Jump to content

how does my piston look?


Recommended Posts

hello. changed my piston after about 25hours for the first time on my 07 yz125.

well this is how it looks now sitting on my table. should i change my pistons earlier? there's a lot of carbon built up at the top due to rich jetting for riding in the sand.

I ride about 70% track and 30% sandpits. the engine had good compression, started up at first or second kick, overall i had no complaints about it. but i did the top-end anyway, didn't want to risk anything.

please tell me what you think. 🙂

20100707-cxx4fwfxcfxxa8y2k36k4eg2jt.jpg

20100707-pt79727pe833r1x98791a3bht1.jpg

20100707-jjpqmkyns7qhy2x7ne327ix84x.jpg

Link to comment
Share on other sites

Looks pretty good considering you were running rich intentionally, theres a little blow-by developed but its not too bad, ring is a little worn.

It actually looks like it almost tried to cold seize at one point but there are no corner scores on the other side of the piston so IDK.

What does the underside of the piston look like?

Link to comment
Share on other sites

Good choice to replace...the yz will break the skirt along the exhaust port bridge. You can see exactly where it wears there...in the pics (it breaks not from sliding wear but repeated load over a small area)

I would not agree jetting looks rich...the more burnt and black the top the piston...the leaner the bike is running.

Link to comment
Share on other sites

Good choice to replace...the yz will break the skirt along the exhaust port bridge. You can see exactly where it wears there...in the pics (it breaks not from sliding wear but repeated load over a small area)

I would not agree jetting looks rich...the more burnt and black the top the piston...the leaner the bike is running.

Educate me here. So if the plug is black, too rich. If the plug is white, too lean. As far as the piston goes, it's the opposite? 🙂

MAX!!!

Link to comment
Share on other sites

Educate me here. So if the plug is black, too rich. If the plug is white, too lean. As far as the piston goes, it's the opposite? 🙂

MAX!!!

Yes, I didn't know this either until someone corrected me. A black piston means your running lean, a clean piston means rich. You got the plug part right, it's the opposite for the piston.

Basically when you see a piston with carbon buildup then it means that the bike is at least running lean or spot on and not rich.

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Reply with:

×
×
  • Create New...