Let's talk pistons and rings...

[pscook]

I popped open my 2011 300 last night for a quick how-do-you-do. Pretty nice, I think. Check out the pics and tell me what you think-

The view from the top-



A peak under the skirt-




A shot of the head (exhaust side is down)



Exhaust side is near, intake is far-

[pscook]

Questions- How does the piston look? What about the underside evidence? Any concerns? Jetting was a NOZG in a 36mm Keihin, it's now a Lectron (as of 6 motor hours ago). Comments?

Now for the specs-

Piston is 2.6(ish)mm above the floor of the exhaust port at BDC. Base gasket thickness of 0.65mm. Squish unknown. Ring gaps are at 0.4mm top and bottom ring at halfway down the bore. Hours on this piston are unknown. I am the fourth owner. The third owner installed an hour meter which currently reads 108.4 hours, previous hours unknown.

I am going to have the bore and piston measured on Monday when the machine shop is open. What do you all think of the ring gap? Plating looks nice, no visible wear or flaking. Ports could use a little love to get matched and smoothed, but everything else looks decent.

Thoughts?

[nknudsen]

The wash on the piston looks good (nice jetting). The carbon isn't all off like if it was real rich. Just a bit of wash by the transfer ports.

[Moto7man]

Is that a Vertex or Wossner piston?

[Jakobi]

Originally Posted by nknudsen

The wash on the piston looks good (nice jetting). The carbon isn't all off like if it was real rich. Just a bit of wash by the transfer ports.

+1 ..Looks as close to perfect as you'd want to be. Small hot spot on the underside is OK.. If the whole underside was as black as the top she'd be too lean. Right now you look like you're on the spot.

[pscook]

Originally Posted by nknudsen

The wash on the piston looks good (nice jetting). The carbon isn't all off like if it was real rich. Just a bit of wash by the transfer ports.

Yeah, I noticed that, too. No heavy lean build up and no "clean" rich wash pattern. But it's so even that it seemed too good to be true...

Originally Posted by Moto7man

Is that a Vertex or Wossner piston?

Wiseco. Wossner (and I believe Vertex) are coated.

Originally Posted by Jakobi

+1 ..Looks as close to perfect as you'd want to be. Small hot spot on the underside is OK.. If the whole underside was as black as the top she'd be too lean. Right now you look like you're on the spot.

Yep yep, just what I wanted to hear. Surprisingly, I run my bikes leaner than "everyone else," for whatever reason. I want to just get rid of the off-idle burble and have the mid-throttle "on the pipe" snap, with a reasonable top end.

So, how's about them ring gaps? I see 0.5-0.8 as the range, with Wiseco recommending 0.004" per inch of bore, which brings me to .0114", which is 0.28mm. Such a deviation, and I'm almost 50% above Wiseco range yet still under OEM recommendations. Do I drop the complete package back into the hole, or replace rings (and possibly piston)? So confused...

[Jakobi]

I run my bikes the same way Phil. Can't handle an overly rich bottom end, or the dullness in the mid range that comes with fatter jetting. I'll be interested to see what the pistons out of the new bike looks like once I open her up.

In regards to the new rings I went with wiseco specs, plus a little extra. Put them in at the tighter end of the spec, and use the 0.9mm max spec as worn out, and kind of gauge the time line it took to get there and use that as a baseline for next service interval. On the 250 I find 85-100hrs is about the right time, and do the rings, piston and little end all at once.

[pscook]

Originally Posted by Jakobi

I run my bikes the same way Phil. Can't handle an overly rich bottom end, or the dullness in the mid range that comes with fatter jetting. I'll be interested to see what the pistons out of the new bike looks like once I open her up.

In regards to the new rings I went with wiseco specs, plus a little extra. Put them in at the tighter end of the spec, and use the 0.9mm max spec as worn out, and kind of gauge the time line it took to get there and use that as a baseline for next service interval. On the 250 I find 85-100hrs is about the right time, and do the rings, piston and little end all at once.

I must run the bestest air filters ever, because I don't believe that Steve installed the new piston, and he put well over 80 hours on the bike before I got to her. It's at 100+ hours and the ring gaps are almost to OEM specs. Maybe I need to measure them at all depths of bore and see if there is a weird cone or hourglass shape to the bore.

Crap. Should have performed a compression test. Double ding against Phil. And I wasn't even drinking when I tore it apart!

[Jakobi]

My 300 was never has hard on rings, but then I wasn't as capable/quick on it either. 250 cops a bit of a hard time; more revs, more often..

[sweeper]

Looks pretty good.
The rings can be changed 2-1 raitio to the piston,standard.
80-100 hours on piston,40-50 on rings, depending upon how hard you ride is a decent benchmark.

If you cant maintain that interval then the bore,or plating is out of spec.
As long as you haven't had any jetting issues or dust and dirt pass through the filter.