Engine Porting - Gases out, Fuel Air in

Hey Egor:
Fairly new to this forum, but not completely new to porting. But porting a 59AB flathead Ford is a different breed of cat. I'm just putting finishing touches on a jack-shaft 5sp OCC Schwinn Chopper with a RAW motor. I'm almost afraid to bring up the RAW engine (80cc?) after reading some of the posts in this thread, but, after reading up on your posts regarding porting of these little engines, I decided to take a shot at it. Upon tearing the head and cylinder off, I found that the existing exhaust port is already showing the 1.1" measurement for the exhaust. My question to you sir, is, would you happen to have measurements for the intake port in relation to the top/bottom of the bore. Not having anything to relate to, I'm wondering if the existing port also reflects an updated port. There is absolutely no casting flash anywhere on the internals, and the overall external casting is fairly decent. I'm looking forward to riding this little ground-pounder......Byron

Egor:
After doing a little more research, there's the question on read valves, reworking the piston for maximum effect, and the ability of the little 80cc? motors to hold up. I'm not after top speed bragging rights, but would like to maximize torque for hill pulling. I have absolutely no idea on the existing performance of my bike with the jack-shaft gears both of the front chain rings and the 5sp rear cluster. It could be that I won't have a problem, but now would be the time for the mod if its going to happen.....Byron

Byron - I have seen a few of the newer engines that have come out with the better exhaust port timing. I have a barrel off one of my engines at work I will try and get a measurement off of it tomorrow. The one thing that the reed system gives is the torque that the happy time is designed for. you will also get a flawless idle. My 59A is relieved from the factory, Ford started to pay atention to the hot rodder's and the things they developed. I think that is the reason that the happy time engine getting better, look at the needle bearing at the top of the rod. My green Hornet will pull Burnett st. In signal Hill ca. and I use a 39 tooth sprocket. Max porting on a Dax 70cc bushed engine. The biggest restriction we have is the lack of cooling fins on these engines. Look at a Bultaco Lobito 100 it looks like a 250 at least with the fins that large, and man would they run. I would like to see the star burst heads we used to use on our Hodaka's come back - they were extruded. Have fun, Dave

Egor:
Thanks for getting back with me. Give me a little more info on this 'reed' setup. Are these custom made, aquired from the go-cart industry, motorcycles, or else where. There was a brief mention about the need to modify the piston for use with a reed. Is there information available somewhere about methods of application......Byron

Subscribes*

if anyone has some safe measurements to grind out on the ports on these 80cc motors and could post some pics it would be awsome! Id hate to experiment on it myself and end up with a pig.

figured id just say i did this a long time ago. dunno if it helped or not (to many variables)

But EVERYTHING is just fine, thats all that matters haha. And i never made it a pig either. I didnt take much off. just what was mentioned earlier.



Just for those who havent torn them apart yet... In this pic, all that DARK area is all casting int he way of that port!!!

all that i removed. But thats along the lines of gasket matching.... as for porting i dont think i took more than 1/16th off each intake and exh, maybe a hair more, so thats probably why i couldnt tell a definate performance increase.

Byron said:

Egor:
Thanks for getting back with me. Give me a little more info on this 'reed' setup. Are these custom made, aquired from the go-cart industry, motorcycles, or else where. There was a brief mention about the need to modify the piston for use with a reed. Is there information available somewhere about methods of application......Byron

Click to expand...

If you adapt a reed from a chainsaw, goped or other, you can port the cylinder
and piston to make it work to your advantage.
You cut a "5th" port above the intake, as high or a little taller than the
other transfers. The top of that port should be angled toward the plug tip.
Then you can drill 2 holes or window the piston about 3 ring thicknesses
below the bottom ring. The window size should be the same size as the
5th port in order to feed the port.
Some folks angle the holes upward, so it helps with flow.

As far as width and depth of the port, you have to experiment per the cylinder.
Too deep and wide, and you'll pop thru the cylinder and it has more of a chance of cracking.
Too shallow and narrow you don't get the gains.
You WILL need to rejet after this mod.

Been trying Butterfly carbs to see what affect they will have on the Two Stroke's. I still have a Honda carb I have not tried yet, soon, I will post the pic's of them. The first one is off an old outboard and the second is off a lawn Mower (Tecumseh) And I will get to the Honda I think this week. I am in Utah this weekend and will go home tomorrow, and get back to work. Have fun, Dave

PS: I like the second one, you can adjust it as you ride. No needle to change and no main jet to mess with. The first one has a main jet and it is fat on the idle. I still need to take this engine apart it has the bad case gasket, sucking air messing up the mixture. That will take a complete tear down. Fun, LOL.

I know very little about 2 stroke engines, but my brother used to run go carts back in the '60s. He had a Westbend 850 (8.5 cubic inches) running on alcohol and nitro-methane that had 4 carbs. 2 in the usual place and two directly into the crankcase (stuffers?). This engine had reed valves. The power output was phenominal, 15-20 HP on the dyno, depending on the fuel nitro mix. Do people still use stuffers and do they help?

Egor said:

Been trying Butterfly carbs to see what affect they will have on the Two Stroke's. I still have a Honda carb I have not tried yet, soon, I will post the pic's of them. The first one is off an old outboard and the second is off a lawn Mower (Tecumseh) And I will get to the Honda I think this week. I am in Utah this weekend and will go home tomorrow, and get back to work. Have fun, Dave

PS: I like the second one, you can adjust it as you ride. No needle to change and no main jet to mess with. The first one has a main jet and it is fat on the idle. I still need to take this engine apart it has the bad case gasket, sucking air messing up the mixture. That will take a complete tear down. Fun, LOL.

Click to expand...

Let us know how they work!