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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!

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.

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.

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.

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?

Ask and ye shall receive

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

Have you been here and had a look..?

Lawn-Boy Service Manual 1950-88 Complete

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?

DPI said:

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?

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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.

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?

DPI said:

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?

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Thanks for the info. I hadn't heard about the Stens pistons until now. It's good to know the option is there. I can't comment on their quality.

My approach to major parts is to constantly search for fairly cheap old mowers on CraigsList. I've got three LBs that I keep just for parts. Things have gotten tight on the Atlanta CL recently (the last year or so) and bargains are scarce.

Two-Stroke said:

Thanks for the info. I hadn't heard about the Stens pistons until now. It's good to know the option is there. I can't comment on their quality.

My approach to major parts is to constantly search for fairly cheap old mowers on CraigsList. I've got three LBs that I keep just for parts. Things have gotten tight on the Atlanta CL recently (the last year or so) and bargains are scarce.

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I wasn't sure if they are still making them or if they were old replacement parts. I just would like to get a new piston since mine is scored on both sides. Would have to take a pic of it and post it to get opinions but it looks borderline to reuse.

I will look at craigslist to see if I can find any compatible mowers for parts, thanks for the tip.:thumbsup:

Also, I found a source for lawn boy engine paint on ebay, but it is $11 + shipping for a 4.5 oz can. Anyone found a better source?

DPI said:

Also, I found a source for lawn boy engine paint on ebay, but it is $11 + shipping for a 4.5 oz can. Anyone found a better source?

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There has been at least one thread here in the LB forum where that was discussed and I remember that there's both official LB green and another, more common paint that's virtually the same.

If you saw my mowers you would understand that I haven't used any paint on them recently. :laughing:

Fireman123 will know this. If you search the forum you'll see pictures of LBs that he's restored that look mint. :thumbsup:

Wait! I just noticed that you said Engine paint... everything I wrote above applies to deck paint. I don't recall seeing paint on any LB engines.

Thanks, but everything looks better in picture form haha. I use Grabber Green engine paint. It's available at your local auto parts store. That may be what you meant by saying engine paint. The engines themselves were not painted. At least I've never seen one that was.

Fireman 123 said:

Thanks, but everything looks better in picture form haha. I use Grabber Green engine paint. It's available at your local auto parts store. That may be what you meant by saying engine paint. The engines themselves were not painted. At least I've never seen one that was.

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Sorry, I meant deck paint. I saw grabber green in the auto zone by me. Going by the color on the cap, it looked different so I figured I would ask all of you what you used.

BTW, I ordered the Stens piston, part #515-510 from a supplier in IL. It is $30 shipped so it is a lot cheaper than the oem pistons I have seen come up for sale.

Grabber is a lighter color, but it is the closest thing to buying overpriced LB paint. However, you may be able to take a paint chip to a place that mixes automotive paints, have it analyzed, and get you an aerosol can of paint made. Good luck.

Thanks Fireman! Don't think I will go that crazy, I will get a can of the grabber green from the auto place up the road from me.

I just bought a lawn boy mechanic's book and it says that you should only use lawn boy 2 cycle oil, not generic 2 cycle like Sears, etc. Is there that much difference in quality? What are you all using?

DPI said:

I just bought a lawn boy mechanic's book and it says that you should only use lawn boy 2 cycle oil, not generic 2 cycle like Sears, etc. Is there that much difference in quality? What are you all using?

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Keep in mind, that book is probably 25 years old or more. There may be some OCD Lawnboy owners that say use it, but I just run whatever is handy when I run into Walmart. The LB oil that was on the shelf years ago was an ashless formula. I haven't seen any around my area for a while. The new LB oil is semi synthetic I believe so I'd say it isn't much different than anything else.

DPI said:

I just bought a lawn boy mechanic's book and it says that you should only use lawn boy 2 cycle oil, not generic 2 cycle like Sears, etc. Is there that much difference in quality? What are you all using?

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I use Poulan oil at 50:1. The newer oils are better -- the technology has improved a lot in 20 to 30 years. I haven't had a problem with that higher ratio.

I'm always skeptical of any company promoting its own product in a manual. And I'm a huge LB fan.

Two-Stroke said:

I use Poulan oil at 50:1. The newer oils are better -- the technology has improved a lot in 20 to 30 years. I haven't had a problem with that higher ratio.

I'm always skeptical of any company promoting its own product in a manual. And I'm a huge LB fan.

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Okay, now I'm confused. I have been using 8oz of 2 cycle oil to a gallon of gas. What exactly are you mixing?

8oz to 2 gal gives you a 32:1 ratio. This is what I use.

DPI said:

Okay, now I'm confused. I have been using 8oz of 2 cycle oil to a gallon of gas. What exactly are you mixing?

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If you mix at 50:1 it works out to 2.56 oz per gallon. The containers that I buy have a second chamber on top and I squeeze the bottom chamber until the oil gets to the line for 50:1.

You've been mixing at 16:1 and I think that's outdated given current oil technology.

Two-Stroke said:

If you mix at 50:1 it works out to 2.56 oz per gallon. The containers that I buy have a second chamber on top and I squeeze the bottom chamber until the oil gets to the line for 50:1.

You've been mixing at 16:1 and I think that's outdated given current oil technology.

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Thanks Fireman and Two-Stroke for the info. All these years, I have just been following the recommendation on the back of the shroud. This is the same mixture for my leaf blower so this makes my life easier.

Another question - when you put the piston and new rings back in the cylinder, did you need to use a ring compressor? The old piston and rings just slip right in and out so I was thinking of just putting a good amount of oil in the cylinder and just trying to slide the new assembly in without the tool.

Just took some pictures so I will upload soon.

You will need some type of compressor. I've used an ordinary worm clamp before but it's a little tricky.

I decided to clean up the original piston and reuse it. Took a while to clean it up but it turned out nice. I got a piston/ring installer from Auto Zone to do the install. If I get enough time, I hope to reassemble the motor tomorrow.

I bought some used mower wheels off of ebay to replace the worn out originals. They look identical, but I noticed that the wheels have slightly larger mounting holes so they are loose with the original mounting bolts. Do I need to get different bolts that fit these wheels?

Well, I put it back together today and I still have about 1/16" play in the crankshaft so I guess I will be either using the F series bearing fix or finding a new crankshaft body. Are all F series bearings the same or is there a specific one I should use?

Unless you just want to take everything back apart, I wouldn't worry about 1/16 of play. ESP if it runs good.

DPI said:

Well, I put it back together today and I still have about 1/16" play in the crankshaft so I guess I will be either using the F series bearing fix or finding a new crankshaft body. Are all F series bearings the same or is there a specific one I should use?

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Is the play up and down or side to side?

Side to side play is fine. There should be no up and down play

I'm rebuilding a D409 motor which is the same as the D601 in the sense that the crankcase & cylinder separate.
I didn't use or need a ring compressor to put the cylinder over the piston and rings.

I made sure the ring end-gaps were opposite each other, oiled it all up, pinched the rings (one at a time) with my fingers & it went straight on, no problem..

A ring compressor might help but it is not a required tool..

There is play up and down and side to side. I don't have another one to compare it too, but I would think that the amount of play I am describing can't be good for the longevity of the engine. I am measuring end play at the end of the crank. I put a dial indicator at that point and came up with 0.028, so if that is the correct place to measure it, it seems excessive.

DPI said:

Also, I found a source for lawn boy engine paint on ebay, but it is $11 + shipping for a 4.5 oz can. Anyone found a better source?

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actually i just got through with the rebuild on my 7084, rustoleum engine enamel grabber green is so close its hard to tell them apart. just waiting to obtain some wheels!!

DPI said:

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?

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I restore vintage lawnboys, and stens pistons are dimensionally correct. Rotary brand pistons are junk.