Whats a chap to do

I have finlly decided to rebuild my ST70. I intend to use it for work through winter. I have owned it for nigh on 30 years.

When it comes to the engine I am in a dilemma.
The ST engine was junked many many years ago and I have a C70 engine. What I want is more power.
I have 2 choices
1) Buy a Stomp 140cc engine for £350 and then have all the hassle of converting to 12 volts
2) Buy an 88cc big bore conversion including the race head with bigger valves and Carb included for £240.

I am favouring the 2nd choice because I keep the more reliable bottom end of the Japanese motor. The company claim to double the power at least so it takes it near to the 140 power.

Anybody done these changes and can give advice

I'd go for option 2 as well, but that's just me.
Take a good bottom engine. (50 or 70)
Make sure it has the L-crank tap ( you don't want the flat Hitachi flywheel, you can't mount an advancing 6v or a CDI ignition)
- 85cc (51mm) piston/cylinder. Any brand will do just fine. (Kitaco / Takegawa / DRP (best buy)/ ...
- original ST70 head - rebuilt or good original condition, fast cam if desired
- hi volume oil pump (180-210-270%)
- check and rebuilt the clutch if necessary, or mount a manual clutch if that's what you want (for example Honda SS50 1-plate clutch)
- choose your faster ignition or convert to a 12v Jingcheng

Option 2 all day long

Thats what I would do anyway, keeps its Honda & reliable.

Just my thoughts.