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.049 cylinder and piston for .051

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.049 cylinder and piston for .051

Post  Darren19 on Thu May 09, 2013 5:45 am

Does anyone know if the .049 piston and cylinder will fit in the .051? I've heard they can fit? That is .049 fit the .051 tee dee?
Thanks!
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Re: .049 cylinder and piston for .051

Post  JPvelo on Thu May 09, 2013 7:23 am

They swap straight across but you must swap the cylinder AND the piston.

Jim
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Re: .049 cylinder and piston for .051

Post  anm2 on Thu May 09, 2013 8:13 am

The .049 and the .051 Tee Dee use the same crankcase. The only difference would be the piston and cylinder configuration. As mentioned above, the .051 piston is not for use in the .049 cylinder.

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Re: .049 cylinder and piston for .051

Post  SuperDave on Thu May 09, 2013 8:35 am

Darren:

You've gotten a number of responses as a "guest" why not join our membership and you'll probably get more as well as other benefits?

SD
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Re: .049 cylinder and piston for .051

Post  Darren19 on Thu May 09, 2013 10:34 am

Thanks SD I just joined thanks!
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Re: .049 cylinder and piston for .051

Post  SuperDave on Thu May 09, 2013 10:39 am

A piston and cylinder must be dimenionally a matched set and not intermixed.

SD
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Re: .049 cylinder and piston for .051

Post  RknRusty on Thu May 09, 2013 4:24 pm

Welcome, Darren, glad to have you on board.

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Re: .049 cylinder and piston for .051

Post  Darren19 on Thu May 09, 2013 5:58 pm

Thank you.
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Re: .049 cylinder and piston for .051

Post  SuperDave on Fri May 10, 2013 10:09 am

Darren:

FYI

The difference between a TD .049 and TD .051 is only .002" thus placing them in two different classifications 1/2A and A for competition purposes according the AMA rules.

SD
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Re: .049 cylinder and piston for .051

Post  pkrankow on Fri May 10, 2013 10:53 am

SuperDave wrote:Darren:

FYI

The difference between a TD .049 and TD .051 is only .002" thus placing them in two different classifications 1/2A and A for competition purposes according the AMA rules.

SD

There are quite a few different engine pairs that do this, from several manufacturers, since it allows the same model to compete in 2 classes with an engine swap. The performance between the adjacent sizes in theory should be identical, in practice it is extremely similar or it wouldn't be a working idea.

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Re: .049 cylinder and piston for .051

Post  SuperDave on Fri May 10, 2013 11:12 am

And to take it a step farher the TD .051 piston has two horizontal grooves that allows contest judges to make the displacement determination.

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Re: .049 cylinder and piston for .051

Post  OVERLORD on Fri May 10, 2013 12:12 pm

Here's a picture of the grooved piston to illustrate what SuperDave just said.

Lieven

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Re: .049 cylinder and piston for .051

Post  pkrankow on Fri May 10, 2013 12:17 pm

Here it is again, side by side.
https://i.servimg.com/u/f83/17/84/87/39/img_2013.jpg


Phil
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Re: .049 cylinder and piston for .051

Post  SuperDave on Fri May 10, 2013 1:37 pm

Yep, and if you look at an .051 piston out of the cylinder there are TWO indentifying grooves.

SD
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Re: .049 cylinder and piston for .051

Post  pkrankow on Fri May 10, 2013 2:50 pm

SuperDave wrote:Yep, and if you look at an .051 piston out of the cylinder there are TWO indentifying grooves.

SD

Seeing I have never seen a 2 groove cox piston, got a picture?

What is the single groove indicate if it isn't .051?

Phil
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Re: .049 cylinder and piston for .051

Post  fredvon4 on Sat May 11, 2013 9:19 am

My ten .051 pistons all have only one groove...

I have seen photos of two groves but have never touched one
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Re: .049 cylinder and piston for .051

Post  SuperDave on Sat May 11, 2013 9:46 am

Fred:

TD .049's don't have piston grooves and SOME, but not all, TD .051's have one OR two grooves. The only TD .051 that I've disassembled that far had two.

Why? I have not a clue but Cox was known for running production variations. Regardless ANY groove was put there to identify .051's from .049 TD's on these engines.

SD
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Re: .049 cylinder and piston for .051

Post  crankbndr on Sat May 11, 2013 10:01 am

In my collection the only .051s with two rings are Killer Bee .051s, all NIB.
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Re: .049 cylinder and piston for .051

Post  fredvon4 on Mon May 13, 2013 7:40 am

Sorry to not be clear in my post. I was just stating the fact that I have a few .051s with only one groove on the piston skirt. I know there are variants out there with two grooves also indicating a .051 piston.

Side note: Because new .051 piston and cylinder sets are hard to acquire, I have had some success with fitting a well worn .051 piston into a new, but sloppy with a .049 piston, TD cylinder using Ken Cook's lapping process...since the lapping reduces the piston and cylinder I assume I have a set that is more than .049 and less than .051...grin
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Re: .049 cylinder and piston for .051

Post  SuperDave on Mon May 13, 2013 9:25 am

Oh what a conundrum this!

YAWN............................... Tired w/ Coffee Read Sad Goodbye

SD
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