[nhvfd71]

hi all i am restoring my second lawn boy. it has a d449 engine with a 2 ring piston. now i couldnt buy a new piston from lawn boy so i purchased one from tulsa engine warehouse. the piston clearly stated that it replaces lawn boy part # 606607 which is what mine calls for, however the picture of the piston depicts a 3 ring piston, i have found many other aftermarket pistons that replaces the #606607 piston that is a 3 ring not a 2 ring. my question is will it work? here is the link Piston Assembly Replaces Lawn-Boy: 606607 please help thanks much

 

[Brad]

I am pretty sure that you can use the 3 ring in place of the 2. Have heard others discussing this. Let me do some checking.

 

[IdBeDan]

Rings serve a purpose, Upper ring/rings is the (compression ring) middle ring/rings are the (scraper rings) and of course the bottom is the (oil ring) The oil ring is wider and normaly looks like a ladder circle. You won't have an oil ring on your lawnboy piston because it's a two cycle. You may just have dual compression rings with one scraper. It should work just fine. Remember to offset your ring gaps 180 degrees apart, compression depends on that. Good Luck

 

[Brad]

I asked a gent that is pretty darn sharp on LB's. He said, and makes a lot of sense, that the photo may be a "stock" photo and might have the correct number of rings, if the indicate it's a replacement.

Also, he said:


If they are OEM 2 and 3 rings, they do not intermix at the rod.
Whole assembly has to be changed if you do change from one to the other.
I am not familiar with after market 3 ring pistons, didn't think you could buy any thing but 2 ring.


Good luck with it !

 

[Fireman123]

hi all i am restoring my second lawn boy. it has a d449 engine with a 2 ring piston. now i couldnt buy a new piston from lawn boy so i purchased one from tulsa engine warehouse. the piston clearly stated that it replaces lawn boy part # 606607 which is what mine calls for, however the picture of the piston depicts a 3 ring piston, i have found many other aftermarket pistons that replaces the #606607 piston that is a 3 ring not a 2 ring. my question is will it work? here is the link Piston Assembly Replaces Lawn-Boy: 606607 please help thanks much

The old 2 ring pistons required 16:1 fuel ratio. That's a pretty old mower you have. Somewhere in the mid-70's they went with the 3 ring pistons and 32:1 fuel ratio. If I were you, I would get the part # of the connecting rod your mower takes. Then compare that to a later model D series engined mower with a 3 ringed piston. R7266 is a model mower you can use to look that information up. If the #'s match, you're good to go. Good luck

 

[Fireman123]

Saved you the trouble of cross referencing that info. According to www.lawnboy.com the 3 ring piston will work. The connecting rods have the same part #'s. Just be sure to mix your fuel at 32:1. This should help the performance as well. There's a video on YouTube of the same mower you have. The guy says he updated the engine with a 3 ring piston. I'd say you've got a rare mower on your hands. I like the top belt self propel drive system and electric start options. Hope I was able to help you.

 

[Lawnboy77]

If you ordered a 606607 piston from Tulsa then you will be getting a 2 ring piston. I just ordered 3 from there and recieved them yesterday. A good looking piston to I might add, I just hope that it will last like the original OMC pistons. The ring gap checked good (.015-.025). What Brad said is exactly right, the 3 ring piston and 2 ring piston are not interchangeable. If you want to convert from the 3 ring to the 2 ring piston, or vice versa, then the connecting rod would also have to be changed, the wristpin on the 2 ring setup is slightly bigger than the 3 ring setup. Not sure why anyone would want to convert from a 2 ring to the 3 ring though, since the 3 ring does not have the needle bearings in the small end of the connecting rod. Most folks convert from the 3 ring to the 2 ring because of the wristpin needle bearings, and it enables the motor to be run at 32-1, instead of the 16-1 that was recommended with the 2 ring piston. From my experience with these old 16-1 machines is that with the plain bearing wristpin, it causes the hole where the wristpin goes through the piston to become elongated, whereas with the 2 ring piston the wristpin doesn't really rotate against the soft aluminum piston boss, so the small end of the connecting rod will last much longer with the needle bearings installed.

 

[Fireman123]

If you ordered a 606607 piston from Tulsa then you will be getting a 2 ring piston. I just ordered 3 from there and recieved them yesterday. A good looking piston to I might add, I just hope that it will last like the original OMC pistons. The ring gap checked good (.015-.025). What Brad said is exactly right, the 3 ring piston and 2 ring piston are not interchangeable. If you want to convert from the 3 ring to the 2 ring piston, or vice versa, then the connecting rod would also have to be changed, the wristpin on the 2 ring setup is slightly bigger than the 3 ring setup. Not sure why anyone would want to convert from a 2 ring to the 3 ring though, since the 3 ring does not have the needle bearings in the small end of the connecting rod. Most folks convert from the 3 ring to the 2 ring because of the wristpin needle bearings, and it enables the motor to be run at 32-1, instead of the 16-1 that was recommended with the 2 ring piston. From my experience with these old 16-1 machines is that with the plain bearing wristpin, it causes the hole where the wristpin goes through the piston to become elongated, whereas with the 2 ring piston the wristpin doesn't really rotate against the soft aluminum piston boss, so the small end of the connecting rod will last much longer with the needle bearings installed.

Thanks for clearing that up. I was backwards with my info

 

[Lawnboy77]

No problem, glad that I could help. Just to further clarify...2 ring (32-1, needle bearings in small end of connecting rod), 3 ring (16-1, plain bearing in small end of connecting rod). Lawnboy changed over at the factory around 1970. generally anything built after 1970 will have the improved needle bearing connecting rod with the 2 ring piston. I think I slipped up once on the fuel/oil mix ratio on my original post, hope that mistake didn't confuse anyone.

 

[Brad]

Very good explanation, Lawnboy77. Thanks!