Crankshaft Bearings

[skipperclyde]

Can modern one piece crankshaft bearings, in the proper size, be used in my 1972 and 74 Piners?  The local bike shop sells them for less than $10.  The originals go for $30+.  Has anyone used modern bearings, and what problems, if any, were encountered?

 

[Heinz Raidel]

If you're refering to the lower end bearings, (not the rod bearings), the answer is NO!

If you can get originals for $30 that would be a good deal. They're about $45 (per) at bearing supply companies.

[skipperclyde]

Yes, you are correct, I was refering to the lower end bearings.  Can anyone tell me why not to use the one piece bearing instead of the oem three piece bearing?

 

[skipperclyde]

Yes, you are correct, I was refering to the lower end bearings.  Can anyone tell me why not to use the one piece bearing instead of the oem three piece bearing?

 

[skipperclyde]

Yes, you are correct, I was refering to the lower end bearings.  Can anyone tell me why not to use the one piece bearing instead of the oem three piece bearing?

 

[Kip Kern]

The crank bearings are a "press fit" bearing on both the case halves and the crank.  The three piece OEM bearing allows for this precise fit.  If you use a standard "one piece" bearing, you will only have a press fit in the case or on the crank.  This could create a "loose" area and possibly spin a outer race or inner race.  To be honest with you, I have seen the one piece used in the Sachs but I would highly recommend the original.  Also,it sure is easier when it comes time to split the case halves using OEM bearings.

 

[skipperclyde]

Aren't the crank and case on modern bikes both press fitted?  The size of bearing i'm looking at have the same ID and OD as the three piece bearing.

 

[sachsmx]

When you have a conventional ball bearing (one piece) and have a press fit on both the OD and the ID, then you must use a bearing with more internal clearance, usually this there is a suffix "C3" after the bearing number. This additional clearance is inside of the bearing itself, not related to the shaft or bore to which it is fitted to. Without this additional clearance, the bearing may bind during operation or at the very least will run too hot due to excess friction. Neither is good. Spending an extra $50 on the correct bearings is cheap insurance compared to the possible damage that the incorrect bearing can cause.
Too many people make the mistake of assuming that just because the ID and OD are the same, the bearings must be interchangeable. There are many factors that go into selecting a bearing for a particular application such as load, speed, lubricants, fitment, etc. This is why you will see ball bearings with plastic cages, steel cages, brass cages and so on. Each has its use for specific applications. I hope this helps clear things up.

 

[skipperclyde]

Thank you. This explanation makes sense.

 

[KTOOM]

THE STOCK BEARING IS CONSIDERED "SELF ALLIGNING".  IT ALLOWS FOR THE CRANK AND THE CASE AT THE MACHINED BEARING LOCATION TO BE SLIGHTLY OUT OF PERPINDICULAR ALIGNMENT.  WITH MODERN C.N.C. MACHINING AND EQUIPMENT, THIS IS USUALLY NOT AN ISSUE, BUT BACK IN THE DAY IT WAS AN ISSUE.  THE STOCK BEARINGS WILL NOT ONLY RUN COOLER AND MUCH MORE RELIABLY, BUT THIS IS ONE OF THE KTM AND SACHS HORSEPOWER SECRETES.   JOE WRIGHT

 

[skipperclyde]

Wow,now you have really convinced me with information that I can understand.  Thanks