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Bearing and seal question

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Hello all

I am changing the crankshaft, I got a Hot Rod crank and Wiseco roller bearings. I change it because the clutch side has a tiny movement, about .3mm and the last time my crank went out I only did change the needle bearing and the roller bearings. I lost about 100ml in 4 hours and my water pump sprocket broke 2 teeth. It went into the gears and did into the 4rth gear chipping one tooth, so now I have ordered Wr426 gears if lucky.

When I compared the side movement between the inner ring and the outer ring the new bearing had almost the same movement as the one I change. Between the both bearings one has more than the other. So I went out and found a bearing with also has a seal into it, called B&S or Bearings and Seals. I think they are from Trinidad, no movement at all plus the plastic ring. Anyway as tried them?

regards

Arnego2

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They are really tight when trying to move, pressuring the inner vs the outer ring. Less movement, or hardly any over the Wiseco Bearing. That B&S bearing has only this number on it > 63/28-2RS plus the name B&S, and Koyo is hard to get over here. In my RM250 with the YZ250 engine I used the Suzuki bearing :smirk:

I also wonder why not using a roller thrust bearing over the ball bearings we have in out engine? Friction?

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A little movement is ok, it has to do with how they are preloaded when they are in the installed state (Elastic expansion of the inner ring and compression of the outer ring). What causes bearings to wear is the surface of the balls. When they wear they'll get noisy which doesnt mean they're bad but indicates reduced load capacity. The deep grove ball bearings are used in the main bearing because there is no side load and they are the most efficient at carrying the rotational movement of the crank. Those deep groove ones can take SOME side load like installing the crank into the bearings. You do NOT want the shielded deep groove ball bearings. They are most likely greased which is why they dont feel as "sloppy" but when the engine is running fuel and oil passes through the bearing lubricating it. What brand bearing does Wiseco use? I would only use Koyo or a japanese or german bearing.

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They are most likely greased which is why they dont feel as "sloppy" but when the engine is running fuel and oil passes through the bearing lubricating it. What brand bearing does Wiseco use? I would only use Koyo or a japanese or german bearing.

I think this part is key. You don't want a bearing that has the seal already in it. The pre-mix needs to pass through the bearing to lubricate it. That's why the seal is separate and gets installed after the bearing is in the case.

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You can't use sealed bearings as mains. And they aren't just bearings, the post about the C3 is correct: specially designed to be used as engine main bearings, not just a bearing from bearings-r-us. Koyo isn't the only one, but they are the OEM supplier and are very well regarded. I wouldn't put unknown bearings in my engine.

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I'm still debating it with myself, after all the engine design has not changed for over 10 (ten) years. I am aware that the factories bearings need to be lubricated by the premix oil. But is that the wisest thing to do? The 2 troke engines have one weak spot, and that is the bearing - seal relation and their reliability.

Sealed bearings could have the option to secure the crankcase against the oil or air from the outer cases should the seals break. Their disadvantage is that the friction is higher. So far I read I think that 2RS only stands for 2 sided seals. I could not find anything else on the bearing or the company. I have to admit I'm tempted to try new stuff on my engine. Question is what will be the consequence?

A sealed bearing specially on the magneto side could safe some engines from melting :smirk:

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I'm still debating it with myself, after all the engine design has not changed for over 10 (ten) years. I am aware that the factories bearings need to be lubricated by the premix oil. But is that the wisest thing to do? The 2 troke engines have one weak spot, and that is the bearing - seal relation and their reliability.

Sealed bearings could have the option to secure the crankcase against the oil or air from the outer cases should the seals break. Their disadvantage is that the friction is higher. So far I read I think that 2RS only stands for 2 sided seals. I could not find anything else on the bearing or the company. I have to admit I'm tempted to try new stuff on my engine. Question is what will be the consequence?

A sealed bearing specially on the magneto side could safe some engines from melting :smirk:

I'm not clear on how you expect to get lubrication to the bearings if they are sealed. Personally, I can't see any advantage, and nothing but trouble ahead. If sealed bearing were an advantage, factories would have used them long ago. But since they need lubrication, seals are not possible. Suzuki used to lube the drive side by placing the seal inboard of the bearing, using the transmission oil for that side. Yamahas aren't designed that way. My guess is the consequence is a locked up engine.

2RS does mean two rubber (or neoprene) seals. Good for wheels, worthless for engine and transmissions.

I have had two stroke Yamahas for years, over 90 of them, probably more, and never once have I had main bearing problems. I run high grade oil, proper jetting, and always the best air filter I can, which I aggressively maintain.

As far as the seals go: when installed, I make sure the surface they seal against is step/pit/gouge free and polished, and pack the area between the lips with moly assembly lube. I never fool with them again until the rod needs changed. In fact, I never have to fool with the crankshaft until it is time for a new rod, which is usually when I've run out of rebores on the engines with sleeves. I had over 55,000 miles on a 1970 CT1 and went through two cylinders and one crank rebuild to get there, but never had main bearing or seal problems. That poor thing was buzzing along at 55 MPH. It had a long, tough life.

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One explanation for a tat of movement I got so I most likely will go Wiseco -Koyo.

For example we may use C3 clearance on bearings where a cold start up application my cause the balls to heat up quickly, the heat needs to go somewhere. Some of the heat gets passed through the outer race to the housing and the inner race to the shaft, this causes expansion which closes up the clearance in the bearing. If you did not allow for this clearance the bearing would not have room for expansion and lead to bearing failure.

Source: Bearing King

In regards to the difference from Suzuki - Yamaha design I beg to differ, well at least between the engine design differences of RM250 vs YZ250 they seem to me of cosmetic nature. A bit longer here a bit shorter there.

I'm sure the engine were top of the mark 1999 when the last engine change was made. But nowadays what gives the R & D department the essential push to see what works better?

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Those bearings aren't sealed... They're "shielded" you need a shaft seal to perfect a seal past atmospheric pressures. i.e. You want shielded wheel bearings to keep debris out. The purpose of the hole going to the transfer ports from the bearing recesses is to allow the flow of premix and air through the bearing when the piston puts pressure on the crankcase.

On a side note.. the premix, more specifically the oil film suspended in it lubricates the bearing and allows it to run protected at a much higher speed than grease (less viscous loss). Also the continual flow of oil through it means its consistently lubricated rather than grease which seeps out due to heat and flow.

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