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Mcdizzy's 270 set up
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Posted by: rea

I was reading about mcdizzy's 270 set up has anyone had success with this set up.It claims to be more reliable than big bore set ups what do you think

Posted by: C-LEIGH RACING

Being a moderator on the Mac Dizzy site, yes I have built a few.

If your cylinder hasnt been ported too much in the boost port area you can use the YZ piston & not have to do the piston ring pin mod.
You can use the YZ piston up to the 70.00mm bore.
Neil

Posted by: matt250r21

I have a brand new Nicks Pro X piston for this setup if anyone needs it. 83-87 YZ250 68.25 bore, includes everything, $65 shipped.

Posted by: rea

So is the wrist pin hole yz piston the same size as the trx piston

Posted by: C-LEIGH RACING

quote:
Originally posted by rea
So is the wrist pin hole yz piston the same size as the trx piston

Yes on the wrist pin.
The YZ piston looks just about like the old 85/86 model R piston except the locating pins for the rings in the grooves are in a different spot which will put the ring ends close to the edge of the boost port.
Neil

Posted by: kiesta00

quote:
Originally posted by C-LEIGH RACING
Being a moderator on the Mac Dizzy site, yes I have built a few.

If your cylinder hasnt been ported too much in the boost port area you can use the YZ piston & not have to do the piston ring pin mod.
You can use the YZ piston up to the 70.00mm bore.
Neil

what's the piston ring pin mod? I ordered a 69.5mm wiseco piston and i've never heard of this before for a big bore piston.

Posted by: C-LEIGH RACING

If your building a 265cc & useing the YZ250 piston in the 250R Honda, the ring pin locaters are in a place in the ring groove that is too close to the boost port.
In other words the ring end is close enough on one side to allmost fall into the port window.

If the cylinder hasnt been ported or the boost port not widened you can run the piston with out the mod & be ok, but its still close.

What the mod to the piston is, that one locator pin has to be ground down flat, a new hole drilled & a new pin inserted to locate the ring ends in a different spot.
Neil