Engine Repowering Project

[bartles]

I am replacing a 10.5 HP 21R707-0145-G1 with an older 17HP 31C707-0154-E1.
When comparing flywheels I see a difference, when the magneto magnets are between the block mounting holes for the magneto, of the flywheel keyway positions. The 31C keyway is roughly located at 2 o'clock, and the 21R is roughly at 11 o'clock. The cam lobe positions are the same comparing the camshafts.

I am assuming the timing difference is to retard the timing for emissions compliance issues?

Do I have to use the 17HP flywheel or will the 10.5Hp work?

 

[Craftsman Garage]

just leave the engines intact with all of their pieces, not a good choice of engine though as all of them have camshaft breaking issues, since the sparkplug ignites as the piston starts to go back down, it might be for emissions but idk about any of the things they do on these to "solve" emissions, if you use your engines with all of their original pieces, they will run much better with eachother instead of having some OEM pieces, but some parts off the 10.5.

 

[Craftsman Garage]

its not a matter of will the camshaft break, its when. all of these engines have camshaft ACR problems - 21xxxx-28xxxx-31xxxx-33xxxx engines, especially the intek ones.