Anyone got bigbore WR or thought of getting one?


11 replies to this topic
  • Assassin

Posted June 30, 2006 - 06:09 AM

#1

I've noticed that most people do free mods and that's it.
I was wondering if anyone got a big bore, possibally the Athena kit and can tell me what they are like?

I would like more power, the cheapest way is bigbore. I already got a race pipe on my bike, that helped lots, but more would be nice. :ride:

  • 04450wrF

Posted June 30, 2006 - 06:15 AM

#2

you can get some good big bore information on this site
http://www.powroll.c...A_YZFWR426F.htm

  • Assassin

Posted June 30, 2006 - 06:18 AM

#3

got anything bigger?

  • bluebike1999

Posted June 30, 2006 - 06:33 AM

#4

how far can they go? i have heard of a 490 kit, but who needs that much power anyway?

  • Drunken Monkey

Posted June 30, 2006 - 06:41 AM

#5

how far can they go? i have heard of a 490 kit, but who needs that much power anyway?

I have seen new 500cc kits from vertex. Sounds like fun.

  • Luke Taylor

Posted June 30, 2006 - 02:56 PM

#6

I have installed and rode a few bikes with the athena kits and they are worth it. They are 98mm that makes them a 480, and they rip with no reliability issues. A pipe only makes them work better.

link to athena kits

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  • Birdy426

Posted June 30, 2006 - 05:28 PM

#7

Dollar for dollar, you get the most bang for the buck by getting your jetting right. Once you've done that, you get the most bang for the buck with cams. About 1/2 the cost of the big bore kit, with just as big (or bigger) performance increase. With that said, I went big bore on top of cams and love it! 426 to 444, baby!

  • BIGchiefKODIAK

Posted June 30, 2006 - 05:28 PM

#8

Yes I am actually thinking of getting one soon if i do I will post.

  • Assassin

Posted June 30, 2006 - 06:56 PM

#9

Dollar for dollar, you get the most bang for the buck by getting your jetting right. Once you've done that, you get the most bang for the buck with cams. About 1/2 the cost of the big bore kit, with just as big (or bigger) performance increase. With that said, I went big bore on top of cams and love it! 426 to 444, baby!

I was thinking about YZ cam and ported head. Bigbore makes more power for about the same money. Both would be awesome.
Jetting is easy. As I said before, already got pipe, NEED MORE POWER :ride:

  • Birdy426

Posted June 30, 2006 - 08:02 PM

#10

I was thinking about YZ cam and ported head. Bigbore makes more power for about the same money. Both would be awesome.
Jetting is easy. As I said before, already got pipe, NEED MORE POWER :ride:


As far as porting is concerned, be very specific with the guy with the grinder. Tell em EXACTLY where you want the power, and what cam grind you will be running. It's real easy to dork up a perfectly good powerband with a porting tool!

  • Assassin

Posted June 30, 2006 - 11:20 PM

#11

As far as porting is concerned, be very specific with the guy with the grinder. Tell em EXACTLY where you want the power, and what cam grind you will be running. It's real easy to dork up a perfectly good powerband with a porting tool!

thanks! I think they really only clean up the casting a bit with a bit of blending.

I would do it my self with a dremel, but I don't have a flow bench!

  • Birdy426

Posted July 01, 2006 - 07:50 AM

#12

thanks! I think they really only clean up the casting a bit with a bit of blending.

I would do it my self with a dremel, but I don't have a flow bench!


If that's really all you're doing, you're not going to see a big power per dollar return. Most of the Yamaha heads (at least the ones that I've seen on my 426, my son's 250, and several riding buddies 400's and 450's) are pretty clean to begin with. To clean and match, you don't really need a flow bench as you are not changing the ports flow characteristics. Just be careful that you don't change the cross section of the ports and you should be OK. Blend the little bit of casting flash and mold runner lines, sharpen up the dividers at the ports to almost zero radius, polish to a mirror finish on both intakes and exhausts, then grit blast the intake sides and you should be good to go. A few cautions: Disassemble the head completely before you start (don't try doing it with the valves installed!), be careful not to nick the valve guides as you grind, and as long as you have everything apart, inspect it all really well, particularly the valve faces, and throw on some new valve seals.

If you have a compressor, a micro die grinder

http://www.harborfre...temnumber=47869

will work lots better than a dremel. They are a little smaller, better balanced, and don't have the rotating inertia that a dremel, or other electric die grinder (like a DoMore) has.




 
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