2 Stroke Cylinder & Case Porting for more HP!

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They had a Reed Fed Cylinder on a 292 Single in the 70's. "VINTAGE 292 RACE PIPES
We have two pipes available for the popular 292 Yamaha single engine. The full race pipe is developed for modified Oval racing and delivers 70 HP at 9000 RPM with Full Race Porting, Reed Valve intake and a larger Carb. We also have a milder pipe that is turned for 7500 RPM and delivers 50-55 HP depending on Cylinder Porting. This pipe is very popular in One Lunger Sno Cross Enduro Races or for Vintage Trail Riding and Restorations."

Some good views of the 70's Yamaha 292 Reed Fed Cylinder Single apart. You can see it has better Porting than Skidoo's Singles.

Skidoo made a Prototype Rotary Valve Single (78mm x 70mm) 334.6cc, 39hp in 1969 with just a Muffler that never got put into Production. Basically, Half a 670 that came out in 1992, 23 years later and made Stock [email protected] There were Small 354 & 454 Rotary Twins released that put them in the winners circle. The 1971 Blizzard 340 Single was the Highest Production HP released Factory Single at 36hp for Skidoo. That 1969 Rotary Valve Single with a Good Tuned Pipe would have been around 58hp at Sled 7750rpms! At Ultralight 6500rpms around 45-47hp with a Tuned Pipe.

I had a chance 3 years ago to buy one of these 292 Yamaha Sleds that was For Sale close by me, whole Sled for $400. Wish now, I had went and looked at it. There is two different Yamaha 292's, a Reed Fed Cylinder, and a Piston Port Cylinder.
Bump
Hi Armilite, my first post here.
A friend of mine had a hotsaw built out of a Yamaha 292 Thunderjet snowmobile engine in the 1980's. Output was 75h.p. and the sawchain ran in a reverse rotation.
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I was drawn to this very interesting thread as I myself am looking to make a single cylinder 2 stroke crankcase out of some 3" thick mic 6 aluminum plate(good choice?)

I presently have a 2 hotsaw build on the go. One is a 1982 YZ125 engine hotsaw I originally built 36 years ago. The other is a 1983 Honda CR250R .
The 125 stock in the motorcycle puts out over 30 hp and the Honda over 40hp.
I am building the saws both with carbon fiber and titanium grade 5 fasteners. They both will be running Mikuni 38mm SBN PWC carbs and tuned cone exhaust pipes.
I have CNC made drive sprockets made for them to drive their sawchain. They both have PVL bi directional analog ignitions.
The YZ125 has road race porting at 202° exhaust/137° transfers.
The Honda is mild at 182°/126 but will be raised to 191°/130° with 29.31blowdown. HP will be over 50 at 8K rpm.
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Armilite

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Bump
Hi Armilite, my first post here.
A friend of mine had a hotsaw built out of a Yamaha 292 Thunderjet snowmobile engine in the 1980's. Output was 75h.p. and the sawchain ran in a reverse rotation.
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Boy that would be a Handfull. Yamaha had two different 292's. The Reed Port version Ruled the Sled Racing World. Rare to find today, I have only seen two for sale in 10 years.
 

Armilite

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I was drawn to this very interesting thread as I myself am looking to make a single cylinder 2 stroke crankcase out of some 3" thick mic 6 aluminum plate(good choice?)

I presently have a 2 hotsaw build on the go. One is a 1982 YZ125 engine hotsaw I originally built 36 years ago. The other is a 1983 Honda CR250R .
The 125 stock in the motorcycle puts out over 30 hp and the Honda over 40hp.
I am building the saws both with carbon fiber and titanium grade 5 fasteners. They both will be running Mikuni 38mm SBN PWC carbs and tuned cone exhaust pipes.
I have CNC made drive sprockets made for them to drive their sawchain. They both have PVL bi directional analog ignitions.
The YZ125 has road race porting at 202° exhaust/137° transfers.
The Honda is mild at 182°/126 but will be raised to 191°/130° with 29.31blowdown. HP will be over 50 at 8K rpm.
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Do you run this Chainsaw as a Water-Cooled Cylinder or do you fill the Cylinder Water Jacket with something? I take it you use this in some Chainsaw competition event. I know in the 70's they used to fill Drag Race Engine Blocks with some form of I think Expoxy about halfway to Stiffen the Block. I got a 550F Reed Fed Cylinder I want to try mating to a 277 Case, or Old Skidoo Single Case. I haven't been very ambitious lately, the wife is taking me to Flordia for two weeks, now that the Snow has melted and I can get out in the Shop. Block of 6061 for a future build.

Billet Block.jpg Resized952020030995062923.jpg
 
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Do you run this Chainsaw as a Water-Cooled Cylinder or do you fill the Cylinder Water Jacket with something? I take it you use this in some Chainsaw competition event. I know in the 70's they used to fill Drag Race Engine Blocks with some form of I think Expoxy about halfway to Stiffen the Block. I got a 550F Reed Fed Cylinder I want to try mating to a 277 Case, or Old Skidoo Single Case. I haven't been very ambitious lately, the wife is taking me to Flordia for two weeks, now that the Snow has melted and I can get out in the Shop. Block of 6061 for a future build.

View attachment 94123 View attachment 94124
Yes these saws are used for speed bucking competition.
I leave the cylinder water jackets empty. We only run them WOT for less then 10 seconds so no worries about overheating, even better when running methonal fuel.

I may have to put some 1750F high heat JB Weld epoxy in the Honda CR250R water jacket when I raise the exhaust port 3mm. I have room to spare but if I do grind through into the jacket I may have a problem.
I have no idea how the JB weld will hold up. Would you suggest laying a thin sheet piece of stainless steel or copper over the hole then put the epoxy on top?

Another question I was looking into building a crankcase for a newer CR250 cylinder out of Mic 6 aluminum cast tooling plate.
I see you use 6061 plate, is there any real advantage using Mic 6 as they say it's tension free ?
I can see the 6061 would be much stronger though.
 

Armilite

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Yes these saws are used for speed bucking competition.
I leave the cylinder water jackets empty. We only run them WOT for less then 10 seconds so no worries about overheating, even better when running methonal fuel.

I may have to put some 1750F high heat JB Weld epoxy in the Honda CR250R water jacket when I raise the exhaust port 3mm. I have room to spare but if I do grind through into the jacket I may have a problem.
I have no idea how the JB weld will hold up. Would you suggest laying a thin sheet piece of stainless steel or copper over the hole then put the epoxy on top?

Another question I was looking into building a crankcase for a newer CR250 cylinder out of Mic 6 aluminum cast tooling plate.
I see you use 6061 plate, is there any real advantage using Mic 6 as they say it's tension free ?
I can see the 6061 would be much stronger though.
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The stuff I'm talking about was a two part Epxoy they poured into Case and then it Hardin up. I don't remember what it was called they used back in the 70's. Yes, you can Block off the holes many different ways, Welding, Clamp a Plate over them. I was thinking about that a couple of weeks ago using one them Big Bore (82mm) Water Cooled Nikasil Cylinders with a Reed Port. I couldn't get anyone to give me the Bolt Pattern to see if feasible. I was thinking if I couldn't find the stuff they used in the 70's, I would just Clamp a Copper Plate on it and take it to a Foundry close by and see if they could just fill the Water Jacket with some Aluminium. Lead could work, but I want to keep it as Light as possible.

I use 6061 for 95% of the parts I make. 7075 if using in Salt Water or High Wear. You can find chunks on eBay fairly cheap. I used to get a lot of cheap Aluminium Stock from Salvage yards. Companies like John Deere throw away New Steel all the time. I want to say I paid $38.99 for that one, 1 pc 3" X 6" X 6" 6061 T6511 solid aluminum plate flat bar mill block. I have bought some cheaper, and Bigger, but not as Thick.

I just got me a new 3D Printer delivered the day I left for Flordia, 400mm x 400mm x 400mm. I'm wondering if you couldn't 3D print a Case out of Nylon or Carbon. You definitely could use it to make a Casting. A Case shouldn't see Max 200F.
 

Armilite

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I found this info: Block filler can improve cooling and cylinder strength, and it can be used in a street engine successfully. The type of filler you want to use is called “short fill,” which means that enough filler is used to partially fill the water jackets in the block. A good engine block filler is called HardBlok.

Cracking Down on Block Fillers. DEVCON SOUNDS LIKE WHAT THEY USED.
https://www.enginebuildermag.com/2014/07/cracking-block-fillers/

BLOCK FILLER..jpg
 
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Armilite, thanks.
It looks like the Hard Blok filler is the top recommended product as Jegs and Summit Racing both sell it.
For my Honda Cr250r cylinder application the filler would also besides porting fixes it will also stabilize and prevent distortion in my cylinder's open deck design.
My spare cylinder is a upgraded semi open deck with 4 support bridges but I'll fill it too.

The crank case build will be a future endeavor with alot more R&D.
Yes CNC and casting is definitely an option. But a simple milling machine can carve out 2 pieces of plate into a matched crankcase too.
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So after more research the cement / iron filler is not the proven choice for a cast iron liner cylinder with aluminum water jackets.
Devcon liquid aluminum 10710 will be my choice with a .500" layer of 2400F rated JB Weld extreme heat on the bottom of the water jacket directly over the exhaust port.
The trick with stiffening up the cylinder with a epoxy filler is a torque plate or the head should be torqued down before it hardens.
Good idea to torque the cylinder base down too.
Machining like boring or honing can be done after it hardens completely.
Again torque plate used when boring or honing.

There is some amazing new 2 stroke big bore cylinder technology come out of the CP Industry plant.
Big resurgence in resurrecting the 2 stroke performance line.
 
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Armilite

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So after more research the cement / iron filler is not the proven choice for a cast iron liner cylinder with aluminum water jackets.
Devcon liquid aluminum 10710 will be my choice with a .500" layer of 2400F rated JB Weld extreme heat on the bottom of the water jacket directly over the exhaust port.
The trick with stiffening up the cylinder with a epoxy filler is a torque plate or the head should be torqued down before it hardens.
Good idea to torque the cylinder base down too.
Machining like boring or honing can be done after it hardens completely.
Again torque plate used when boring or honing.

There is some amazing new 2 stroke big bore cylinder technology come out of the CP Industry plant.
Big resurgence in resurrecting the 2 stroke performance line.
===============

Is there a Weight Difference in Block Fillers? I would Ceramic Coat the Piston Top, Head Combustion Chamber, Cylinder Exhaust Port, and Exhaust.
 
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Is there a Weight Difference in Block Fillers? I would Ceramic Coat the Piston Top, Head Combustion Chamber, Cylinder Exhaust Port, and Exhaust.
Yes the Devcon is lighter then the water it replaces but weight is not my concern.
From my R&D the filler needs to be similar to the material that it is filling with the same heat expansion and dispersion rates.
Coatings? I'm looking at preserving my cylinder bore and porting with Nikisel.
Millennium Industries does great doing this and that is my plans. A professional Honda engine builder from California has special piston rings for Nikisel coated cast iron cylinder liners but I haven't committed to buying yet
Second, third opinions are always nice.
I don't know alot about ceramic coatings but I do know Yamaha tried it on their YZ stroke mx race bikes years ago. But I think they discontinued that.
Wossner and Wiseco are now using a black polymer looking coating on their race pistons.
I noticed the frying pan industry has done a similar transition.
 
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JamesF

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Don’t want to be stupid, but could you mix aluminum powder with epoxy for use to fill the water jacket? You could use just enough epoxy to allow the mix to fetgle onto the area that you want to fill.
just a thought.
 
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Don’t want to be stupid, but could you mix aluminum powder with epoxy for use to fill the water jacket? You could use just enough epoxy to allow the mix to fetgle onto the area that you want to fill.
just a thought.
That's a good question James.
I thought about packing aluminum powder of some sort into the water jacket surrounding the cylinder.
Then seal it with a layer of JB Weld extreme 2400F heat epoxy on top.

My Honda CR250R liquid cooled motor is only used for 4 to 10 second bursts speed bucking a log in a competition. I'm allowed a minute of warm up time prior.
 
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FWIW, regular JB Weld is OK up to 650*F.
I've used it in VW cylinder heads, repairing 'overzealous' porting and polishing.
No, not in the combustion chamber, nor the exhaust port.
Yes I've have had good success with regular JB Weld over the years. One project is almost 40 years old and the JB is still holding strong.
The new 2400F extreme heat JB mix sounds like a good product. It should withstand alot of exhaust heat as a aluminum cylinder's melting point is about a 1000F lower .
Still don't think I'd trust with it being on direct line of fire in the exhaust port with the risk of the JB Weld being sucked back into the piston's path if it breaks free if it doesn't have the same expansion rate as the aluminum.
 

Armilite

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Yes the Devcon is lighter then the water it replaces but weight is not my concern.
From my R&D the filler needs to be similar to the material that it is filling with the same heat expansion and dispersion rates.
Coatings? I'm looking at preserving my cylinder bore and porting with Nikisel.
Millennium Industries does great doing this and that is my plans. A professional Honda engine builder from California has special piston rings for Nikisel coated cast iron cylinder liners but I haven't committed to buying yet
Second, third opinions are always nice.
I don't know alot about ceramic coatings but I do know Yamaha tried it on their YZ stroke mx race bikes years ago. But I think they discontinued that.
Wossner and Wiseco are now using a black polymer looking coating on their race pistons.
I noticed the frying pan industry has done a similar transition.
============================================

You don't Nikasil Cast Iron, only Aluminum. You can take out the Cast Iron Sleeve and use an Aluminium one. The Dark Gray is a Moly Coating for the Sidewalls, Ceramic is for the Piston Tops to fight Heat.

CERAMIC COATINGS 1.jpg
 
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You don't Nikasil Cast Iron, only Aluminum. You can take out the Cast Iron Sleeve and use an Aluminium one. The Dark Gray is a Moly Coating for the Sidewalls, Ceramic is for the Piston Tops to fight Heat.

View attachment 94678
That gold ceramic coating looks just like what my new aluminum frying pans coating.
Cast iron sleeves or liners can be coated with Nikisel.
Today Millennium Industries is the leader in the new application process.
They don't even have to remove the sleeve from the aluminum cylinder.
This wasn't possible 5 years ago but they got it perfected now.
Customers no longer need to resleeve their cylinders when they get to the maximum overbore.
Expensive porting work on a damaged cylinder can be kept with a light bead of weld on a scratch, light bore and a fresh coat of Nikisel.
 

Armilite

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That gold ceramic coating looks just like what my new aluminum frying pans coating.
Cast iron sleeves or liners can be coated with Nikisel.
Today Millennium Industries is the leader in the new application process.
They don't even have to remove the sleeve from the aluminum cylinder.
This wasn't possible 5 years ago but they got it perfected now.
Customers no longer need to resleeve their cylinders when they get to the maximum overbore.
Expensive porting work on a damaged cylinder can be kept with a light bead of weld on a scratch, light bore and a fresh coat of Nikisel.
===============================

I stand corrected, I had never heard of them Nikasiling a Cast Iron Sleeve.

"Millennium Technologies specializes in Nickel Silicone Carbide (NSC) plating of aluminum cylinders, but we still offer a wide variety of services for cast iron cylinders. The options depending on damage to bore are:

Overbore and hone to next piston size
Cheapest, most common repair. Most engines have multiple oversize pistons available through OEM and aftermarket vendors. Required piston size would be dependent on the severity of damage to the bore.

NSC Plate Cast Iron Bore
There are two reasons to plate a cast iron bore: improve the performance or save a cylinder past its service life. We can save that cast iron cylinder when over size pistons are no longer available or the cylinder is larger than the biggest over size piston. We typically can put back at least .020 and sometimes more. Contact us for our restoration services. For the performance minded, plating a cast iron bore will improve wear resistance and lower the coefficient of friction.

Purchase and install a new cast iron sleeve
We have vendors that can supply us sleeves for most common 2 and 4 stroke engines. We can machine out the existing sleeve and size cylinder for replacement sleeve. Then install the sleeve and hone to the finish size.

Option for most cast iron 4 stroke cylinders
Manufacture, install and plate aluminum sleeves

Typically done on older inline 4 cylinders, but really can be done on any 4 stroke. We remove the sleeve, manufacture a replacement aluminum sleeve, install and plate it for the benefits of decreased weight, increased cooling capacity, and increased cylinder bore service life."

I've heard of Nascar guys who fully DiamonDyze their Pistons before using other Coatings. I would like to try that on some 2 Stroke Pistons.
DiamonDyze Pistons 2..jpgDiamonDyze Pistons 3.jpgDiamonDyze Pistons 1.jpg
 
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Thanks for the heads up about the DiamonDyze piston process.
This would be good application for my mx 2 stroke engines with their reverse rotation that puts the major thrust on the exhaust side of the piston.

I talked to the Millennium guy on the phone last week, he says they Nikisel coat alot of older cast iron liners in older snowmobile engines.
They don't have to remove the iron liner from the aluminum cylinder.
The cost in Canadian $ for my mx single cylinder is $468. They do a very thin rebore and then apply the Nikisel followed by a hone job.
 
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