yz426 yz450 cam upgrade

[dave58]

what are your opinions on cam upgrades? i have a 2001 yz426 with 13.5 piston everything else stock. are the stage 1 hot cams worth the money? i am told to use yz450 cams will they work ? what seems to be the best choice for cams? what about the auto decompression cams how do they work,this thihg kicks over like i'm trying to start a bulldozer !! i just bought this motor have only ridden it just to make sure its all there , so i can tear it down for rebuild, want to start out fresh. i will be running this quad local district mx racing . any advice greatly appreciated.....

[xrxmxcx]

for the performance gain, and the overall gain of no more decomp lever, id reccomend getting the hotcams, i made that decision and ill never regret it!

[dietz]

i second that, hotcams autodecomp all the way. my friend still never can get his started wen its hot or even wen its cool. im puting a yz450 motor in my ex instead of the 426 because of trying to start his, i have yet to do it lol.

[dave58]

so whats the difference then between the decomp lever and the auto decomp cam? if i use the decomp lever it kicks real easy but will not start at all...

[ss440ex]

By holding the lever in....you are holding a exhaust valve open.

[dave58]

i understand how it all works , i am trying to figure out if there is a difference with the cable system and the auto system. if i hold the lever in and kick it over it kicks very easy but i can not get it to start at all. if i hold the lever in to get it to top dead let it go then kick it it kicks like a mule but after 3-4 kicks it starts. i am about 230lbs and can hardly kick this thing over. should it start on full decomp or am i doing something wrong? also would valve adjustment have anything to do with this starting problem? i have not checked them yet just wondering...

[dave58]

whats the difference in th 426 cams and the 450 cams. are either any better performance wise, or is it just the auto decomp feature. i have seen both 426 & 450 hot cams both with auto decomp .

[xrxmxcx]

450 cams have autodecomp always, stock or aftermarket

426 stock cams dont have it, so you can do the 450 mod, or just save urself the hassle and get the 426 hotcam..

remember you dont need both the cams, its just that performance is best with both the intake and exhaust, so you could get just the 426 exhaust hotcam and you wouldnt have to worry about starting troubles again...


also remember if your going autodecomp order a billet decomp plug from k&k or any other company, 8 bucks isnt much....

[dave58]

so how will it kick over with the auto decomp cam?

[xrxmxcx]

it will kick over like it normally does, except it wont get that feeling of it freezing up (which is really since there is so much compression thats not realesed that it cant go any farther)

in the end it will kick over continueosly, and you will no longer need the lever or any of that junk

[matt250r21]

For detailed info on the 426 auto decomp cam mod go to Thumper Talk fourm YZ450 YZ426. They have like 100 pages on this subject. I have a similar 426 motor setup as you, high comp piston but I have the YZ450 auto decomp cam mod, mine starts pretty easy once you know the trick. Sounds like your valves need adjusting or your carb tuned.

[dave58]

thanks for the info