SPI pistons = crap?

[POS Pol]

I was just wondering if anyone else has had this happen. I rebuilt my 04 800with new crank and re-plated cylinders and SPI pistons. After 300 miles I noticed my compression had dropped off, so I tore it down to find the head of both pistons were all dinged up. Removed the jugs and found both ends of the ring the go over the alignment pin had broke off and chewed up the head and the cylinder. Both pistons are the same.
What the hell caused it, just bad rings and pistons or something else? I check the ring end gap when I did the rebuild and it was with in specs. I will post some pics later.
Any information would be great. Thanks

 

[swrev]

I had good luck w/ SPI in my '04. Put in a new set in before I sold it three years ago and it's still going strong.

Detonation can knock the locator pin loose. Not sure if SPI is more prone to that happening or not because I had good luck.

Running Wossner now in all the sleds I rebuild. Those are some nice pistons if you decide to go another route.

 

[Tahoepow]

kinda off topic but still is about top end rebuilds. My 06 rev 800 will be for sale this fall and its got 2600 miles. Probably needs a top end. Havent done a compression check yet But should I sell it as-is and let the next owner decide what to put in it or sell it with a top end done?
Seems like there are lots of choices pistons/rings ect... Wouldn't want to install some SPI stuff and have the next potential owner start hating on it.

 

[winter brew]

Pistons installed backward?

 

[POS Pol]

No the pins are on the intake side angled towards the mag side of the motor.

 

[snowmobiler]

upside down rings?

 

[whitefish]

Any signs of detonation? Most likely cause since it was both of them.

 

[lost]

I had good luck w/ SPI in my '04. Put in a new set in before I sold it three years ago and it's still going strong.

Detonation can knock the locator pin loose. Not sure if SPI is more prone to that happening or not because I had good luck.

Running Wossner now in all the sleds I rebuild. Those are some nice pistons if you decide to go another route.

What was the price on the Wossner pistons and where did you get them from?
Thanks

 

[POS Pol]

Rings were install right and there is no signs of detonation. The plugs have a good brown color and the wash looks good.

 

[sled_guy]

SPI pistons are very good pistons.

I'm betting detonation. It pounds the rings until the ends break and then the fun begins.

sled_guy

 

[Red-eye]

Did you measure the squish?

 

[Danzick]

circlip fell out of my SPI pistons after about 800 miles. went with the rk tek ones and well over 1000 miles without a problem.

 

[swrev]

What was the price on the Wossner pistons and where did you get them from?
Thanks

I got them through SHR. Don't recall the exact price. I'd have to find the slip.

 

[adam8781]

I keep hearing more and more spi & mcb piston failures, falling apart, piston ring locator pins falling out.

wossner forged is best, (wiseco if they are correct sizes) rktech drop ins are forged wossner pistons, big john sells wossner as well

Apparently snox pistons are doing well in the 800r as well.

 

[BIG JOHN]

OK for starters MCB and SPI are different...and nothing "falls apart" its CAUSED by something..

1) any ring land, pin failure is from DETO...I add a thicker basegasket to run safely with todays ??? fuel

2) I/MCB use wiseco circlips in all kits...doo/SPI clips are to thick and can break or pop out if not installed correct

3) wossner is the best forged piston and I offer them (no stock 800HO direct drop in)...

4) call for details..BJ

 

[zilla]

I'd have to agree, then there's the guy that tells you he was low on gas and just poured half a tank of the old siphoned out gas back into the tank to have a little more fun. lol

 

[Red-eye]

Read up on ethanol based fuel, phase seperation, how long fuel lasts and why is there so many products out there to stabilize fuel. Then complain to the fuel makers or the government, for regulations and on making products that kill parts.
I have seen fuel go dead in 30 days. If you are getting fuel that has been in a tank that is old already.........what are you putting in your sled?
Any tank that is open to the air is gathering moisture and starting the phaze seperation process! Engines don't like water and flat fuel.
It is not the parts, it is the fuel!

 

[freekweet mods]

Variance in cylinder bore and/or out of round cylinders will cause the ring to hammer out the locator pin also.

 

[Red-eye]

Thus, when the ring bulges out into the exhaust port and then is stuffed back, the end of the ring is pushed into hard contact with the pin, and after a sufficient number of hard blows (and these accumulate rapidly at, say, 10,000 rpm) the pin begins to loosen and it will gradually enlarge the hole in which it is inserted enough to work completely loose. Then the ring is free to rotate, and it quickly works its way around to catch the end in a port.



Gordon Jennings two stroke handbook quote
Food for thought.

 

[Red-eye]

http://www.snowestonline.com/forum/archive/index.php/t-142247.html


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