rod on the crank, it does not spin freely, without help. It feels egg shaped and gets tight on the one side.
To me, since the cap was not torqued correctly, and from the marks on both the rod and crank, I think it was oil starved and locked up.
I'm surprised it lasted an hour!
What options do I have at this point?
Have any pics?
 

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Discussion Starter #11
No I didn't take any.

I'm taking them to the machine shop today after work to see if either one can be repaired.
This is the same shop that bored the cylinder and I know this guy has been doing this stuff for years, so I know I can at least trust him!
 

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That sounds like a plan. Other thing that concerns me are the rod bolts. If they were overtorqued then they were stretched and could possibly fail if re used.

I bet the your machinst will find the rod bearing bore distorted and out of round. Building a small engine correctly is no different than a BBC, it's all in the details.
 

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You can normally clean the crank up with emery cloth. Don't turn it or you'll end up with clearance issues. The rod is junk, there's nothing you can do to fix it that's worth less than the rod.
 

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Discussion Starter #14
Update: Took the crank and rod in to the machine shop on Friday. He told me he has seen a lot worse and both can be cleaned up. He did say the sides of the rod journal needed to be cleaned up a little. I trust this guy, he's been around forever at this machine shop and from the looks of his shop, he must do a lot of small motors. I saw more of them, that I did of any V-8's...LOL
 

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I would still be concerned with cause of failure. Also the rod bolts, get some new or equivalent grade 8. Will the machinist assemble it for you using a torque wrench ?
 

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Discussion Starter #16 (Edited)
I need to bring this thread back alive because guess what just happened.

I got the machine rebuilt again, in May 2015, I fired it up to run the gas out of the carb and make a few adjustments. This time the motor was easier to pull and after I made some carb adjustments, it sounded pretty good but because the shop only had 10w40 oil to install, I was told to change it before I ran it again. I put it away for the summer.

As most of you know, here in PA we were facing a serious snow storm coming in for the weekend. I got the snow blower out, changed the oil to 30wt and fired it up.
After a minute or two of running, it just stopped.

I go over to pull the string and it's locked up again.

What is this guy doing? This is the second time he rebuilt it and it locked up.

How can I tell if he installed the rod in the correct order? I was told if he had it backwards this would cause this problem. I know the dipper or slinger is in there, I saw that.

How many times can one of these motors be rebuilt?

All I know is, I will not take the motor back to him again.

One last question, I put about a cup of VP 110 octane racing fuel in the tank.

Would that cause an issue?

I don't think so, because the shop that I got it from asked me if I was putting this in some yard equipment.

I'll take a stab at rebuilding it this time.

Thanks
 

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just put a predator motor on it. considering you had to rebuild it twice the motor more than likely has some sort of internal damage you cant see. at this point any effort you put into the old motor will be pointless and a waste of time imo
 

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+ 1 with the repower option.
A 212 Predator will have a very noticeable difference in performance over a 5HP Tecumseh. You will be happy you did it.
 

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Discussion Starter #19
just put a predator motor on it. considering you had to rebuild it twice the motor more than likely has some sort of internal damage you cant see. at this point any effort you put into the old motor will be pointless and a waste of time imo
Is that a direct replacement for this motor?
I was told they didn't make a replacement motor because the one I have has two shaft?????

Thanks
 

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I think your right Bruce.... it's likely the rod is bad at the very least. It should spin freely . There is no bearing the rod itself is machined to fit the crank. Not much to 'em. If the rod material has embedded into the crank which I bet it has - you really need a new rod and crank. However - There is this method I was enlightened on to salvage the crank by soaking them in a muratic acid solution to remove the aluminum. Don't sand or try removing it in any other way..... they are treated and you don't want to ruin it. Just clean it up good and buy a new rod. You may be able to get away with only that.
 
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