Are there any small, OHV (ideally OHC as well, but not necessarily) four-stroke engines out there that have an engine head you can remove? The smallest I've found is the 50cc QMB139 engine used on imported scooters. http://www.partsforscooters.com/cyli...9&category=465
I'd like to find something in the range of 25cc.
Honda, Subaru/Robin, Stihl etc all have small 25cc engines, but the head and block are cast as one piece.
I want a removable head because I need to adapt this head to another engine. Obviously an OHC engine would work the best because I just need to link the overhead camshaft to the crankshaft with a timing belt.

Another possibility is using the cam and valves from the Honda GX and fabricate my own head. I imagine this would be pretty difficult though with machining the valve seats/guides and the complex geometry of the intake and exhaust manifolds. I imagine a 5 axis CNC mill is needed. I have a 4 axis cnc mill. Another method that people used to use to make experimental engine heads with complex gemoetry before the advent of CNC was to machine a bunch of thin plates at incremental cross sections and stack them together, like how composite resin molds are made. Does anyone have any experience with making engine heads?

Or another way is to cut off the head from the GX and weld a plate to it, machine it, and bolt it onto the engine I have.

If any of you are wondering why I have to adapt a head to an existing engine, it's for a competition and it's part of the rules, so there's nothing I can do about it!

I'd like to hear some of the experts' advise on this forum!

Thanks!