wr 400 and 2 different wiseco pistons??

7 replies to this topic
  • thriller

Posted November 17, 2004 - 07:57 AM


I was just looking in the dennis kirk catalog and see there is 2 different pistons you can get for the wr 400 from wiseco. There was a 12.5 to 1 and a 13.5 to 1 compression ratio. Anybody have anything to say about them - good or bad. What is the stock yamaha piston at? :cry:

  • mousemeat

Posted November 17, 2004 - 08:14 AM


Stock is 12.5. If you go for the 13.5 one you will need to be careful about what fuel you use. Ask in the YZ forum as well, as there are a few guys there with 13.5 pistons. Unless you are racing or are a total animal stick with the 12.5

  • thriller

Posted November 17, 2004 - 11:25 AM


thanks I will ask over in the other side. :cry:

  • Oasis_Flame

Posted November 17, 2004 - 12:28 PM


I run a 13 to 1 piston in my WR. I now have 2000 miles on this piston and it makes very good power useing pump gas with no problems. No pinging and starts very easy. :cry:

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  • Jethrro

Posted November 17, 2004 - 05:43 PM


I think the 13.5:1 is the canadian model.

  • Gadsen

Posted November 17, 2004 - 06:46 PM


The 12.5 to one is your stock replacement, the 13.5 to one is custom, will produce more energy (power), but fuel is critical. You'd have to go to a fuel distributor and buy it by the 5 gallon jug and its pretty spendy and not always conveneint. I'd stick with 12.5:1 IMHO

  • thriller

Posted November 18, 2004 - 05:53 AM


I do ride at 3500 to 6500 ft. does that make a difference? Also what kind of fuel do you need with the 13.5? 91+ octane?

  • Oasis_Flame

Posted November 18, 2004 - 11:05 AM


3800ft. to 7500ft., pump gas, 13-1 piston. No problems just change main jet and go. :cry:


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