450 Cam mod (on WR426) how many pins??

14 pins is correct..... you need to move the exhaust cam "back' (counter clockwise) one tooth.

Seems we have two different answers from two experienced camps. What to do?What to do?

Answer me this: If I was off 1 tooth (like some of you say I am) would the bike start? If so, how would the engine run?

At its present timing the previous owner said it ripped all the way through the throttle range (never had a problem). After picking the bike up (had been sitting in owners garage for 5 months w/o riding) I have discovered a bog from 1/2-full throttle that I cant seem to jet out (with the help of James and Burned). Would being 1 tooth out be a possible cause of this type of problem?

one tooth off would "retard" the timing and may contribute to the bog. Also being timed like it is would cause it to be a little harder to kick start.

Move it to 14.....that is where it needs to be for optimal performance....bog or no bog. Then if you still have a bog problem...you know its within the carb.

if it is an OEM YZ450 (not wr) then time it exactly like in the pic

450CAMMODpg1.jpg

Will do!

I'll update when its done. I'll have to pick up shims tomorrow if they're needed.

Thanks for everyones help keepin' this ball rolling!

If you are thinking that you will need to reshim just because you change the cam timing this is incorrect. You will not need to shim unless they are out of tollerance now. Good luck, I hope you have a better time than I am having with mine.

Josh

According to the dealer work order, its a YZ450 cam(part#5TA-12180-00-00) from an 03' with yz timing, throttle stop removed, grey wire clipped, decomp hole plugged.

So,

Q: With YZ450 cam in, how many pins represents wr timing and how many pins represents yz timing?

Here's a pic of my timing as seen from both sides. what do you think?

Left side

Right side

looks to me that your one tooth out and the crank was off TDC when the right side (marked left) was taken :applause:

How do we ever get to 14 pins? My manual shows 14 pins but I dont know if that is due to a pitch change in the chain from pre 2003 to post 2003. That might explain the confusion

For Pre 2003 WRs:

For WRF timing there should be 13 chain pins between the top marks on the cam sprockets. For YZF timing there should be 12 chain pins between the marks.

For 2003 and newer WRs:

YZ or WR cam should be the same 13/14 pins between the punch marks ( needs confirmation)

The 03 WRF exhaust cam is the same as the 03 YZF with a subtle difference in pin height for auto decomp and the punch marks timed on the sprocket is one tooth retarded.

:applause:

That was pretty much my take on it which is why Im confused.

I advanced the cam tonight (1 tooth counter clockwise) so now there's 14 teeth between punch marks. But since I dont want to re-use the paper gasket on the tensioner I will wait until tomorrow and try and get one here in town before trying to crank over by hand. Plus my torque wrench is WAY to big to fit so I'll pick up a 3/8 drive torque wrench and finish the job. Should have something to post by dinner tomorrow if not earlier.

Hang tight.........

How do we ever get to 14 pins? My manual shows 14 pins but I dont know if that is due to a pitch change in the chain from pre 2003 to post 2003. That might explain the confusion:

The cynlinder head shape may have a lot to do with it i'd say, maybe the cams on the later models are further apart with an increased valve angle ??

Well, I advanced the ex. cam 1 tooth (14 pins now). Here's all 4 pics for comparison purposes. One thing that Indy mentioned was that he didnt think I was at TDC when taking the 'before' pics. I swear Im on the "I" mark when I took all 4 pictures but after trying to check valve clearances (I can just fit a 0.100mm feeler under the exhaust cam) Im thinking he's right. What can I do if my cam punch marks dont line up at TDC and my "I" mark doesnt line up at TDC. If I cant find TDC then I cant check my valve clearances.

Here's the pics:

Before

Left w/ 13 pins

Right w/ 13 pins

After

left w/ 14 pins

Right w/ 14 pins

The 14 tooth looks right according to my manual. The punch marks are exactly where they need to be. It looks like you are exactly at TDC with this shot. My manual also shows the auto decomp rotated 1 tooth clockwise from the 14 pin shot but that seeems right if the YZ cam is the same except for the punch marks being off one tooth clockwise. The punch marks should be flush with the top of the head. :applause:

Well, I advanced the ex. cam 1 tooth (14 pins now). Here's all 4 pics for comparison purposes. One thing that Indy mentioned was that he didnt think I was at TDC when taking the 'before' pics. I swear Im on the "I" mark when I took all 4 pictures but after trying to check valve clearances (I can just fit a 0.100mm feeler under the exhaust cam) Im thinking he's right. What can I do if my cam punch marks dont line up at TDC and my "I" mark doesnt line up at TDC. If I cant find TDC then I cant check my valve clearances.

Here's the pics:

Before

Left w/ 13 pins

Right w/ 13 pins

After

left w/ 14 pins

Right w/ 14 pins

You can verify TDC with a small dowel, just be sure that it is long enough that it won't fall all the way down into the cylinder. You put it into the spark plug hole and turn the engine over until it is at it's highest point. This will be TDC, if you are still too tight then you will need to reshim your valves. Hope this helps.

Josh

TDC is easy to figure out.....align it with the "I" right in the middle....use something to hold it in position ( I used a socket/wrench and left it on the flywheel and triple checked it to make sure it did not move).

It appears that your right on if it showed TDC when you took the pics.

As stated before....you should not have to reshim....unless it was need anyway. On a YZF....it is highly unlikely! :applause:

I had 220 shims in there and I took a measurement on the exhaust cams as being .130 (feeler guage was .127 so I rounded up). According to the exhaust chart I will put in 210's which I just picked up tonight. Will install and give a report when its buttoned up.

I appreciate all the support on this guys!!!!

Looks like the cam is in the right position now. Let us know how it works out.

Its just NOT my day!!!!

Confirmed TDC was indeed at the "I" by using a straw through the plug hole. Changed shims so now my clearance is within spec. Buttoned the cams back together and rotated the crank by hand without any problems. I rotated several cycles listening/feeling for any resistance.....NONE! So I elect to put the bike back together and light it up. Well Im out in the driveway ready to kick it over and I take the first kick SUPER SLOW just to be safe. It won't go!!! Feels like I cant kick through TDC like when the decom was still on the bike. So, I pull off the left side plug so I can try to rotate the crank by hand again and it wont go. Just for shits and giggles I pull what's left of the decomp mechanism (little shaft is still inside the head) hanging off the outside of the head and now Im able to hand rotate past TDC.

What's going on here?

Now Im worried I've done all this in vain.

I would go back to 13 pins before as it has run and started OK. :bonk: I will have my cam cover off soon to do the vavles clearances and confirm the stock pin count between punch marks. Does anyone out there have their cam cover off on their WR450's right now? :applause:

I think you are on the right track with the 14 pin position. Rotating the cam should not cause the problem you are describing.

With the plug in and reassembled, it should take a little more effort to turn the bike over.

What do you mean, "what's left of the decomp mechanism?" Possibly the decompression shaft was interferring, but I'm not sure how. If it were too tight, it would press down, leaving the valve open. That would not prevent the bike from turning over.

Indy, I might be missing something here, but if he has a 450 cam in a 426, then the number of pins should not be the same as your 450. You have to install a 450 cam in a 426 by looking at the right side of the bike to make sure the lobes are in the correct position. The timing marks on the 450 cam do not line up when installed on a 426.

Can you look at these and tell us which TDC position looks coreect for a 426 with a YZ450 cam:

picture #1

cams_006.jpg

or picture #2

camsADVANCED_004.jpg

Thanks. :applause::bonk::cry:

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