Hey all!

top pic is the rt1, bottom is the old crusty rt3 .

I couldn’t find any pistons for an RT3 online for the life of me, so I ended up buying a RT1 piston. 

Will it work? I compared it to the RT3 one, all the measurements seem to jive , just the ring location is a bit lower  down on the piston itself. 

any thoughts or first hand experiences anxiously welcomed . 


 

Also, it’s .25 OS. Don’t know if that is relevant or not .

Youll have to check to make sure the ring gaps dont go into the boost port.

Enduronut and/or DEET here on the forum may well have what you want.

crusty one not so bad looking, perhaps it would clean up nicely if bore isn't shot?

The sizing of the RT3 piston is important . If that isn't a .25 oversize as well it isn't going to work.
The RT1 piston won't have the skirt holes on the intake face .
It would run I'm pretty sure , but wouldn't run as strong in the mid range , as with proper RT3 piston .
I'd recommend a more thorough search for the correct piston , and in an appropriate size .

I used one in my RT2 but was a modified motor & cut a big hole in the skirt. Got worried about it after a time & took it out purely because the hole i cut was crazy big. I guess i decided the ring peg location was ok, was long ago. I've got the piston somewhere for a pic for a laugh, as just felt penned the inlet port shape onto the piston a bottom dead center the started drilling, then decided way too big but can't put it back. Bike went like hell although using a 250 crank now i think back so not going so far up & down 325cc or something.
Ok--just put it in as it is because i want to know if it's noticeably down on power compared to the correct piston. You might be onto something & could run sweeter than original. Be a very interesting experiment with boost port only getting boosted for about half the down stroke before inlet port is covered.
Possibility i might've only used the top ring if the second one showed in the inlet at bdc.

Here's my piston along side an RT2 type. RT1 has ring pegs 26mm apart & RT2 are 29mm apart.Looks like i used both rings but by memory the second ring was 'just in the port at bdc but only alf the height so still "just safe", talking inlet port not boost port. But i see the RT1 second ring is a lot lower down the piston "so is the top one" so chance for the second to show in the port is greater.

Just to confuse but don't read too much into it--i had 6mm off the top of the cylinder for 250 crank stroke but think 360 crank will end up the same at bottom. I think i used a 311 rod on the 250 crank, shorter rod but shorter stroke so piston ended up ok at bdc. Ignore that for yours. I'll separate what's important in the top bit. Pics--forgot. 

Thanks for the replies guys. I’ll definitely be posting my findings , I’m gonna give er a go once the correct rings come in and report back to the mothership !

There are a couple of traps to fall into with RT1 pistons and rings .
There are pistons with ring lands machined for plain rings ( 00 suffix on part number ) ,
and pistons with ring lands for Keystone rings ( 01 suffix ) .
Pistons with Keystone machining usually have a K stamp on the crown .
Subsequently , there are plain rings and Keystone rings .
As your RT1 piston is a First Oversize piston , plain rings will have an -10 suffix ,
while Keystone rings will have probably -11 suffix .
They need to be a matched pair to work properly .