big bore question

1

144viper

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Oct 9, 2009
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saskatoon
hey guys just traded my stock top end 4 a mystery big bore kit so i am trying to figer out what i got. these are the numbers on top of the piston 4896j 9865m 73.00mm piston also has a rectangular port on the intake side dont know if that will help or not. also got a set of pipes. where the pipes meets the flange it is rectangular and and the pipe slides into this flange ,this flange is dubble walled the pipe slides in between the walls. each pipe has its own stinger. i can post pics if need b. thanks guys http://i874.photobucket.com/albums/ab310/jonny0_00/viper013.jpg http://i874.photobucket.com/albums/ab310/jonny0_00/viper011.jpg http://i874.photobucket.com/albums/ab310/jonny0_00/viper010.jpg http://i874.photobucket.com/albums/ab310/jonny0_00/viper006.jpg http://i874.photobucket.com/albums/ab310/jonny0_00/viper003.jpg
 
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from the pics of the 780 kit i have seen its way diffrent. the port on the front is way more square and there are 6 smaller holes around it. but still no idea as to what it is
 
you've got a cpr 780 w/cpr tripple pipes. those little holes you speak of, are probably on the exhaust side of the piston. jeff simons likes to do that, to try and lube the exhaust side of the piston a little more. looking at the piston wash on the good piston, i can see that she is lean. no wash at all. the one on the right, is now a good paper weight......lol.
 
i figgered the pipes were his but the pistons being a 73 mm through me off there r no holes anywhere on the pistons and the port in front is a diffrent shape. but if it is a 780 kit it should be easy to find a jug and piston
 
The pistons I think are from Pat Hauck. He had a run of pistons that had that heavy thick ring similar to the photo and had that rectangular hole. I don't recall the part number. Hope the cylinders are good. I have a stock Yamaha head re-chambered by J. Simons to 780 if you need one. Post a pic of the underside of that piston and the opposite side and I tell for sure. I have run a couple of sets of the pistons with J simons small oil holes and a couple set without. I saw no difference with respect to better oil retention.
 
Here is a pic of J. Simons oil retention holes. Also P. Haucks thick ringed Wiseco with the rectangular port.
 

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That is definitely a Pat Hauck piston. It is very heavy making the engine take longer to reach max RPM. Also that thick ring creates more drag. I originally though the piston would hold up better due to thicker heavier construction and would last longer but now after trial and error believe the other Wiseco piston is a better choice. You should consider venting to atmosphere not airbox. Make sure you spend the time to ensure jetting is correct. These motors will not tolerate leaner jetting. Use synthetic oil. Go just shy of - full pull on the oil adjustment. Good luck and enjoy. 165 HP is alot of fun.
 
k well i need one piston so maybe i should just buy three i also need a jug or need to send mine away. so they r haucks pistons is simmons big bore? i also read on another post that a bear cat piston is the same is this right? any advise is appreciated thanks
 
i have for sale, 3 viper cylinders, that were bored out to be for a 780 (72.9mm) bore. they will need to be plated and ported yet. interested?
 
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