KR-1S.co.uk Forum

hi gentlemen

wich pistons can we use for the KR1s as replacement
MJ already mentioned TZ 3TC
are these oem still available ?
are 4DP and mitos usable?
any other brand TZR/DTR 125 oem parts ?

tz pistons are dead reliable but are bloody hard to find and arent really needed unless your engine has been heavily ported. the ports end up so wide the ring ep location ends up in one of the 2nd transfers when std pistons are used. also you will have to remove 2mm off the bottom of the barrels as the 4dp 3ak 3tc ect have different pin/deck height. in other words there too short. 26j and 59w work as std but you really need to machine the head to match the different profile. padgetts may beable to help but prices are very high. cant think off top of my head. wossner and wiseco do piston s for the kr i think?? std pistons are good for std ish engines anyway.

BDK can supply a replacement Makito (spelling) piston which is very good. Kawak pistons were still available last time I looked.

Cagiva Mito SP pistons are very good, but are made to work with a 110mm rod. 4DP pistons are also very good but 2mm shorter in the deck height, again will go with along rod conversion. Both of those are flat top so some cylinder head mods will be needed. When you come out of that you will have a state of the art set up.
I get all my TZ pistons direct from Japan which landed costs seem to be cheaper than wholesalers here in Australia, and about $100 less than the Yamaha dealer. The wonders/power of the internet
If someone has the part number for the 3TC piston I'll check on p&a

Don't forget the wiseco 559MO5600 from the YZ125 86-88. Almost a straight swap apart from being 1 mm higher. It is a domed piston but I can't be sure if the angle matchs a standard head. Someone much more clued in than me modified mine for race gas anyway. Single ring and very strong.

Don't forget the wiseco 559MO5600 from the YZ125 86-88. Almost a straight swap apart from being 1 mm higher.

dito voor the TZR 250 3MA piston ......unfortionally NLA also


cheers for all the info on this

TZR 250 3MA pistons have been superceded by 3XV pistons. I rebuilt my 3MA with them and it was fine. Not sure if a close enough match for use in KR1 though.

Hi I have just got some replacement pistons for my 3MA, these were supplied by BDK Eng' they are now using DT125R pistons and are a direct replacement made by Mitaka, cost around £45 (cheapaer on flebay)
Nothing was mentioned about 3XV ones unless these wlll also fit?? as i probably would like to stay with Yamaha OEM stuff.

Fowlers claim Yamaha list the 3XV pistons as replacements for original 3MA. I fitted them and derestricted airbox, exhausts and CDI on my 3MA and it went like stink on track days, so must be OK or it would have lunched itself.

Will the 3XV pistons be suitable for ultra wide highly tuned KR ports, or are the only ones suitable for tuned engines the;

• 26J TZ250 H, J, K, & L
  3TC 1990 TZ250A (or 89 YZ125)
  59W 1985 TZ250N
  4DP 1992-99 (Flat top)

TwoStroke Institute wrote: If someone has the part number for the 3TC piston I'll check on p&a

Fondseca quote these pistons at 65 GBP each - part number 3TC-11631-01-b0

Please let us know what price you are able to acquire them for

wondering whether anyone has prices for 3TC pistons

I checked in Japan and they show no stock of those pistons.The Fondseca price is pretty good .............only 6 available though

What size pistons (A,B or C) would anyone recommend?
Or does this depend on the bore wear of the individual cylinder to which the piston is to be fitted?

Piston size to suit your bore. I used to start with A and then move up to B. Never used C.