Spree exhaust porting, how to

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Spree exhaust porting, how to

Post by noiseguy »

Thanks to Keithw for this tutorial on exhaust porting!

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Hello all,

By popular request, how to port the exhaust on a Spree. The same procedure should work on any two stroke scooter. The Spree has very conservitive exhaust porting (140 degrees) so this really helps.

The basic stock Spree cylinder, also fits the Pal.

http://datsunroadsterranch.com/scooter/export01.jpg

Exhaust port from inside the cylinder

http://datsunroadsterranch.com/scooter/export02.jpg

Looking into the outlet. There is a really narrow spot in the exhaust port. No doubt to limit the power so they won't go too fast.

http://datsunroadsterranch.com/scooter/export03.jpg

Layout dye so marks will show up, Sharpe or Magic Marker also work.

http://datsunroadsterranch.com/scooter/export04.jpg

http://datsunroadsterranch.com/scooter/export05.jpg

I've done a couple where I raised the port the reccomended one ring width. On this one I am going two. Push the ring(s) into the cylinder with a piston untill the edge of the ring is at the top edge of the exhaust port. Then take a sharp tool such as an Exacto knife and mark a line in the layout dye.

http://datsunroadsterranch.com/scooter/export06.jpg

Remove the rings and you have a nice line marking where you want to grind to.

http://datsunroadsterranch.com/scooter/export07.jpg

I use 3/4" EMT for my custom pipes so I use a bit to mark the exhaust flange.

http://datsunroadsterranch.com/scooter/export08.jpg

This one is very important! Use a long thin stone and only go in from the exhaust flange. The stones I use for this are sold as chain saw sharpening stones. If you go in from the cylinder bore you will bugger it up. I use an air powered die grinder but a Dremmel will also work.

http://datsunroadsterranch.com/scooter/export09.jpg

Take your time and carefully grind away the top of the port untill you get to the line. Looks like I might need to go back in and square up those corners.

http://datsunroadsterranch.com/scooter/export10.jpg

Using your long thin stone along with some shorter ones open up the exhaust port out to the exhaust flange. The walls are not any too thick so pay attention so that you don't grind all the way through the side.

http://datsunroadsterranch.com/scooter/export11.jpg

http://datsunroadsterranch.com/scooter/export12.jpg

The grinding leaves a ragged edge. Use a bit of crocus cloth to smooth the edge.

http://datsunroadsterranch.com/scooter/export13.jpg

A cut head, ported cylinder, piston, rings, wrist pin, and odd bits. How much better does it get?

http://datsunroadsterranch.com/scooter/export14.jpg

Remember, you are responsible for what you do to your scooter. This works for me but I can not guarantee your results.

keithw
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Honda Pal (Speed-o-scooter) JDM Spree with varator trans.
Honda Spree, 1985.
Another Honda Pal

Let's give it a try, how hard could it be?
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