needle bearings

[cameron da river rat]

i was reading in my personal watercraft illistrated magazine and came accross a section that said, caged roller bearings are not a good choice when puting a new top end on your sea doo. they said that you should use the stock style, loose bearings with thrust washers, because caged bearings have proved unreliable in sea doo engines.

my remanufactured 720 engine came w/caged roller bearings, and my sea doo 650 came with them stock! are they just not reliable in the 787/951's?

does it really make that big of a differance?
[img]tongue.gif[/img]

[Bill O'Neal]

Cameron,
This argument has continued for years amongst engine builders, and I believe both have their good points to argue.

The ease of assembly with a caged bearing creates lots less mistakes in the assembly process. The lenght of hours that the average watercraft runs before it needs a new top end or rebuild, which my guess is shorther than it should be due to the marine enviroment, give credit to the caged bearing argument. Also, there is a valid argument about the amount of exposure to oiling that can be considered. Some think that the two rings at the ends of the bearings block too much oil to get enough lubrication to the bearings. I'm not sure I agree with that though, especially with aftermarket rods with oil holes in them.

But, the extra bearing surface gained by not having cages increases the bearing surfaces by about 25-30%. That you cannot argue with, IMO. More bearing surface equals longer wear and a stronger bearing.

Now, knowing that the first paragraph is very true, I choose to use caged a bearing wherever I can, but use cageless bearings in some motors too.
Also, there are some cheaper caged bearing from Taiwan that just don't hold up real well, and often have premature cage failures. The caged bearings that come from Japan and Germany seem to be much better.

Eitherway, barring the Taiwan made bearings, you can usually assemble a motor for a pwc without fear of having a premature wristpin bearing failure if you keep the water out of the motor. I see alot of rusty bearings and rods in motors that fail and need to be rebuilt. It doesn't matter much which type of bearing you use in a rusty motor, it will fail no matter which bearing you choose to use.

[RGCRX]

Bill:

I know the article that Cameron is referring to and I too am curious about this debate as I'm in the process of doing a top end job on my '00 RX.

This is my first Sea-Doo and I'm not used to the uncaged needle rollers. I don't have a problem working with them but have always used Japanese caged needles, which have always been reliable.

Question is - do you recommend the use of the caged needles in the 951 and, if so, where can I get a set of good quality ones? Water intrusion is not a problem.

Thanks in advance.

[steve]

Doesn't Ski Doo use caged bearings on some of their sleds? And don't those sleds put out some serious HP even in stock form?

[Bill O'Neal]

RGCRX,
Wiseco lists them in their catalog, but I have been told they are on backorder for months now.
Go ahead and use the oem cageless bearings, you cannot go wrong that way.

Steve,
Yes Rotax uses caged bearings in some of their sled motors with 20mm wristpins, but I know of none that are made by Rotax that have the 21mm wrist pin that comes with the 951 motor.