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I am in the process of rebulding a S19ZPNB walk behind mower. The 1978 manual I have says an F engine should have 33 rollers on the connecting rod. Then replacement roller set I ordered has 32 rollers. Which is correct?
Thanks
Tom

Could it be that the new bearings are larger to accommodate a smaller crank? You are going to turn the crankshaft down right?

I am replacing the half shells in the connecting rod along with the rollers, but I do not plan to turn the crank. I do not see any special size rollers for doing this.
Tom

These roller bearings you bought did they come with a spec for the crank journal? Or do these bearings rest in the wrist pin?
Can you mic the old bearings and see if they are the same diameter as the old bearings. Something does not add up......
How about you post some pictures....we like pictures:biggrin:

Perhaps Lawnboy changed the spec. for the rollers on the connecting rod bearing. The F series engine manual says there are 33 rollers. The V series engine manual says there are 32 rollers. The Lawnboy parts listing shows connecting rod bearing 683911 for both F series mower S19ZPNB and V series mower 10227. The crankshaft diameter is listed the same, so have they changed the bearing spec?
Also, what is the best sealer to use for the crankshaft halves?
Thanks.

TomW said:

I am in the process of rebulding a S19ZPNB walk behind mower. The 1978 manual I have says an F engine should have 33 rollers on the connecting rod. Then replacement roller set I ordered has 32 rollers. Which is correct?
Thanks
Tom

Click to expand...

Something sure dosen't sound right. If it was me I would do my homework on that one. If the old rollers look good I would use them over that way you would be safe.

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the bearing strip part # 677963(33 needles) is superceded to part # 683911(32 needles.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 useing the 677963 bearing strip in a repair, discard one needle so you have 32.

You really know your stuff, sawman. I hope you visit this forum often.

About the original question in this thread... In my experience, it's rare that one of these engines needs major work like crankshaft or rod bearings. So I don't have any experience with these problems.

I loved working on the Lawnboy "D" Series engines.They were my favorite.Second fav was the Briggs easy spin starting 92900 series.

Thanks for the reply. The Lawnboy service manual on their website has never been updated and says 33 rollers in the D manal and 32 in the V manual. I agree that with proper care the engines last well. This one appears to have been run in very dusty conditions without the air filter being oiled. The air filter was fairly clean but dry, although when washed turned the water brown. However, the choke plate had about 1/16" of dirt caked on it and grit was laying in the crankcase. The piston was grit-scored and the bearings worn. A little care could have avoided this.

As for the crankcase sealant you will want to you Permatex Surface Prep # 765-1154 and Loctite Anaerobic Gasket Maker #515, this is what I use and have great results, just follow the instructions and you will have no problems.

I just rebuilt the engine on my 10518 (F series engine) and when I took it apart only found the 32 needles but there was a large gap between the needles, enough that the 33rd needle would fit in very easily with no binding. So being none the wiser I reassembled the engine with the 33 needle bearings and it runs great. Should I be taking this apart to remove the extra needle or just leave it in? I am really surprised that the large gap between the needles is acceptable.

I tried to find the posted service bulletin but had no luck finding it to read why they went from 33 to 32 bearings. Can someone post the service bulletin or provide a link to it?

Any comments would be appreciated, especially if I will damage my engine with that extra needle bearing.

Thanks!