eoin Posted March 29, 2021 Report Share Posted March 29, 2021 looking for a 2nd oversize piston for a TY250 twin shock can anyone help Quote Link to comment Share on other sites More sharing options...
feetupfun Posted March 29, 2021 Report Share Posted March 29, 2021 27 minutes ago, eoin said: looking for a 2nd oversize piston for a TY250 twin shock can anyone help New piston kits are available. They are usually in the manufacturer's catalogue as YZ250 or DT250 or MX250 rather than TY250. Wossner make a good quality piston kit for them. You may need to source a little end bearing different to the one in the kit depending on what conrod is in your motor. Quote Link to comment Share on other sites More sharing options...
majesty Posted March 29, 2021 Report Share Posted March 29, 2021 https://www.tytrials.com/trailandtrialsuk/prod_2768676-812-Full-Piston-Kit-TY250-Twinshock.html Quote Link to comment Share on other sites More sharing options...
eoin Posted March 29, 2021 Author Report Share Posted March 29, 2021 16 minutes ago, majesty said: https://www.tytrials.com/trailandtrialsuk/prod_2768676-812-Full-Piston-Kit-TY250-Twinshock.html Thanks , they are out of stock at the moment Quote Link to comment Share on other sites More sharing options...
eoin Posted March 29, 2021 Author Report Share Posted March 29, 2021 1 hour ago, feetupfun said: New piston kits are available. They are usually in the manufacturer's catalogue as YZ250 or DT250 or MX250 rather than TY250. Wossner make a good quality piston kit for them. You may need to source a little end bearing different to the one in the kit depending on what conrod is in your motor. Thanks I will have a look 1 Quote Link to comment Share on other sites More sharing options...
eoin Posted March 30, 2021 Author Report Share Posted March 30, 2021 Ordered one from Wossner , thanks again Quote Link to comment Share on other sites More sharing options...
Tillerman6 Posted June 29, 2021 Report Share Posted June 29, 2021 On 3/29/2021 at 2:04 AM, feetupfun said: New piston kits are available. They are usually in the manufacturer's catalogue as YZ250 or DT250 or MX250 rather than TY250. Wossner make a good quality piston kit for them. You may need to source a little end bearing different to the one in the kit depending on what conrod is in your motor. Quote Link to comment Share on other sites More sharing options...
Tillerman6 Posted June 29, 2021 Report Share Posted June 29, 2021 The only direct replacement for a TY 250 piston- Yamaha OEM is from CMSNL. They are not cheap. I don't think Wisseco makes a direct replacement either. The DT 250 pistons will not fit without modification as the piston skirt shape is different and the weight of the piston is heavier than the TY 250 piston. I went thru this whole scenario recently and had to get CMSNL to send me a genuine TY 250 piston after they sent me a DT 250 piston with a skirt that hits the flywheel weights. If you are not replacing the con rod, you will have to go with the stock piston anyway, as any changes there will make it necessary to change the piston too most likely. Quote Link to comment Share on other sites More sharing options...
feetupfun Posted June 30, 2021 Report Share Posted June 30, 2021 15 hours ago, Tillerman6 said: The only direct replacement for a TY 250 piston- Yamaha OEM is from CMSNL. They are not cheap. I don't think Wisseco makes a direct replacement either. The DT 250 pistons will not fit without modification as the piston skirt shape is different and the weight of the piston is heavier than the TY 250 piston. I went thru this whole scenario recently and had to get CMSNL to send me a genuine TY 250 piston after they sent me a DT 250 piston with a skirt that hits the flywheel weights. If you are not replacing the con rod, you will have to go with the stock piston anyway, as any changes there will make it necessary to change the piston too most likely. As a visual reference, here are photos of a TY250 cylinder I recently had rebored and the Wossner piston that is going in it and a couple of very old original TY250 pistons. The Wossner piston ASSEMBLY is the same weight as an original TY250 piston ASSEMBLY. If you compare just the bare pistons, the Wossner piston is heavier. The Wossner wrist pin is very light. Quote Link to comment Share on other sites More sharing options...
eoin Posted June 30, 2021 Author Report Share Posted June 30, 2021 Managed to source a Wossner piston although I had to go for a bigger o/s and get a rebore Thanks Eoin Quote Link to comment Share on other sites More sharing options...
Tillerman6 Posted July 1, 2021 Report Share Posted July 1, 2021 I think it's possible to put a TY piston into a DT 250, but not the other way around. The TY piston skirt is wider next to the flywheel circumference for the larger diameter of the TY flywheel. I think the diameter on the original TY 250 A piston is 69.96mm I don't know if Wossner makes one in that diameter. It's interesting to know that the wossner wrist pin is lighter than the stock Yamaha wrist pin- I might go with wossener next time around when I need a 1st or 2nd oversize. The CMSNL stuff is going for a premium. 1 Quote Link to comment Share on other sites More sharing options...
tony27 Posted July 1, 2021 Report Share Posted July 1, 2021 Wossner do make a standard size piston, strangely enough TYtrials shows a 1st oversize for a 70.25mm bore then 2nd, 4th, 6th & 8th oversize, aftermarket pistons generally only come in 0.5mm steps so 2nd, 4th, 6th & 8th 1 Quote Link to comment Share on other sites More sharing options...
jon v8 Posted July 27, 2021 Report Share Posted July 27, 2021 I've just fitted a 2mm O/S Wossner piston and ring kit into my old banger of a TY... It was the only size I could get, but not bothered because I have spare barrels. Pleased to report it runs very nicely, I did remove some unnecessary weight from the inside of the piston with a Dremel drill. The wrist pin is shorter than the old one and was a fair bit lighter. The assembly was just over 1.5 Oz lighter than the old one. It has certainly made the motor much more zappy, and the big bonus is the lack of rattling ! Just need to get used to riding a 2 smoke again... 1 1 Quote Link to comment Share on other sites More sharing options...
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