4hp upon inspection?

Has anyone tore down a 4hp flat head? Its very odd compared to its larger and smaller relatives. Does anyone know more about these? They seem to be built very well
 
The one I took apart was just a small bore version of the 5 hp.

I played around with offset bore(cool bore engine). I think there was some potential.
 
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Yes it's funny how they retool and redesign things .
When they could alter the intervals and change the power and size .
The external size would stay the same , which is one reason . The bean counters also have a say , more material that's uneeded . A new hot shot engineer with a better idea . And of course manufacturing techniques change .
 
Absolutely. Oddly it has a significantly larger bore that 5hp about half the stroke and valves the size of the 3 hp. Same crank case cover as 3hp and its own head design. External appearance resembles the old 5hp cool bore engine. I'm hoping its gonna be a good match for the mini bike I have because the 5 hp is gonna be too tall and despite the no quit performance of the 3 hp, literally couldn't ask for more out of the bone stock one i have right now. I feel like I could a little to a lot more MPHF than it has to offer. Again very impressed with what the 3 hp brings to the table. I just hope the 4 and 5 hp flatties are as impressive. #thelittleenginethatcould_
 
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