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Discussion Starter · #1 ·
hey peter talked to you before about a 70mm stroker. have you experienced using different pistons. it has ho rods in it but don't want to use the l-groove rings. mickey from 8x-treme mentioned running arctic cat 650 wildcat pistons. the pins are the same size, just curious on the distance between the pin and top of piston. thanks, brian
 

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I have a wiseco 2349PS 900 triple cat piston here that came out of a 990RLE Doo stroker. 76.5mm bore, 1.280" pin centerline to deck edge, 2.930" overall length and a 20mm pin. Hope that helps. I thought I had a 650 wildcat piston here but can't find it yet. If I do I'll post those dimensions too.
Tom
 

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Discussion Starter · #3 ·
I have a wiseco 2349PS 900 triple cat piston here that came out of a 990RLE Doo stroker. 76.5mm bore, 1.280" pin centerline to deck edge, 2.930" overall length and a 20mm pin. Hope that helps. I thought I had a 650 wildcat piston here but can't find it yet. If I do I'll post those dimensions too.
Tom
thanks tom. one of my worries is the window for the piston pin. if it's cut out to much toward the exhaust side of the piston it will short circuit itself with the wing of the exhaust port. it's a 1000 ps motor.
 

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In the case of the Wiseco 900 cat triple piston it is completely closed in on the exhaust side of the pin, so that isn't an issue. I have a wildcat piston here some where but can't put my hands on it right now, so I don't know about that one.
Tom
 

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I had some thoughts on some other pistons you might want to look at. With the 70mm stroke, max bore would be 78.5mm . 98/99 Cat Powder Special 600 2391MO7850, 2000 MXZ700 2416MO7850, and the 93 to 99 670 non HO 2379MO7850. I don't know if any of those would fit the bill but they are all 20mm pin and 78.5mm bore.
Tom
 

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Discussion Starter · #6 ·
I had some thoughts on some other pistons you might want to look at. With the 70mm stroke, max bore would be 78.5mm . 98/99 Cat Powder Special 600 2391MO7850, 2000 MXZ700 2416MO7850, and the 93 to 99 670 non HO 2379MO7850. I don't know if any of those would fit the bill but they are all 20mm pin and 78.5mm bore.
Tom
thanks tom. if you can place that wildcat piston that would be great. i have a mxz 700 piston which would work. not sure about the one ring though. it has a flatter piston top then the 670 piston. the problem with the 670 is the notch where they cut the pin in short circuits and i'm not a fan of the l groove. i'll have to look at the other cat piston.
 

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Does the Wiseco version of the 670 non HO piston have that cutout? For some reason I was thinking that one was filled in. I would be interested in hearing some opinions on the flat top versus domed top.
Tom
 

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Discussion Starter · #8 ·
Does the Wiseco version of the 670 non HO piston have that cutout? For some reason I was thinking that one was filled in. I would be interested in hearing some opinions on the flat top versus domed top.
Tom
yeah, i'm not sure of the flat top also. i'm not a car motor gearhead but isn't that what most high hp guys run in cars is a flat top piston? the difference between the ho and non ho is the same, the ho has a flatter piston top.
 

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You bet. The HO had a completely different head more like the 700/800 and of course that flat top to go with it. As for the automotive stuff, the idea is to not have anything in the path of the flame front like a big dome. Our 2 stroke domes are basically nothing so I would think it would have little effect in that way. I do wonder about transfer flow. Not sure what it would do to it +/- but it may be effected. I built an 1107 cat with flattops, but haven't dynoed it yet. Even then I won't be swapping pistons and domes back and forth, so it won't really tell a guy anything anyway.
 

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Brian. Not really sure why the stock 670 piston would short circuit. The Wiseco version used to have L rings but I think they are no longer available. 700 Ski-doo pistons will work as will 670 HO pistons but the dome will have to be re-worked and yes a flat top is a better piston to work with. Not sure about the Cat pistons.
 

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Discussion Starter · #11 ·
Brian. Not really sure why the stock 670 piston would short circuit. The Wiseco version used to have L rings but I think they are no longer available. 700 Ski-doo pistons will work as will 670 HO pistons but the dome will have to be re-worked and yes a flat top is a better piston to work with. Not sure about the Cat pistons.
peter wiseco still offers the piston in the L-groove. the problem with the piston is when they make it they put a window where the piston pin goes in. if you mark the window and put it in the cylinder the window is in the wing of the exhaust port prob 1 mm. the 700 piston just has the circle where the pin goes in so no problem with the short circuit. was mentioned about the cat piston but i see it is 68mm long to the 700 73mm. then i would worry about the bottom of the exhaust port showing when the piston is all the way up. thanks for the info guys.
 

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I was wondering how much opening it would take to really make a noticable difference. .040" isn't that big of an opening and I wonder how much pressure differencial there really is at the point in time that the cross talk is happening. Add to that, the extremely limited time there is at RPM. Not saying there aren't gains to be had by eliminating the cross talk, but how big of an opening would there have to be to show power loss.
 
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