Rz350 bored out 66.5mm.

[Bruiser]

Hi guys,

I want to build a second engine.

I have a set of RZ350 Cyls that are 66.0mm and are in need of a rebore. I have heard that WISECO can supply pistons 66.5mm.

I would like to know if anyone out there has bored out their RZ350 cyl to 66.5mm and have fitted WISECO 66.5mm pistons successfully!

Is there any reliability problems, advice or any stories that anyone can share?

Bruiser

[Nath]

I think it comes down to the individual barrel set.. they are not exactly uniform..

if you bore is offset from the center of the sleeve towards the PV's then you are going to have probs.

I think that is really the only consideration.. making sure you have enough meat so you are not clipping them.

[Bruiser]

Hi Nath,

I have noticed that the cylinder bores are offset, do you know why that is???

Also, what do you mean about "I think that is really the only consideration.. making sure you have enough meat so you are not clipping them"

Is there a minimum thickness requirement for the cylinder bore, that is exposed at the power valve exhaust port?

Do you know, of anyone that has rebored the RZ350 cylinders out to 66.5mm and have installed Wiseco 66.5mm pistons and have received successful results?

Thanks.

[Sean'o]

would be cheaper to get an Athena 390 big bore kit than new wiseco pistons and a rebore, just another option.....

[aaronmvrider]

you will need to machine the head for larger pistons and have larger gaskets made ..... for piston clearances... power valves clearance is probably the biggest issue

cant see any reason why it would be less reliable if done correctly

[JonW]

PV will be a problem I would think. not many go above 66mm and get away with it. I would look at the Athena kit as well unless you can chat to your engineering company about how they can help you with your cyls as most would just run the cutter thru without any thought for the PV area etc. if you need new pistons and rebore and messing with PVs the cost will be around half to 3/4 of the athena kit, so its worth thinking about... its what i would do. I love the PV engine, but i would be worried with that oversize.

[rzman]

I ran 66.5 for 3 years,that includes drag racing,,no probs at all,,no custom gaskets needed,cometic make the gasket kit for all size wiseco piston kits.

you will have to grind the pv,s a tad, but they should be done anyway to match the ex port roof.

you will also need to machine stock head(chambers)/or just get an aftermarket one as i did.

[hr_186]

66.5mm

My RZ is currently running (67.00mm) blaster pistons with a 4mm stroker crank ...

NOT at all an ideal setup (with those pistons), but it's been working fine for about 5,000km's ...

i've got a really nice set of 65mm cylinders for the new motor ... but i wanted one last go with these old barrels to squeeze every bit of life out of them i could.

Obviously, close attention has to be paid to clearance with PV's and head. in the end though, it got me out of trouble and is still running really well.

When boring to 67mm, only a small amount of alloy could be seen at the top of the boost port ... we gave them a go anyway, and it's paid off.

[Bruiser]

Hi rzman,


Wow!...That is good to know... was your bike also ridden on the road for any length of time?

How did you grind the power valves back & what was the clearance you used?

When bored out to 66.5mm, the bore linner will be very thin! did this create any problems or any other problem areas that need addressing at the cylinder or ports?

Any other info in this mod would be greatly appreciated.

Thanks

Bruiser.

[rzman]

Pm sent

[Bruiser]

Thanks all, anyone else have any input?

rzman, I sent you a Pm back.

Bruiser