Urgent 2 stroke porting advise needed

[Frank ZX]

I've ported a few sets of V8 heads with fair success but I'm new to 2 stroke porting. This engine isn't used often I'd guess but there's got to be some power hidden in it.
It's a Tecumseh Hsk850. I'm building it for my mobility scooter project to haul in the back of my old F100. I'll use it at car shows and other auto events to get my crippled a$@ around. Lol
I am a gear head and I like to go fast or atleast quick.
Can someone guide my how these 2 stroke ports should be opened up?
I'm guessing the exhaust and intake ports should be opened to the port size???
The transfer ports on the sides is where I'm struggling.
Please help.
Pictures coming.

 

[Randy H]

http://www.diygokarts.com/vb/member.php?u=16813

This is probably a real good place to start. Desertduler knows a lot about two strokes, gear head stuff in general.

 

[mckutzy]

Take you pics in landscape not portrait please, not all of like craning our necks...

 

[Frank ZX]

Thank you.
I'm having trouble loading pics again. Lol
Desertduler is incredible!!!
Ok, here's pics of intake, exhaust, and both sides of the transfer/boost ports I think it's called?
I'm a little more humbled after watching Desertracers work. Lol
I have rejetted a few 2 strokes in my days. My last bike was a KTM 250SX sat up for woods riding. I've also played with both Yamaha Banshees and Blasters...just pipes and jetting. No 2 stroke porting experience.

 

[Frank ZX]

I'm porting conservatively until I get some clear advise from someone that's more knowledgeable than myself.
Here's what I did in a few minutes. I stopped for the night.
I hope someone chimes in soon.
This is a $40 engine and it seems likes it's very undesirable. Keep in mind my intended purpose. It's just to blast around the shows and get me around at the drag strip when I go. I have a sweet Polaris 2 stroke but it's physically too big for my mobility scooter.
I may build a off road kart with the Polaris another day.
Here's a few more details about my scooter.
Gearing is somewhere between 6.6:1 and 6.8:1. I am going to use a jackshaft so gearing is easy to change.
I'm using a Wilwood manual brake caliper. I have a Tillison HL360 on the way and a 3qt aluminum fuel tank. The wheels and tires are some sort of racing kart takeoff. The rear axle is 1 1/4 aluminum. I weight 160lbs. The finished scooter will be under 75lbs is My Guess. The chassis is all square tube aluminum.
Oh, I'm mounting the seat as low as possible.
The rear axle is 34" wide so outside to outside rear tire width is about 45". It should be fairly stable as long as I use my body weight in hard corners...I hope.
Now, back to the porting

 

[Frank ZX]

Take you pics in landscape not portrait please, not all of like craning our necks...

I'll try It next time. Thank you!

 

[Frank ZX]

Take you pics in landscape not portrait please, not all of like craning our necks...

I'll try It next time. Thank you!

 

[Randy H]

I tuned up your pics a little bit. As for porting this engine is a bit more complicated than a 4 stroke. Your dealing with more than flow and velocity, port timing/ mapping is a big deal. Maybe a compression boost (difficult on your engine) , a properly designed expansion chamber, and carburetor will get you the desired results.

Here are some links that may help.

https://www.manualslib.com/manual/1089012/Tecumseh-Hsk840.html#product-HSK850

http://www.macdizzy.com/

http://www.eric-gorr.com/index.php/tech-self-help

On Scribd you can find publications by Gordon Jennings (Two Stroke Tuners Handbook), and Gordon P. Blair.

 

[NewbCarter]

If i may add ,

2 Stroke performance tuning by A. Graham Bell is also very useful .

EDIT : I have been following this youtube channel for a while , also some great stuff
https://www.youtube.com/channel/UCHRXYmO1vdp-Bi1-w11R7WQ

22 HP out of a 50cc engine !

 

[Frank ZX]

I did port the cylinder a little more. I don't feel very confident in the results. Being I don't have a carb yet, I drilled the main jet circuit one size bigger than a #70 drill bit. It started up first pull. It sounds kinda lazy when revved up. The pipe stayed fairly cool the few minutes running it so I don't think it lean.
I did notice the engine doesn't smoke near as much as it did before I ported it. IDK if this is good or not.
I got a Lawnboy sitting on the side. That maybe the direction I go. I usually don't give up easy. I will make a 2 stroke fly.