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Intake camshaft cap binding!

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I recently adjusted my valves on my 2001 wr250f  and I had some binding going on while trying to turn the cam.  I got it resolved somewhat and figured it might just be a little on the snug side.  I ran the engine for about 30 seconds to see if the timing was right.  I decided to pull the cam cap back off the intake cam to make sure things were still good.  There is signs of it being too tight, cam cap is rubbed and there is light marking on the cam, head side is fine.  Did some investigation, It was only binding in one position, cam lobes straight up, the rest of the travel was free.

My question is, if I resolve the binding, do I need to get the head machined since it took the mirror finish off of the cam cap?  Or can I resolve the binding and run it?  Thoughts?

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First question you have to ask yourself, is if it is binding, why now? What changed to cause it? Assuming you did not warp it, perhaps a fleck of debris was there. Binding at the cam cap when the lobe is pointed up is very strange. It possibly would be understandable if it were while depressing the bucket but you say that is not the case.

Remove all three buckets, noting which valve the belong to. Ditto with the shims, you want it to go back where they came from./ Put the cames in and (leave teh cam chain off) and rotate the cam as much as you can without the lobes hitting anything. How does it feel?

The marks on the cap are not all that significant.

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First question you have to ask yourself, is if it is binding, why now? What changed to cause it? Assuming you did not warp it, perhaps a fleck of debris was there. Binding at the cam cap when the lobe is pointed up is very strange. It possibly would be understandable if it were while depressing the bucket but you say that is not the case.
Remove all three buckets, noting which valve the belong to. Ditto with the shims, you want it to go back where they came from./ Put the cames in and (leave teh cam chain off) and rotate the cam as much as you can without the lobes hitting anything. How does it feel?
The marks on the cap are not all that significant.


My best guess is two things. First is I thought I could do without the torque wrench and use the 1/4 drive 2 filter rule. I honestly probably didn't torque it enough, or just ever so slightly over. So I have a hard time believing I warped anything. What I did do was tightened criss cross from the outside in instead of inside out, that definitely caused some binding. I am able to snug it down now inside out and there is no binding if I mess with the tightening pattern. The inside cam gear side bolt is the one that seems to determine the binding. Based on what I saw experimenting, I think a lack of torque and variance was the issue. I am buying a 1/4 torque wrench tomorrow and hoping for the best.

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When I say messing with the tightening pattern, I mean snugging down the inside cam gear side bolt last. That seemed to eliminate the drag

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I removed the buckets and shims, and intake cam still grabbing when lobes are pointed upwards.

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11 hours ago, 0macman0 said:

t I did do was tightened criss cross from the outside in instead of inside out, that definitely caused some binding. I am able to snug it down now inside out and there is no binding if I mess with the tightening pattern.

Not sure what your service manual says but when torquing down large assemblies (say an automotive cylinder head)

working from the center (inside) gradually moving to the most outward fasterners is the common method. 

Also using 2-3 steps to reach the desired final clamping force.

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I will be trying again tonight.  I read reports of using emory cloth to polish the cam shaft a bit.  I talked to Fastheads today and they even mentioned taking some emory cloth to the edges of the cam caps to see if they are mustroomed a bit?  I may try this very gingerly, but unless a miracle happens I we be sending the head off to fastheads or engine dynamics.  I will be purchasing plati-gauge on the way home tonight to check the clearances.  Wish I knew why it sticks only when the lobes are upright... maybe cam runout?

 

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Miracles happen in July apparently. I purchased a 1/4 torque wrench and after torqued properly in 4 steps, the binding was essentially gone! It was nothing short of amazing! This is what I learned:

1) a cheap torque wrench is better than no torque wrench
2) my binding was due to not applying enough torque since I didn't have a torque wrench, and not applying it evenly enough.
3) seat the caps with the end of a screwdriver lightly and visually check each mating surface for contact
4) 86 in/lbs might be excessive, I found the best results at 76 - 80 in/lbs, with light binding occasionally at 86 in/lbs. settled on 75 then 80 for the last two steps. keep it 90% on the light side.
5) the bolt on the side of the cam away from the gear and forward the back of the bike can be sneaky. Double check the finishing torque on it since it's hard and awkward to reach.
6) Use moly assembly lube. It's worth it just in case you do have minor binding on startup!

Basically, these heads are touchy. I'm shocked at how touchy they are. Even torquing to spec can produce minor drag at certain spots of the cam travel, keep it a little under for safety!

Overall, I'm happy as a clam.

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Also, I checked with plasti gauge and I had 0.01 clearance, the minimum on both bores. This I think is an argument for doing 90% recommended torque for safety.

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What are people's thoughts on not tightening to 86 in/lbs, but more like 75 in/lbs?  

 

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That's roughly a 400 lb loss of clamp force per bolt. Simply running the bolt loose isn't solving your issue.


I'm not sure I follow. The binding was eliminated but after extensive testing I found that occasionally at 86 in/lbs there can be drag in the cam bore. I've seen posts about people saying 86 in/lbs was excessive, and they do more like 75. Based on my observations, this is much safer. 400 lb loss of clamp force seems excessive for less than 1 ft/lb (11 in/lb) reduction in bolt torque?

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I'm not sure I follow. The binding was eliminated but after extensive testing I found that occasionally at 86 in/lbs there can be drag in the cam bore. I've seen posts about people saying 86 in/lbs was excessive, and they do more like 75. Based on my observations, this is much safer. 400 lb loss of clamp force seems excessive for less than 1 ft/lb (11 in/lb) reduction in bolt torque?


Silly me, I was thinking 87 in-lb, it's actually around 330 lbs difference. Assuming a .14 friction coefficient, it's approximately 2270 lbs clamp load vs 2600 lbs.

The Yamaha engineers knew what they were doing. At 1point in time, your cam spun freely while properly tensioned. You need to figure out what changed.

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1 hour ago, 0macman0 said:
55 minutes ago, ohiodrz400sm said:

 


Silly me, I was thinking 87 in-lb, it's actually around 330 lbs difference. Assuming a .14 friction coefficient, it's approximately 2270 lbs clamp load vs 2600 lbs.

The Yamaha engineers knew what they were doing. At 1point in time, your cam spun freely while properly tensioned. You need to figure out what changed.

 

 

Hopefully you do not feel like I'm attempting to insult your intelligence, as that is not the case.  It looks like even though it's a 330 lb difference in axial clamp force, it is still 87.3% of the original clamp force.  I don't disagree that Yamaha designed it a certain way either.  The key point here is that 85% of the time torquing to 86 in/lbs produced ZERO drag.  (I literally put this together 10 - 15 times) The other 15% of the time it was there, just slightly.  I am chalking this up to variance in the wrench (most affordable torque wrenches are +-4%), meaning you could be over or under torquing 4 in/lbs across the bolt pattern.  Not to mention the gauge on them is not always easy to read when setting the torque.  With how tight the clearances are, and the amount of variance possible with torque wrenches and other factors,  I won't be going over 80 inch pounds ever, because when I flirt with 86"/lbs, the risk is too great for over torque-ing ever so slightly, inducing drag from too much axial clamp force.

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Hopefully you do not feel like I'm attempting to insult your intelligence, as that is not the case.  It looks like even though it's a 330 lb difference in axial clamp force, it is still 87.3% of the original clamp force.  I don't disagree that Yamaha designed it a certain way either.  The key point here is that 85% of the time torquing to 86 in/lbs produced ZERO drag.  (I literally put this together 10 - 15 times) The other 15% of the time it was there, just slightly.  I am chalking this up to variance in the wrench (most affordable torque wrenches are +-4%), meaning you could be over or under torquing 4 in/lbs across the bolt pattern.  Not to mention the gauge on them is not always easy to read when setting the torque.  With how tight the clearances are, and the amount of variance possible with torque wrenches and other factors,  I won't be going over 80 inch pounds ever, because when I flirt with 86"/lbs, the risk is too great for over torque-ing ever so slightly, inducing drag from too much axial clamp force.


I can't speak to the quality of your wrench. The margin of error could be 60% for all I know. Some error IS assumed in recommended torque values. I don't know what Yamaha's are but the company I work for assumes 10% error and makes recommendations accordingly. If it was my torque wrench and I was in your situation, and would find another wrench to confirm the results.

Honestly with the provided information, it isn't possible to give you an answer with 100% certainty that everything is ok and I rather error on the side of caution. As a general rule though, lowering torque to stop machined assemblies from binding isn't an acceptable solution.

Do you have granite counter tops or a piece of glass you could use to measure the flatness of your cap with?

Have you run the engine yet? I'm not trying to be Mr-Know-It-All. I just don't want your next post to be that you went riding and now have a damaged head.

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I have not ran it yet.  Where I confirmed that the binding was gone, I'm inclined to run it.  It was just the variability of the results on re-assembly that made me nervous.  Once I have the cam chain on I can't rotate it obviously to where the drag was.  I will probably run it later today up to temp, and tear down again to confirm that everything is gliding along nicely.  If the problem persists, I will send the head to engine dynamics.  I did purchase a more expensive torque wrench with a lower range than standard to verify results.  Do you recommend click type or beam type for this work?

You do bring up two good questions though.  I have a granite counter top I could use to measure the caps, I have never done that before but I guess it involves feeler gauges?  The other thing is I would like to measure cam runout.  I find it odd that when it was dragging, it was only dragging in one position (~25 degrees of the 360 of rotation).  I understand normal V blocks are too large, how do you measure runout?

Edited by 0macman0

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I prefer clicker

Yes, you hold it flat down and slide the feelers under the mating surfaces of the cap.

If you don't have V blocks you could try to use the head itself.
Do you have a dial indicator and mag base? You may be able to securely stick the base to the frame and careful rotate the cam by hand to get a reading.
I've have been fortunate enough to never have a reason to measure the run-out of a camshaft

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I prefer clicker

Yes, you hold it flat down and slide the feelers under the mating surfaces of the cap.

If you don't have V blocks you could try to use the head itself.
Do you have a dial indicator and mag base? You may be able to securely stick the base to the frame and careful rotate the cam by hand to get a reading.
I've have been fortunate enough to never have a reason to measure the run-out of a camshaft


Do you think the reason it only grabs in love up position a reason to measure runout?


Do you think the reason it only grabs in love up position a reason to measure runout?

*Lobe up

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