[kirrbby]

Why not just build the engine that you have? Something like this...

TBParts - Stroker kit 2 108cc for Z50 CRF50 XR50 CRF70 - TBW0967 - Big Bore and Stroker Kits - Pit Bike Engine Parts - TBolt USA, LLC

Shop at TBoltUSA: TBParts - Stroker kit 2 108cc <br> for Z50 CRF50 XR50 CRF70

tboltusa.com

I think that kit would give you more than enough power for your needs.

 

[kirrbby]

I think it might be tough to get a estart engine THAT big. The started wouldn't be able to spin it. Whatever you end up with...you might want a kickstart option with your estart.

I'm wondering if you could just buy a TRX90 estart engine...add a simple big bore kit for 105 or 113cc of really good power, and excellent reliability. Your LAST engine