Lots of carbon scoring.. Is the piston toast?

Other side

Hard to get good pics. You guys think the piston and cylinder will clean up OK?

That doesn't look too bad...should clean up nicely. Some new rings and a light hone and you should be good for another 20 years or so.

No gasket is required in between the crankcase mounting and the muffler plate. Just a gasket at the jug exhaust ports.

Super, then that's what we'll do. The seals are just maybe pried out and then driven in using a bearing tool?

Let me see if I have this right, the needle bearings, if they happen fall out are counted to make sure they are all there, and maybe held in with grease long enough to reassemble that part. Thought I saw in the manual there are needle bearings at the piston wrist pin area too? They used a lot of those things in these mowers.

Suppose someone could take all this stuff to a garage (or something like that) and have them run everything through a parts washer? Maybe a machine shop? Heck they can do a light crosshatch hone too now that I think about.

OK, got it completely disassembled tonite.

The crankshaft looks pretty good, so does the lower bushing & seal, but if the limit is .006" it's loose as a goose. That is just installing the two remaining parts - the crankshaft into the case, it "wiggles" enough for a tape measure at the end of the crank. Not sure under what conditions end play is measured.

The connecting rod is marked 606609 and has needle bearings on both ends. 33 on the bottom end.

How many on the small end? lol I think I got 'em all. One wrist pin clip flew across the garage. I always replace those, but.

The manual sez the connecting rod # is 682865, it looks like the liner is available separately. There is a connecting rod "kit" that includes the liners and the lower needle bearings, but not on the piston rod end?

Yeesh. :)

Not sure how many needles are included on the small end of the connecting rod. I think I have a part number for a caged set if you want to replace them, or you can take it down to the nearest bearing supply and they will match it up. I'm pretty sure all those bearings will be available at the local bearing supply except the big end of the connecting rod, the bearing supply that I use never found an aftermarket source for those needles and 2 ea. liners, so it's pay the big bucks and buy the OEM, or clean and reinstall. It's your call. The bottom end of the crank exceeding .0065 may warrant a machine shop to bore it out to accept a new needle bearing set. Probably not a must, just up to you and how much you want to spend. Many old timers say they don't worry about the lower end play as long as they can get the oil seal to seal properly seal.

Right, not sure on the sideplay either. It is leaking, the question is whether it's the seal or not. I'll run with it next year, I guess, and see about boring it if warranted.

It's 27 needles for the small end, and 33 for the big end. Didn't lose any either! Got the spark plug threads tapped and ready for the insert. Ordered a Flex-Hone and will cross-hatch meself.

On the connecting rod, the big end has two liners on each half. There looks to be a little fretting or wear. I'd like to replace those, they are kind of expensive but available. How are these installed? The old ones are maybe loctite'd on? But I mean the actual installation.

Also these wheels look like the right part number. They wouldn't "look" right but I could live with them. Think they'll work? Course need new bolts.

http://m.ebay.com/itm/LOT-OF-LAWN-BOY-STEEL-BALL-BEARING-WHEELS-2-8-2-6-/310177009379?hash=item4837fd8ee3%3Am%3AmupjIhG8gBefiZu7ocOYjww&_trkparms=pageci%253A0b1e5a13-c0de-11e6-84c7-005056b25309%257Cparentrq%253Af610fd011580a78574252c65ffd7b1d4%257Ciid%253A1

Seems to look good, no scoring, but not sure if "looks good" means anything.

Those liners are just placed In the bore with the detents in the holes in the rod cap and rod. No loctite needed.

Those wheels will be perfect. Those are the wells I used on both my 1964 and 66 restores.

So no contortions for the liners, just fit and torque the bolts, they'll crush down?

Can buy a connecting rod kit with new needle bearings on both ends, and liners, for $50, or the liners alone for about $20

This is getting out of hand LOL

Seals don't look excessively worn either, but again don't know what I'm looking at.

I would recommend installing new seals and gaskets, no matter what they look like. The bearings can be reused if good. Yes, it can get expensive for sure, and as parts become more rare it's only going to get worse.

Yep, ordered a gasket kit and seals already, and a bunch of other bits and pieces. The lower seal doesn't look worn at all, but it's kinda hard. Not bakelite territory, but. I'm wondering if it's just lost the ability to flex, and therefore leaking.

How are the seals installed? Manual doesn't say. Pry out old ones, seat new ones with a socket? Any sealer or loctite used, RTV?

Not to get ahead of myself here, but with new rings and honed cylinder is there a "break-in" procedure? Spring is right around the corner... ha!

Seals can be pryed out with small common tip. Installed and driven in with a piece of PVC pipe close to the same diameter. No loctite required.

Perfect. Sure appreciate the help!

The needle bearings look like a PITA to get reinstalled, the manual says to use grease and put 17 on one side of the rod and 16 on the other. Yeesh. The liners, if replaced at the same time would really add to the fun. Do they sort of snap in, and stay put?

Once done, take it out and cut grass with it, that will break it in. That's all I do with them to break them in. That question is like an oil question, you ask 4 people and you will get 4 different answers.

Yes the liners will pretty much stay in place, not really a snap in though.

Allrighty then, think I have a good handle on this for now. Ordered new liners and needle bearings for the low end, the liners looked pretty beat up.

I see how the rod liners work now, no sweat, finally popped them out. They are expensive, they look to be silver plated at least. My checkbook is pretty beat up after tonight, but I expect it will run pretty well when I'm done.

Ordered lower and upper seals, gasket set, wrist pin, rings, circlips, connecting rod lower end needle bearings and rod liners, and magneto plate bearing, set of 4 wheels, bolts, cylinder ball hone, helicoil... I better quit now...!

Found it interesting the manual describes clocking the blade on installation in relation to the piston set at TDC (to reduce vibration), had never heard of this, though did notice from time to time differences in vibration level after re-installing the blade, since I sharpen and balance it often.

OK, have been reading up on this lower bushing business. Way above my skill level. If you look at the above pic, you can see the crankshaft is basically grinding its way down into the crankcase. Why didn't they use a thrust washer or something like that?

I can see boring out the bushing to size, and installing a needle bearing, but what mods prevent the crank from continuing to boring its way down? This changes where the crankshaft rides and might twist the connecting rod? See where I'm going with that? Since I'm in for a penny I'm in for a pound now, might as well get the lower bearing repaired w/ a needle bearing at least.

The article you referenced by Mike72, I can't seem to find that, have found other sites have some mention of what needs to be done and some of the details. I'll have to find a machine shop of course and be able to explain, that article on the MTF would be great if you have a link, thanks again.

Check this out - from another website:

sawman024 said:02-23-2012 01:11 AM

Re: Connecting rod needle roller question

SB-7 was issued out in 4/'87.

The bearing strip part # 677963 (33 needles) is superceded to part # 683911 (32 needles) on all Lawnboy engines using the 677963 bearing strip in a repair, discard one needle so you have 32."

!! I give up LOL

Okay I'll look for Mike72's thread on the lower crank mod and try to post a link here. As far as the crank grinding down in the lower surface of the crankcase, I've never really heard of that being an issue on the D series engines, but I know the F series had some issues with that and that's the reason for the addition of thrust bearings in the later generation F series. I suppose you could go ahead and have the machine shop remove some material in the bottom of the crankcase to make room for a set of those F series thrust bearings/washers in addition to boring out to accept needle bearings to cure the axial play. If you go that route I would recommend giving the machinist the specs for end play and also all the parts that will be a factor, including the mag plate. I would also include the thicker gasket of the two mag plate gaskets from the set. The gasket set you ordered will contain two top end (mag plate) gaskets, a thick one and a thin one, normally you would use whichever one will give the best end play. He is going to need to temp install all those parts to calculate how much material to remove from the bottom of the crankcase to get the end play within specs, at least that is how I imagine it to be...I'm no machinist, but that would seem logical.

In reference to the service bulletin where it's telling you to remove one needle to make a total of 32 for installation. I think the new bearing strip that you ordered will already have that production change incorporated, so the new strip will probably just have 32 needles anyway. I know you removed 33, but your engine was more than likely assembled prior to the production change and service bulletin.

Somebody could make a nice little cottage industry out of selling or exchanging D series blocks, say for a usable core.

I hadn't planned on making the fouled spark plug a career, lol. See that second to last photo of the inside angle, can see where the crank has worn into the casting quite a bit, no?

Digging around, I see one guy bored out from the crank side. Mike72 suggests boring from the seal side, and installing from that end, and counterboring the rest of the bushing so the crankshaft doesn't ride on it at all anymore.. I know it's not rocket science, but am concerned a machine shop might not hit all the little details that the lawn boy gurus know about. No big deal probably. Will try to call around today. Glad I started this job in September ha ha

Called around a bit, there's no shortage of machine shops around, but it's more difficult to find somebody both willing and able to do the job than I expected. Did find a real character at a big machine shop that will probably set me up after the first of the year when things aren't so busy.

Has anybody ever thought about making some type of a sleeve or shim of some kind? Sort of like the liners that go around the rod end of the crank, or those "speedi sleeves" that give new life to spindles and dampers/balancers, things like that.

Heck, years ago guys would stuff leather strips into bearing halves to take up the slack on high mileage engines and it would last pretty good. Just sayin'.

Here is a link to Mike72's method of installing needles in a D series crankcase

http://www.mytractorforum.com/155-walk-behind-mowers/137085-installing-needle-bearing-d-crankcase.html

Here is Zeeker's technique for installing an F series bearing in the lower end of a D series

http://www.mytractorforum.com/155-walk-behind-mowers/112798-f-bearing-d-crankcase.html

Thanks, for some reason my google-fu was not successful finding Mike72s article, can I send off the crankcase to him!? That would be the hot ticket right there.

I've bookmarked those discussions and photos and will show my new machinist friend, he'll know what to do.

One thing the feller said was "bring in the whole shootin' match". I'm figuring crankcase, crankshaft and magneto plate would be everything he would need?

Course there's the matter of the bearing itself. One of Santas little helpers is sending the same needle bearing used for the magneto plate. With those nice photos figure let him run with it.

The specification for ring gap is .015" to .020" "top and bottom", though I read that as they mean both rings are set the same? It looks like the "F" series had different ring gap specs for the upper and lower rings.

Where exactly in the cylinder is the ring set in the cylinder in order to accurately measure ring gap? Halfway? Top of cylinder?

Has anyone found connecting rod replacement needle bearing sets that are usable for the wrist pin end? LawnBoy did not offer these separately except as part of a new connecting rod assembly.

Have also read that for break-in (on any 2-stroke) double the oil ratio (!!!) to help lube bearings and seat the rings. I don't believe LawnBoy had any special break-in procedures when new.

Does anyone know if this mower would have come with a modular "utility" carburetor? Wouldn't think there would be much difference as to the way it would run in any case, but I don't kniw, noticed there is no drain valve installed the float bowl as well.

Looks like the modular carb to me. I've never dealt with those, but I have heard that they are problematic. I remember one of the former employees at Galesburg talking about the troubles they were having with those even before the machines left the factory.

http://www.partstree.com/parts/lawn-boy/mowers-walk-behind-lawn-mower/7265-lawn-boy-walk-behind-mower-1976-sn-600000001-699999999/model-d-601-carburetor-models-used-on-5244-5274-7226-and-7265/

Noticed after cleaning off the reed plate one of the passages was drilled and has a lead plug or solder at the top of the casting. Is that factory?

Seems to me if I can find an older style carburetor and reed plate it should bolt right up correct? The governor rod will line up and everything? Would need an air cleaner box and gaskets too.

I don't know if that drilled hole with plug is factory or not. I have no experience with that reed plate modular carb combo. I will say that I have never seen anything like that with the D-400's I have worked on. If memory serves me correct that hole and journal is a lube journal to feed the upper main bearing.

The carb swap idea is very doable. I have read on various forums that it is a fairly common upgrade. I'm not sure what all is required other than the reed plate. I want to say that the governor rod will be a different length between the D-400 and 600, don't know for sure though.

The rod length is different between the 400 and 600.

The LawnBoy part number for the 600 series carb 679710 is the same, as near as I can tell, whether early style and the later modular. The reed plates are inexpensive enough, and they share the same number too, though they are not interchangeable (679711) hopefully see if I can't find a decent priced old style carb to try. I *think* the governor rod will be interchangeable.

The metal governor collar was pretty chewed up, so I ordered one of those, a thrust ring, and some other bits. Found an NOS piston and decided to use a new one just because. The flex-hone and the wheels, crank seals and needle bearings should arrive today.

Okay gotcha, I was thinking that the carb swap would be with a carb from a D-400, which is probably also doable, but yeah with the metal D-600 carb it would be much easier with little to no mods required. That's going to be a great little mower when all done. You don't cut corners that's for sure.

You should talk! I saw the photos of your stable of restored mowers and wow!!!! Your lawn too, looks phenomenal. I bet your neighbors hate you haha!! :)

Yeah, this is just a labor of love kinda thing at this point.

The new wheels look like they will work great. They use a big washer and little one same as original wheels right? No slop on the shoulder bolts, and the wheels have internal ball bearings. The overall idea of course is to have a stable deck.

Thanks for the compliments on the mowers and the yard. The don't know about the neighbors being jealous, they probably just think I'm crazy for having so many old mowers around.

Yeah those wheels just require the shoulder bolts and nothing else. The good thing about those is that they save the shoulder bolts, whereas the old LB triangle plastic wheels will chew them up. It also saves those old plastic wheels to and if you want to sell it later with original wheels they should be good to go.

No washers at all? I did a real quick test fit one of the small front wheels in case I ordered the wrong parts, and it looked to me as if the thick washer wasn't enough, it was still a little sloppy. So I installed one of the shoulder bolt washers against the head of the bolt, as well as a thick washer, and that seemed OK, at least slop wise. It appears that this method is the only way the ball-bearings in the wheel itself would be utilized. That's why I asked about it. Looking at the diagram LawnBoy actually used four (4) washers on the wheels?

Yeah I didn't install any washers and don't think the bearing race will turn much during use, but yeah I see what you are saying, it would be even better if I shimmed that up with to where the wheel race was kinda tight to prevent premature wear of the race and shoulder bolt. I just went out to the garage and checked the clearance and yes it could stand a washer, or shim. I think I'll address that the next chance I get, thanks for pointing that out. The parts catalogue is showing one washer between the wheel and mounting adjuster, but I don't think there will be clearance for the thick one on my applications. The best I can remember there was very little clearance and that is probably why I ditched the washers. Peelable washers/shims should do the trick though. Your mower is a 1977ish, so the IPC will have added the extra washer and the felt gasket/washers to the inside and outside due to the plastic wheels that yours originally came with.

Ok, I'll see how that works when there's something to mow. -18F last night, warmed up almost to 0 today, it's gonna be a while!

Pulled the lower oil seal on the crankcase and now see better what needs to happen with the machine shop, it should be no big deal just have to find somebody to do it. The sideplay limit is .0065" measured "next to seals"; pretty close tolerance. Thought about just running new seals but the crank is so sloppy in there.

Happy Hanukkah and Merry Christmas everybody!

One of the things I looked close at is the upper connecting rod bearings. With a new piston, rings, wrist pin, etc it doesn't make much sense to re-install worn bearings here, and after cleaning them up the liner portion or cup I guess it could be called, had worn through the plating in some areas. It's marked Torrington Y-88, with 27 needle bearings.

The LawnBoy manual cautions here on disassembly not to lose any of these, as "Bearing replacements are not available. Must be purchased as part of rod and bearing assembly"

Except, this isn't exactly true. Torrington Y-88 is available for under $10, so I pressed the old bearing out and installed a new bearing. Looks fine to me, but.

Why did LawnBoy not have replacement bearings available then? Are there technical reasons this should not be attempted, or was this a marketing or "bean counter" directive?

I don't know of any reason for them to say they are not available, who knows what was available back in the day when those instructions were written. I think you did good by pressing in a new on. I usually do that as well on the restores that I do. I'm glad they went to needle bearings in the wrist pins in 1970. Those plain bearings prior to 1970 just took a beating and usually ended up with severe wear over the years.

Ran the flex-hone through the cylinder today, they do a great job of removing the glaze in just a few seconds. It's important not to overdo it, just clean up the cylinder walls and get a nice crosshatch.

Unfortunately there is a fairly deep score line that won't clean up by simple deglazing, it would need to be bored and oversized piston installed.

Well I got it all back together! Man, there are a LOT of little fiddly bits on these things that have to be done just so in order to work right. Without the manual, forget it.

I used an old metal D600 carb and a used reed plate. The primer line was too calcified to fit well as it has a larger diameter barb, but I will work on that.

One head scratcher - I used the same spark plug as last summer, NGK BPMR4A, and it wouldn't start, because it wouldn't prime, as the hose popped off. Wanted to hear it run so I thought maybe I'd squirt a shot of fuel in the cylinder. After removing the plug I saw why it wouldn't start - the piston had banged the electrode and shorted the plug! I knew the Champion CJ-14 had quite a bit shorter reach. After digging around for a while I found one and it started right up.

Runs great, very smooth and everything other than the primer hose works as advertised. Turning the altitude needle in from 1.5 doesn't do anything, but turning it out from there smoothed it out and brought the RPM up a little. I didn't use the tach but it sounds right Low/High. Let it run till it warmed up, will try retorquing the head bolts tomorrow.

I'm at a loss as to why the spark plug clearance is different now, anyone??

Sounds like the project is coming along good! I don't know how to explain the contact of the spark plug with the piston with the NGK plug installed, as far as I know there are only 2 different D series jugs, the D400 and the D600. You have a D600 with slightly higher compression, so usually with higher compression it will also have tighter clearance above the piston. Lawnboy says the jugs are not a 2 way interchange because of the different compression ratios. I don't think that should be an issue, but worth checking to make sure that both of the jugs are the same. The other thing that comes to my mind is that maybe the replacement jug is defective, or someone replaced the plug insert and now the plug will go further into the jug before seating.

It could be, thinking out loud, I was never able to torque the plug down to spec because of the stripped threads. With a new jug maybe the 12 to 15 ft lbs makes the difference.

It's a moot point now, after going over the parts manual, it's almost certain the original problem was caused by a missing carburetor float spring - the modular "utility" carburetor (only) uses a spring below the float. I assume it will always flood without it under certain conditions. Part #609016

Took a walk down memory lane and dredged up the old eBay listing to refresh my memory on the howlers the seller posted, as near as I can tell hardly any of it was true. Caveat Emptor, sure, but what a jackwagon.

Up for bids is a 1976 model year Lawn-boy 2-cycle 21 inch walk-behind mower. The model # 7265, the serial # 7531893. This mower has a D-601 series 2-cycle engine that has been fully tuned up. I have put on a new muffler gasket and sleeve, put on a new governor kit, brand new old stock carburetor, new air cleaner, new gas line, new champion CJ14 spark plug, and the blade has been sharpened and balanced. The muffler and exhaust ports have also been cleaned. The engine has 115 lbs of compression and is very powerful.

The lower bronze crankshaft bushing has hardly any play and feels tight like a new engine would. There is hardly any vibration from this mower when running. It is a very smooth running machine that has lots of life left in it.

The housing has no cracks or repairs done to it and only has light to normal pitting on the bottom side as you can see. It has been completely taken apart, sanded, and repainted with automotive grade epoxy piant.

This mower comes with a side discharge plate only. If you would be interested in a side bag kit, I have a used one for an additional $30.00. This housing is made of Magnesium making it extremely light weight and yet durable. This is even lighter than the Aluminum housings which were made in 1977 on up.

Much better

Looks good!

It shows 110 PSI cold after 4 or 5 pulls. I did retorques on cylinder head and reed plate bolts after a couple hot/cold cycles and they did loosen up quite a bit, this is probably something to check again after a good summer mowing session too. After the third run they are holding.

The manual recommends loctite on the magneto plate bolts and screws that secure the reeds, I can see why now.

First mow of the season! Can't say that lawnmowing is my favorite activity, but it sure helps to have a reliable horse. Started first pull! The lawn wasn't overgrown but certain areas needed it more than others, it was ready and put it under a load. It runs very smooth and the governor system is quick to respond. It sort of burbles under load, hadn't heard that in a long time. I think it runs better than when it was new.

New wheels make a big difference, set the cutting height slightly low to aid in spring green up, and it didn't scalp like it would have before. Clocking the blade as mentioned in the manual, (a new sharp blade) relative to the crank is a neat trick that lowers the vibration level noticeably for smoother running. It just plows through thick, lush turf like butter. Thanks for everyone's help, be back in 25 years or so for the next overhaul!

Good deal! Long live the Lawnboys!