98cc Engine Mods

GoldenMotor.com
T

twalsh341

New Member
Apr 10, 2013
17
0
0
Philadelphia
So I shaved the cylinder head, new head gasket and I'm onto removing the gov. and looking inside the crank case.

Does anyone make a performance connecting rod for the 98cc, or a metal cam to replace the plastic one?

Current compression is 7.5:1, but I'm looking to run on E-96 with 12-14:1. I have to see whether I can get the combustion chamber TIG welded so I can remill it to size, or I will just have to cast a new head.
 
T

twalsh341

New Member
Apr 10, 2013
17
0
0
Philadelphia
It's the flathead version of the doodlebug engine, which is made I think by Lifan.

One of my student workers does alot of engine work with minibikes and the like and he suggested a flathead as the best type to use if I was intending to get the high compression.

I know the new ones are OHV, but I managed to find one with only a short run time on Craigslist.
 
T

twalsh341

New Member
Apr 10, 2013
17
0
0
Philadelphia
Here is a pic of the shaved head, I still have a few milling marks to grind out. When finished I'll have a dead flat mating surface for the head gasket. I packed the combustion chamber with clay so I could take a measurement of the resulting chamber and have something for a welder to visualize when I ask to have some of it TIGed in.

Right now I'm not sure what my combustion chamber geometry constraints are, I know how much clearance I need for the valves, but other than that I don't know if I'm encroaching too much. So I need to read about combustion chamber fluid dynamics and see if I'm still okay.

At 7.5:1, this shaved head will run alcohol decently and the risks of distorting the head too much to mill out, or have a welding "oopsie" are pretty high. I think the best option is going to be to design a new head, then cast and machine everything.
 
You must log in or register to reply here.
Top Bottom