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Discussion Starter #1

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looking at this 686 piston kit and wondering if anyone has anything to say about the quality. the piston is 11:1 compression according to the manufacturer.

http://cgi.ebay.ca/YAMAHA-RAPTOR-660-686CC-BIG-BORE-CYLINDER-PISTON-KIT-NE-/280557892402?pt=Motors_ATV_Parts_Accessories&hash=item41528db332

thanks
As long as your sleeve is in OK shape, No crack's & what not you can have it board to 102mm, 686. Then you can bye a piston of your choise .I went with Wiseco but thair are a bunch out thair.
Good luck, Chris..
 

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I'm a little slow on the uptake today so I probably missed it, where was the 11:1 statement? I didn't see anything that stated it was an 11:1 piston, and if those pictures are the actual product I doubt it's more than stock 9.2:1 compression. The description reads forged piston, but that looks cast to me like the stocker.

Honestly that kit looks OEM....VERY OEM. Though I don't know of any 660 derived motor with a 686cc displacement that would be cast into the cylinder like that.

I guess I don't know about the quality. The nearly 4k positive reviews of the ebay member and the 99.7% positive rating is difficult to cast too much doubt on though.
 

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i was under the assumption it was a stock compression piston aswell so i emailed the vendor the question and he responded that it was a 11:1 compression. is there a way to tell by looking at the piston? if you look closley at the cylinder it says 686 cast in the side. i think this guy makes the cylinders and the pistons. thats why im curious about the quality and reliability. the price is to attractive to go any other route for a 686 kit.
 

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It's possible that the seller is using a stock photo. The price isn't that bad for a complete kit however, I would like to know who's parts are included (i.e. Wiseco, JE, CP) as well as the bore and hone. Send another message to the seller asking them to provide the brand piston and part number and ask if the cylinder was finish honed with that matching piston ready to install. If they do not provide a recognizable brand piston and did not finish hone the cylinder to your piston then take your time and shop around or have a local reputable machine shop bore and hone your cylinder to the piston of your choice.
 

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It looks like a stock cast piston to me, I agree with the previous poster, the cylinder should be sized to the piston to specs of .002 to .003'' for clearance.............
 

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Discussion Starter #7
i emailed the vendor and here is the response "These are aftermarket NYC pistons with machined HSUN cylinder. Parts are plug and play, piston is 100% aligned with cylinder, and cylinder is bored and honed."
never herd of the piston manufacturer, but i think HSUN makes those cheap atvs and dirtbikes.
 

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sounds uninformed a tid bit. seems uninformed even more due to the lack of information on the description on that listing. ask if its the actual pic or not. if so, maybe 102mm, stock compression maybe? ???
id stick to products from reputable manufacturers, just my opinion though.
 

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if your on a budget go with an 11:1 wiseco, and just get your stock sleeve bored out. If you find the right deal, this can be done under 200, but usually will run ya 250 or less once said and done
 

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if your on a budget go with an 11:1 wiseco, and just get your stock sleeve bored out. If you find the right deal, this can be done under 200, but usually will run ya 250 or less once said and done
+1

Mic your cylinder (or have you machine shop do it) and determine which size piston you need. If the cylinder is in good shape maybe a good hone and a good 100mm piston will save you the over-bore charges. Otherwise, find a good deal on a Wiseco, JE or CP piston at 101mm or 102mm, buy it, take it to the shop and have the cylinder prepped for the piston you purchased. This way you have the luxury of stepping up to 11:1 compression like dyce said.
 

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Discussion Starter #11
when my rod snapped it destroyed the bottom of the cylinder liner, so to go with the wiseco piston, i would need a sleeve and bore and sleeve install, that would run almost twice the price. this guy on ebay has sold hundreds of these, i think i might give it a try and report back on quality and post up some pics of what i got. i cant see anything being wrong with the cylinder, the piston might just be crap, if so nothing ventured nothing gained. who knows this kit might be a diamond in the rough.
 

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Discussion Starter #12
the kit came in, looking for opinions on the compression ratio emailed twice asking the manufacturer and got two different answers 10:1 and 11:1?
based on the pics what do you think the compression is?
 

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You can look at my build thread to see what I got, I took some pic's like you did. It's Banshee2Raptors 1st 4 stroke build, under 660 modification's. I have a 11:1 102mm Wiseco piston & what not..
Best of luck to ya, Chris...
 

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Stock piston is dished. This one is flat, so I say 10:1. But, this piston is cast, not forged. It looks like a Chinese clone piston to me. I would not run that. Collateral damage can be very expensive. Send it back if you can.
 

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the kit came in, looking for opinions on the compression ratio emailed twice asking the manufacturer and got two different answers 10:1 and 11:1?
based on the pics what do you think the compression is?
It's not an 11:1 piston, 11:1 pistons have more done and valve relief. It does look like a cast Made-in-China knock-off. As you said in a previous post:

"nothing ventured nothing gained. who knows this kit might be a diamond in the rough."
 

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You can buy a 102mm CP 12:1 for $183. Have it fitted to your cyl for $80, and $50 for gaskets. Then you are way ahead. The chinese parts are not worth the risk of the hole in the cases. IMO.

One more thing....It looks like the oiling holes on the oil ring groove do not go all the way around the piston. Thats a problem!
 

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i was under the assumption it was a stock compression piston aswell so i emailed the vendor the question and he responded that it was a 11:1 compression. is there a way to tell by looking at the piston? if you look closley at the cylinder it says 686 cast in the side. i think this guy makes the cylinders and the pistons. thats why im curious about the quality and reliability. the price is to attractive to go any other route for a 686 kit.
Hey Adam sorry to jump in your conv here, I also sent some emails to the retailer from Ebay and they stated it was a 10:1 piston or 11:1 and it is 102mm but I was sketchy about the quality of the piston, I've heard of people buying the kit but using other pistons,so I'm going to go the route as well,I saw on one of your other post that the cylinder has a 700 sleeve,I was looking at L.A. Sleeves website but maybe I won't have to after all,what's a good Stator and CDI?

Sent from my SM-N950U1 using Tapatalk
 
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