Wiseco pistons

[tony27]

Are wiseco pistons any good in CZs, I have a reed ported cylinder coming which has a brand new wiseco piston with holes cut in the skirt to match the needs of the reed valve. I plan on trying it at some stage using the GEM reed block
From photos it appears that they only run a single ring unlike the genuine which is easily gotten for about $120us

[John Orchard]

I would think those tiny holes would do jack, I'd be making larger round holes (round holes not having any corners for cracks to start from), finished a little nicer.  I'd also grind an arc on the bottom of the skirt, although you can't go far because the holes are so low.

I'd also be looking down the intake port to see how wide the piston holes can be before going past the edge of the port.

[Lozza]

What were the holes cut with a tommahawk?  The holes just allow a path into the crankcase, but the holes need to be exposed to the reed around TDC

[tony27]

Not so sure about the holes either, the 1 drawing I have seen regarding holes in the piston for reed valves on CZs had from memory 13mm drilled holes.
Being a piston port motor standard the skirt is above the ports towards tdc Lozza, I guess these would be at close to bdc. From the photos of cylinder it appears that there are 2 extra boost ports machined to feed from the intake ports, would the holes be to allow some mixture in between when the intakes close & the transfers open?
I'm thinking a new genuine piston kit may be the best way to go, that way I can drill & radius to match the drawing
I had the reed block out of my yz465 today & was surprised to see the intake port closed off by the piston at btc, was expecting to see it open

[SON]

To me Wisecos are pistons of last resort,
Those windows certainly need some help

[Lozza]

Not so sure about the holes either, the 1 drawing I have seen regarding holes in the piston for reed valves on CZs had from memory 13mm drilled holes.
Being a piston port motor standard the skirt is above the ports towards tdc Lozza, I guess these would be at close to bdc. From the photos of cylinder it appears that there are 2 extra boost ports machined to feed from the intake ports, would the holes be to allow some mixture in between when the intakes close & the transfers open?
I'm thinking a new genuine piston kit may be the best way to go, that way I can drill & radius to match the drawing
I had the reed block out of my yz465 today & was surprised to see the intake port closed off by the piston at btc, was expecting to see it open

errm intake flow only happens from 90 deg btdc to tdc when the piston is rising  no intake flow at bdc.

[tony27]

So you're saying just get a new genuine piston & not bother with the holes?

[Brian Watson]

If you are going to run the reed .. you should have the holes... otherwise there is little or no benefit from the reed ..

[shelpi]

if you are going to run Seizeco do not use their piston to bore clearance (go wider) like as in you think your putting in a worn out piston run it in I mean as in really run it in, and use lots of oil, and rich on the carb then seize it up, cost me an Aussie title,
probobably best to get it ceramic coated better still get a few thou of ceramic put on you old piston as long as its in ok nick ie piston ring groove tolerances are in the servicable range

[SON]

If you are going to run the reed .. you should have the holes... otherwise there is little or no benefit from the reed ..

Actually a hinderance

[SON]

if you are going to run Seizeco do not use their piston to bore clearance (go wider) like as in you think your putting in a worn out piston run it in I mean as in really run it in, and use lots of oil, and rich on the carb then seize it up, cost me an Aussie title,
probobably best to get it ceramic coated better still get a few thou of ceramic put on you old piston as long as its in ok nick ie piston ring groove tolerances are in the servicable range

Bore it to Wiseco tolerances as per their instructions,
Run the piston as per their instructions,
Then pull it down again, wet rubbing any wear marking / high spots on the piston,
ALWAYS without exception warm up the engine before engaging the power band !!!

[Lozza]

So you're saying just get a new genuine piston & not bother with the holes?

With a reed it controls intake timing  not the ports in the piston that helps fill the crank case. Run the piston just radius the ports in the piston. 

[shelpi]

if you are going to run Seizeco do not use their piston to bore clearance (go wider) like as in you think your putting in a worn out piston run it in I mean as in really run it in, and use lots of oil, and rich on the carb then seize it up, cost me an Aussie title,
probobably best to get it ceramic coated better still get a few thou of ceramic put on you old piston as long as its in ok nick ie piston ring groove tolerances are in the servicable range

Bore it to Wiseco tolerances as per their instructions,
Run the piston as per their instructions,
Then pull it down again, wet rubbing any wear marking / high spots on the piston,
ALWAYS without exception warm up the engine before engaging the power band !!!

yep did that twice 1st time it tried to seize was on 1st start up it started squeeking after shut down when ya kicked it over, any who after 2 rub downs, was not happy with the marks appearing, so then took it out (honed) another thou or two, was assembled everytime with lots of oil, then run in alot, best part it didn't seize at the first race meeting it seized at the 2nd race meet

[Davey Crocket]

I know guys that have had the same issue, would run it in, re check everything and after a couple of meetings would seize.

[shelpi]

I know guys that have had the same issue, would run it in, re check everything and after a couple of meetings would seize.

gone back to original kit, hard to find so just shop for bits all the time now have some spares, but ya gotta admitt seizco are the piston that keep on giving or is that takeing