Rotax 650 Engine Rebuild (BMW)

[Spyker]

Won't it be cheaper to order the complete gasket set rather than individual gaskets? When I rebuilt my Dakar I ordered the complete set.

[ericsbr]

Originally Posted by Spyker

Won't it be cheaper to order the complete gasket set rather than individual gaskets? When I rebuilt my Dakar I ordered the complete set.

I did the math and the kit was more $ than the individual gaskets/seals i needed. I'm reusing the cam cover gasket. If not the kit may have been the better deal.

[ericsbr]

More parts have arrived! New counterbalance shaft bearings are sealed vs old ones that were open. Every other internal engine bearing is open. Hmmm? What's better? Sealed are dependent on the grease that was put inside for its lifespan. Any wear particles are stuck inside too. Open bearings get constantly flushed and lubed with engine oil. Maybe better cooled by the oil too? Let the debate begin!

[divimon2000]

My vote is for using what BMW currently makes (in this case sealed). Why? I have a feeling the boys at BMW engineering in Munich and the corporate structure of ISO 9002 (or whatever they use probably more sophisticated) for QA production naturally create a better part (in general).

[Spyker]

Originally Posted by divimon2000

My vote is for using what BMW currently makes (in this case sealed). Why? I have a feeling the boys at BMW engineering in Munich and the corporate structure of ISO 9002 (or whatever they use probably more sophisticated) for QA production naturally create a better part (in general).

I'm pretty sure BMW doesn't make bearings. They just repackage SKF, NTN etc.

[Spyker]

Originally Posted by ericsbr

More parts have arrived! New counterbalance shaft bearings are sealed vs old ones that were open. Every other internal engine bearing is open. Hmmm? What's better? Sealed are dependent on the grease that was put inside for its lifespan. Any wear particles are stuck inside too. Open bearings get constantly flushed and lubed with engine oil. Maybe better cooled by the oil too? Let the debate begin!

By the way, when I pulled the bearings for replacement some bearings only had a seal on one side. the workshop manual states to press the new bearings in with the seal on the outside. So I pried one of the seals off the bearings.

[ericsbr]

Originally Posted by Spyker

I'm pretty sure BMW doesn't make bearings. They just repackage SKF, NTN etc.

true. my old were NTN, new were NSK. each bearing maker prob has different levels of quality for different customer needs.

[ericsbr]

Originally Posted by Spyker

By the way, when I pulled the bearings for replacement some bearings only had a seal on one side. the workshop manual states to press the new bearings in with the seal on the outside. So I pried one of the seals off the bearings.

what year is your dakar? what workshop manual were you using?

[Spyker]

Originally Posted by ericsbr

what year is your dakar? what workshop manual were you using?

I have a 2004 twinspark. Drop me a PM and I will send you the link

[ericsbr]

interesting NSK technical article on sealed trans bearings-

http://jeep.yager.net/docs/trans-toy...nsmissions.pdf

[divimon2000]

That's a confirmation for sure. Sealed is better. Whaddya gonna do? Keep em as is, or you going rogue?

[ericsbr]

Originally Posted by divimon2000

That's a confirmation for sure. Sealed is better. Whaddya gonna do? Keep em as is, or you going rogue?

dont rush me divimon! i still have time to flip-flop. could end up a coin toss. i would agree that sealed would be better if the engine/trans oil was very dirty or metal contaminated, but if the oil is kept clean and the engine/trans is "healthy" then more oil exposure seems better.

[mcma111]

Do your self a favor and pop one of the seals off and see how much grease is in the bearing.

You might decide that there is not enough lubricant for the long haul after all. If it were me I'd pull the seals and let the motor oil do it's thing but that's just me.

[Kawidad]

Originally Posted by mcma111

Do your self a favor and pop one of the seals off and see how much grease is in the bearing.

You might decide that there is not enough lubricant for the long haul after all. If it were me I'd pull the seals and let the motor oil do it's thing but that's just me.

KTM did this same thing with the cam shaft bearings on the early RFS motors. The original ones were unsealed, to be lubed by engine oil. Then they were superceded by new bearings that were sealed. However, even though sealed they were still in an oil bathed environment. I spoke to some bearing experts (real professionals, not hacks) and they said KTM was crazy because oil is thin enough to seap into the bearing past the seals. When it does this it washes out the grease, but does not provide enough lubricant to keep the bearings running properly. KTM worked around this by recommending the bearings be replaced frequently.

So I guess the point I'm making is that not all factory ideas are that good. (Not to mention, the original KTM bearings were the lowest quality/cheapest bearings sold in Europe (again according the bearing pros), which is mostly likely why they failed in the first place.

[ericsbr]

Originally Posted by Kawidad

KTM did this same thing with the cam shaft bearings on the early RFS motors. The original ones were unsealed, to be lubed by engine oil. Then they were superceded by new bearings that were sealed. However, even though sealed they were still in an oil bathed environment. I spoke to some bearing experts (real professionals, not hacks) and they said KTM was crazy because oil is thin enough to seap into the bearing past the seals. When it does this it washes out the grease, but does not provide enough lubricant to keep the bearings running properly. KTM worked around this by recommending the bearings be replaced frequently.

So I guess the point I'm making is that not all factory ideas are that good. (Not to mention, the original KTM bearings were the lowest quality/cheapest bearings sold in Europe (again according the bearing pros), which is mostly likely why they failed in the first place.

what i have learned so far is not all sealed bearings are the same. wheel bearings for instance would be lubed for life with grease, and sealed to keep grease in and water and road dirt out.

my new bmw bearings are designed for transmissions. they are greased only for initial lubrication, then the seal allows engine/trans oil to "leak in" to do the lubrication after the grease is washed out. they are designed this way.