Auto decompression on a 426

9 replies to this topic
  • Jeff_Magnusson

Posted November 08, 2002 - 12:29 PM


Does anyone know if the 250f cam is similar to the 426f exhaust cam. I have checked on Yamaha of Troys website and the two models I could look at showed almost an identical part number between the two bikes. The only difference was in the first three numbers which looked like they were changed only because of the year. If the 250f cams are the same it would be a cake walk to install auto decompression onto a 426 using a 03' 250f cam. I did not believe that the 450f and 426f cams would be the same since it appears they have changed the head significantly. Any Ideas?


Posted November 09, 2002 - 10:27 AM


Aftermarket cam makers could copy the yamaha decompression design, pay the royalties and sell thousands of 'em for the 400 thru 426 mounts.
C'mon american aftermarket people, MAKE OUR DAY!

  • yamaha.dude

Posted November 09, 2002 - 11:46 AM


I'm trying to figure this one out myself... a dealer who frequents this board is getting a 03 450 cam to see if it is possible with that one, or if the 250 cam is the way to go... at the moment, the best chance seems to be the 250 cam... If I find anymore out, I will let everyone know... (once I get my cam ordered!) There has been talk of Yamaha stopping ordering of existing 03 250 cam parts... check out the 250F forums for more details...


  • Jekel

Posted November 09, 2002 - 01:06 PM


PLEASE let someone figure this out. I have a 400 itching for the mod :)

  • cjh426

Posted November 09, 2002 - 02:49 PM


god speed to any one looking for the right answers, I need that cam!!!!!!!!!!!!!! :)

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  • Sylvain

Posted November 11, 2002 - 08:54 AM


You got my attention !!!
An auto decompression would be fine, Keep us inform , please :)

  • sabin

Posted November 11, 2002 - 12:13 PM


REAL MAN don't need autodeco, nor electric start ... you pu$i$ :)

Just kiding! :D

I wander how come no one said this yet ???

Another thing is that you cannot broke what you do not have (gee my english sucks) I love my xr for not having radiators!

  • blue_beast_wins

Posted November 11, 2002 - 12:26 PM


Hey sabin, maybe these guys should just waight untill there bike has done 140,000ks, there compression will be starting to get a bit low by then and they wont have to worry about changing camshafts. :) :D

  • sabin

Posted November 11, 2002 - 09:54 PM


Did you just pic 140000km or you have some real data?

My bike is about 10 000 and I have to adjust valves, I was wandering if I also change rings, as my engine is out of the frame for winter inspection.

  • blue_beast_wins

Posted November 11, 2002 - 10:28 PM


Just picked it, if your bike isn't using oil or blowing smoke i wouldn't worry about the rings. i have learnt of a 426 that has done 18,000ks motor untouched.


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