TY250 E Piston

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David Lahey
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Re: TY250 E Piston

Postby David Lahey » Sat Mar 05, 2011 7:26 pm

Stan please compare the distance from the top of the exhaust port to the top of the cylinder. I'm thinking the E distance might be greater than the A.
Please also have a look and see if the conrods look different. I remember reading that one of the improvements that came with the B model was a lighter conrod compared with the A. I think this might be right too because my B and D motors have much less motor frequency vibration than the A.


relax, nothing is under control

Stanm
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Re: TY250 E Piston

Postby Stanm » Mon Mar 07, 2011 9:21 pm

Hi David
I measured up most dimensions on the A & E cylinder and taped off the transfer ports and measured their volume by filling with water. I have attached the scribble results. From results conclusion is from the outside they look different but inside they are quite similar. Will investigate the crank and crank case volume next.

Cheers

Stan
Attachments
StanMSCAN01.jpg



Stanm
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Re: TY250 E Piston

Postby Stanm » Mon Mar 21, 2011 10:29 pm

Hi David
Finally got around to checkingthe bottom end of the A vs E

I have both with the cylinder off at the moment.

Filled both cranks with petrol and got close to 490ml in both so not a great difference there.
Crank wieghts on E may be very slight ly thicker but only by 1mm.

Con rod on the A has markin of '311" and is 8mm thick

Con rod on the E has "498" marking and is 6.5mm thick

I got an original piston from Ebay and I believe it is a DT piston. It is almost 30gms heavier than the original Piston.

I will let you know how it goes.

Cheers
Stan



David Lahey
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Re: TY250 E Piston

Postby David Lahey » Mon Mar 21, 2011 10:50 pm

Stan I'm amazed that the port timing was so close between your TY250A and TY250E cylinders. I'm wondering if your A model is of a later type to mine. My A model has a very low ID number so I think it is an early one.

The first photo shows the front of the cylinder on my TY250A. Does your A cylinder have the flat round bit above the exhaust pipe like this one, or does it look like the cylinder in the second photo (which I think is an early B model cylinder) with the fins going all the way across the front?
David
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P9140029.JPG
P9140033.JPG


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Guy53
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Re: TY250 E Piston

Postby Guy53 » Tue Mar 22, 2011 11:45 am

David, I have 2 434 cylinder and none of them as that flat round above the exhaust.

Guy



Stanm
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Re: TY250 E Piston

Postby Stanm » Wed Mar 23, 2011 7:47 pm

Hi
My A has the flat bit. So the major difference that is obvious is the con rod and the piston weight. Maybe some small portimg difference that are not so obvious. Would be great to get the porting specifications!
My feeling is the gearbox is a contributor to the performance difference but have not studied it.

Cheers

Stan



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Re: TY250 E Piston

Postby Stanm » Wed Apr 13, 2011 9:36 pm

Hi
I ended up purchasing a DT piston Kit from ebay USA. Got the cylinder rebored and checked the ring gap. 2nd ring was 26th so not happy as standard was 16.
As mentioned before my original piston was 218 gms and the DT was approx 246. The TY has a noticably thinner skirt so i hacked off about 10gms with a die grinder. As mentioned by Guy the TY shirt is also cut back slightly so I did that.
Bought a set of TY rings from ebay and they were better but still out of spec. So the rebore guy must have got it wrong. Also the new TY top rings stuck a bit in the DT piston groove. DY piston kit came with two sets of under piston springs. According to my TY parts manual the TY has only one spring under the second ring. I installed a spring under the top ring and this stopped the sticking.
Not real happy again but not about to waste a piston and rebore so installed the DT piston and rings gave it a test run last weekend and it went pretty well.

Just a warning to watch what you get from ebay. Also I would go for a TY piston next rebore over a DT for the lightness.
Or just get a wiseco one.
Cheers and thanks for your input.



Guy53
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Re: TY250 E Piston

Postby Guy53 » Fri Apr 15, 2011 8:06 pm

Hi Stam
Be warned, the Wiseco piston are not what they use to be, a friend bought one and got a China made '' object '' less than perfect

Guy




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