Engine Porting - Gases out, Fuel Air in

[misteright1_99]

how did you tied the piston to the chuck when lowering the head?? cos im thinking of lowering the head too for a little more compression but i can't figure out how to allign everything so that i have an even cutt throughout all the surface... thx

Looks like he shaved the head to lower it, not the piston. Picture #3 looks like the head spinning on the lathe. He cut the piston skirt... VERY nice work............

 

[Egor]

I have never fooled with the compression. I wish I could find one of the sunburst heads we used to install on our Yamaha's. That would get the compression up and add the needed cooling. As the HP goes up so does the temp. Have fun, Dave

 

[Flapdoodle]

A note to us older folks. I ported my bike and now regret it. Although I have greater power and speed WOT, it requires more pedaling the get started in town due to losses at low RPM.

 

[misteright1_99]

A note to us older folks. I ported my bike and now regret it. Although I have greater power and speed WOT, it requires more pedaling the get started in town due to losses at low RPM.

You could move up to a larger rear sprocket Flap, and with the higher speed and greater power at WOT, you might just go as fast, as well as improve low end torque.

 

[Egor]

Flap - All the ones I have done run better all the way around. I seldom if ever have to use the pedals, and I am using a 39 tooth sprocket. Wonder why yours lost low end. Have fun, Dave

 

[Flapdoodle]

A note to us older folks. I ported my bike and now regret it. Although I have greater power and speed WOT, it requires more pedaling the get started in town due to losses at low RPM.

Fixed it! I drilled eight 3/16 holes in the bottom plate of the exhaust baffle spaced evenly around the center tube, four 3/16 holes in the upper plate, and some smaller holes in the lower part of the tube below the "pinch". Then I added a generous amount of course steel wool between the two plates. Idle speed is noticeably higher.

I can not really tell that it is any louder, but letting the bike slow to the idle speed then going WOT gives plenty of acceleration.

My guess is that after porting to get better flow, the gasses need to go somewhere.

 

[Rgvkid]

Im running a 33 Poulan Chainsaw for my friction drive. I've heard of drilling holes in the muffler to open it up a bit. Would this actually benefit? I use it for a 30 mile commute and would like to see if i could get a little more punch out of it but if it is tuned too lean it will over heat and shut down. If i run it rich it doesn't shut down but i can feel the lose in power. I know i need a bigger motor for my needs but it will have to do for know.

Any tips would be greatly appreciated.

 

[jvirginillo]

Anyone consider making a kit?

Modified (ported and cleaned up) head and intake manifold for us 'challenged' individuals?

I could probably deal with the intake and exhaust matching but opening up the ports I am uncertain of.


Would be an interesting offering from some of the vendors.

Thoughts?

 

[Egor]

Im running a 33 Poulan Chainsaw for my friction drive. I've heard of drilling holes in the muffler to open it up a bit. Would this actually benefit? I use it for a 30 mile commute and would like to see if i could get a little more punch out of it but if it is tuned too lean it will over heat and shut down. If i run it rich it doesn't shut down but i can feel the lose in power. I know i need a bigger motor for my needs but it will have to do for know.

Any tips would be greatly appreciated.

It would probably help for the top end but I doubt you could stand the noise for that long. I would construct an new header and muffler for that engine any way and move the noise down and away from the rider. Have fun, Dave

 

[seca40]

So i just reassembled my pk80 top end after doing this porting. First I matched the intake and exhaust. I'm sure this alone would be a big improvement in the way this engine runs. The parts don't even look like they belong on the same engine except for the bolt holes. Then I lowered the intake from .895 to .725 measured off of the bottom of the sleeve. .170 total. I tried not to change the shape otherwise. I raised the exhaust up only about half of the recommended distance. 1.135 from the top. I also lapped the head and deck of the jug on a piece of polished granite using 220 sandpaper. Then reassembled using a thin film of copper sealant as recommended. The engine spins freely without the head gasket installed. (.058 ) Hopefully it will do the same at operating temp. I'm pretty psyched to see what a difference it makes. I'll report back when I find out how she runs. Kitten, Beast, Hand grenade... We'll see.

This engine only has one gallon of 20:1 fuel through it. When I took it apart to do the porting I noticed some slight scoring on the cylinder wall. I could see it but had to try real hard to feel a groove. I know that's not good but how bad is it? Should I replace the jug? Should I take the whole thing to the gun range? Really though, any thoughts on this would be appreciated. Oh, with the engine set up this way what do you all suppose would be a good starting place would be for spark gap? .30?

Thanks to all who have cotributed to helping me understand a little about what this engines shortcomings and needs are. It's been fun reading these threads.