Plastic M20 bearings pros / cons?

[penton117]

Hi guys,
Heres one for the collective brain trust. I heard this was mentioned in a recent newsletter, but I didn't catch it. Anyway here goes . . .

My local bearing house said they could supply FAG M20 bearings. I ordered a set for my Sachs crank and when they arrived the cage which holds the ball bearings was made of plastic instead of the brass I am accustom to. Does anyone have experience or opinion on the use of these plastic-raced bearings? thanks as always,

Don


 

[Doug Wilford]

Don;
Production costs and engineering, are sure the reason for the change.  I am sure the longevity of the bearing is the same.   As far as I know there have been no problems.  Trust the manufacturer, they don't want any premature failures either.

 

[Kip Kern]

Don

Check out some of the bearings in modern race bikes, you will find plastic cages in a few!

 

[BrianTaylor]

Hi Don ..just to put my 2 cents in ..I work for Canadian Bearings and have been in the business for 30 years. The FAG m20 didnt ring a bell with we so i called Fag in Canada and they had no listing of a m20. I asked if they made a polymide cage (which looks like plastic) and they responded with no not as a standard. Now everyone knows anyone will make anything for the right qtys and costs so i am not saying it wasnt done but if it was me buying those bearings i would not put them in my Penton. I would stick to the steel cage or brass cage not the polymide ( which tends not to do well under high heat applications..... just my 2 cents...bt

Brian Taylor

[Dr.2Stroke]

here s my opinion about differences in the cage material: KTM built in in the 125-400 ccm main bearings with brass cage until 1980. then in middle of 1979 ,the 420 engine came up,and this engine had M 30 bearings with polyamide cages.these polyamide cages have lower friction resistance than brass cages have,and the thermical factor doesnt matter so much,because usual two stroke engines are as cooled in the crank space due to fresh are taken in,so it doesnt matter about of material which is built in. it is also easier for a constructor to produce polyamide cases due its facility of setting  the bearing complete in comparison of complicater cases of brass.i would say,you can built in what you want or get!

 

[john durrill]

I agree with Dr 2 Stroke,
 once the engine is assembled the cages dont do a lot. but they could generate drag on the balls.
I have some plastick cage bearings in my engine and they seem to work fine. I know of at least 2 others on the list that have used them with good results. one is Teddy and he is winning MX and not haveing to rebuild every other week. that in it self is a good sign.
 Brian can you find out some more on what the differences are on the cage materials? The M20 is used in elecrtic motors still and thats what i have to tell the bearings house for them to find it listed usualy.
John

 

[BrianTaylor]

John i can send you all you want to know about bearings if you want. I dont think i can send attachments to this board so i could send direct to you. All the above statements are peoples personal views which is ok but some is not factual The main reason of the cage is to keep the rolling elements at an approiate distance from each other and to prevent immediate contact between two neighbouring rolling elements (friction and heat)  Polyamide should not be used with certain lubricants were temperature exceeds 100 -120 c or temps -40c polyamide cages become brittle if dehydrated ..pressed steel cages are the standard, cages are affected by lubrication , temperature and also contribute to noise in a bearing Just to inform and if you need further info or documentation just ask..thks BT

Brian Taylor

[john durrill]

Brian,
 I would like that very much.
 That's 212Deg F to 248 deg F on the high side. the -40 c wouldn't matter cause my hands would be frozen to the bars *GRIN*
What kinds of lube do the polyamide cages not like? what kinds of lube will, if any extend the temp of safe operation?
what causes them to dehydrate?
the stock Bearings had brass cages.
I have gotten both the polyamide and the brass cages in the last 6 months from bearing supply houses so I know they are still available. just need to specify which you would like.
I don't know what the crank case temp runs at but the bearings are bathed in a continues bath of cool fuel and oil if the motors running.
 thanks in advance for the info you might send.
My e-mail addy is
[email protected]
John


Edited by - John Durrill on 08/01/2002  3:53:28 PM

[BrianTaylor]

OK john i will scan some stuff for you in the next few days,....its getting like work here :}...BT

Brian Taylor

[BrianTaylor]

OK john i will scan some stuff for you in the next few days,....its getting like work here :}...BT

Brian Taylor

[Heinz Raidel]

Good points and good questions all around.

  I had some concerns about the "plastic" parts pieces in my crank bearings also,  i have put about three really hard hours on the 250 engine so equipped and its holding up.  This doesn't mean it won't fail the next time i start it.

My question would be is there anyone who has had a lower end failure due to the "plastic" in their bearings?

HR

[BrianTaylor]

Guys I wouldnt be alarmed if i saw polyamide(plastic) cages in my motor but if i had the choice of having or not having i would choose not too..I remember one time i was playing around with a synthetic oil (Klotz) and i had just torn my engine down and replaced crank brgs , went to 200 mile enduro finished and after torn my engine down again for some reason and i had noticed the brgs were very very rusty looking i attributted it to the oil burning so clean and hot it left no lubrication on the surfaces and thus oxidized quickly. Needless to say that was the end of my testing. Moral of the story i think temps were a lot hoter than anticipated could have the polyamide cages been damaged???... maybe .BT


Brian Taylor

[mikey]

re; Klotz and synthetics,,many moons ago an old motorcycle mechanic told me synthetics "bean oil" are only good for the cart guys who race every week and tear down the motors regularly,.,for the dirt bike guys who ride and park them for longer periods of time always use a petroleum based oil.,.the bean oils have zero rust prevention in them and you all know what condensation does to metal..for what its worth!

 

[Dr.2Stroke]

Hey guys, you have one of the best,no: THE best oil in your country,which is from Pennsylvania! what is it? Valvoline! Valvoline competition SAE 50 semi synthetic two stroke oil. i use it for over 14 years,and i have never seen corrosion in engines,also after staying over three years. believe me,i dont have a contract with valvoline,and the motorex guy always wants me selling his sausage,but i would cook my pommes with valvoline!not necessary to say that you have practically no oil coal under the piston rings! And really less engine(con rod bearing,piston) damages than with other oils!and i have tested every two stroke oil available here in switzerland. There can be only one! Dr.2Stroke