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Discussion Starter #1 (Edited)
I think of my 1983 Honda CR250R engine with its non PV cast iron sleeve cylinder being the closest design to a ATC/TRX 250.
Honda's CR250 development through the 1970's into the 1980's is fascinating how they set the standard in MX / ATV engine design amongst all the other big name companies.

I have a question about my 1983 CR250R cylinder and spare cylinder. One has a open cylinder deck, the other is a semi closed deck with 4 bridges cast in the water jacket to support the cylinder bore. This must be an upgrade later on in 1983.

I can see the benefits of an open deck cylinder eliminating cylinder wall distortion when the cylinder head is torqued down.
But for a vintage performance race built which cylinder would I be better to stick with.
Here's some pics of the open and semi closed deck cylinders. 20200122_121952 (1).jpg 20200122_122015 (1).jpg
 

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I think of my 1983 Honda CR250R engine with its non PV cast iron sleeve cylinder being the closest design to a ATC/TRX 250.
Honda's CR250 development through the 1970's into the 1980's is fascinating how they set the standard in MX / ATV engine design amongst all the other big name companies.

I have a question about my 1983 CR250R cylinder and spare cylinder. One has a open cylinder deck, the other is a semi closed deck with 4 bridges cast in the water jacket to support the cylinder bore. This must be an upgrade later on in 1983.

I can see the benefits of an open deck cylinder eliminating cylinder wall distortion when the cylinder head is torqued down.
But for a vintage performance race built which cylinder would I be better to stick with.
Here's some pics of the open and semi closed deck cylinders. View attachment 62187 View attachment 62189
The "closed deck cylinder" is the best choice; more stable than the open deck...however; IMO neither is a 'better' choice than later year Honda CR cylinders.

Carlos
 

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Discussion Starter #3
The "closed deck cylinder" is the best choice; more stable than the open deck...however; IMO neither is a 'better' choice than later year Honda CR cylinders.

Carlos
For my hotsaw application the compactness of the 1983 cylinder and its super lightweight crankshaft along with great intake breathing capacity in stock form makes this engine a great pick.
I don't think I'd go as far as making a oval exhaust port with auxiliary ports along with added dual transfer boost ports but anything is possible. Haha.
20200126_152027.jpg 20200122_145920.jpg 20191221_004832.jpg 20191211_140849.jpg 20200129_122112.jpg
 

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I would consider the Later Year Honda TRX250R Cylinder, specifically 86-88, 89 uses the 88 cylinder. My first choice would be 88, followed by 87, 86 and finally 85...basically the same weight, size, and better Intake & exhaust track. You don't need "auxiliary" or "dual transfer" ports to make these scream.

Carlos
 

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Discussion Starter #5 (Edited)
I've been doing lots of R&D for the last few months about the evolution of Honda's CR250R and ATC/TRX from 1981 to 2007 is very interesting with the new upgrades then dropping them and then reapplying them years later.

My 1983 Cr250r cylinders have the excellent port arrangement of the newer CR250 design but unfortunately I can't use a TRX big bore piston because my 1983 piston has a 41.20mm pin compression height .
In 1984 Honda went to a 8.6mm shorter cylinder and shortened the piston pin compression height to 38mm.
Plus the ring stops are 3mm narrower to each other.
So I'll just stick with the 68mm Wiseco 446P8 piston pictured below. Less chance of transfer short circuiting with no side cutouts around the pin bore and I like the modified ring land area. These pistons were from the 1990's from what I've heard.

I'll get wings added to the bridged exhaust ports and maybe put in the small "Mac Dizzy " ports into the rear transfer ports plus seeing my 68mm cylinder has a semi open deck with bridged support I'll Iower the top deck 1.5mm to get the piston crown edge to zero. Then machine a new squish and dome profile in the head.

I have a question...I can get my 68mm iron sleeve nikisel plated for $350. Is there any advantage in friction reduction running a nikisel coated iron sleeve versus a bare iron sleeve?
Thanks
Willard
 

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"I have a question...I can get my 68mm iron sleeve nikisel plated for $350. Is there any advantage in friction reduction running a nikisel coated iron sleeve versus a bare iron sleeve?"

Yes on the Nikasil Plating, No on the friction reduction properties. Also, most don't even know this, that includes builders, Wiseco Rings as well as ProX, in all standard piston Kits for Steel or Iron sleeves, are NOT made to run in a Nikasil plated cylinder. Only specific rings designed and made to run in Nikasil cylinders should be used.

If and when you stop by BDT, I can show you the difference in Rings, and why they are designed different.

Carlos
 

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Discussion Starter #7
"I have a question...I can get my 68mm iron sleeve nikisel plated for $350. Is there any advantage in friction reduction running a nikisel coated iron sleeve versus a bare iron sleeve?"

Yes on the Nikasil Plating, No on the friction reduction properties. Also, most don't even know this, that includes builders, Wiseco Rings as well as ProX, in all standard piston Kits for Steel or Iron sleeves, are NOT made to run in a Nikasil plated cylinder. Only specific rings designed and made to run in Nikasil cylinders should be used.

If and when you stop by BDT, I can show you the difference in Rings, and why they are designed different.

Carlos
Thanks Carlos,
My family and I still have our flight and place to stay in San Francisco booked. We watched Alcratraz on Netflix tonight so we're getting primed up for the trip, Lol.
I will try everything in my power to make the drive to your shop. Timing couldn't be more perfect.
I did lots of research and along with your advice a iron sleeved cylinder puts out way more compression and ring seal then a distortion prone nikisel lined aluminum cylinder.
In my case for my hotsaw application with no coolant for a quick 8-10 second run the iron sleeve heat retention will deliver the reliable hi rev power needed.
We are allowed a 1 minute warmup .
I understand power will drop after temperature rises after160°F on a well tuned 2 stroke.
So Nikasel coated iron liner is no longer in my plans unless you can convince me with the proper rings.
It would be nice to preserve the future porting in the 68mm last oversize iron cylinder.
 
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