40mph speed secrets revealed

foureasy · #1 09-12-2009, 12:17 AM

i will periodically add pictures and the reasons why, for a few of the things that i have done in the quest for speed.

i did this to my combustion chamber to make it a more efficient "squish" type chamber. it helps to promote a more even flame travel and less risk of detonation. not to mention the added benefits of increased compression. the ideal size of the squish band is 1/2 of the bore area, which i have come pretty close to.

weld it up

face it and grind it out

i got five on it

Rockenstein · #2 09-12-2009, 01:40 AM

Nice job with the fill welding trick

I wondered about attempting that on a spare head I have but the welding guy I talked to said it would likely warp real bad...looks like yours survived so I may take it back and tell him to go for it.

To others that try foureasy's mod a nice finishing trick to use once you've roughed out the combustion chamber shape by hand or in a lathe is as follows...

Grab a few lengths of 1 1/2" - 2" hardwood dowel and shape the ends to the desired combustion chamber shape with a belt or disc sander. Get some various grits of sand paper and glue them smoothly to the shaped dowel ends with contact cement. Starting with a 180 or so grit work the dowels in the combustion chamber like your starting a fire the hard way...the end result should look real nice and be smooth enough to avoid any possible detonation issues.

PS: foureasy is this your finished and running head? Wondering if you touched up the pitted areas on the squish band or not? I'm concerned glowing deposits could get in lodged in them and cause some unexpected detonation...

Venice Motor Bikes · #3 09-12-2009, 08:06 PM

Let us know how it runs!!

foureasy · #4 09-12-2009, 09:03 PM

it runs great, this thread is based on the things that i have already done to do 40mph at 8000 rpms.

rock, those pitted areas are as good as i have the patience for. they are right where the filler rod meets the base metal, (whatever that is). i have seen no evidence of detonation so far. the only issue i've had with this motor is the connecting rod bearing on the small end. i picked up some nice american made bearings to replace the stocker.
sometime in the near future i'm gonna mill up a billet head that is hugely oversize, to combat the heat issue here in tucson.

foureasy · #5 09-12-2009, 11:34 PM

sometime soon, i'll port a used cylinder i have laying around and show some of the layout tricks

here is a sneak peek of my exhaust port

here is an intake port

foureasy · #6 09-17-2009, 11:28 PM

here is a working cylinder head as a blank canvas. i'm picturing swiss cheese.

cobrapowered1 · #7 09-18-2009, 05:45 PM

Far out head foureasy, is that a dual carb setup ? Nice.

foureasy · #8 09-19-2009, 01:03 PM

it is a dual carb setup. here is the aforementioned swiss cheese. sorry about the cell phone pics.

azbill · #9 09-19-2009, 01:45 PM

that is a lot of drilling !!!
does it help you enough to be worth the expense/effort ???
enquiring minds want to know

foureasy · #10 09-20-2009, 01:01 AM

i was having huge headgasket issues. every cold start resulted in a whistling head gasket until operating temp was reached. i think i need to go back and drill the holes a little bigger, it still seems to get too hot. i still want to get a billet chunk twice as thick and put some radial fins in it like the old two strokes