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Engine Rebuild Hh120


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#1 chiefgoodman OFFLINE  

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Posted September 02, 2013 - 10:35 AM

This coming week I plan on starting an engine overhaul on my HH120 which is mounted on a 1972 Massey 12H. I have not taken it apart yet but I believe my connecting rod has broken off the piston head. I have looked on eBay for a rebuild kit. I have found many and I am wondering if the attached link is a good set to buy. I know the piston head won't fit my HH120 but everything else should fit correct? 

 

http://www.ebay.com/...d=141022292023



#2 boyscout862 OFFLINE  

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Posted September 02, 2013 - 11:44 AM

Take it apart and mic the cylinder and crank before you even think about parts. That set said standard size only. If this is going to be your first rebuild pick an easier and cheaper engine. Pick a cheap engine to prctice on. Try doing a swamp yankee overhaul where you disassemble, hone, lap, polish, clean and reassemble the engine with new gaskets and seals. IF it wasn't too warn, it will run pretty good. Good Luck, Rick


Edited by boyscout862, September 02, 2013 - 11:46 AM.

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#3 OkieGt OFFLINE  

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Posted September 02, 2013 - 11:59 AM

Take it apart and mic the cylinder and crank before you even think about parts. That set said standard size only. If this is going to be your first rebuild pick an easier and cheaper engine. Pick a cheap engine to prctice on. Try doing a swamp yankee overhaul where you disassemble, hone, lap, polish, clean and reassemble the engine with new gaskets and seals. IF it wasn't too warn, it will run pretty good. Good Luck, Rick

Thats right always mic the cylinder before buying the piston, but in this case he knows he cant use the piston and is wondering if the rest of the kit will work. I'm not sure, maybe some of you Tecumseh pros can tell him


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#4 MH81 ONLINE  

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Posted September 02, 2013 - 12:05 PM

As long as the rod is what's broken (not the piston) and the crank isn't bent or needing undersized... You should be good with that.
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#5 chiefgoodman OFFLINE  

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Posted September 02, 2013 - 12:05 PM

What do you mean by mic?
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#6 boyscout862 OFFLINE  

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Posted September 02, 2013 - 12:18 PM

Thats right always mic the cylinder before buying the piston, but in this case he knows he cant use the piston and is wondering if the rest of the kit will work. I'm not sure, maybe some of you Tecumseh pros can tell him

I'm not sure what is meant by the piston head. Is it the piston or the cylinder head? I mic the cylinder first to deterrmine whether to hone or bore. I've still never used my boring bar in the 34 years that I've had it. Good Luck, Rick


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#7 boyscout862 OFFLINE  

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Posted September 02, 2013 - 12:24 PM

What do you mean by mic?

That is short for micrometer. It means to measure the diameter of the object in question to an accuracy of 0.001". A standard 1" mic can do the crank but you need an inside mic and the knowledge to measure the cylinder bore. Good Luck, Rick

 

When using measuring instruments you have to use a light touch or you can damage the instrument.


Edited by boyscout862, September 02, 2013 - 12:27 PM.

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#8 DH1 ONLINE  

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Posted September 02, 2013 - 01:14 PM

Since you live in the US best place to buy from is these guys, they do have SOME oversize pistons.

 

http://www.psep.biz/...umseh_parts.htm


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#9 chiefgoodman OFFLINE  

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Posted September 02, 2013 - 01:21 PM

What determines oversized and undersized?

#10 DH1 ONLINE  

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Posted September 02, 2013 - 01:41 PM

When the cylinder wears too much you need to bore it larger so you need an oversize piston.

When the crank wears too much you need to machine it down to a smaller dia, so you need an undersize rod.

Some rods can be re-sized to fit your crank at a machine shop.


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#11 chiefgoodman OFFLINE  

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Posted September 02, 2013 - 01:57 PM

So how would I know what to do? Simply measure?

#12 DH1 ONLINE  

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Posted September 02, 2013 - 02:01 PM

In theory yes.

I have put a few of standard size kits in Tecumesh engines and they do run better but some are still a little noisy.

If you want a like new, really good quiet running engine go to a machine shop, they have the tools an know how to do it better than I can.


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#13 boyscout862 OFFLINE  

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Posted September 02, 2013 - 02:44 PM

What determines oversized and undersized?

There are standard sizes for the components of a particular engine. I suggest that you download the Repairmans Manual for Briggs and Stratton engines. It has several excellant excellant sections on engine troubleshooting and rebuilding. I will post this and then try to add the link. Tecumseh may have a good manual too. You can download three free manuals per day. Good Luck, Rick

 

Take some time to read this manual for general knowledge  http://gardentractor...pairman-manual/

 

This manual may be for your specific engine http://gardentractor...hh120-overhaul/    There is a section that shows the standard sizes and specifications of components.

 

I suggest that if you have never done something like this before find a cheap engine to learn on. I pickup free lawnmowers at the transfer station. They are perfect for learning on.


Edited by boyscout862, September 02, 2013 - 02:52 PM.

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#14 chiefgoodman OFFLINE  

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Posted September 02, 2013 - 03:00 PM

Thanks for the info ill read up on it.

#15 Canawler OFFLINE  

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Posted September 02, 2013 - 03:09 PM

Try doing a swamp yankee overhaul....

 

Wow!  I just had to look that one up. :thumbs:

 

Sure enough, there's a Wikipedia page for "swamp yankee"


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