piston sizing ?


3 replies to this topic
  • pitster1

Posted August 13, 2009 - 12:29 AM

#1

I own a 08 yz450f and have now done 80 hours trail riding on it,
Im going to fit a new piston kit to it and am using a forged vertex piston .
I want to get as much info on the piston sizing as possible before i pull it down .
This is still runnning on the stock piston and hasnt been pulled down yet .

I have already been supplied with a vertex b size piston (which i can swap for an a ,c or d

My manual says that the stock piston sizing is a 94.956 mm- 94.980mm and the stock size is " p "

Now the vertex piston sizes are as follows "a" = 94.93mm
"b" = 94.94mm
"c" = 94.95mm
"d" = 94.96mm
the manual states that the piston to cylinder tolerance should be 0.020-0.045mm and a 0.1mm limit

Does the new piston require any more clearance because its forged ?

If the stock piston is "p" why does vertex make a,b,c,d pistons all smaller than the stock ?

Which piston is comparable to my stock cast one ?

I know the cylinder may have wear on it which i will try to measure when i pull it down , im just trying to get my head around how the sizing works

Thanks

  • grayracer513

Posted August 13, 2009 - 07:32 AM

#2

I have already been supplied with a vertex b size piston (which i can swap for an a ,c or d

My manual says that the stock piston sizing is a 94.956 mm- 94.980mm and the stock size is " p "

Now the vertex piston sizes are as follows "a" = 94.93mm
"b" = 94.94mm
"c" = 94.95mm
"d" = 94.96mm
the manual states that the piston to cylinder tolerance should be 0.020-0.045mm and a 0.1mm limit

Does the new piston require any more clearance because its forged ?

If the stock piston is "p" why does vertex make a,b,c,d pistons all smaller than the stock ?

I don't know where "p" came from, but it doesn't matter, because it doesn't refer to anything relative to the Vertex sizes, so forget it.

If the Vertex requires more clearance than the OEM pressure cast piston, it should say so. otherwise, the assumption is that it uses factory specs, and the "b" piston you have is the same as the smaller side of the stock piston range.

The factory clearance in inches is only 0.0008-0.0018" (0.010mm = 0.0004", roughly). To determine what clearance you have, you'll need to fit the piston and measure it. Remember that Niksail plating is usually less than .001" (0.025mm) thick, and any really measurable wear means replating is needed.

Which piston is comparable to my stock cast one ?

In what way?

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  • pitster1

Posted August 14, 2009 - 01:57 AM

#3

In what way?[/QUOTE]

Sizing if i had to allow for more clearance being a forged piston
which it does not say to anyware .


So i just need to replace the piston with the same size as long as the cylinder has not worn which is at minimum going to be a vertex c piston (94.95mm )


If the stock oem piston is 94.956 - 94.980 mm , why does vertex make 2 pistons smaller ( a 94.93 and b 94.94 ) than stock ones ?

thanks for your help

  • grayracer513

Posted August 14, 2009 - 06:32 AM

#4

You'd have to ask Vertex that question.





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