Bearing Sludge

[klickitatsacket]

Well by now most every one on here knows that my company is rebuilding bearings and installing ceramics balls. Because we are rebuilding bearings on a fairly regular basis we tend to pay more attention to those things that we never looked closely at before at least not in the same light.

One of the things that I started noticing since we started rebuilding bearings is the amount of oil sludge inside the bearings. The following picture is of a set of races from a 066 bearing. The saw was running when it was taken down for a rebuild. The mix used was 50:1 and the saw had about 800 hours on it.

The reason I am pointing this out is because bearings produce heat from friction and hard run saws over the course of time will burn oil on the races. This in turn builds up sludge and will shorten the life of your bearings and robs horse power.

I am not saying that things are so bad that every one needs to put ceramics in their saw. I would however suggest any one who rebuilds their top end; while you have it off; you might want to use some good parts cleaner or brake clean and wash out their bearings before installing a new top end. Pour it into the case and soak them for a while and then rotate you crank. Do this a couple of times and rinse them out really good. If you are really retentive, maybe even pull your top end down every few hundred hours and wash them out. The last suggestion is for those who do not have a warm girl waiting at home for you.

 

[jack-the-ripper]

Dean, is fair to say that those who choose to run their oil mixed at say 32:1 could have even more build up over time on the bearing races. Just wondering.

 

[klickitatsacket]

I would think that is possible but I do not know for sure. Too little could cause a problem too if it is cause too much friction. it's always about balance; too much oil can be bad and have it's issues and so can too little.

 

[bwalker]

I would think that ingested dirt, and saw dust contribute greatly to bearing sludge.
Increases in oil concentration my help with the sludge pictured, by virtue of the bearing running cooler and by the increase in detergents moving through the motor.
The race motors I have seen run at 16:1 are very clean internally.

 

[Sprig]

Dean, I am just wondering lookin' at the build-up on those races whether the saw was run on synthetic oil mix or just regular. That seems to be a lot of crud considering the hours, (gah! maybe not!), hm, 800hrs=130+days working, but still..... Is there any protection (ie., a lip or something) around where the bearings sit, do different saws seat them differently, cover more of the bearings, is it a seal thing? etc? It is my curious nature that makes me ask this and I am wondering if you ever question the cutomers as to what exactly they are using in their saws, types of oil/mix, just to sortta give you an idea if there is maybe a trend for tendancy. Is there anything, as in bearing lubes, like something moly or teflon based, that could lessen that effect? Like I said, just a wonderin'.



Serge

 

[klickitatsacket]

This particular saw was run 50:1 orange bottle. The oil is burned and has the consistancy of a dry sticky paste. It is definately caused from heat. If you happen to have your saw aport (or home alone and frustrated) then take the time to rinse your bearings out.

 

[klickitatsacket]

sorry I got a call and side tracked. all bearings are mounted the same in these saws no matter the brand. they are open to the case and allow the fuel mix to coat the bearings.

 

[Sprig]

sorry I got a call and side tracked. all bearings are mounted the same in these saws no matter the brand. they are open to the case and allow the fuel mix to coat the bearings.

Thanks, I did not know that. So, if I understand this, it is exaust 'mist' in the crankcase that eventually causes this build-up? Or is it sort of a mix of both uncombusted and combusted fuel (my guess) ?
Is there anything that would reduce this buildup or is it something that 'just is'?

 

[klickitatsacket]

exhaust does not enter the crankcase. bearings are int he crank case and have no protection from the fuel entering into the case. The fuel is allowed to coat the bearings. The sludge is created by heat from the bearings burning the oil that is coating them. It may not be every saw but I do see it quite often for what ever reason.

 

[PES+]

I find that it is often pitch that ends up in the bearings and causes some of the sludge....also if the crank is not pretty true it allows the seals to suck in some fine saw dust and grit.

How did the crankcase look in that saw Dean? The sludge invariably forms more on the PTO bearing due to the higher load and therefore more heat I reason

 

[klickitatsacket]

Thsi was the clutch side bearing. However both looked about the same. the case did not look unusual.

 

[PES+]

Just a thought

I clean out cases with carb cleaner or sea foam and then re-oil the bearings with mix oil to avoid a dry start until the fuel mix gets to the bearings

 

[Lakeside53]

I've seen it both ways.. low time saws with sludge and high time was clean a as a whistle. The saws I've seen inside from Rbtree and other run entirely on run on synthetic, are clean and high time. I've seen BR420 blowers run on synthetic all their lives look like new after 5 years of hard use.

If you are concerned about sludge, just pull the seals... that will tell you how much junk is accumulating...

 

[Lakeside53]

exhaust does not enter the crankcase. bearings are int he crank case and have no protection from the fuel entering into the case. The fuel is allowed to coat the bearings. The sludge is created by heat from the bearings burning the oil that is coating them. It may not be every saw but I do see it quite often for what ever reason.

I'm not so sure I agree.. assuming good oil mix, I believe blow-by is the biggest contributor to junk in the bearings. If the bearing is getting hot enough to burn the oil, the Nylon cage would be charred.

 

[klickitatsacket]

if you are getting blow by then generally your piston is worn bad. Lake, do you see a lot of brittle cages from heat. I run into it quite often.

BTW, the point of this thread was just give guys a heads up to flush the bearings while they have the top end off. Just a good practice.

 

[PES+]

Have you ever taken a bearing apart to look inside the races lakeside?
Even if they look clean they usually have the sludge inside

Hey Dean....why not show a few pics on how they come apart

 

[ShoerFast]

is there a chance that this sludge happens more in the winter then summer? Or is related to cool wet running conditions?

To explain my question, could crank-case condensation help brake down the surface tension of the oil-film causing centralized heat problems?

 

[klickitatsacket]

is there a chance that this sludge happens more in the winter then summer? Or is related to cool wet running conditions?

To explain my question, could crank-case condensation help brake down the surface tension of the oil-film causing centralized heat problems?

explain how it causes centralized heating. I do not understand

 

[Lakeside53]

Have you ever taken a bearing apart to look inside the races lakeside?
Even if they look clean they usually have the sludge inside

Hey Dean....why not show a few pics on how they come apart

Yes.. and I often use an otoscope when assembled to look in the races for galling and other problems.

The shop even has a cool little tool to remove the bearing races from a saw (not all saws..) without spitting the crankcase....

 

[PES+]

There is some talk about regarding alky blend fuels and certain synthetics causing bearing failures. It was mentioned in another thread here that Jonsered is advising against all synthetics and this is due to an increase in crank failures and I am checking a bunch of the cranks myself to see what damage there is on the crank pins. The Jonsered problem is usually the big end failing and they had been telling the locals to switch gas stations.

We do get some strange smelling gas up here and it varies
none of it is labelled gasahol or ethanol beld but most of it smells like alky especially the premium