What is the purpose of the tiny hole in the front of the piston?

motopsycho87

Member

Dec 26, 2010

152

2

• May 26, 2011

• #1

What does it do?!
kdx200sr model (usd)

*i took a picture but the site wont let me post links yet

 

J

julien_d

Member

Oct 28, 2008

1,788

1

• May 26, 2011

• #2

A few things. Primarily, it allows some charge directly under the piston crown for cooling. Also acts as an additional transfer port, allowing more charge into the crankcase. I have run windowed and non-windowed pistons in my 200 and honestly do not notice a difference between the two from a performance perspective.

 

motopsycho87

Member

Dec 26, 2010

152

2

• May 26, 2011

• Thread starter
• #3

How about from a wear perspective?

 

J

julien_d

Member

Oct 28, 2008

1,788

1

• May 26, 2011

• #4

lol, found a new place to cause trouble?

No difference either way that I have seen. Of course, obviously it's there for a reason on some pistons. There's plenty of theory's out there on the interwebs, but not much solid. I've thought about playing around with window sizes and placement, but just never found the time. Not sure it would be worth the effort anyway.

 

B

Bonehead

LIFETIME SPONSOR

Mar 15, 2001

406

1

• May 26, 2011

• #5

If you are talking about the front or exhaust side and the cylinder has an exhaust bridge then it is for lubrication and cooling. This works well on two strokes.
If you are talking about the intake side then it is to get more fuel into the cylinder The bigger the hole the bigger the transfers need to be then the more compression then the bigger the exhaust needs to be then the better the ignition need to be and so on and so on.

I have built lots of 125's with big holes in the intake side of the piston

 

whenfoxforks-ruled

Old MX Racer

~SPONSOR~

Oct 19, 2006

8,129

2

Merrillville,Indiana

• May 26, 2011

• #6

Does his bike have an exhaust bridge Julien?

 

J

julien_d

Member

Oct 28, 2008

1,788

1

• May 26, 2011

• #7

Negative, no exhaust bridge.

 

motopsycho87

Member

Dec 26, 2010

152

2

• May 27, 2011

• Thread starter
• #8

julien_d said:

lol, found a new place to cause trouble?

No difference either way that I have seen. Of course, obviously it's there for a reason on some pistons. There's plenty of theory's out there on the interwebs, but not much solid. I've thought about playing around with window sizes and placement, but just never found the time. Not sure it would be worth the effort anyway.

Click to expand...

Please note how I'm only getting decent answers straight away :), I think theres something in the water over at KDXrider :coocoo:

 

J

julien_d

Member

Oct 28, 2008

1,788

1

• May 27, 2011

• #9

Mmhmm. We'll see how long that lasts. One thing I've learned over the years: No matter where you go, there you are.