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Cam and rocker arm damage

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I'm helping a friend troubleshoot his 400. It started making noise from the top end. We took the valve cover off and found the cam and rocker arms in bad shape. Basically, they are all shot.

My friend is not the original owner, but the bike is a 98 and appears to have been treated pretty well. What would cause this? I've always heard that low oil is the culprit when you see this kind of damage. What do you guys think?

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I lost my top end stuff a few months ago. My cam went flat, rockers scored. I had rob barnum harden the rockers and add a new cam. Hardening the rockers consists of welding the same material the cam is made of onto the rocker tips, then regrinding to stock specs. That way the rockers and cam wear in together. I also went with stainless valves, heavy duty springs ad titanium retainers. Rob can give you more details. Barnumsproproducts.com

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Low oil probably isn't the culprit but crap for oil is. NEVER run an automotive oil in your motorcycle. XRs will tell on this before anything else due to the RFVC head that develops a lot of heat. I have seen this many times when people insist on using Castrol GTX instead of Castrol Motorcycle oil. I highly suggest a 100% synthetic or at least a Semi-Syn with a JASO [MA] rating.

Cher'o,

Dwight

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Dwight - I know for a fact that he has been running Motul 5100 oil for 4-stroke bikes. He's been using it ever since he bought the bike. I believe that is a semi-syn, and I know a lot of other guys around here using it with no problems in KTM's and CRF's. Based on that, would you tend to think it ran low on oil, or could he have another problem?

I hate to put a new cam and rocker arms in it and have them go out quickly.

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Keith - could you determine what caused your parts to crater? I do know that my friend was riding in Colorado when his started making noise. I wonder if it was a heat issue? Final question - how much did it cost to get your parts repaired and does that include repair to the cam? I looked at suggested retail for the cam and rocker arms and looks like $300-325.

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I just pulled the top end off of my bike and had the same problem (flat cam and worn rockers) I don't know if it was a bad adjustment or what. I found the rockers through Honda but nowhere else, and I'm going to put a Hotcam in. I don't know if having a 440 with a stock cam would have been the culprit. :thumbsup:

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likely a combination of things certainly oil is a big factor but the lack of adjustment will do that as well.

One should at least check the valves after every 2nd or 3rd race or 3-4 times a season for the casual rider

, its a small price to pay.

The intake generally are the ones that get tight, when the motor runs real hot the valves start to mushroom inwards after a while,.

Aside from the noise which is generated the other sign of poorly adjusted valves is the bike not starting in the first 2 kicks .

Being a 98 a complete head job is not a luxury, valves guide seals , seats recut possibly new intake valves , whatever it takes , its money well spent, it is unfortunate about the cam and rockers but it is one of the hassles when buying used bikes.

good luck

stu

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Dwight - I know for a fact that he has been running Motul 5100 oil for 4-stroke bikes. He's been using it ever since he bought the bike. I believe that is a semi-syn, and I know a lot of other guys around here using it with no problems in KTM's and CRF's. Based on that, would you tend to think it ran low on oil, or could he have another problem?

I hate to put a new cam and rocker arms in it and have them go out quickly.

Was your friend using the Motul or was the guy he bought it from using it also ?

If this isn't the problem as I am sure Motul is a decent oil, maybe the oil filter is stopped up or the oil passage tube is stopped up. For some reason you are not getting oil to the cam and followers. If this didn't start with oil failure. I would have thought that the upper rod would have gone out also with low oil levels. Be sure to check there for damage to the rod and wristpin and or Piston Galling.

Cher'o,

Dwight :thumbsup:

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My friend has always used the Motul, but I can't say what the original owner used.

I tend to agree with Stu that maybe the valves were out of adjustment (too tight) and the rocker arms put too much stress on the cam lobes.

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If the valves were too tight the bike wouldn't start correctly or it would burn the valves so they would need to be replaced.

The only way to put too much stress on the cam lobes is with too heavy a spring. The guy he bought it from may have been running GTX and the damage was already started and once the chrome is worn off the progression of damage will quickly happen.

Good Luck,

Dwight

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KTMConnell, I put in a new cam and left yhe stock rockers etc. I think I should have changed rockers with the cam to break everything in together. Rob said there was no unusual discoloration on the rockers. We couldnt really pin it down as to why the cam went. I just didnt want to do it again so I went way over the top with new everything and hardening. I had other things done at the same time so I dont know exactly how muvh the top end cost, but I think it was around $1,000.00 and that included the punch out to 426 and all that goes with that as well.

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