Rebuilding a model 7266

[DPI]

Hi all. I am rebuilding my model 7266. It was still running good but I decided to take it apart when I found play in the crankshaft on the bottom of the mower. Figured it was a good time for a rebuild after 36 years. :laughing:

I took the engine completely apart and this is what I found. My piston was scored up on both sides so I am looking for a new piston right now (606607). Cylinder itself should clean up with a good honing. So my question involves the crankshaft play. The crankshaft still looks good with no scoring, so I am not sure if it is upper bearing wear, or maybe the lower bronze sleeve? How much play is acceptable? I already replaced the upper bearing, but have not reassembled everything else yet. Just would like to get an idea about tolerances before I put everything back together.

Thanks in advance!

 

[Two-Stroke]

I've got a 7266... it's right near the top as one of my favorite mowers. :thumbsup:

Sorry I can't answer your question about the crankshaft tolerance but you might ask at a machine shop -- and remind them that it's a two-cycle, air-cooled engine. It's a good idea to get rid of any excess play in the shaft. Among the reasons: if the shaft isn't steady it will wear out the seal very quickly.

Have you found a piston? There was a discussion here (LB forum) about the difficulty of finding pistons for D-series engines. If you don't know a source, you might look on eBay.

Please let us know how you progress.

 

[DPI]

Thanks for the reply, I will ask a machine shop. Can you tell me how much shaft play you have on your mower? If you grab the blade, is there any side to side play? I seem to remember that there was not any but I do not have another mower to compare it to.

 

[Fireman 123]

The lower bronze bushings were 'poured' in, and from what I've found, they have to be bored out with an end mill bit. Probably a $50 job at your local machine shop. Most replace it with a needle bearing from a F series engine.
As for free play in the crank, I don't know what the min acceptable amount is, but I would shoot for none. Good luck.

 

[DPI]

I called a couple of lawnmower machine shops to ask about clearance of the lower shaft today. One laughed at me and the other said that's so old they wouldn't have a clue. Very helpful people. I put the engine together without the piston to check for end play and it seems pretty tight. Still a small amount of play and I will get an accurate measurement of end play and hope someone can give me a good answer as to what is acceptable.

Fireman - thanks. I am not familar with that type of modification. Would have to find a serious machine shop that knows something about these engines. Is there a how to thread on that?

 

[Fireman 123]

Ask and ye shall receive

http://www.mytractorforum.com/showthread.php?t=112798

 

[EngineMan]

Have you been here and had a look..?

Lawn-Boy Service Manual 1950-88 Complete

 

[DPI]

Thanks for the links! Both very helpful.

I found the correct piston for my engine on ebay but lost it in the last minute of the auction. Someone went crazy and jacked the price up beyond resonable so I gave up. It was for an OEM piece. I have seen listings for Stens replacement pistons too. Anyone here recommend them?

 

[Two-Stroke]

Thanks for the links! Both very helpful.

I found the correct piston for my engine on ebay but lost it in the last minute of the auction. Someone went crazy and jacked the price up beyond resonable so I gave up. It was for an OEM piece. I have seen listings for Stens replacement pistons too. Anyone here recommend them?

Good for you -- you showed restraint when the bidding went wild.

Do you remember the final price?

Anyway, it's nice to know they're available.

 

[DPI]

It went for $88. Maybe that's not too bad but it was more than I wanted to spend. There are listings for Stens replacement pistons on ebay for $30-40. Are they any good or is it worth the extra $$$ for the oem?