A forum for owners of Yamaha TTR250 trail and enduro bikes!

davecambo · Senior Member

Wiseco pistons

davecambo · Senior Member

http://www.procycle.us/wiseco/wisecoyam4-str.htm just going from this link. Even replacing the same size piston requires a hone though doesnt it? So may as well go up on size while barrel off?

TTRfan · Super Guru

Standard piston 10.2:1 compression, Wiseco say 10.5:1

Be careful honing the barrel - it is easy to take off more than intended!

If the bore is in good shape it is possible for a DIY job using wet and dry paper at 45 degrees to bust the glaze and get a cross hatch effect to help hold a bit of oil.

Best to do some Googling to get an expert eye view instead of my ramblings wink

TTRfan · Super Guru

If it is higher compression then it will definitely give you more power! What is the Wiseco piston reference please?

davecambo · Senior Member

So they are high compression? Probably best to go up a size then to be safe with the bore work

mww916 · Veteran Member

I reckon it would be better to buy something else than voluntarily change the engine on the TTR if it power you are after They are so reliable as they come, that mucking about for a few hp would be diminishing return I reckon Unless of course you just want to play with your bike setup - then fair enough.

armcosurfer · Member

If you're going to hone or glazebust a used bore it's best to use a ball hone,about 320-400 grit.. Use plenty of thin oil(I use a 50/50 mix of white spirit and engine oil),run the hand drill at very low speed but use a very quick up and down motion, 30 seconds of this will be enough.Thoroughly clean the barrel afterwards.

TTRfan · Super Guru

armcosurfer wrote:
If you're going to hone or glazebust a used bore it's best to use a ball hone,about 320-400 grit.. Use plenty of thin oil(I use a 50/50 mix of white spirit and engine oil),run the hand drill at very low speed but use a very quick up and down motion, 30 seconds of this will be enough.Thoroughly clean the barrel afterwards.

It's good to have an engineer on board wink

Are these flexi devices any good?

http://www.ebay.co.uk/itm/Flex-Hone-Cylinder-Ball-Hone-320-Grit-77-83mm-Triumph-Tiger-800XC-2011-/180835264868?pt=Motors_Automotive_Tools&hash=item2a1a9f2964#ht_4159wt_952

Tataros · Newbie

Hello, happy to find this forum ! I salute you all ! I want to ask why are there wiseco 78 mm pistons for XR250R and only 75 mm pistons for TTR.

Kaos · Senior Member

Any bigger than 75mm would require boring of the cases, unfortunately so 263cc

ttboof · Super Guru

I put a wisco piston I'm my ttr it's been great

The most noticeable thing is its a lot lighter so the engine changes its character a bit in that it picks up a bit of power and revs a bit free er

Also a lot cheaper and readily available. Used cometic gaskets been a couple of years with no issues