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7.2 ft-lbs (86 in-lb) too much torque for cam cap bolts?

10 posts in this topic

I'm the process of installing a 450 exhaust cam in my 99 WR 400. When I torque the cam cap bolts down to 86.4 in-lbs, I can't rotate the cam. If I put the stocker back in and torque it down to 86.4 in-lbs it spins freely. Any suggestions on the minimum torque I can safely get away with?

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Danger! DANGER Will Robinson!

Something else is wrong. Use a micrometer to measure the diameter of the cam journals and see if they are the same. When you torque the caps they shouldn't pinch the cam. If they do and you just don't tighten the caps fully it will still screw up the cams and your head.

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Well, you being observant just saved you from galling a spendy 5 valve head, along with a spendy cam. I suspect the cam journals are different diameter. Mic them for size, compare it with the original unit.

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Hmm :cry:. I'm using a brand new OEM YZ450F cam. Lots of people have done this mod to their 400's and I haven't heard of anyone complaining about binding cams. I wonder if people have tried to rotate the cam by hand before firing up the bike. I noticed if I torqued the cam cap bolts to 5 ft-lb (60 in-lb) the cam spins fine. I haven't progressively tried to increase the torque until it just starts to bind.

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You might have gotten a bad cam or a cam that was mismarked. Like others have said, something is wrong elsewhere. :cry:

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Everyone here is right about measuring the cam lobes. Here's something else to consider. Did you check the adjustor tabs, those little disks that are installed at the top of each valve under the cap? You didn't mention if you disassembled the motor to this level, but it's something else to look at.

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I would say u have a valve that is to tight. Be sure you havn't installed one of the caps backwards or in the wrong place. Make sure all the dolwe bosses on the caps are in place to.

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I have not done any work on my head yet but is there a chance you have zero clearance on your valves. with the cam torqued in place can you place a feeler gauge underneath the lobes. There is a very good chance you need to adjust your valve clearance anyway.

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some [@#$%&*!] of a mechanic overtorqued the inlet cam on my bike, but I didnt notice it until I decided to check clearance myself and do the YZ timing

since it was the first time I did that, I was working step by step, checking all possible things

when I removed both cams, I tried to remove the lifters (out of curiosity), but the inlet ones were stuck due to the damaged cam seats on the head (at that point I really thought i need a special tool for removing those)

removed the head, peeled and brushed off (PIC) the defective material, polished the cam seats on the head and on the camshaft cap to even the surfaces with 1000 sandpaper, slowly, and checking often

before i began sanding, the cam could not rotate by the force of hand, and after the job was done, it rotated smoothly as the exaust one, when torqued to the spec

I fixed it myself :cry:, since then I checked it twice for deformities, and it all looked OK, valve clearances solid

(never trust your yamaha to a husqvarna mechanic)

proof more that a yamaha HQ and hi-tech bike can be repaired with tools for everyday use, only cost was new head gasket and time spent for repairs

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The cam may be slightly warped. I tweaked mine by being in a big hurry and not setting the engine to TDC when I loosened the cap bolts. The cam spun freely before I took it out but was tight (only in one spot) when I re installed it. I didn't think those little valve springs had enough power to bend the cam but they did.

Try turning the cam with the cam chain off to see if it has a loose spot. The cams are hollow and you may have gotten a bent one.

Since I live in the middle of nowhere with no bike shops or parts and I was still in a big hurry to go riding I very gently sanded inside the caps until the cam would rotate freely. It didn't take much, only a few swipes. It may blow up tomorrow but it lasted 2 years so far. :cry:

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