Bumps on Cam Bearings

I know there I saw a thread on this same thing somewhere, but I spent almost 2 hours searching for it on here and the archive with no luck. I must suck at using the search function!

Some of my cam bearing inserts have little raised bumps on them. Is this a problem?

Jake here's the thread you're looking for:http://kzrider.com/index.php?option=com_kunena&Itemid=116&func=view&catid=11&id=340793

It's my build thread, and I must say that my bearings look exactly like yours. So far, the consensus on here was to re-use them as-is. However, my bumps are raised just like yours. Personally, I'm not comfortable re-using them, so I'll either replace them with an ebay set or buy new. They sure are proud of those little guys. IIRC they are about $7 a peice.

BTW I have the same problem with the search feature, but fortunatly the search nazis aren't too bad here.

Thanks, I knew I saw that somewhere!

You said yours were all on the top halves, but mine are mostly on the bottoms. The worst one (pictured above) is one of the intake bottom halves on the left of the motor.

I'm still deciding whether to replace them or not, Z1E has them for $7.50 each or if you buy a set of 16 - $6.50 each, that's still $104 for new ones.

If I do reuse them should I try to sand off the bumps or just put them back in the way they were?

Replace, replace, replace...

When in doubt, THROW IT OUT! :laugh:

These bikes are supposed to cost a lotta $$$... :laugh:

GL

I personally don't like the idea of sanding. If one of those silicon oxide grains gets imbeded in that bearing, then it's gonna eat that cam for lunch. If I were reusing those I would just clean them and re-install. Judging from the witness marks left by your cam, those bumps were the only thing making contact.

Here's one question that still bothers me. Does this engine not rely on those bearings having good fit to maintain oil pressure? Mine are significantly out of round, and I'm used to bearing clearances being measured in the neighborhood of 0.0002" That's not happening on these bearings. I think my bumps were at least 0.005" tall.

Edit: I agree with what tek9ine says. I'm still replacing mine.

Don't use them whatever you do, they'll throw off the pressure gradient in the oil, and you wont get proper hydrodynamic lubrication. And that will lead to premature wear on your cam journals, and who wants that?

No way would I use those bearings, looks like something went wrong during the mfg process and the chance of them flaking off and getting into the rest of the motor are just too great for my comfort.
small price to pay for new ones now rather than mess up the rest of the motor later

Jake are those bearings from your Z1r? That bike sat up for a few years if I remember your post about it. I'd like to know what causes the bumps and it would help to put 2 and 2 together.

If the bumps are thicker than the oil film (and I'm betting they are) they will make contact with the cam journals. Judging by the dark spots in the center of some of the bumps (which look like a sign of wear) they already have been rubbing. I would toss them for sure. Ed

Testarossa - Yes, these are from the Z1-R, it did sit for 13 or 14 years. It has about 19,000 miles on it. It seems to make sense that these bumps grew, then as I ran it last summer the tips of the biggest bumps got worn off like 650ed mentioned.

There will be a brand new set in my next order from Z1E.

This might be an important thing to check on any bike that has been sitting for awhile.

I've never seen any looking like that. It would seem likely to be some form of contamination in the oil that corroded the metal.

When engines run, they gradually contaminate the oil with acid, water and left over chemicals from gasoline that makes it's way past the rings. I would suspect the engine sat with very old oil in it for all those years.

Jeff.Saunders wrote:

I've never seen any looking like that. It would seem likely to be some form of contamination in the oil that corroded the metal.

When engines run, they gradually contaminate the oil with acid, water and left over chemicals from gasoline that makes it's way past the rings. I would suspect the engine sat with very old oil in it for all those years.

Mine sat for about 15 years with dirty oil in it. Unknown miles, but I'm guessing not too many since the cam lobes were still in spec. It would be interesting to see if any other bikes that have been stored for extended periods have this issue. I have never seen bearings look like this in any engine that I have dissasembled of any type. It makes two KZ motors with this.:huh: