Where to get quality ball bearings

W

whodathunkit

New Member
My 80CC engine seized up this weekend while on a 15 mile cruise through the Eastern PA mountains at ambient temperatures around 85 degrees. The engine only had about 100 miles on it, and was running about 30:1 oil at the time. Three other identical bikes/engines that I built as part of a 4 bike project made the trip without incident. In fact, One of the other bikes towed me (I had a tow rope just in case!) about 12 miles back to our base.

After disassembling & inspecting the upper end (cylinder & piston), it appears that the problem may be a bad cranckcase ball-bearing on crankshaft ends. I'm planning a tear-down to replace this, but I'd like a suggestion on a better quality replacement. The parts list in the engine manual describes it as a "202 E-grade" bearing. Can anyone supply more specs on this bearing, and possibly a cross-reference to a quality Japanese equivalent?

Thanks

Joe
 
FWIW,

"E" grade is about the cheapest you can get. It means it is made for mass produced electrical items like alternators or small motors. Bearings are rated by either "ABEC" or "ISO" class. ABEC ratings are 1,3,5 & 7. Sometimes you see ABEC 9 but in most cases this is not true. ISO is 0,2,4,5 & 6. The higher the number is both systems means the better the bearing. Better meaning the tolerances are held tighter but we are talking microns or ten thousands of an inch. Nothing you will ever notice. The higher rating also means it can handle higher RPM's but also cost more $$. (High rpm's like in machine spindles. 10,000+ rpm range)

You also have bearing pre-load and how it is sealed. Pre-load is how much internal stress the bearing is under from the manufacturer. Some bearings rely on axial load to give them their radial stiffness. (Called angular contact bearings) The bearings these motors use are called deep row bearings which is a standard type. Most of them will have between 0.0000" and 0.0005" of preload. Seals. Usually they are shelded or sealed. Z=almost alwayse means sheild on one side. ZZ= sheild on both sides. Seals will typically be stated as 2R.

For these motors and almost any general use bearing application standard ABEC 3 is fine. Generally the only reason to use the higher numbers is for high RPM applications or unusual environments. Again most general applications get nowhere near these ranges so why waste your money. You will also see ceramic bearings out there as well. These are usually for very high temp applications or unusual environments.

Bottom line, a standard ABEC 3 or 5 bearing is all you need. Good bearing manufactures are IKO, FAG, Fafnir, NBM, NSK, INA & Torrington. (I am sure there are more) All of these companies will put their name and the bearing ID on the bearing. Usually on the face of the bearing. The bearing ID always tells you the ABEC or ISO rating. Do not believe what is on the box. Read the bearing code and look it up on line as all of these manufactures have online resources. Search online for a bearing house near you. Most of them will sell you what you need.

When installing the bearing, do not force it. Apply even pressure only to the race that is being pressed. Otherwise you will trash the bearing. Also you should never double press a bearing. That is press the ID and OD. The bearing will not last long.

More then i planned to write.... Hope it helps.
 
I finally got around to disassembling the motor yesterday. As I suspected, the crankshaft ball-bearing on the drive-gear side of the shaft was fried.

The engine has 4 near-identical ball bearings; 2 unseald units on the crankshaft, and 2 sealed units on the sprocket drive-shaft. Can you think of any reason why two of the original equipment bearings are sealed while the other two aren't? The replacements I ordered for the crankshaft are sealed both sides. What are the pro's/con's of using the double-sealed units I bought? As I see it, on the one hand the new bearings are packed with grease and sealed- maybe that's good. On the other hand, I can forsee small amounts of fuel getting into the 'sealed' bearing, washing away the grease, and insufficient fuel being able to flow through it to lube and cool it. Which way should I go? If I want it unsealed on one side, can I just cut away the plastic seal on one side of the new bearing?

Joe
 
whodathunkit said:
I finally got around to disassembling the motor yesterday. As I suspected, the crankshaft ball-bearing on the drive-gear side of the shaft was fried.

The engine has 4 near-identical ball bearings; 2 unseald units on the crankshaft, and 2 sealed units on the sprocket drive-shaft. Can you think of any reason why two of the original equipment bearings are sealed while the other two aren't? The replacements I ordered for the crankshaft are sealed both sides. What are the pro's/con's of using the double-sealed units I bought? As I see it, on the one hand the new bearings are packed with grease and sealed- maybe that's good. On the other hand, I can forsee small amounts of fuel getting into the 'sealed' bearing, washing away the grease, and insufficient fuel being able to flow through it to lube and cool it. Which way should I go? If I want it unsealed on one side, can I just cut away the plastic seal on one side of the new bearing?

Joe
Click to expand...

http://www.youtube.com/watch?v=pVBSOi2HTYk
 
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