trappermike
ArboristSite Guru
Probably at some time you need to replace your crank's main bearings or would like to upgrade them to something better.
First thing is that any bearing assembly's weak point is always the bearing's cage,whether it be a main ball bearing,a rod big end bearing or a piston bearing the cage is the "Achilles heel" and what almost always fails,usually causing damage in the motor. The cage does not have much other purpose than making the bearing easy to manufacture or easy to install. In fact bearing cages have haunted 2-stroke performance engine designers for a long time,cages exploding or coming apart. In the old days some engines were built with needles or rollers only,having more increased their load carrying ability by more rollers or needles without a cage to fail. Almost every saw motor I've seen had the metal cage main bearings fail,twisted and broken metal bits destroy the motor. However modern engine assembly has no use for this more time-consuming process of induvidual rollers or balls, so caged bearings are with us today. The normal ball bearing assembly installed in saws was improved with Stihl's use of a "Teflon" or plastic cage. Much lighter and slicker than the traditional steel cages these bearings were far more reliable and rarely come apart.
Also bearings come in a C1,C2,or C3 rating,designating how tight the bearing clearance is,the older Stihls used the tighter rating than their Husky/Jonserd counterparts,and last longer but are "stiffer"(More drag) when new.
As a side note I have seen "Full compliment" ball bearing assemblies,these have no cage and are all balls,but only available in bigger bearings,sadly our 6202 and 6203 bearings are left out,but they do exist for the Mac 101.
So when I order main bearings from a bearing supplier,I stipulate I want Teflon(plastic) cages,non-sealed. Now if your new bearings do come sealed,simply pop the seals out with the tip of a small sharp knife,you don't want them,better to let cool fuel/air/oil charge to the main bearings.
You can buy the good bearings from any good bearing supplier for much less cost than factory replacement.
First thing is that any bearing assembly's weak point is always the bearing's cage,whether it be a main ball bearing,a rod big end bearing or a piston bearing the cage is the "Achilles heel" and what almost always fails,usually causing damage in the motor. The cage does not have much other purpose than making the bearing easy to manufacture or easy to install. In fact bearing cages have haunted 2-stroke performance engine designers for a long time,cages exploding or coming apart. In the old days some engines were built with needles or rollers only,having more increased their load carrying ability by more rollers or needles without a cage to fail. Almost every saw motor I've seen had the metal cage main bearings fail,twisted and broken metal bits destroy the motor. However modern engine assembly has no use for this more time-consuming process of induvidual rollers or balls, so caged bearings are with us today. The normal ball bearing assembly installed in saws was improved with Stihl's use of a "Teflon" or plastic cage. Much lighter and slicker than the traditional steel cages these bearings were far more reliable and rarely come apart.
Also bearings come in a C1,C2,or C3 rating,designating how tight the bearing clearance is,the older Stihls used the tighter rating than their Husky/Jonserd counterparts,and last longer but are "stiffer"(More drag) when new.
As a side note I have seen "Full compliment" ball bearing assemblies,these have no cage and are all balls,but only available in bigger bearings,sadly our 6202 and 6203 bearings are left out,but they do exist for the Mac 101.
So when I order main bearings from a bearing supplier,I stipulate I want Teflon(plastic) cages,non-sealed. Now if your new bearings do come sealed,simply pop the seals out with the tip of a small sharp knife,you don't want them,better to let cool fuel/air/oil charge to the main bearings.
You can buy the good bearings from any good bearing supplier for much less cost than factory replacement.
