125cc performance upgrades?

[DANP]

I have very limited experience working on engines. That being said is there anything that can be done to hop up performance of my vintage 125cc engine? Can the head be milled? I'm getting the feeling there are not a lot of things to do. Here is what I'm working with.. 1970 Aermacchi Harley Davidson 125cc

 

[Brodie]

Usual things such as bigger carb and better flowing exhaust.

Depending on how quick you want the bike to go you can always change out the sprockets to give you a bit more take off at the expense of top speed.

 

[Walms]

In the hands of decent tuner, you could double the HP, but on the same token, in the wrong hands, the motor could be ruined.
Being a single cylinder, it won't break the bank either. Just do your homework to find someone to port the motor that you trust.

 

[Brodie]

I have bugger all knowledge about 2Ts but I know that a properly engineered expansion chamber will do wonders for peak power.

 

[VonYinzer]

Overbore with forged piston (if there is such a thing for such a motor), proper porting, expansion chamber, carb...

There isn't much info to be found (in my quick Google search) but if you do the research, a lot can be done with what you have. In general, two stroke engines were relatively de-tuned from the factory to save wear and tear. Open it up, let it breath with modified stock parts a big pipe and you should see some noticeable performance gains.

That said, it's a 125 single designed in the 50s. May be better to build it to run and look great without overstressing the power plant and find a proper performance oriented smoker (RD, Kaw triple, etc...) to get the go fast from.

All really depends on how much you want to spend in money, and more so time.

 

[Walms]

I have bugger all knowledge about 2Ts but I know that a properly engineered expansion chamber will do wonders for peak power.

+1

If you are at all interested in tuning up the ole 2 stroke on your own, checkout this book. I have the hard copy and it's my favourite bathroom reader!

http://3cyl.com/mraxl/manuals/bell/performance-tuning-graham-bell.pdf

The Bell book IMO is an easier read but Jennings book is another excellent resource.

http://3cyl.com/mraxl/manuals/jennings/twostroketuner.htm


For $30 or close to it, this software will get the job done for you for the pipe design.

http://www.buildandclick.com