# 2 Stroke Cylinder & Case Porting for more HP!

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#### Armilite

##### Well-Known Member
Torsional vibration, whirl and misc flex can do all sorts of weird and unpleasant things. Not all two strokes used in aircraft were designed to have a prop hung on the end of the crank. Some are fine, others are not. A lot of direct drive car engine conversions need an extra bearing to be reliable.
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#### pictsidhe

##### Well-Known Member
Yamaha, an early adopter of reed valves, didn't put them on the TZ250 racer till the 80s.

#### Armilite

##### Well-Known Member
yes.....only thought about it.
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#### pictsidhe

##### Well-Known Member
Yamaha were putting reed valves in road and dirt bikes for over a decade before they put them in their hp-is-king 250 road race bikes. The RD250 had them 12 years sooner than the TZ. It's a reasonable bet that Yamaha knows far more about two strokes than everyone on HBA?

#### jbiplane

##### Well-Known Member
A bit offtopic, but sometimes dreams and expensive technologies not so expensive.

We make simple tuning for serial parts. First 3d scanning, make 3d model and finally mill it in 5-axis.
This way 172cc cylinder with integrated head - see on video will weight below 1000 grammes, originally 3400.

One cannot believe, but this milled cylinder become better cooled and have more TBO hours compare stock.
More radical approach mill of cylinder of top tange bullet. Exist some good alu alloys with vanadium and
silver which are superior any used for mass production.

We do experimental production of crancases of foam aluminum (at moment very expensive here and subject
export regulation). The part of foamed aluminum have ~1mm solid surface layer and foamed inside.
Today exist a bit worse, but cheaper approach 3d metal printing. May be already affordable for amateurs.

BTW if someone is interested in expert engine tuning exist cheap, but very good software
http://vannik.co.za/EngMod2T.htm
We got 2 licenses and it worth each cent

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#### pictsidhe

##### Well-Known Member
I knew about open cell Al foam, using NaCl. I googled closed cell foam and found this article.
Supposedly patented by Canadians so we could find out the details.
Is the Russian foam similar?

#### jbiplane

##### Well-Known Member
Is the Russian foam similar?
A bit offtopic, in this thread. So will short.
I saw it first here in ~1980+- Alu Mg and Ti and know a few, just use for some light parts to reduce milling

Ptoduced at least in 4 variants
20x1200x600 mm flat and bended sheets with closed surfaces
closed surfaces castings with porocity up to 85%
powder metalurgy - premixing by layers different and thermo explosion in molds like pop corn

and structures with big bubbles - the last picture was taken by google search, dont know origin, but close to last variant

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#### pictsidhe

##### Well-Known Member
Interesting. A blowing agent. The canadian process mixes air in with a rotating paddle. Do you cast in hard points for fasteners etc?

#### jbiplane

##### Well-Known Member
The canadian process mixes air in with a rotating paddle. Do you cast in hard points for fasteners etc?
We use here magnetic mixers. It can mix any metals better than paddles
Yes, sure. I use steel or hard aluminum inserts for bearings and threads in magnesium, foams and composites.

#### AJLiberatore

##### Well-Known Member
Yamaha were putting reed valves in road and dirt bikes for over a decade before they put them in their hp-is-king 250 road race bikes. The RD250 had them 12 years sooner than the TZ. It's a reasonable bet that Yamaha knows far more about two strokes than everyone on HBA?
Pictsidhe,

You made me dust off cobwebs here . Yes The RD350LC ( unobtainium {sort of} here in the U.S. ) and the RZ350 from the Mid 80's with the Cats had Reeds, and the YPVS ( Power Valve ). Yes their history of being on their game is real. A bit small and the prices are pricey now that everyone is restoring them, however I often wondered why someone didn't try a 3 cyl. variant of the RD350/LC/RZ architecture for Av-Use. The only thing missing an EFI type system.

Tangent DNA: The "Ryger Engine", Torq-X by Husqvarna, KTM's new Port Injection ( branch of Husky if my memory is correct ). If it wasn't for the patent cost and Gen Av liability, their is a lot going on in the 2 stroke arena, and by using some or all of what I mentioned in the right combination might make a better mouse trap for us. Sadly are market is so small, if they were used in various applications to get the run rates up, (minus the EPA in the equation ) such an effort might have a running start....

#### pictsidhe

##### Well-Known Member
Kawasaki Kh 250, 400, 500, 750, suzuki GT750 were triples.

#### pictsidhe

##### Well-Known Member
The RDs etc probably wouldn't last too well in aviation use. A little highly tuned. Maybe the YPVS with the powervalve locked down. Yamaha France entered TZ750s into the bol d'or a few times. Despite being detuned, they never managed a finish. They did humiliate everything else before going bang, though.

I'm a bit out of touch with bikes, but there is likely some cylinders out there that might be useful to us. Something like a scooter that is going to spend a lot of time at high throttle.

#### BensenB8M N521LW

##### New Member
I'm still a fan of the McCulloch 0-100. 4 cyl. opposed fires 2cyl at a time for 72HP at around 4GPH on my Bensen B8M N521LW. Some ported and added a dual carb to get 90HP but this weakened the centercase and caused big problems later on...

#### pictsidhe

##### Well-Known Member
Outboards are likely the best hunting ground for engines to repurpose. High duty, weight sensitive. The main thing that I dislike about them is that they tend to have a long watercooled exhaust port: more cooling load.

#### jbiplane

##### Well-Known Member
Outboards are likely the best hunting ground for engines to repurpose. High duty, weight sensitive. The main thing that I dislike about them is that they tend to have a long watercooled exhaust port: more cooling load.
Vous avez raison! Exactly. I know few sucsessfull local experiences based on local spares:
Inline 2-cylinder 210cc engine based on outboard crancase "and crankshaft + 2 cylinders of chainsaw
Inline 2-cylinder 350cc engine + 2 motorcycle cylinders.
The only part to make was adapters crancase to cylinder.

My idea is to use Yamaha crankshaft (3 cylinder inline and 4-cylinder V90) + Rotax 503 cylinders.
This way you will need only mill crancase... Resulting engine will be better balanced and easier to start than opposites.