Galled Cam Journals


16 replies to this topic
  • FFRacing79

Posted June 25, 2004 - 04:39 PM

#1

If the Cam journals are overtightened(manual spec), the journals may gall on the cams from not enough clearance. After this happened to my $3500 head, I was really worried. Sent the head off to Mike at Engine Dynamics(EDCO) and they repaired my head to better than new. They use some sort of welding process to build the journal material up and then linebore them back to spec. Mike recommends torqueing the cam journal bolts to 5 ft/lbs to avoid the galling problem.
Edco did a fantastic job repairing my YZF head...very good people and top notch service. Tdub

  • MN_Kevin

Posted June 26, 2004 - 09:41 AM

#2

T:

that 5 ft-lbs...did you use a ft-lb torque wrench or 60 in-lbs...???

  • SFO

Posted June 27, 2004 - 09:16 AM

#3

I am glad it worked out for you and I am glad you liked Mikes work.
It is easier to have it done by Mike than to try to do this on your own.
It reminds me of a funny story.
The Night before our teams first race with Doug the head tied up on our race motor. The ball bearing came out of the end of the oil passage on the intake cam cap and ripped up the bucket bores in addition to killing the intake cam and the cam journal bores.
We had a spare oem head but all of our development was with the ripper big valve head. I spent an intense night in the trailer wrapping sand paper around sockets lapping in the bucket bores and the cam journals getting the good head operational again and by the time I fired it up in the morning the sun was starting to come up. Doug went on to beat Jeff Ward in his heat race and the whole time my stomach was turning inside out knowing what that cylinder head had been through. He finished third in the main after falling down and we got our first national podium. This feeling of anxiety never got much better though, every time the bike was on the track I would be hearing every pop or missed shift terrified the bike was going to explode.
I don't think I have the nerves for it in retrospect, sorry for my digression, I am just getting nostalgic...
(Don't try the socket sandpaper thing at home guys...)

  • Hamish

Posted June 27, 2004 - 09:56 PM

#4

If the Cam journals are overtightened(manual spec), the journals may gall on the cams from not enough clearance.


thats debateable. Regardless of how tight you do the cam caps, the bearing clearance wont change. The bottom of the cam cap seats against the cyl head when the cam cap bolts are tight. Overtightening the bolt will do nothing apart from damage the thread in the head. This theory is backed up by the fact that all the torque setting in the service manual for a M6 bolt into an alloy thread are 10NM(7.2 ft lbs), be it a clutch cover or cam cap.

Hamish

  • sirthumpalot

Posted June 28, 2004 - 01:30 AM

#5

The caps are aluminum I believe. Aluminum is very fragile and will warp and distort easily. I would not doubt that over tightening the caps would cause less than spec clearance, which could be enough to simply block sufficient oil flow and presto, wear problems.

  • Hamish

Posted June 28, 2004 - 11:12 PM

#6

you cant distort a piece of alloy the size and style of a cam cap with a 6mm bolt into an alloy thread. Try using plastiguage at the specified torque, then increacing the tension and I think you'll find the clearance will remain the same. Not trying to start WW3, just trying to point out that the galling problem probably has another cause.

Hamish

  • tc66nova

Posted June 29, 2004 - 12:32 AM

#7

I agrre and disagree at the same time. You can definitly distort the cam cap and even the head itself by over tightening the bolts. That is why torque plates are commonly used when boring cylinders. But to distort the cam bores enough to cause galling is doubtful. I still believe that most galling problems start when guys rev the engine before it is THOUROUGHLY warmed up. Oil flow is sluggish until it is warm and the clearances are tight until the the engine is up to temp. Remember that aluminum has an expansion rate nearly ten times that of steel. So the running clearance at temp is alot more than when the engine is cold and there is little oil flow. Bore distortion and oil flow issues have been a major concern in the racing engines that I have been building for the last thirty years. In my drag racing engines we always heat the oil and water before we fire the engine.

  • motocrosschump

Posted June 29, 2004 - 02:05 AM

#8

I over tightened mine over time and the engine would barely turn over. I had to take it to a machine shop.

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  • YAMAKAZE

Posted June 29, 2004 - 09:55 AM

#9

Mike did an Primo job on my YZ 400 , after my mechanic forgot to use assembly lube on the Cams after an engine overhaul.

Bonzai :thumbsup:

  • SFO

Posted June 29, 2004 - 02:19 PM

#10

It is funny, cam seizure has happened to quite a few experienced mechanics.
Mike@ edco has repaired a lot of these heads, in addition to other plain brg cam journal problems.
If Mike says 5ft lbs it is for a good reason and I would tend to believe him, without measureing these bores with a good tenth reading bore gauge and applying different torque values and measuring the distortion( as I am sure Mike did) speculation is as rhetorical as plastigauge.
This bore comes from the factory with less than .001" clearance at least that is what I have measured on each head I have done.
The service limit is .003" if I remember right.
I set them up at .002".
I also bought a new inch pound snap on digi-torq which has a 1%accuracy throughout its entire range, just for doing cam caps.
This is the only plain bearing in the entire engine and it deserves respect.
:thumbsup:

  • Eddie Sisneros

Posted June 29, 2004 - 03:21 PM

#11

well said! :thumbsup:

  • MN_Kevin

Posted July 02, 2004 - 04:20 AM

#12

I also bought a new inch pound snap on digi-torq which has a 1%accuracy throughout its entire range, just for doing cam caps.




Bill count me in here ae well. Mine is NOT a Snap On however...

  • FFRacing79

Posted July 03, 2004 - 08:46 AM

#13

If you look at the cam supports, you will see where the dowels fit. There is not as much material for support in these 4 locations as there are at the other 6 locations. This is where Mike informs me are the trouble spots. For someone who "occassionally" removes their cams for lash adjustments, this might not pose a problem. But for some of us who frequently remove and reinstall the supports or journals, I can see where Mike has a valid point.
I have also been using the practice of replacing my head bolts after 3 or 4 uses, leary of the high torque required causing the bolts to fatigue.
To answer another question, I have both a low reading in/lb(0-120) and a low reading ft/lb(0-25) torque wrenches. These are a must for accuracy at low torque requirements.
OT...I just returned from the Amateur DT Nationals where like usual, FFR bikes and riders dominated the Youth classes. The high point of the week was one of my riders receiving the Youth DTer of the Year Award(Youth Horizon Award).

  • BigBlueWR

Posted July 03, 2004 - 04:27 PM

#14

This topic has me worried....

I installed the auto decomp cam in my '99 WR. I didn't have a torque wrench so I just 'hand torqued' the cam covers. My bike runs great, but I only have about 10 miles on it....So do you think I'm in for trouble down the road?

Am I in the minorty here, did most folks torque their cam caps to spec?

Anyways I need some advice on what type of wrench to buy. Do I need a in/lb or a ft/lb? I'm new to this, but it seems like with such a small torque setting I would need a high $ wrench.

Thanks for the advice.

Happy 4th to everyone :thumbsup:

  • MN_Kevin

Posted July 03, 2004 - 04:49 PM

#15

I just bought an inch pound wrench.

You want a wrench where the "setting" you need is between 30%-70% of full scale.

Anything outside those parameters starts to get in the "not so accurate" zone.

5 ft-lbs would essentially be a 7 > 15 ft-lb wrench.

  • Flattracker60

Posted July 03, 2004 - 05:25 PM

#16

What rider won the award?? OT, I talked to ron while you were gone about my YZ. I am going to need to call you, I am a little confused about what to do to this motor to get 55-58 hp. We all agree that the Web Cam and his carb mod are a good thing. He is telling me to not port the head :thumbsup:. I don't want to rob your cam thread any more than I already have. We'll talk more later. Chris from Wi.

  • Hamish

Posted July 03, 2004 - 10:18 PM

#17

I 'hand torqued' every bolt on my bike bar the head bolts and the case bolts. I've probably put over 1000KM's of hard riding on it since then with no problems. Same goes for every other engine I have built over the last 10 years, and I'm yet to have a failure.





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