Diff'rent Strokers

[eire_kp61]

Ive heard yz125 1988 1989 pistons will fit with slight modification to the oil transfer hole,

ive also heard 3ma pistons are a match ?

does anyone know of any other pistons that are a direct replacement because performance pistons are not listed anywhere for the 3xv

[arlurt]

Hi Chris, nice to see you're back on it.

Does this mean you've got a crank rebuilt?

I don't think 3MA pistons will fit, remember the 3MA is a "Reverse Cylinder"... I'd heard that pistons from one of the Yamaha 125 'crossers would fit, but that it had to be the right year, and that they're single-ring pistons.

I've bought them for my 3XV from my Yamaha dealer here in the UK, pricey but right. I've had them from eBay, and from Yahoo Japan. I believe TZ250 pistons fit, but again you need the right year (3YL, 4DP, 4TW, 5KE are all V-Twins), and they're single ring too.

If you buy from Yamaha remebere that when you buy a piston, that's all you get. No rings, clips, or gudgen pin. These all have to be bought separately...

Let us know how you get on.
_________________
Light is right.

[eire_kp61]

Well karl ,

Finally going back at rebuilding the 3xv now yea
hoping to have it all done for when the cold and frost is gone.

Well i sent the first crank to stan stephens and it needed a web so i sent a second one and asked him to quote on rebuilding one good crank combining the two and it was over 600 euro so hopefully he still has my parts after all this time , il just get him to return the bits and il store them as spares .

warrick on the site here has a useable r crank for me but due to circumstances with work "or more like the lack or work" i havnt been able to get time or money to press on untill now , so hopefully he still has it for sale.

Il be on the search for a good sp crank once the bike is back up and running.

so all i need now is 2x pistons 2x base gaskets 2x little end bearings and 2 gudgien pins

hopefully it wont blow up as quickly next time

[Wb]

3MA pistons are very different and won't fit. Some YZ or TZ pistons are possible, but they are both single ring and not quite the same as 3XV pistons in design in any case.

For simplicity and longevity you are probably best off using genuine 3XV pistons, but as Karl says, it's an expensive route unfortunatley. BDK list a Prox kit for the 3XV, but I've no idea what they're really for (no-one made aftermarket kits for the 3XV as far as I know? Maybe in Japan, but I've never seen any) and how suitable they really are. Maybe ask them for details - or even better pictures showing the locatioon of the cooling cutouts, ring pegs etc,. And whether they are round or dome-top (if you are running an R/RS top end, you want domes, if SP you need flat tops).

[eire_kp61]

went to my local yam dealer and gave him the part numbers for 2x pistons 2x base gaskets , and 2 x ring sets and i got a price of €560 euro


so i started a search for matching pistons from other bikes ,
the only bikes i could find accurate piston measurements for were moto cross for some reason .

but ive found two bikes had very close pistons so far , both available in wossiner forged type

ive got a yamaha piston measuring ..

Overall lenght 58mm ( 3mm longer then 3xv at the skirt )
crown height 20mm ( from top of pin , same as 3xv )
dome height 2.5mm (same as 3xv)
bore size 54mm std ( 56mm available)
gudgien pin 16mm

the piston has an intake side lube hole like the original piston
and the ring peg position is 13.00mm so i think it should avoid any ports

its a single ring piston but looks like a good match if 3mm was skimmed from the skirt

is this window on the 3xv piston skirt nessecary ?

[eire_kp61]

ive also found measurments for a kawasaki piston ....

same bore ...
some gudgien pin ...

crown height is 21.5 flat top where the original is 20mm to the same point.
dome height is 0.00 because its flat top but at 21.5 overall could the head be skimmed .75 - 1mm and compression ratio be returned to normal with this piston