Jump to content

ty250 piston


eoin
 Share

Recommended Posts

 

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.

Link to comment
Share on other sites

 
 
 
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

  • Like 1
Link to comment
Share on other sites

 
 
  • 2 months later...
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.

 

Link to comment
Share on other sites

 

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.

Link to comment
Share on other sites

 
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.

 

20210630_174232.jpg

20210630_174355.jpg

20210630_174952.jpg

Link to comment
Share on other sites

 
 

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.

 

 

  • Like 1
Link to comment
Share on other sites

 

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

  • Like 1
Link to comment
Share on other sites

 
  • 4 weeks later...

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...

  • Like 1
  • Thanks 1
Link to comment
Share on other sites

 

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
 Share

×
  • Create New...