YZ cams


51 replies to this topic
  • KennyMc

Posted May 12, 2013 - 12:33 PM

#21

Ok, so here are some pictures of the stock cam and it's decomp pin and the Hotcam and it's decomp pin:

Stock cam on the left, Hotcams on the right. The Hotcam pin measures .5mm shorter than the stock cam pin. I will be sending this back to hotcams for them to look at to determine if they installed the wrong decomp pin or...

Attached Thumbnails

  • IMG_0014.jpg

Edited by kenshaw720, May 12, 2013 - 02:22 PM.


  • KennyMc

Posted May 12, 2013 - 12:35 PM

#22

duplicate

Edited by kenshaw720, May 12, 2013 - 12:41 PM.


  • gcally

Posted May 14, 2013 - 07:15 AM

#23

Educate me on these cams.

Why are you guys using the Hot Cams instead of the OEM YZ cams?

Cost? Better performance?

Edited by gcally, May 14, 2013 - 07:16 AM.


  • Krannie McKranface

Posted May 14, 2013 - 07:43 AM

#24

Educate me on these cams.

Why are you guys using the Hot Cams instead of the OEM YZ cams?

Cost? Better performance?


The YZ cam has to be modified to make the decomp work correctly.
Until about a week ago, I did not have confidence that this was a reliable mod. Now I do.
The HotCams YZ spec cam for the WR has been getting great reviews, better than the single exhaust cam from the YZ.
Unfortunately, HotCams is a big-ass company with lots of employees, and they have been making lots of mistake on the quality control.
That is the issue to date.

  • beezer

Posted May 14, 2013 - 08:08 AM

#25

How do you modify the YZ cam so the e-start works?

I have Hot Cams sitting on my shelf but my bike runs so good now with the YZ exhuast cam I don't want to mess with it.

The only problem I have is the bike doesn't like to start with the e-start.

  • Krannie McKranface

Posted May 14, 2013 - 08:14 AM

#26

How do you modify the YZ cam so the e-start works?

I have Hot Cams sitting on my shelf but my bike runs so good now with the YZ exhuast cam I don't want to mess with it.

The only problem I have is the bike doesn't like to start with the e-start.


The YZ exhaust cam decomp pin must be ground down to match the height of the stock WR decomp pin.
That's it.
About 1mm.

  • RipGroove99

Posted May 14, 2013 - 08:17 AM

#27

I put a yz cam straight in mine with no mods, starts and runs fine (2003). No e-start though as that was taken off before hand.

Edited by RipGroove99, May 14, 2013 - 08:19 AM.


  • Krannie McKranface

Posted May 14, 2013 - 08:18 AM

#28

I put a yz cam straight in mine with no mods, starts and runs fine (2003).


2005 it changed. Changed again in 2007. Changed again in 2012

  • RipGroove99

Posted May 14, 2013 - 08:21 AM

#29

2005 it changed. Changed again in 2007. Changed again in 2012


That'll be it then.

  • beezer

Posted May 14, 2013 - 08:27 AM

#30

The YZ exhaust cam decomp pin must be ground down to match the height of the stock WR decomp pin.
That's it.
About 1mm.


Thanks!

Picture of my Hotcam.

http://Posted Image

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  • KennyMc

Posted May 14, 2013 - 09:20 AM

#31

Damn you guys, getting to learn off of our trials and tribulations.... :lol: :thumbsup: There is also a lot of prior stuff too that we both have been reading so props to them as well :ride:

  • Krannie McKranface

Posted May 14, 2013 - 09:28 AM

#32

Thanks!

Picture of my Hotcam.

http://Posted Image


That pin looks correct.

  • Krannie McKranface

Posted May 14, 2013 - 09:33 AM

#33

Here's a pic Ken took of stock and *defective* hot cams. See the pin difference?

Posted Image

  • KennyMc

Posted May 14, 2013 - 12:55 PM

#34

Here's a pic Ken took of stock and *defective* hot cams. See the pin difference?

Posted Image


Where's the picture of your Hotcam??? :devil:

  • Krannie McKranface

Posted May 14, 2013 - 12:56 PM

#35

Where's the picture of your Hotcam??? :devil:


Mine is officially now a 'ColdCam'.

It's in the mail.

  • KennyMc

Posted May 14, 2013 - 01:34 PM

#36

Mine is officially now a 'ColdCam'.

It's in the mail.

WHAT?!!!!! No pics, why you no good, $(@:, $@-&:"$, :&-:!;@\^#^%,¥\. }*>-)¥~

Mines on the way back. Should be in the hands of my engine builder on Thusday. Their engineer examined it and compared it to my picture I provided of the stock one and agreed their pin was not tall enough. That was rectified by putting in a taller pin which is almost equal to stock but should be just a bit shorter.

  • grayracer513

Posted May 14, 2013 - 01:35 PM

#37

The length of the pin, all by itself, is not the issue until it gets too short to even raise the lifter at all. What it really comes down to is a matter of timing. I had occasion to degree the cam on a YZ450 recently, and after determining that it was where it was supposed to be, I checked the point at which the decomp pin re-seats the valve, for my own curiosity. The valve was reseated at 27º BTDC.

The way the decompression system works is simple enough; a flyweight rotates shaft that extends a pin that raises the left exhaust valve off the seat before the start of the compression stroke and seats it before the end of the stroke, which shortens the compression event and lowers the cranking compression to a reasonable level. The pin extends through a bore in the camshaft perpendicular to its axis. The '03-'05 YZ450 exhaust cam shaft is identical to that of the '03-'05 WR450. The only difference is the position of the sprocket, which changes the timing of the cam, with the WR being more advanced by about 19-21º. If the same decomp pin were used in the WR, the exhaust valve would then be reseated at around 47º BTDC instead of 27 or so, and you'd have too much compression to crank.

There are two ways in which this could have been fixed: Yamaha could either have made a different camshaft for the WR with the hole for the decomp pin drilled 20º farther retarded, or they could have done what they did; use a longer pin in the WR, which would cause the valve to reseat later in the cam's rotation, and correct for the change in timing.

What does that have to do with the Hot Cams or any other-than-stock cam? Just this: pin length may not be the best way to compare these when addressing starting problems. Checking the reseat point, both OEM and aftermarket, with a degree wheel will give you a much better idea of whether and how much modification the pin would need to match up. If the cam manufacturer indexed the decomp pin bore in such a way as to reseat the exhaust valve at 25-30º (or whatever the figure is for an OEM WR cam) when using a short pin, then it has no need of one longer or shorter than that.

Hopefully, that understanding may help eliminate some trial and error.

  • Krannie McKranface

Posted May 14, 2013 - 01:48 PM

#38

No, not trial and error. They installed the YFZ cam pin instead of the WR to YZ spec cam pin, by mistake.
My cam, same cam, has the correct pin. Ken got the bogus pin.

My problem is that the intake cam gear was degreed wrong. It was set to approx 27degrees of overlap. It ran, but had no power until 9k.

I dont' want to re-learn degree'ing for fourstrokes and neither does my engine builder. So we sent it back.

  • KennyMc

Posted May 14, 2013 - 02:40 PM

#39

Hotcam's built their YZ timed cams for the WR in a way as such to utilize a shorter than WR OEM pin but longer than YZ OEM pin. For my "issue" they have switched out the shorter pin, installed a longer pin and it is now on it's way back.

  • n16ht5

Posted May 14, 2013 - 07:23 PM

#40

Makes me glad I just retarded my WR cam... free an e start works...




 
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