OzVMX Forum

Clubroom => Tech Talk => Topic started by: noisy toy on January 11, 2014, 05:30:54 pm

Title: yz490 piston
Post by: noisy toy on January 11, 2014, 05:30:54 pm

Has anyone seen a port like this in a yz490 piston before? good or bad? I will attempt to post a pic.....
cheers, shane.(http://[URL=http://s398.photobucket.com/user/noisy-toy/media/SAM_4061_zps1a59dac1.jpg.html][IMG]http://i398.photobucket.com/albums/pp61/noisy-toy/SAM_4061_zps1a59dac1.jpg)[/URL][/img]

Title: Re: yz490 piston
Post by: noisy toy on January 11, 2014, 05:58:23 pm

(http://i398.photobucket.com/albums/pp61/noisy-toy/SAM_4061_zps1a59dac1.jpg)

Title: Re: yz490 piston
Post by: noisy toy on January 11, 2014, 05:59:25 pm

aha it worked! helps when you copy the correct link.....

Title: Re: yz490 piston
Post by: Lozza on January 11, 2014, 11:01:12 pm

Makes no real or measurable difference  except for maybe making the skirt a tiny bit weaker

Title: Re: yz490 piston
Post by: motomaniac on January 13, 2014, 10:50:42 pm

its for more top end power .I wouldn't think that it was a good idea on a bigbore for motocross.

Title: Re: yz490 piston
Post by: Lozza on January 14, 2014, 02:59:20 pm

Any ideas how that port would make more top end HP?

Title: Re: yz490 piston
Post by: vandy010 on January 14, 2014, 05:21:37 pm

Dont know much about big bores but we did this mod many
years ago on a mates YZ80F and it made a big improvement.
I thought it was mainly to provide extra lubrication/cooling to the
small end and was more of a bottom end power mod???
Anyone else?

Title: Re: yz490 piston
Post by: Lozza on January 14, 2014, 06:31:24 pm

Did similar things a dynoed them back to back and found no difference in the output of the engine.