Author Topic: Hard To Find Or Custom Piston Rings  (Read 1910 times)

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Offline Al Smith

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Re: Hard To Find Or Custom Piston Rings
« Reply #10 on: December 22, 2011, 03:09:58 pm »
 I might mention some of the British motorcycle sites have all kinds of tips for getting the most out of 2 cycle engines .Those guys will spend months lapping in and tweaking  say a Yamaha 250 from the late 60's and cranking out 50 percent more power than it had new .Strangley though they seem to have a time doing the same with a saw engine .

Then again if you think about it they have to adhere to a lot more regulations laws and edicts than we do so probabley that prevents them from much saw souping up . I'd bet though that if they could they'd turn out some dandys .Probabley a few do they just don't blab much on the internet about it . ;)

Offline 660magnum

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Re: Hard To Find Or Custom Piston Rings
« Reply #11 on: December 22, 2011, 04:10:58 pm »
Most of the model airplane guys in Europe/Great Britain have noise limitations that many in the USA do not have to contend with.

Some in Western Europe seem to be able to do pretty good with the tuned pipes though




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Offline Al Smith

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Re: Hard To Find Or Custom Piston Rings
« Reply #12 on: December 27, 2011, 04:53:35 am »
The tuned pipe thing is another one .Between the Brit MC sites and RC sites I've gotten more info than any and all locations dealing with saw  engines combined  ."top secret" I  guess .No big deal where  there's a will there's a way  .  ;)

Offline 660magnum

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Re: Hard To Find Or Custom Piston Rings
« Reply #13 on: December 27, 2011, 07:53:03 am »
All the mods done to a chain saw like turning the edge (squish region) of the piston down to a minimum thickness above the ring and then taking the base of the cylinder or top of the crankcase down to make the squish be .020" were all things done to the Homelite 25 (weed whacker) R/C boat engines more than 20 years ago.

They were turning the fins off the cylinders and slipping a water jacket down over the cylinder.

These engines had cantilever cranks so the the rear of the crankcase was cut to place the plain back plate as close to the crank pin as possible, etc.

Some would change the cylinders by cutting off the original head and replacing with a new head to gain compression without moving the ports to far out of position.

The boat engines would be changed to run 15,000 instead of the 7000 they were designed for.
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Offline Al Smith

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Re: Hard To Find Or Custom Piston Rings
« Reply #14 on: December 27, 2011, 06:55:05 pm »
 ;D The thing about a small bore engine is the fact you don't have to be very far off with a die grinder to really screw it up . I little miscalculation can really  spell disaster .

I've never done any soup up work on a true RC sized engine .I can say though something tiny like a Stihl 200 or a Mini Mac is real tough to see what you're doing in a tiny blind hole .

Offline 660magnum

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Re: Hard To Find Or Custom Piston Rings
« Reply #15 on: December 27, 2011, 07:24:27 pm »
I never noticed any closed port cylinders under 45cc?

The Zenoah/Redmax 45, 62, and 80 twin are all open port.

The Chinese DLE 20 & 30cc cylinders have very generous open ports but the 50 & 55cc are closed port reed valve engines
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Offline Troutfisher

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Re: Hard To Find Or Custom Piston Rings
« Reply #16 on: December 27, 2011, 08:18:16 pm »

real tough to see what you're doing in a tiny blind hole .

I haven't had that problem since college, but I don't think she was blind......just cross-eyed ;D

Offline man of stihl

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Re: Hard To Find Or Custom Piston Rings
« Reply #17 on: December 27, 2011, 08:38:37 pm »

real tough to see what you're doing in a tiny blind hole .

I haven't had that problem since college, but I don't think she was blind......just cross-eyed ;D
That made me chuckle! ;D
Ron

Offline Al Smith

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Re: Hard To Find Or Custom Piston Rings
« Reply #18 on: December 28, 2011, 05:11:42 am »
 :D Blind hole ,aye .

About the only closed port itty little engine I can think of is a Mini Mac .What like 2.1 cubic inch .There are made just about like the reed engines with welch plugs over the outside of the tunneled transfers except they only use 2 tunnels where a reeder uses 3 .

The engine wasn't a bad design it's just the rest of the saw is a POS .

Offline 660magnum

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Re: Hard To Find Or Custom Piston Rings
« Reply #19 on: December 28, 2011, 07:43:19 am »
I've got a Mini Mac that will run for a couple minutes. Someone gave it too me some 10 years ago.
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