WR426f Timing nightmare continues... Finally FIXED!!!


53 replies to this topic
  • Reedus

Posted February 28, 2008 - 08:48 AM

#1

I posted a thread titled "Valves Kissed the Piston" for the first series of the nightmare. Here is part two: After redoing the entire topend again thanks to a forgotten circlip, I am having issued timing the bike. The bike has a new Wiseco std. bore piston and the topend has 5 new valves with the seats cut and the head milled. At TDC the timing is way off for some reason. If I time it so the marks on the cam are level with the head on both the intake and exhaust, I have 12 pins between marks. The only problem is that when I crank it over with the flywheel and a 14mm wrench, i am hitting a valve on the exhaust stroke. Pretty sure it is one os the intakes. So I retimed it totally disregarding the cam sprocket marks and going by the lobe positions on the clutch side. Here is what it looks like. The flywheel mark is dead on with the "I". My question is: why am I hitting valves with it timed according to the sprocket marks? Second question: are the lobes sitting in the right position for TDC? I can turn it over now without hitting valves, but I don't dare start it for fear of losing another 600 bucks in a topend again. Consider me a little gun shy. Anybody care to elaborate what the problem might be?Posted Image

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  • Frostbite

Posted February 28, 2008 - 09:02 AM

#2

I posted a thread titled "Valves Kissed the Piston" for the first series of the nightmare. Here is part two: After redoing the entire topend again thanks to a forgotten circlip, I am having issued timing the bike. Anybody care to elaborate what the problem might be?Posted Image

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Are the cams new or original – are these the same cams that were in the engine when the valve met the piston? If so, it’s possible that the sprockets slipped on the cams, throwing off the timing marks. This happened to me with adjustable sprocket Hot Cams, and I have heard of it happening to pressed on sprocket stock cams. I used a degree wheel and dial indicator to reset my cam sprockets.

If the cams are OK, the second thing I’d do is verify that the TDC mark on the flywheel is actually TDC of the piston.

If the cam sprockets are OK, and the engine TDC is correct, perhaps the milling of the head has decreased the clearance too much.

Also, you said that you had the valve seats cut. Are the valve clearances set properly? It doesn't take much to throw things off. A few thou difference in clearance changes the actual individual valve timing quite a bit, 10 to 20 degrees on my 400. This means that one of the intake valves amy be opening earlier than the other 2, due to differences in valve lash clearance.

  • GCannon

Posted February 28, 2008 - 09:05 AM

#3

The Lobes look too far apart to me:excuseme:

Make the Cam gear marks (dots Level with the head surface )then the cam gear dots should be straight up. The I and E should be level

  • Wiz636

Posted February 28, 2008 - 09:23 AM

#4

The Lobes look too far apart to me:excuseme:

Make the Cam gear marks (dots Level with the head surface )then the cam gear dots should be straight up. The I and E should be level


What he said. Looking at the sprocket side of the cams you need to remove the cam chain and rotate your ex cam one tooth clockwise and the intake cam one tooth counter clockwise.

The lobes should be facing out like they are now but tilted slightly up.

  • ncampion

Posted February 28, 2008 - 09:35 AM

#5

I believe the cams are mis-times as shown in the photo. First of all there should be either 13 or 14 pins between marks (YZ vs WR timing). Also the lobes look too flat as viewed from the clutch side. You could check to see if the sprockets have slipped, but that is a little rare. I think if you re-time the cams using the stock marks and either 13 or 14 pins you should be OK. Check this link for more info and a picture.

http://s18.photobuck...0cam_Page_1.jpg

  • Reedus

Posted February 28, 2008 - 12:00 PM

#6

You guys didn't catch the second part of my post. When it is timed like it should be, with the cam lobes slightly up and the sprocket marks aligned with the head, I am hitting the piston with valves on the exhaust stroke. I turn the flywheel with the 14mm wrench and sure as shit, when the intakes come around to open the valves up, it hits the piston. The marks on the sprockets are useless. I think that Frostbite hit it on the head with a turned cam sprocket. The aftermarket cam was on the bike when it I forgot the circlip and the valves were destroyed by the piston the first time. The above pics are of the stock exhaust cam with the intake that was on when the valves smashed the piston. I think the intake is the culprit. Anyhow, what is this degree wheel talk? Would a machine shop be able to reset the cam?

  • Frostbite

Posted February 28, 2008 - 12:40 PM

#7

You guys didn't catch the second part of my post. When it is timed like it should be, with the cam lobes slightly up and the sprocket marks aligned with the head, I am hitting the piston with valves on the exhaust stroke. I turn the flywheel with the 14mm wrench and sure as shit, when the intakes come around to open the valves up, it hits the piston. The marks on the sprockets are useless. I think that Frostbite hit it on the head with a turned cam sprocket. The aftermarket cam was on the bike when it I forgot the circlip and the valves were destroyed by the piston the first time. The above pics are of the stock exhaust cam with the intake that was on when the valves smashed the piston. I think the intake is the culprit. Anyhow, what is this degree wheel talk? Would a machine shop be able to reset the cam?


A degree wheel bolts to the crankshaft and lets you exactly identify any point of rotation of the crank - Top and bottom dead center, and any degree in between. A dial indicator is used to tell exactly when the valves begin to open and close. In the pic you can see the degree wheel, and the dial indiator is above the exhaust cam.

Posted Image

The cam specs will say open and close at a certain degree, so with a degree wheel and dial indicator you can pinpoint your timing perfeclty, and you don't need the flywheel or cam sprocket marks at all. Even if your cam sprocket's spun, you could set them back in proper timing using this method, but the marks on the cam sprocket wouldn't line up. You could simply put new marks on the sprockets, or have a shop press them off and back on in the correct orientation.

Is your intake cam stock pressed on sprocket, or does it have a slotted adjustable sprocket?

  • matt4x4

Posted February 28, 2008 - 12:51 PM

#8

cam side looks good - just like ncampions reference pic except that pic has everything move to the left (counterclockwise) half a tooth, but there's 14 pins between timing marks - this difference could be a difference in where TDC is located between the two machines and most likely is just that.
Now turn it over and look at the cam view side, if you move everything half a tooth (now clockwise because we went to the other side), the intake cam would be slightly up where it should be, BUT, the exhaust cam would be slightly down, moving the exhaust cam back a tooth so the pin count is 13 would fix this.
So what is the pin count for stock WR timing with stock WR cams - 13 or 14??
If it's 13, moving the exhaust back should by rights line everything back up correct visually speaking......right down to the timing marks on the sprockets.



Reedus - just on the side - I believe you do know what you're doing but just want to make sure - is everything shimmed to spec already or are you using the old shims?

  • Reedus

Posted February 28, 2008 - 01:55 PM

#9

I thought I knew what I was doing. I checked valve lash and everything was to spec. After I took the above two pictures, I retimed the cams so that the dots line up. The cam lobes from the clutch side look exactly as they should too. (somebody pipe in if I am wrong) But when I turn the crankshaft over with the wrench. the intakes are hitting valves right as they begin to hit the buckets. At this point, the piston is barely past TDC and heading down when the intake hits valves. ***???

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  • Reedus

Posted February 28, 2008 - 01:59 PM

#10

The second set of pics is with the hotcams exhaust cam. I am certain it is not the exhaust lobes hitting valves, becasuse I have advanced the exhaust so that the lobes are not touching the buckets when the intake lobes begin to open the valves and hit them. Wow, what a train wreck.:smirk:

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  • MotoGoalie

Posted February 28, 2008 - 02:01 PM

#11

Dude, your cam sprocket has spun, you NEED new cams.

  • Wiz636

Posted February 28, 2008 - 04:56 PM

#12

the intakes are hitting valves right as they begin to hit the buckets. At this point, the piston is barely past TDC and heading down when the intake hits valves.


I don't understand what you are saying here...

  • Reedus

Posted February 28, 2008 - 05:09 PM

#13

See if I can clarify: There are two time that the piston is at TDC. Once on the compression stroke and next on the exhaust stroke. On the exhaust stroke, the piston hits TDC and then begins to drop. Just as the piston begins to drop back down, the intake cam strikes the buckets and begins to push the intake valves down. At that point, the intake valves are hitting the piston. :smirk:

What I can't figure out though is the cam lobes "appear" to be in the right position on the clutch side. Slightly pointed up and away. If I retard the intake cam one tooth, the valves clear the piston, but the bike will not start. I am at loss of what to do at this point.

  • maxtherat

Posted February 28, 2008 - 10:09 PM

#14

Sounds like you have a dilemma on your hands.Here's my opinion.For now forget the theory that the sprocket slipped.Pull the cams out, pull the plug, stick something long in the hole to the top of the piston, rotate the engine until your gauge is at it's highest point from the plug hole. Now look at the TDC indicator. Is it in or really close to the correct spot? If not, something is off on either the crank sprocket or the flywheel weight.Was the keyway forgotten when the flywheel was last installed? If it is good then leave it where it's at. Put a socket on the nut and tape the ratchet handle to the foot peg. Install exhaust cam first and pull the slack from the chain as you put it on the cam sprocket. Do the same to the intake cam. Now are the tips of the lobes at 10:00 and 2:00? If yes, are the dots on the cam gears parallel with the top edge of the head? If no to the last two, then one or both of the sprockets have slipped on the cam(s). Now if all looks good and you rotate the motor and your valves still hit the piston then my next thought is that there is a problem with the milling on the top of the piston or the length from center line of the wrist pin to the top of the piston. Sorry this was so long, but I wanted to take it step by step and verify each part as you progressed. Good luck!

  • Reedus

Posted February 29, 2008 - 07:56 AM

#15

Thanks Max! I'll give it a whirl and keep you posted.

  • Frostbite

Posted February 29, 2008 - 08:12 AM

#16

But when I turn the crankshaft over with the wrench. the intakes are hitting valves right as they begin to hit the buckets. At this point, the piston is barely past TDC and heading down when the intake hits valves. ***???


Just after TDC on the exhaust stroke, the piston begins moving down on the intake stroke and the intake valves open. Your intake valves can hit the piston while it's on it's way down, because the cam lobes open the valves much faster than the piston is moving out of the way.

This sounds like your intake timing is advanced - for whatever reason.

I think you have to start from Square 1 and verify TDC with your flywheel marks. Simply testing to see when the piston is at the top of it's travel is not accurate enough to verify the TDC marks on the flywheel. The piston actually stops moving for maybe 10 degrees of rotation, and you don't want to be that far off.

It should be easy to tell if the flywheel is set properly on the crank, and if it is, then your TDC marks should be fine. Do you have a puller - can you remove the flywheel to check it? If the key slot in the crank and flywheel aren't damaged, and the key is not damaged and is in place, then TDC on the flywheel must be correct, unless you twisted the crank when you blew the engine, and I doubt that. The cam chain drive gear is right behind the flywheel and it would be nearly impossible to twist the shaft in that inch or 2.

If your TDC is correct, then the problem has to be the cams. If the sprocket marks line up with the head mating surface when the flywheel is in the correct position, and the valves are still hitting the piston then A - the sprockets spun on the cams, B - the piston to valve clearance to too tight (milled head, or piston in backwards as someone mentioned earlier) or C - too high lift on the cam (improper valve clearance, or maybe it's the wrong cam).

This stuff can be very frustrating, and sometime so hard to explain through typing. If you want to talk live, PM me and I'll give you my phone #.

Cheers

Frosty

  • maxtherat

Posted February 29, 2008 - 09:16 AM

#17

"I think you have to start from Square 1 and verify TDC with your flywheel marks. Simply testing to see when the piston is at the top of it's travel is not accurate enough to verify the TDC marks on the flywheel. The piston actually stops moving for maybe 10 degrees of rotation, and you don't want to be that far off."
Frost you are correct, but I wanted to express the possibility that the piston could be on it's way up or close to TDC when the cam begins to open the intake valves. If you know the piston is at TDC just before/as the point it begins the intake stroke and all of the valves are closed(cams timed properly with correct shims), but you flywheel weight TDC marks are off by a noticable margine then you may have an issue in the lower end. PS hows that new 450 treating you?

  • Frostbite

Posted February 29, 2008 - 09:35 AM

#18

"I think you have to start from Square 1 and verify TDC with your flywheel marks. Simply testing to see when the piston is at the top of it's travel is not accurate enough to verify the TDC marks on the flywheel. The piston actually stops moving for maybe 10 degrees of rotation, and you don't want to be that far off."
Frost you are correct, but I wanted to express the possibility that the piston could be on it's way up or close to TDC when the cam begins to open the intake valves. If you know the piston is at TDC just before/as the point it begins the intake stroke and all of the valves are closed(cams timed properly with correct shims), but you flywheel weight TDC marks are off by a noticable margine then you may have an issue in the lower end. PS hows that new 450 treating you?


Hi Max
Sorry if I sounded a bit preachy there:prof: , I didn't mean to. I used to check TDC the same way, but discovered how far out that could be when I started using the degree wheel, only a couple of months ago.

The 450 is still teasing me, sitting in my livingroom, the half that I took with me. The other half hasn't arrived yet.:smirk:

  • maxtherat

Posted February 29, 2008 - 09:56 AM

#19

Hi Max
Sorry if I sounded a bit preachy there:prof: , I didn't mean to. I used to check TDC the same way, but discovered how far out that could be when I started using the degree wheel, only a couple of months ago.

The 450 is still teasing me, sitting in my livingroom, the half that I took with me. The other half hasn't arrived yet.:smirk:


No worrys Frost. We both know how these things work and w/o a degree wheel this is the next best way to rule out some other issues that may not have been considered prior to us chiming in. My thought was just to get an idea of where the piston was in relationship to the TDC mark. If the piston is topped out and the mark is really close and he can rotate the motor to the point the the TDC mark lines up and the piston has not started moving down then his may lie elsewhere. Best of luck with the other half of the bike!I certainly respect your perseverance. I probably would have quit riding and taken up ice skating.

  • Wiz636

Posted February 29, 2008 - 06:43 PM

#20

Totally random thought here...is there any chance that the piston was installed backwards? That would cause the outside intake valves to make contact with the piston as they would not line up with the valve recesses in the top of the piston.




 
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