motor blew up

[mboddy]

RZ pistons? You know you must chamfer the inlet side to stop it catching in the port.

[BRG1200]

Can anyone post a pic of a YPVS piston to show the little tang on the skirt that runs on the bridged inlet port compared to an LC piston? And a pic of a YPVS inlet port. illustrates how different the two cylinder types are instantly.

In your opinions what is the best method of removing that tang (to go into an LC barrel) without putting undue distortion force into the skirt? Dremel and small file to tidy up? Genuine question.

[DuncanB]

Just out of interest, and possibly ignorance... Why are people using RZ pistons rather than RD ones?

[hybrid]

Can anyone post a pic of a YPVS piston to show the little tang on the skirt that runs on the bridged inlet port compared to an LC piston? .

Here's a pic I took years ago.
You need to file the tab back to the dotted line.

[ken007]

i only mentioned this(getting rid of tab) to an engine builder last week and he quickly said absolutely not, what does one do?

[hybrid]

Generally you should not be removing bits of a piston, but maybe he's not familiar with the RD vs RZ cylinders.

[ken007]

gday hybrid, well after much study, im going to remove it ,i just wont tell him, is there a safe way to do it just right? any tips would be appeciated, ken

[DuncanB]

I want to know why RZ pistons are the go, rather than std RD ones? I'm just about to rebore, so which would be the best?

[ken007]

my understanding is yamaha rdlc pistons are best but they only go up to 1mm o/s, what size are you going to?

[hybrid]

The inlet windows are bigger in the RZ pistons, but often it's a case of better availability also.

[DuncanB]

Well... It's a bit debatable at the moment. The bores are on 0.5 but a ring locating pin has shit itself and gone up the bore and I need to clear that. On the other side, it looks like some fuckwit has had a go at some porting by filling the bore itself to somehow chamfer the exhaust port... It aint too deep, so maybe 1 - 1.5 may clear the worst of it. I'd post a pic if I could work out how!
I saw pistons right up to 2.5 on Yambits. I'm hope so, as I might need them!

[ken007]

mine that blew up were on 2mm o/s, the liner is getting very thin, im not sure if id go anymore than 2mm myself, the mitaka piston have the tang and when you see original yamaha ones they have a flat bottom, im starting to understand more now and what went wrong, i will be doing a couple of things a bit different.

[DuncanB]

Experience can be an expensive tool sometimes, Ken.

[hybrid]

Here's a good pic.
LC piston on the left, RZ piston with the tab removed on the right.
There are a lot of people saying that they learned the hard way by NOT removing the tab.
So my advice would be either use LC pistons, or definitely remove the tab from the RZ (aka YPVS) pistons.
For the record, my bike has been running for 10 years with filed down RZ pistons.

[DuncanB]

Does it make much difference performance wise, Hybrid?