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Cam caps

By yamadoggy,
in YZ400F/426F/450F/450FX

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yamadoggy

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Hey guys- just curious on how everybody torques the camshaft caps. Is there a better way than spending 150 bucks on a Snap-On torque wrench? The only thing I can think of seems pretty okie but, how bout using a piece of pvc pipe fitted over the 8mm wrench (one foot long) and pulling to 6 lbs. using a fish scale. I know its pretty redneck, but I just cant afford a wrench that goes down that far. All the craftsmen models start at 10-15 lbs. Jason

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Grand Master

grayracer513

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Craftsman, Indestro, Proto, and any number of others sell inexpensive Beam Type 1/4" drive torque wrenches ($30?) that are a hell of a lot easier to use than a fish scale, and much more accurate, I'm certain. You'll need to pick up a couple of sockets to go with it.

Torquing the cam caps properly is probably one of the most seriously sensitive operations you will ever have to do on one of these little engines. Do it carefully and do it right. ?

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FFRacing79

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Couple of points...

First the torque value in the manual(8 ft/lbs) is too high...take them to 5 ft/lbs.

Second, before you install the cam chain, make sure the cams spin free when the caps are torqued down. Many times they do not, even on new bikes. If they don't, just polish them where they sit in the journals with emery strip. easiest if done in the lathe, but not required. JMO Tdub

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grayracer513

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First the torque value in the manual(8 ft/lbs) is too high...take them to 5 ft/lbs.

I tend to agree, but I use 6 ft/lbs (72 in/lbs)
Harbor Freight is an OK place to buy some things that you aren't planning to use very often or keep very long, but I wouldn't buy any measuring or precision tools of this type from them under any circumstances. A good clicker costs at least $100. One sold for $28 is worth just about what you'd guess. They may say +/- 4%, but it won't be that way a year from now.
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642MX

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I have a question for grayracer513 and FFracing79.......

Why not torque the bolts to the recommended spec that Yamaha clearly states in the shop manual? Running the bolts loose, seems like it could cause the cam to smack the head and the cam caps causing excessive wear? Or worse, the bolts could back out? Also do you lock tite the bolts? and if so, which lock tite do you use?

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FFRacing79

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I have a question for grayracer513 and FFracing79.......

Why not torque the bolts to the recommended spec that Yamaha clearly states in the shop manual? Running the bolts loose, seems like it could cause the cam to smack the head and the cam caps causing excessive wear? Or worse, the bolts could back out? Also do you lock tite the bolts? and if so, which lock tite do you use?

The YZF cams come with .001" clearance(supposedly) with the journals. Not much room for error. Most of the cams, aftermarket and OEM I have installed were on the tight side. They would not hardly turn when the journals were torqued down. 5 ft/lbs is not loose for these bolts. They will not "back" out. I set my cams up at .003" right from the start. I use no locktite.

Why not torque the bolts to the manual spec? Cause it is too tight, and cam galling can and will occur. Tdub

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FFRacing79

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Good answer FFRacing79. Great, now I need to pull my valve cover again. I guess I will use plastiguage to see what clearence I have and go from there? Or should I just loosen them to 5 ft.lbs. ?

As long as the cams spin freely when torqued down, your clearance should be OK. As far as what you torque them to, from experience I recommend 5 ft/lbs. Tdub

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grayracer513

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I have a question for grayracer513 and FFracing79.......

Why not torque the bolts to the recommended spec that Yamaha clearly states in the shop manual? Running the bolts loose, seems like it could cause the cam to smack the head and the cam caps causing excessive wear? Or worse, the bolts could back out? Also do you lock tite the bolts? and if so, which lock tite do you use?

The torque on the bolts does not set the clearance in the cam bore. So long as the cap is properly clamped in place by the fasteners, the clearance is the result of the machine work on the two parts involved.

One of the things that has come out in the last 8-10 years from GM (I was a Chevrolet Master Technician for 20 of my 34 year career as a professional mechanic) is that torquing by angle, the amount of rotation applied to a bolt after it reaches a particular torque level, is a far more accurate a guage of the actual force applied by the bolt. This because of differences in bolt length, friction variations under the fastener head, etc. As FFR notes, the cam caps are reasonably easy to distort if they are unevenly torqued, and could be subject to localized twisting around the bolt holes at high torque levels as the bolts are turned. From my experience with using torque angle as a measure of proper torque, I think the cam cap bolts on a YZF rotate too far when torqued to 86 in/lbs (7.2 ft/lb as called for in my '03 manual), and I choose to substitute 75 in/lbs (6.25 ft/lb) instead. I do not locktite the bolts, and they do not work loose. The 8 ft/lbs mentioned elsewhere is 96 in/lbs, and is way too high, IMO. I don't know where that came from, but neither of my bike's manuals list that spec.

Do I know more than Yamaha? I would hope not, frankly, but I have a lot of experience as a mechanic, and I've seen a lot of engineering mistakes made in that time. My decision to use a different torque value for this application is my own,based on that experience, and input from other members here. You make your own

?

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FFRacing79

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The torque on the bolts does not set the clearance in the cam bore. So long as the cap is properly clamped in place by the fasteners, the clearance is the result of the machine work on the two parts involved.

One of the things that has come out in the last 8-10 years from GM (I was a Chevrolet Master Technician for 20 of my 34 year career as a professional mechanic) is that torquing by angle, the amount of rotation applied to a bolt after it reaches a particular torque level, it far more accurate a guage of the actual force applied by the bolt. This because of differences in bolt length, friction variations under the fastener head, etc. As FFR notes, the cam caps are reasonably easy to distort if they are unevenly torqued, and could be subject to localized twisting around the bolt holes at high torque levels as the bolts are turned. From my experience with using torque angle as a measure of proper torque, I think the cam cap bolts on a YZF rotate too far when torqued to 86 in/lbs (7.2 ft/lb as called for in my '03 manual), and I choose to substitute 75 in/lbs (6.25 ft/lb) instead. I do not locktite the bolts, and they do not work loose. The 8 ft/lbs mentioned elsewhere is 96 in/lbs, and is way too high, IMO. I don't know where that came from, but neither of my bike's manuals list that spec.

Do I know more than Yamaha? I would hope not, frankly, but I have a lot of experience as a mechanic, and I've seen a lot of engineering mistakes made in that time. My decision to use a different torque value for this application is my own,based on that experience, and input from other members here. You make your own

?

Very well said...

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dirtgood1

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This is just a quick reply to the whole harbor freight torque wrench thing. I have one of the same wrenches and after a fulls years use, I took it to work and had it calibrated and it was dead on. Its true that a "good" torque wrench can cost a pretty penny, but even one of the most exspensive wrenches is not good if it is not calibrated annually, and it doesnt take much to throw them out, simply knocking it off your work bench and it landing on the garage floor can send it out of cal. Just my 2 cents.

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