camshaft/head damage

[jetmechmarty]

Do I have to replace the head and cams, or is it OK to continue to run this way?

I'm replacing the chain and adjusting the valves. I did not want to find this.

[jetmechmarty]

The 1st photo is the #1 position on the exhaust. The 3rd is the #4 on the intake. The last is just a single groove. I can't imagine what got in there. I change oil and filter regularly.

[trbig]

Looks like it sucked up some grit there at some point. Hard to tell from pics, but mic the cam carefully and see it it's in spec. If so, run it. If not, pull the valves and throw the head away. (Or pull the little studs and recycle it.. aluminum.) I'm thinking it will be fine though. I've pulled apart worse that were running just fine.

[trbig]

I can't imagine what got in there. I change oil and filter regularly.

You can take your little bell off now. You sucked that little gremlin on through..

[jetmechmarty]

There's no telling how long it's been that way. I'm afraid that if I take the thing apart, I'll find more damage. That being said, I guess I'm going to run it as it is.

[motoman]

There's no telling how long it's been that way. I'm afraid that if I take the thing apart, I'll find more damage. That being said, I guess I'm going to run it as it is.

May as well............damage has already been done. I would imagine the bottom end looks similar. Even the cam lobes have pitting. Not good. If bottom-end bearings look similar, a spun bearing IS in the future, at which time a good 'paired' cases is gonna be needed allong with ALL spinning pieces new. Bottom line, if run till cratered, good excuse for a replacement motor anyways. Hell, may as well run it till it knocks. May surprise you how long that will take though. By the same token, all those that pull the cam end caps to change shims ARE running on borrowed time, so guess it don't matter much as those cams are 'dancin' in the mount too....

[trbig]

all those that pull the cam end caps to change shims ARE running on borrowed time, so guess it don't matter much as those cams are 'dancin' in the mount too....

Huh??? Please explain yourself.

[Lonerider62]

I saw something like that once before when a guy swapped cams but didn't pay attention to which caps went where. We ended up putting it back together after determining that the damage was already done and wasn't much more could be done. He rode the thing at least four more years and as far as I know, it's still being ridden. Who knows, something else may blow it long before the cams.

[motoman]

Huh??? Please explain yourself.

Well, all it takes is once of improperly matched end caps or bearing caps, and what the pic shows is whats gonna happen.......eventually. And yes, with the valve train pressures at different intervals, that cam WAS doin the dance with the INITIAL damage. Who knows how long before things failed. In actual answer to the question.....better find a complete known good head WITH the cams and valves in it. Even at that, you have no way of actually knowing for sure if cams had ever been seperated from head or not. Once pulled down to spec. from factory and being aluminum, loosened they'll never have the same oil clearance spec. as original even though torqued to original spec. Not sure if this would necessarily cause this kind of damage, but the original clearance spec. won't be exactly the same. This type of damage(and yes, the head and cams ARE trashed), my first suspect would be at the filter or if washer/spring in housing was placed on wrong side of filter(only takes once for damage to be done). Seeing the tiny pits in those cam lobes makes them a 'no-go' cam anyways. Even though these cams are smaller in size, too often I see them mishandled, thrown in parts trays, etc. with some of the past pics inavertantly showing a parts tray. In the automotive world, if I see ANY cam that's gonna be re-installed for whatever reason, and it's not in a journal supported container or not standing up vertical and not leaning against the wall somewhere, that pretty tells me that person is just a 'wanna-be' engine builder. These bike cams being short, I don't know that would be an issue, but I DO see them being handled hap-hazardly. In Jets case, the only way to determine the REAL cause would be to split case. If the mains looked similar, then contamination would be suspect. If the mains showed nothing more than normal wear, then something was done improperly with the associated trashed pieces shown, mixed parts or incorrect torque/or torque sequence........or all of the above.

[trbig]

Well, all it takes is once of improperly matched end caps or bearing caps

LOL.. That's why the little guys in lab coats put arrows and numbers on them. If you mess that up, you shouldn't have been taking anything apart in the first place, because you obviously weren't following the manual at all.

Your argument of oil clearance specs changing after taking a cam out... I just don't see it. ESPECIALLY when the guys from Yamaha tell you to do just that for inspection. I've put thousands and thousands and thousands of miles on motors with cam bearings looking worse than what he pictured. I suspect that some PO ran it too long in between oil changes so that it hit bypass mode from a plugged filter. I've taken cams in and out and in and out, dozens of times, and have used this same head/cams on three different motors now.

Maybe I've just been very lucky, but I also think you don't understand how tough these motors are. I know one that went many miles with ZERO oil pressure. At full throttle it was slowing down because the motor was starting to seize... he let it cool a bit, then rode it further to get to a place we could work on it, and it was starting to seize again.

Oil pump put back in place and many thousands of miles later, that motor is still doing fine.

[motoman]

Since being associated with these scoots since there conception, you can be assured I know there durability. Have seen stranger things occur that would beat out the average scoot motor. I am also aware of the dropped oil pump story too......when it took place BTW. Am aware of the correct orientation marks, but you and I both have seen, even on here where they were incorrectly installed. Like I stated, looked to be an oil contamination issue, and only way to REALLY know would be to open up bottom end checking crank bearings. Otherwise running it the way it is, least I would'nt opt to sail down the superslab some 500mi. at 75mph and 5,000rpms with that cam singin' at 10,000rpms. But, that's just me.

[trbig]

I would'nt opt to sail down the superslab some 500mi. at 75mph and 5,000rpms with that cam singin' at 10,000rpms.

You've got it backwards. Cams are halved. BUT... with bearings and such, these motors will let you know something is wrong generally LONG before anything catastrophic. In the case of a chattering cam, you would think there would be a much more pronounced deformation of the soft aluminum, especially at the cap which is directly opposite the lobe. Either way, you can check these caps and cams with plastigage, per your manual.

If the crank bearings are getting bad, you can generally pull your alternator cover, grab the rotor and pull it up and down and check it for any free play. But if the bottom end isn't making any strange noises and the crank seals don't leak, you're not getting movement down there, and I personally wouldn't tear apart a motor and split the cases just for curiosity's sake. Plus, if you do that, then the oil clearances will never be the same again on the crank, right? lol.

My point in all this is... have any of you even heard of a cam failure in a head? I'm sure there has been at some point, but the occurance of it is so extremely low, that with the number of motors out there running, and with the relatively few I've had apart and seen this type of marks and worse on a lot of them, (And knowing the horror stories of all the PO's out there with lack of oil changes) I'm just throwing my 2 cents out there to say that as long as the current owner changes his oil.. and more importantly, the filter... he'll get many many more miles and years from these cams.

[skids]

My point in all this is... have any of you even heard of a cam failure in a head?

I have only heard of one. There was a guy that may have called himself "fireman" who had a cam shatter like glass. This doesn't seem like the type of failure that would occur with the situation at hand.

[fredintoon]

Do I have to replace the head and cams, or is it OK to continue to run this way?
I'm replacing the chain and adjusting the valves. I did not want to find this.

Hi Marty,
it's only a bike and it ain't gonna quit at 20,000 feet over the Rockies so lower your standards.
Polish the camshaft galling with crocus cloth, carefully reassemble and it'll run OK for years.

[jetmechmarty]

I'm going to just run it. I see little option. I have no clue how long it has been that way. I'll keep an eye out for a spare engine.