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Workshop => Engine and Bottom End => Topic started by: ytman on July 20, 2013, 02:35:03 PM

Title: How big?
Post by: ytman on July 20, 2013, 02:35:03 PM

ok...many of you have experience with big bore motors. How big is too big for a super reliable engine? Obviously a vibration free 4 sumthingsumpthing would be awesome. I raced a Pro cross 310 in the Nevada 2000, changing a piston and rings at 1000 miles. Believe it or not, top end was not as important as torque and mid range. How much bigger could you reliably go? Would you go with a Puma or a Sphynx? A powervalve? Just curious .

Title: How big?
Post by: Pumashine on July 20, 2013, 02:42:48 PM

When your piston goes bigger than 80mm, the  crank balancing becomes necessary. But after the crank is balanced correctly I have not ever had a problem with the reliability of the Puma motor. I know I have 5 years and at least 100 hours on my 431  Puma. So the question comes down to how much you want to spend. Much more economical to go with a Sphinx than a Puma. You will save at least $500 not having to balance the crank.

Title: How big?
Post by: ytman on July 20, 2013, 03:07:59 PM

Is there a different size range for each of those cylinders?

Title: How big?
Post by: ytman on July 20, 2013, 03:16:42 PM

Ohhhh . I just found the cp industries site.

Title: How big?
Post by: Pumashine on July 20, 2013, 03:59:08 PM

Quote from: ytman;4795

Ohhhh . I just found the cp industries site.

Yes but those sizes are not what they usually bore them at. The Saber comes in at 95mm, the Puma at 85mm, and the Sphinx's come in at 78mm. Other sizes may be requested but are not always available whith in a reasonable amount of time.