Porting

[KCvale]

KcVale
The transfer ports in the grubee are too high up in the cylinder.
This is bad for low end power. I can make the Grubee Rev alot more but it will lack bottom end compared to a PK cylinder.

Are you talking about Skyhawk motors? Becaue the ports seem pretty low to me.

This is my 66 with a little sticker misprint ;-}

I was looking at your ported pic 21006, it looks like a straight shaft, how can the carb fit? There is only about 1/2" it can go down before hitting the clutch cable and it can't go down at all with the air cleaner on, it already touches the seat post.
Or does the shorter tube allow it to fit?

And for my 48, I mounted it in a tough build with a jackshaft.

I have zero room to move the carb anywhere, so I guess there just isn't anything I can do with them?

 

[KCvale]

Thanks for the heads up guys.
I read through all the great articles here and on MotorizedBikes about porting and it seems straight forward and logical to me.

I have 2 new Grubees here so I am going to give it a shot myself.
The hitch is I don't have a Dremel. I do however have a spiffy little drill press and some cool bits that I think would do a good job pretty quick and easy.

I'll post a little a topic about it, or add to one here about porting if it seems to work out well. With pictures of course ;-}

 

[GearNut]

Porting with a drill press!??!! That's a new method I haven't heard of yet!
It sounds like you will need an even steadier hand.

 

[KCvale]

I don't know yet, just adapting to the tools I have.
I won't be doing anything to the cylinder with it, but it should be a breeze to use on the intake and exhaust ports.

I'll put some pics up when I start as I will using that same blown out tailpipe to test on.

 

[Stan4d]

I'll post a little a topic about it, or add to one here about porting if it seems to work out well. With pictures of course ;-}

Please add to an existing thread. That is how we can keep all the info in one place. It also makes the subject easier to search. Help your fellow MBcr's out.

 

[KCvale]

Will do stan, I made and operate multiple we sites like this about different things, "all in one place" is a good thing ;-}

I got a new sale yesterday and going to port match this SkyHawk 48cc before I drop it in the GT1 bike without using a Dremel because, like a big vice for bending tailpipe, I don't have one.

 

[KCvale]

Wow Jim, your example is a motorcycle with pedals! Very cool.
And I agree with you about having the interest, funds, and skills to make anything new for sale.

All I have done is my ignition system upgrade and it took a lot to make it a product.

 

[Creative Engineering]

Wow Jim, your example is a motorcycle with pedals! Very cool.
And I agree with you about having the interest, funds, and skills to make anything new for sale.

All I have done is my ignition system upgrade and it took a lot to make it a product.

Thanks KC,

I saw your keyed ignition on another thread...nicely done!

Jim

 

[KCvale]

I apologise for stuffing up names.
Fabian

No harm no foul ;-}

I tried my drill press, no joy. There is just no bit for grinding that thick of steel.
The Dremel tools and available bits looked like a joke to me, I didn't see any carbide steel grinding attachments and those stone ones look like they would wear out before you could do 1 pipe.

While browsing I did however find this tool.

It looked so promising I bought it and an air compressor and the whole hose/fitting kit.

I fired up the compressor and gave it a try and it ran out of air in like 5 seconds.

In short the compressor can store 100 PSI but can only put out about 40 continuous, and the air file needs 90 PSI.

I'll give it a shot at the tire store tomorrow but from what I seen it looks like the perfect tool to make short work of filing the tailpipe inside to match it better to the cylinder port.

 

[Creative Engineering]

KC,

That air file does look promising!

I haven't spotted that air file in our local store, but I will look for it next time I'm there. That has ALL kinds of possibilities in the shop in addition to porting.

Unfortunately most air tools are; air hogs. When I set-up my shop I bought an old Quincy, 1961, 20 horsepower compressor. It is more than I need, but we never run out of air...

Pro porting tools are pricey:

http://www.ccspecialtytool.com/

I use the air version of these. They are between the large die grinders that you typically see at the stores and dental tools.

Jim