does this look right?


21 replies to this topic
  • tammie

Posted February 27, 2007 - 10:54 AM

#1

hey guys i just installed the HOTCAMS exhaust auto decomp camshafts in my 1999 yz400f........here is a picture is this right? Im just checking for confirmation.

piston is at TDC, cam caps are back on and torqued to spec, cam chain tensioner is reinstalled.

I just wanted to make sure it is right, the instructions were not the greatest....

the peened marks on the sprockets are all lined up with the top of the head hard to tell in pic but they are.
Posted Image
Posted Image

  • tammie

Posted February 27, 2007 - 11:05 AM

#2

oh yah I measured valve clearances and the INTAKE was fine(as i didn't change that cam) but the new hotcams valve specs were way out(as could be expected) however it was really out, instructions say HOTCAMS exhuast valve lash should be 0.17mm to 0.22mm i measure 0.45mm on the one lobe and 0.55mm on the other lobe so there is way too much space between the lobe and valve lifter Im goign to get some larger shims to bring up the space to spec.

  • grayracer513

Posted February 27, 2007 - 11:30 AM

#3

The timing looks exactly right.

But, I'd call Hot Cams on the valve clearance. The clearance they gave you is for a YZ250F exhaust. A YZ400 should be .15-.20mm on the intake, and .25-.30mm on the exhaust. Since the necessary valve clearance for most engines is determined by the construction of the cylinder head and the valves, the only change that you usually see with aftermarket cams is that the more agrressive ones may need to be looser than stock, if any different at all. It sounds to me as if they got the wrong instruction sheet in the box, and I'd want to ask them about it.

  • tammie

Posted February 27, 2007 - 11:35 AM

#4

well i went online and printed off the Yamaha YZ400/426 camshaft installation instructions and they quote exhaust as 0.17mm to 0.22mm for the auto decom HOTCAM exhaust cam.... so this must be right??

i know in my manual for the OEM cam its 0.25mm-0.30mm but that is for STOCK

  • grayracer513

Posted February 27, 2007 - 11:48 AM

#5

Even with the stock cams, the two engines mentioned use two different clearance settings, and again, it's because the use two different kinds of valves. The 2000 and earlier models use the same specs yours originally had. The '01 & '02 426 uses .20-.25mm on the exhausts because that engine has titanium valves.

The specs listed online could be right, but they do not follow convention, in my experience, they don't make sense to me, and they seem wrong on the face of it. I would want some sort of verification, if it were me.

  • tammie

Posted February 27, 2007 - 12:01 PM

#6

ok this is where i got the information
http://www.hotcamsin...w&productid=488

click on YZ426 installation it comes up as "YZ400/426 camshaft installation"

on page 3, 3rd paragraph down it quotes the intake and exhaust specs

these are the models that the cam i have is good for according to the part number
For Model(s):
1998-2000 Yamaha WR 400
2001-2002 Yamaha WR 426
1998-1999 Yamaha YZ 400
2000-2002 Yamaha YZ 426

  • grayracer513

Posted February 27, 2007 - 12:18 PM

#7

I never doubted that you saw that in print, but I continue to be less than comfortable with the information, nevertheless, and would still want verification.

  • YZ426F Rider

Posted February 27, 2007 - 02:32 PM

#8

Hmmm...I don't remember the big change in specs when I installed the Hotcam in my '02. When I get home I will see if I can find my install sheet.

  • tammie

Posted February 27, 2007 - 03:01 PM

#9

yah it seemed kinda strange to me that there would be that much of a difference....i'll have to call I guess to confirm as I have installed everything as per instructions torked everything down and used my feeler gauges to check clearances. I could already tell the one exhuast cam lobe was way out before i used the gauges as i could actually see light through the bottem of the cam lobe between the lifter and the lobe i knew right away it was going to be too much of a space...

  • tammie

Posted February 27, 2007 - 03:44 PM

#10

when it is stated to check piston to valve clearance how is this measured?

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  • grayracer513

Posted February 27, 2007 - 05:36 PM

#11

There are a couple of ways to do this.

The first method is to use clay stuck on top of the piston in a layer thicker than the minimum allowable valve/piston clearance, assemble the head and cams, and turn the engine through one full cycle. Then remove the head and check the thickness of the compressed clay where the valves pushed it in.

Another is to assemble the engine using very light dummy springs in place of the real valve springs, and check the valve clearance by manually pushing them down to the piston at several points as the piston moves over TDC.

Either of these obviously requires repeated extra assembly work and is time consuming. Mostly, this is required when there is a significant increase in valve lift, or a major alteration of the event timing (increased duration, more overlap, etc.). If you bought the basic stage one cam, it probably isn't necessary.

  • tammie

Posted February 27, 2007 - 07:20 PM

#12

yah that seems like a lot of work, i didn't do anything major so i think i'll skip that.........thanx was just curious how that would be measured.

  • YZ426F Rider

Posted February 27, 2007 - 08:25 PM

#13

Here's the card that came with the cam for my '02...not really a change as my bike's factory spec is .20 - .25. The card does say for all YZ/WR 400/426 though. :applause:

Posted Image

  • tammie

Posted February 28, 2007 - 06:14 AM

#14

thanx for taking that pic......yah i got that same card with mine....im surprised it does not say a range in the HOTCAMS written instructions from their website it says 0.17mm to 0.22mm when u swapped your exhaust cam out did you notice a big change in specs on the exhuast side like ive measured?? i measured 0.55mm on one lobe and 0.45mm on the other exhaust lobe, seems so out.....

  • Hot Rods

Posted February 28, 2007 - 07:42 AM

#15

Timing is correct, as long as your crank position is right. Valve lash will be as close to .20mm as possible (one shim size in either direction)(.05). The base circle (heel) of those lobes are reduced from the stocker, so you will have at least .25mm larger shim to start with.

  • YZ426F Rider

Posted February 28, 2007 - 09:51 AM

#16

thanx for taking that pic......yah i got that same card with mine....im surprised it does not say a range in the HOTCAMS written instructions from their website it says 0.17mm to 0.22mm when u swapped your exhaust cam out did you notice a big change in specs on the exhuast side like ive measured?? i measured 0.55mm on one lobe and 0.45mm on the other exhaust lobe, seems so out.....


I do recall having to reshim but I don't recall if I needed a big change or not.

  • Markopolo400

Posted February 28, 2007 - 01:27 PM

#17

Timing is correct, as long as your crank position is right. Valve lash will be as close to .20mm as possible (one shim size in either direction)(.05). The base circle (heel) of those lobes are reduced from the stocker, so you will have at least .25mm larger shim to start with.


Now that's customer service. :applause:

  • tammie

Posted February 28, 2007 - 05:39 PM

#18

well i called HOTCAMS today and they just reshim to the correct specs and that is fine. So after going to the local shop twice today I got the proper shims.....

the specs are 0.17mm to 0.20mm

on both lobes i got the 0.20mm feeling gauge in but it was tight fit but it went in and out so is considered a reading of 0.20mm?

and yes crank position was at TDC

  • grayracer513

Posted March 01, 2007 - 08:41 AM

#19

well i called HOTCAMS today and they just reshim to the correct specs and that is fine. ...the specs are 0.17mm to 0.20mm

on both lobes i got the 0.20mm feeling gauge in but it was tight fit but it went in and out so is considered a reading of 0.20mm?


So, they do want you to use their clearance settings instead of the OEM. Remember to use Yamaha's figures on the intake cam.

With a feeler gauge, you are trying to feel when the gap between parts is the exact size as the gauge. This will be when a .20mm gauge goes into a .20mm gap. Such a situation will produce a "light drag" on the gauge, but will not feel like a "tight fit". It may be that there is no gauge that will produce this feel; that the smaller one will feel loose, as if it is not as large as the gap, and the next larger is too tight, in which case, the gap is in between those two.

The specified range, in this case, .17-.22mm, is .05mm, or about .002" wide, so that's how accurate you should try to be.

  • tammie

Posted March 01, 2007 - 09:41 AM

#20

yah i used the OEM specs on the intake cam they are all right in the middle of the spec range so that is perfect....well the .20mm goes in but is a tight fit and the 0.15mm goes in loose so i will assume that its in between 0.15 and .20mm which is in spec. i think its probably 0.17, 0.18 or 0.19mm which is ok. thanx for everyones help





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