[SparkyMJ]

Hey folks, wanted some weigh in.

Working on my project K4 750, and it's got about 40k+ miles. It had pretty worn camshaft lobes, so I replaced the camshafts with used ones that were in better shape than my set. The wear looked like scratches/scuffing on the lobe tips, no chunks missing or anything that crazy, but enough I thought that replacing with used better ones would help it last longer. Haven't run the engine at all yet since replacement, due to other parts being worked on.

Anyhow, I've never opened up a bike engine that had lifters/buckets with any tangible wear. Sometimes they have visible wear patterns, but absolutely nothing you could feel with a fingernail, pick, or anything. The camshafts on this bike in particular as I mentioned had some pitting on the tips of certain lobes.

I guess the pitting on the lobe tips didn't cause tangible wear on the lifter/buckets. The pitting was very mild, but enough to me that I would like to try and not run those. The lifters looked absolutely flat, uniform, and good, with one exception, and it had a circular wear pattern on the head of the bucket, but again nothing I could feel in any capacity.

Question is, if you never run a stock motor out of oil or abusing the engine or anything like that, when or how would camshafts and lifters wear enough to warrant actual replacement?

Are lifters harder materials, and hopefully would result in only camshaft lobe wear, and not both? What level of wear is unacceptable for lifters?

What do you guys think?
Thanks in advance.
-Mike

 

[Beairsto Racing]

The crank & rod bearings will have oil starvation...ending the suspense, long before you have to worry about the top end.
Top end wear is usually indicative of crappy oil, extended oil change service intervals, lack of maintenance (valve sets) etc.

 

[SparkyMJ]

Good to know. Lines up with my personal experience as well. My other bike has 55k miles or so, and the top end looks superb. Better than this 750 in fact. I was pretty religious with my oil changes.

But now that the bike has some amount of top end wear, would it speed up further wear even if I do the oil changes and maintenance as prescribed? Like, when should I stop using those top end parts if they have accelerated wear? Manual just says stuff along the lines of "any wear is too much wear, remove and replace"

Thanks for the input.
-Mike

 

[Beairsto Racing]

It's one of those questions...how long is a piece of string?
Worn is worn.
Or just ride the thing.

 

[SparkyMJ]

Yeah that is true. Probably ride it, and visually monitor those components from time to time.

 

[nick49]

If you have uneven wear or light scoring on the lobes that you can actually feel sometimes you can smooth them out using a stone, then polishing. It's important to keep everything on the same plane. Think of this as increasing the surface area of contact. Yes you will be removing a few tenths or more but it may be the lesser of evils.

Often stuff like this starts during long periods of storage with temperature changes. Inside a motor you have a micro climate with condensation forming acidic water droplets that hang off certain areas and attack metallic components by etching into the surface. This is what may have caused the pitting you see.

The only way to prevent this is regular oil changes, storage at a constant temperature and possibly adding a moisture absorption device or packet. Starting the motor or at least turning it over often will circulate oil and preserve your precious motor components.

 

[SparkyMJ]

Yeah I think that is a good conjecture about the causes of this. My other bike with much more miles shows way less age, and I rode it nearly every day.

I actually did bring those camshafts into a shop to have the tips ground down at a perfect right angle. They unfortunately didn't have the tooling to make that work, but indeed I understand the concept. I was willing to live with losing a few thousandths of valve lift to have the peace of mind, but it was just cheaper to find used camshafts in better shape than pay hundreds of dollars to fix my ratty ones.

But yeah I think I just need a monthly ride on all the bikes to keep stuff like this from happening or worsening. Probably the real cause on machines with almost two decades of age on them...

-Mike