426 decomp: Hot Cam or 450 Cam ????


37 replies to this topic
  • grayracer513

Posted June 30, 2005 - 04:40 PM

#21

Lots of people have used the 450 OEM cam in the 426, and NONE have reported having any chain related problems with it. Zero.

You might have to reshim, or not, but not very much.

  • 426ing-in-MD

Posted June 30, 2005 - 05:27 PM

#22

My advice is to fix the starting issue, then, decide on the CAMS.

When I bought both 2002s, a WR426 and a YZ250F, they both were hard starters. This was one of the reasons they were being sold. Bottom-line, jetting was the issue. The YZ250F was especially a problem for my son.

I have both bikes starting on first kick every time now. We are very happy with these bikes and neither of us see a big need to go to the decomp cam.

Here are some tips:

1. change the spark plug right away. You must eliminate the spark plug as an issue. Partially fouled plugs can cause hard starting. After jetting correctly, a plug should last a long, long time.
2. When ice cold, the bike should require the choke to start the first time. It should sound good for about 30 seconds, then start sounding like it is "double stroking", After 30 seconds, when you put the choke in, it should sound perfect and the idle should decrease.
3. When hot and riding hard, on a stall, you should start with the hot start.
4. When hot and riding hard, after a 10 or 15 min. break, you should start with no hot start.
5. When cruising at high speed, low throttle, if you turn off the bike, it should start again right away with no hot start.
5. When you dump or crash the bike, if it does not start after a few kicks, it is flooded. Turn the gas off. Hold the decomp lever all the way down and cycle through the kick starter around 10 times. FLOOR the throttle while doing this. Turn the gas back on, kick one time (without touching the throttle) and it will start.

If you dial in the pilot circuit, this will work everytime.

6. NOTE: When the bike is ice cold, if it starts fine and idles fine WITHOUT the choke, then the pilot jet is too rich. When ice cold, without the choke, it should kick over then die. It should not hold idle.

Most likely, since, it is hot out, you are rich. Buy one size smaller pilot jet and test. If that does not fix it, but, things get better, then go down 2 sizes on the PJ. Proper jetting is the difference between an enjoyable bike and a nonenjoyable bike. It makes a world of difference. :)


that seems to be a alot of good info, thanks

  • FZ1426

Posted June 30, 2005 - 05:40 PM

#23

Lots of people have used the 450 OEM cam in the 426, and NONE have reported having any chain related problems with it. Zero.

You might have to reshim, or not, but not very much.

Thanks,
Has anybody ever measured and/or posted the actual sprocket pitch? One of the guys at Beach Yamaha said a Yami engineer emphatically insisted the pitch was different.

  • grayracer513

Posted July 01, 2005 - 07:24 AM

#24

The pitch is different, but I have never seen the specifics. It obviously isn't very different, though, or something bad would have developed in at least one of the many 426's using this cam by now.

  • Sylvain

Posted July 01, 2005 - 11:22 AM

#25

Hello Thumpsters,
[COLOR=Red]So my question is does the decomp cam make life just like a 2-stroke ??

Do you have to push the piston to a certain point or can you just get on and kick ??

Is it still very hard to kick thru??

And which is a better route to take a HotCam or a YZ450 Cam ???[/COLOR]

I appreciate any tips!!
:D


I made the mod with a 450 yz 2003 autodecomp cam this spring and I can say " I should of done it before". I wouldn't say it starts like a two stroke, but it's light years ahead of what it was.

I don't have to place the piston. It starts on 1 or 2 kicks most of the time when cold. I use a Dr. D. hot start when hot or after a spill. So it's a get on and kick affair.

It's easier to kick but it's a follow through motion, not just a jolt kick.

I believe you will be pleased any of the two cams. The power curve of the 450 is a bit different from the 426, more progressive as some people would say.

There is a lot of infos available to make the mod. Just take care of not :: dropping the half moon clip of the cam covers in the engine :D . Otherwise :) :)

  • FZ1426

Posted July 01, 2005 - 12:32 PM

#26

The pitch is different, but I have never seen the specifics. It obviously isn't very different, though, or something bad would have developed in at least one of the many 426's using this cam by now.

Well...if it's different, at best it's going to wear the chain and then the other two gears, eventually altering the cam timing slightly. It may run forever that way, but I can't see deliberately installing a known non compatable part in a motor to save $100. Hotcams it is then.

  • 426ing-in-MD

Posted July 01, 2005 - 12:35 PM

#27

thanks !!

  • grayracer513

Posted July 01, 2005 - 04:16 PM

#28

... I can't see deliberately installing a known non compatable part in a motor to save $100.

In principal, I would agree, but it's been in use long enough to now be a known compatible part.

  • Satch0922

Posted July 02, 2005 - 07:37 AM

#29

Well...if it's different, at best it's going to wear the chain and then the other two gears, eventually altering the cam timing slightly. It may run forever that way, but I can't see deliberately installing a known non compatable part in a motor to save $100. Hotcams it is then.



we are still talking about this? :) I suppose the 900+ posts to the "450 cam mod" thread where all for not! :)

Go with whatever you feel comfortable with. I get no commision on either part! LOL However....the OE cam is compatible and it will last longer than you will have the bike. People act like they want something that will last forever and then end up only keeping the bike a few years and MAYBE ride once a month. There are guys on here who did the cam mod in early 2003 and raced ever weekend with NO reported failures or abnormal wear. My 426 had almost 2 years of weekend abuse on it with the cam mod. No abnormal wear, no failure, just lots of fun.

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  • grayracer513

Posted July 02, 2005 - 04:46 PM

#30

I thought you'd never show up, Satch. :)

  • Thrash1

Posted July 02, 2005 - 08:46 PM

#31

Intersesting.. I'm going to have to do some more research on this....


Thanks for the Post/Info Guys :)

  • Satch0922

Posted July 03, 2005 - 04:04 AM

#32

Intersesting.. I'm going to have to do some more research on this....


Thanks for the Post/Info Guys :)


Here is all the research you need to do....just keep in mind that the thread started in November....OF 2002 !!!!! Read the entire thread and you will see that the mod is easy, cheap and safe.

http://www.thumperta...ead.php?t=60381

  • FZ1426

Posted July 03, 2005 - 05:12 PM

#33

In principal, I would agree, but it's been in use long enough to now be a known compatible part.

Principal it is then! Is it correct to say that a Hotcam does not provide the same "sweet" power difference that the OEM cam does?

  • Thrash1

Posted July 03, 2005 - 05:23 PM

#34

Well I spent most of the morning reading the thread 96pages :) So I decided to go riding.

Some of the links in the thread are bad. Does anyone have the YZ450 Exhaust Cam Installation *.pdf on an FTP site?

TT Store has the YZ450 Exhaust cams with Auto Decomp for less than $100 bucks :) I'm going to have to do this mod this winter when I do the valve clearance checks.

Hot Cams........$189.00

  • grayracer513

Posted July 03, 2005 - 05:50 PM

#35

If you have Acrobat Reader, you don't need an FTP site. Open the PDF in its current location, and choose Save a copy from the file menu in the Adobe Reader menu (not the browser menu)

  • Satch0922

Posted July 04, 2005 - 03:51 AM

#36

Here ya go !


Posted Image

Posted Image

  • ca412686

Posted July 04, 2005 - 06:21 PM

#37

Just a quick question. I just bought a Hotcams Intake cam, can I use the 450 exhaust with the hotcams intake??? Also, would this be a safe setup for Supermotard on a high speed (high rpm) track?? Thanks for the help guys

  • Satch0922

Posted July 04, 2005 - 07:19 PM

#38

I have no idea.....





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