028 super porting

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Agent smith

NJ tornado enthusiast
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Jan 28, 2018
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Ashtabula
So ive been messing around with porting for a little while now and I've started on this 028 super. First I'll start off with saying I've been doing research for a long time and i have been reading Jennings book trying to make sense of two stroke theory. Ive built a few good runners with the help of others on here and i wanted to share what im doing with this saw to see if im going in the right direction on my own. Advice is welcome. Here's what i started with #'s wise:

OEM 028 super jug no gasket

108° 144° duration
125° 110° duration
73°. 146° duration
.023 squish
 
First off this jug is more or less a practice jug. Its still useable and ill run it to see how it performs but has scratches from the saw losing a crank bearing

cut the base and squish. I cut the squish at a 1° taper

These are the numbers i decided to go with and so far i hit the exhaust and transfers right on the money:

105° 150° duration
120° 120° duration
76° 152° duration
ended up at .019 squish

Got the exhaust and transfers started. Going to tackle the intake tomorrow. For the exhaust i wanted to straighten it the best i could as its at a serious angle factory. I decided to try a step in the exhaust too. Any thoughts on that?
 

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Numbers seem good. When planning things out use a ring to set your heights in the jug and then mark them. You’ll hit your numbers every time.
 
Numbers seem good. When planning things out use a ring to set your heights in the jug and then mark them. You’ll hit your numbers every time.
I do when it's a flat top piston. Not with domed pistons as it'll be off a few degrees. In that case i put the piston at whatever number im going for and use dykem and a scribe
 
Post a cutting video when all said and done.

Are you planning on polishing things up?

Timing advance?
i usually finish off the exhaust with 320 grit and a fine buff. I don't polish intakes and transfers. I smooth those off with 120 grit and thats it. Im gonna file .020 off the key
 
I’m about the same. 500 grit for the exhaust and 80 for everything else. I’m very curious to see how it runs, and what compression ends up at. I won’t start on mine until Monday

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Got the intake done. Didn't lower it as it was where i wanted it. Just widened it a fuzz, smoothed out the tract and matched it to the boot. Also shortened the septum and blended it in. Finished up the exhaust and blended the upper and lower transfers together
 

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Good work. Personally I would never make the exhaust flange that thin but it’ll probably hold. Excited to see this saw run.
 
Good work. Personally I would never make the exhaust flange that thin but it’ll probably hold. Excited to see this saw run.
Yeah its thinner than i wanted but this is more or less a test jug. If it works out I'll do another jug the same but do a little less with the exhaust and see what happens
 
Got the muff mod done. 5/8 id tube. Not the prettiest but its hard to weld this thin steel with a 220v mig. Atleast i didn't burn through i guess. Went with a oem wt194 carb as it has a slightly bigger venturi than the hu40/wt16 carbs and these are good running carbs.
 

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These are the numbers i decided to go with

105° 150° duration
120° 120° duration
76° 152° duration
ended up at .019 squish

I checked the numbers on my saw last night, which is the oldest version of the 028 with a super top end and meteor piston.

This is with no base gasket and squish at .025

Stock #s 105/131/72

I'm going to double check the transfers.
 
You'r putting me in a awkward situation. Do you like it or should I make some suggestions?
 
The difference in blow down between our cylinders is interesting. I double checked the transfers and my first reading was correct. My jug has a BD of 26 stock. I just took .025 off the base last night and now my intake sits at 76. I plan to take the exhaust up to 103. The blow down though has me thinking. Also with my saw i'm going mild with it.
 
The difference in blow down between our cylinders is interesting. I double checked the transfers and my first reading was correct. My jug has a BD of 26 stock. I just took .025 off the base last night and now my intake sits at 76. I plan to take the exhaust up to 103. The blow down though has me thinking. Also with my saw i'm going mild with it.
Well if your transfers are indeed that low for some reason then youre in a good spot! You can run it where they are now and then move the transfers up gradually and see how it likes it.
 
I mean i think its alright but nothing to write home about. Compression is 190. Im wondering about raising the exhaust a few degrees but at the same time i don't want to take away any compression either
 

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