Another great discussion! Remember the cage’s only purpose in life is to keep the rolling elements in place as they rotate around the bearing inner and outer races. The Conrad type bearings you have are radial load bearings that can only support a small amount of axial load but not very much. The cage in a bearing will come apart if an axial load is applied beyond the designed use. Plastic or metal. The nylon is more flexible in that area but much less durable. Then factor in all other elements of heat, speed, contamination etc. most bearings will notate something such as “ECP” or “ECM” in the part number or on the outer race. ECM or ECP corresponds to “Extra capacity metallic or Extra capacity plastic” as a reference to the retainer. Another factor is “end play” in the crankshaft which will cause axial load detrimental to the bearings design. Doesn’t take much and in this situation too little is just as bad as too much.
Due to the inertia forces at high rpms, plus the rotation of the steel balls in their races, I don't think its possible to apply enough force in one specific spot during use to damage the cage, no matter the material. Stationary, maybe. Try it with a nylon cage bearing, put a rod in it and twist. I couldn't do much.
Most of the nylons I see that failed let the balls loose in the saw, did a series of video's on that years ago. Dead Saw Salvage series on 372 XT's. Nylon will last if the temps are within specs, no "coking" and no abrasive debris. Steels handle temps better and can survive a little debris and even some coking cooked onto the races. The nylons I've seen fail did usually because the nylon got brittle and crumbled. There was a real short time from when the saw went lean to catastrophic as the balls got crunched around in the case and in the top end. Nylons tend to dampen vibrations better. AND if kept clean and cool will last as long as steels. Just when the heat and dirt enters the equation.... I have Husqvarna's from the 1970's like l77's with copious hours with their original bearings. I can't remember seeing a steel bearing fail in the 200's and OE 300 series. It wasn't until the XP-W's and XT's where there was a rash of PTO side failures. And then the 500's with their nylons. Most heat related. The XT's and XPW's went to nylons because of vibration in my opinion with the heavier pistons the the OE 372's. Saw a couple of XPW's and early XT's with the cases just rattled apart with steel caged. Just a thought & opinion. But to the less destruction concept? Go back and watch one of my video's on those "dead" 372xt's :) Had one where the balls were crunched/pressed INTO the case material :) Nothing salvageable
Thanks for chiming in Walt! Maybe the nylon cages can't take the radial load as well as the steel cages. It's another thing to discuss. But we're on the same page in regards to steel cage bearings. I don't claim to be an expert, but I'm willing to learn from real world and technical info.
Other thing is also chain tension with sharp or dull and how that saw was treated on the pto side as heat will transfer to the crank through all the clutch components will add to to failure as well as added pressure from too tight of chains way I view it anyways. When people are told the pto side failed and they question why and i give that explanation it makes sense to those folks. I prefer steel caged personally but it seems to be becoming less and less to find for some saws
Just did a complete short block replacement on a ms290 a couple months ago with the short block kit from Bailey's. Seal went out so the old bearing cage wore out and broke apart then melted through the spark arrestor in a plastic mess! I try my best to get metal caged bearings because being in Alaska it gets cold and sometimes we are cutting wood at -40° F and most plastic or polyamide caged bearings are only rated to -20 or less.
Yeah I think you're onto something here Richard. I haven't torn down as many saws as most folks but based on the ones I have -- the bearings in the 2 series Husqys (with the steel cages) seems to have more wear than the 0 series Stihls (with the nylon cages). I also find that the Husqy seals seem to stay softer compared to the Stihl seals - but perhaps the seal discussion is one for another day...
Hey Richard, good discussion. From my experience with the Husky 562’s, 555’s and 550’s, it’s normally the clutch side bearing that fails…I believe it’s due to the torque load from chains too tight, rakers too low and heat ( either a lack of chain lubrication or dull chains creating heat that works its way in from the clutch to the bearings). Additionally the ones with the stuffers seem more prone so maybe the oil in the air/fuel mix doesn’t make it in there as well? Anyhow, what I wanted to point out is that very often the bearings themselves are going thru the crankcase, transfers and get pinched between the piston and cylinder at the upper transfer port, taking out the piston and cylinder…that’s been my experience on over half of the ones I’ve dealt with. I’ve got a little video of one I did, there are 3 parts to it, but I’m just attaching a link to the first part. ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-R8-CLL0GofE.htmlsi=kpKj0god81F3ilHg
In case you didn’t know, Ski Doo uses completely sealed bearings in their 2 stroke snowmobile engines. They have for at least years. They are greased in the manufacturing process and that’s it. The can last a surprisingly long time.
The shielded bearings are a NO GO! They will fail as the fuel mix is prevented from washing the bearing clean and lubricating. Stihl had a TSB on this exact problem in 1996-98 The solution was to remove the shields from the bearings. The saws you have are the reason for the TSB.
For 2t crankshaft bearings, I'm with you👍🏻 would much rather have caged bearings than shielded. Still on the fence about metal vs plastic cages but modern plastic blends can be incredibly heat resistant!
This was very interesting. The nylon caged bearings you showed looked kind of shielded to me. With nylon. Not a very good conductor of heat. My take is they might work well on a stock saw. If you want to modify a saw it seems to me that the steel caged non shielded bearings would be the best option. People that take the time to modify a saw will probably make sure they have good air filtration. So then we have lubrication and heat conduction, on both counts I would think steel caged is superior. On the other hand I recently purchased some 6201 bearings. Both shielded and rubber sealed were rated at 22,000 rpm . In both cases the bearings were steel caged. So I don't really know. Maybe crankcase bearings take more of a pounding, that's why they don't use sealed bearings?
I’ve been running 2 stroke RC engines for over 30 years, we moved away from steel cage and protected/sealed bearings long ago now. We actually use hybrid ceramic bearings these days. We no longer have to replace bearings twice a season, new hybrid ceramic bearings last 2 full seasons and the nylon cages work very well. Would be great to run hybrid ceramic bearings in a saw, but many are licensed and can’t be copied.
I have a Moki 1.80 cubic inch (30cc 2 stroke) model airplane engine that burns methanol. This engine had a metal cage failure in flight, it happened just as I closed the throttle. When I disassembled it I found that the cage went up the port where the piston caught it. Surprisingly all I needed to replace was the piston, ring, and bearings. It has a chrome plated aluminum cylinder and there wasn't a mark on it. In methanol airplane engines, between 15% and 20% oil is required.
I tore down a saw with a ton of crankshaft play. When I split the case the nylon cage was gone as well as one of the ball bearings. There was zero damage to the cylinder and piston from the ball. I replaced the piston as it had minor damage to the piston skirts from the melted cage. Somehow the ball made it through without making contact with anything.
I don't know what kind of bearings my machines have. Maybe you know because you disassembled thousands of machines... MS230 (2005), MS311 (bought 16mo ago) and FS120 (2016). Thanks!
When I discovered that my 572XP had "plastic" bearing cages, my opinion of it quality suffered.. How can it withstand the heat. Your explanation of the relatie heat down in the lower case really helps ease my worry; but on hot days that saw gets HOfnT. I do not think the plastic bearing cases are nylon. Derlin (sp) maybe, HDPE less maybe; but either are somewaht heat resistant, especially Derlin, and somewhat lubricious, especially HDPE. I enjou Scot's videos too.
The new strato charged engines seem to run way cooler than first couple generations. My 572 is 5 years old hard use logging. Only problem was a coil 2 years ago.
Great video Richard. I think it's a trade off. The shields block debris but they also block some of the fuel/oil mix trying to get where it's needed. I've taken shields off lots of times and never had a failure. Shielded bearings always have a metal cage. At least all I've seen have. I think the metal cage will outlive the shielded or plastic gage. I've seen plastic cages mealt then the rolling elements skid and ruin the cases.
I will say that when the nylon shielded bearings fail the plastic chunks WILL wreck an otherwise healthy piston. As in there were large chips above the ring groove. Overheated clutch to engine failure pipeline.
Very interesting topic about the bearing cage's and shielding. I will be building a new bottom end for a Husqvarna 372xp in the near future. I will have to investigate some shielded bearings for it. Thanks for the idea's! P.S. I do suspect the white coating on the MS400 piston that is coming off will be very abrasive to crank bearings.
The greatest enemy to a chainsaw is combination of a dull chain and an overly pridefull saw owner. The single greatest creator if heat. The only bearings i ever had fail were on a 372 x torq/turd that i tried to make run at a higher power output. My fault Keep your saw sharp.
Great info Rich, Have you happened to looked into the availability of these “shielded” bearings? I’m asking because I’ve recently in the last couple years have caught the bug of fixing older saws. I have a 440 that I got off marketplace that’s going to need more work than i originally thought(not a big deal cause it was cheap) I will ask the guy in my tool room at work where we source our bearings as we get a lot of NICE brand bearings, I won’t know measurements untill I get the saw apart, hopefully in the next couple weeks. Great video!!
Those shielded bearings is not a good idea , I tried them In one of my R&D saws that I was experimenting with and those bearings failed cus of lack of lube !!! And that saw that's on your bench someone put those shielded bearings in there cus Stihl don't use them !!
My concer re: nylon (plastic?) cages is chemical compatibility, ie: how well the cage holds up to various lubricant chemistries. Is it possible these might fail due to lack of proprietary additives in competing 2-stroke lubricants?
@@richardflagg3084thats kinda why i thought OEMs used them because i assume you can get away with less air filtration with the more forgiving material
I think this is really good discussion. I’m definitely not a chainsaw expert, but it’s something that I’m interested in and hoping to understand more about. I agree with you 100% if a bearing fails it’s due to a combination of outside factors. I’m currently have two 10 mm 044 red switch saw that I bought blown up. I’m going to have to have the cylinders re-coded because they don’t make the slam fins anymore. Aside from that and the bearing wear .They’re in decent shape but they need to be gone through 100%. If I wanted to order shielded bearings, how would I go about doing that? Thank you
The flywheel bearing is a standard size. You'll be able to source a 6202 C3 rated bearing from whichever manufacturer you choose. The Clutch side bearing is a proprietary bearing. I've yet to find a name brand bearing company that makes them. There are Chinese aftermarket ones, but I'd avoid those.
I would like to see why everyone says the chinese 372 clone saws need their timing advanced via the removal of the flywheel key and advancing it one key width! Where is the difference coming from the chinese flywheel key notch placement, or is it in crank notch or coil.. Husqvarna uses a built in key in their flywheels at least the x torque ones do.
I think the benifit of the shielded bearing is it will allow the fuel/oil mix in and then keeps more of that mix in the bearing instead of there being only a micro thin coating on the bearing surfaces.
