Is this an F Series engine?

[RENeal]

I have a Lawn Boy Gold Series, Model # 10515, Serial # 5904247, with a 4.5 HP commercial engine. The last couple times I used it, I could hear the engine getting tight, then it would stop. After it cooled, maybe the next day or so, it would restart and run, but again tighten up. Finally, it quit. The fuel mixture is OK and I use the same fuel in other 2 cycle engines with no issues.

After taking it apart, realized the rod broke near the crank.
Couple questions:
1.) What would cause this to get tight and eventually break the connecting rod?
2.) Is this a "F" Series engine? I have been looking for parts and need to be sure the engine type.
3.) Any suggestions as to where to look for parts, or a replacement engine?

Thanks

 

[mechanic mark]

Lawn Boy 10515 - Lawn-Boy Gold Series Walk-Behind Mower, 1995 (SN: 5900001-5999999) ENGINE ASSEMBLY Diagram and Parts List | PartsTree.com

https://www.google.com/search?sourc...=lawnboy parts&aqs=chrome..69i57j0l5.8239j0j8

https://lookup3.toro.com/ttcGateway/acrobat/manuals/lball.html I know this is not your manual or year, may help answer questions regarding engine.

 

[Phototone]

Yes, that is an "F" series engine.

If it appears the engine is getting tight, then you don't have your gas/oil mix rich enough in oil. You should use only 2-cycle oil, and mix 32-1, so 8 oz. of oil and 2 gal. gas.

 

[beg]

I have run across 2 of that model with the same broken rod issue and have another that's knocking. All are the 10515 gold series. Could this be a production issue? My other F models seem to run forever. However I got them used and do not know the previous history and what oil was used. Also due to the high rpms could hitting an object such as a grounding stake take out the main bearing which in turn would destroy the rod? Also will any f motor swap on to the 10515 meaning will any f motor bolt to the 10515 deck?

 

[Phototone]

View attachment 27344I have run across 2 of that model with the same broken rod issue and have another that's knocking. All are the 10515 gold series. Could this be a production issue? My other F models seem to run forever. However I got them used and do not know the previous history and what oil was used. Also due to the high rpms could hitting an object such as a grounding stake take out the main bearing which in turn would destroy the rod? Also will any f motor swap on to the 10515 meaning will any f motor bolt to the 10515 deck?

I wonder if the mixture and rpm changes to achieve the higher horsepower of the "GOLD" series might be the cause of shorter engine life? AFAIK, the blocks are the same for all "F" engines. Having worked on "F" engine mowers from the first pre-compliance models up to the latest "GOLD" models, it appears the block casting is the same as far as attaching to the muffler plate. You just have to use a muffler plate designed for the type of deck you have (steel or aluminum deck).

I think its true that the higher RPM, the more potential for engine damage if you hit a big rock or stump that stops the blade. Also an unbalanced blade would vibrate more violently at higher RPM.