Cross Performance 660 top end failure

[Heffalump]

Looks great. What grit do u use on them and what do u hone the cylinder with? Thanks

Jeez Jim that's Purdy. Not much bevel though. ...those run ok for ya ? I'm always worried about not having enough bevel

That is beautiful work!

I can attest, that thing runs like a raped ape.

I tried using it to free-hand cut some half-dovetail notches on a couple of log ends last weekend......it eats the wood so fast I can't stop it at the marks I made!

 

[Brewz]

Boy do I agree with this post.

Would love to see a hybrid P&C for the 440 kits next.

Tony, was your cylinder ruined, or just your piston?

Big gouge on the exhaust floor but if it's tidied up, that shouldn't effect it too much

 

[Brewz]

Mmmm, couple marks and chunks out of other places too, I'm calling it snotted!

 

[Mastermind]

Bruce is sending another.

 

[Brewz]

I noticed that and it's much appreciated

 

[94BULLITT]

So what caused it to hang a ring?

 

[MustangMike]

So what caused it to hang a ring?

I'll take a stab at this: The Cross MMWS cylinders have wider ports that a stock cylinder, so the bevel on the ports becomes more important in order not to hang a ring (the wider the port, the more important the bevel).

I think several of the Cross cylinders did not come with proper bevel on the downside of the ports, the side you can not see by just looking into the cylinder. I basically checked mine by "feel", and added some sandpaper bevel to top & bottom of all ports as a routine. The old adage, "better safe than sorry".

 

[Mastermind]

Sanding the port edges is a good idea, but you'll never change the bevel with fine grit by hand. Try sanding thru the plating by hand and you'll see what I mean.

 

[Adirondackstihl]

Sanding the port edges is a good idea, but you'll never change the bevel with fine grit by hand. Try sanding thru the plating by hand and you'll see what I mean.

Perzactly

 

[Adirondackstihl]

You'll need a diamond ball stone in a straight shaft or a flame shape diamond stone in a RA hand piece to effectively bevel any port.
Sandpaper.....meh.....good luck

 

[Wonkydonkey]

So can someone measure them both (farmer-whatever and the cross type) I'd love to know if there's much of a difference

The reason being, I brought a SH ms660 it ran like a hot rod.. Till it hit a nail and buggered up the teeth, then when I showed it some more wood (I was milling) it did not grab/self feed, it over revved an lean seized . (Darn f-words came out of my mouth)
So the bit I'm getting at is, I was not gonna get a new stihl p&c, I got a hyway, it looked good, I slapped it on and took the othe p&c off to find it was an AM p&c with 1122 on the side,
I was still pissed about the whole thing, I tried to clean it up and thought it's junk and took a pic or two, and tossed it in the trash.
Then I joined this forum,

I now relised it was a ported am p&c , and I should of got some timings from the jug Doh....

Now I got a lovely hyway and it don't go like the last one did..
Still there's no chance of me lean seizing it again as I turned up the Hjet.

 

[MustangMike]

See my Flying Tiger thread in the Chinese 660 section.

 

[Wonkydonkey]

See my Flying Tiger thread in the Chinese 660 section.

I've been following every build in the rice burner sub forum, not just yours

I ve got a ms 660 and liked it !! Before I lean seized it.. Now it's got hyway ummm.. Good but not as good....now i a want a clone as well, to play- port -mod etc,
So I've been following and learning, but the porting is still a bit of an unknown, although I'm getting the hang of timings. Which has been good to hear all the numbers in each thread and the vids of the saws working
Like I said, I wished I'd known what my last AM timings were on my 660 and that id kept it to compare,

But that's been binned now it's read and read some more

Cheers
Keep up all the good work,

 

[MustangMike]

I posted some port width #s on an 066 thread, I will have to look and find them again. The ports on the Cross MMWS are wider than stock.

 

[MustangMike]

OK, I found my notes on comparing the Cross MMWS #1 (#2 is on Fyling Tiger) to the OEM 066 cylinder, which ran very well.

Cross Intake approx 1/16" wider, Exhaust approx 1/32" wider, Exhaust is lower, Upper Trans about the same, and Intake Opening is lower.

On the Cross #2, the Exhaust was lower (than #1) and the Intake was higher.

This is a copy of my measurement paper (OEM, C1 (first Cross), C2 (second Cross).

 

[bikemike]

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That's 1 heck of a way to advance exhaust timing with the piston

 

[Wonkydonkey]

Here's my AM p&c and the hyway p&c I'm gonna get the timings sometime soon

 

[Wonkydonkey]

That's 1 heck of a way to advance exhaust timing with the piston

Can you explain a bit more, for my not so bright brain, ? Is it there's a small but big difference in Pistons and therefore timings changed

 

[bikemike]

Can you explain a bit more, for my not so bright brain, ? Is it there's a small but big difference in Pistons and therefore timings changed

Yeah look at the exhaust port. The top of the piston is is allowing the exhaust to start opening before the piston has even cleared the exhaust port. It was a sarcastic comment cause some of the top is gone

 

[Wonkydonkey]

Yeah look at the exhaust port. The top of the piston is is allowing the exhaust to start opening before the piston has even cleared the exhaust port. It was a sarcastic comment cause some of the top is gone

Ar I see, doh silly me.