MAIN BEARINGS FAILURE, MUST CHANGE

RE: Re: RE: New test

So what are the specifications and performance characteristics that make this bearing any better than a quality 206 bearing? That's what I want to know.......

I still think you're all looking in the wrong direction........

Simon

Re: RE: Re: RE: New test

Simon said:

So what are the specifications and performance characteristics that make this bearing any better than a quality 206 bearing? That's what I want to know.......

I still think you're all looking in the wrong direction........

Simon

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The reason why we tested it was due to the problems KTM had with the crate motor.
After a while the Husaberg Factory teams who gets thier engines from R&D in Orebro Sweden, have been using them., we disided to test and it works for us.
According to SKF main office( you all know that SKF is from Sweden), told us that the spec of bearing is very strong, we have to belive that the people there have the right knowledge.
Only disadvantege: PRICE!!!
I can only say that we have had some trouble with main bearings due to our RWHP output and by testing we can at this moment say its a improvment.
If you dont test then its just talk, talk, talk and talk.
Regards
Thomas

Re: RE: Re: RE: New test

Enginehardware said:

After a while the Husaberg Factory teams who gets thier engines from R&D in Orebro Sweden, have been using them., we disided to test and it works for us.
According to SKF main office( you all know that SKF is from Sweden), told us that the spec of bearing is very strong, we have to belive that the people there have the right knowledge.

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I agree with you 100% - one must trust the people who have the right knowledge

I would also put my trust in what the technical department of SKF would tell me. I'd be much less inclined to put engineering trust in the sales representatives :wink: As you'll have learnt by now, I'm just a bit pedantic me, I like to know what is meant by better and stronger because in the world of metals they can mean very different things, that's all. It all depends on the application.

Enginehardware said:

Only disadvantege: PRICE!!!

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As is so often the case...

Enginehardware said:

If you dont test then its just talk, talk, talk and talk.

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I agree with you 200%, but sometimes talk can be priceless too, when dealing with the relevant things in hand with the relevant knowledge, that is. Unfortunately on forums like this people often get hung up on the latest snake oil to be released and the issues get very confused.

I'm very grateful that you're out there testing and playing around with these things because it is invaluable, especially because you're also letting us know your experiences. Every theory clearly needs to be tested out there in the real world... Due to medical reasons I am no longer able to do that but my experience and continued experimentations in other relevant areas may still count (because I am still playing with the engines).

Personally however, I believe (and I have tried) a sensible discussion that takes this topic out of the box away from bearings or crankshaft in isolation might yield some very positive results (and in saying that I am not criticising your work in any way ).

Thanks for your updates.

All the best,
Simon

RE: Re: RE: Re: RE: New test

08 650 FE

crank end float 0.52 new, 0.42 at 10 hours, checked every 10 hours since at 0.42.

suddenly float at 80 hours 0.33. and 85 hours back to 0.52

now monitoring float and checking magnetic plug before every ride .

crank runout measured on RHS is always the same so I don't think that the pin is moving in the webs from crank flex although it may well be.

more likely I suspect one or both mains to be loose in the cases at some set of operating temps.

just another possible factor. end float may perhaps go to zero in this condition if the bike copped a big enough hit at the right set of temps during a fall. unlikely but possible?

regards

Bushie

RE: Re: RE: Re: RE: New test

Bearing movement in the case is the only logical thing that could explain your changes. What runout reading do you get? If the crank spreads, the increase in vibration is quite noticeable.

Has anyone checked the crank endfloat whilst the engine is at operating temperature & then at set temp intervals whilst it cools down ? The SKF bearing rep that now works for us says that you should only have a press fit on either the outer or inner race but not both. Expansion in the race is the biggest killer according to him & he has researched using ceramic bearings in go karts here that don't fail at massive revs ( not quite the power output of a berg though ) when the thing gets hot. He has suggested possibly using an NU bearing instead of the NJ as it doesn't have the inner flange & wont put extra pressure on the bearing when thermal expansion is at it's worst. He has also said that not all bearings are the same. NTN are made in 3 different factories so QA isnt the same as japanese bearings use better quality steel than their Taiwanese & Chinese counterparts.

Wildman, end float in my engine grows by 0.1 when warm and 0.15 to 0.2 when nice and hot. seems like the cases expand more than the crank even during warm up. haven't checked on cool down.

good info from the SKF guy, the china/taiwan thing is a good point. I have seen really really crappy NTN bearings and often send them back. the guy aways mumbles something about china.

Is the SKF guy talking about the thermal expansion of the rollers or the crank?

nielE runout is not true run out I measure it on the "flywheel" outer just for relative purposes. was 0.02 new and has been 0.08 since first 10 hour check.

say one bearing is loose when hot and a flatout pancake stack lifts then slams the bike into the deck on its side, the Gs would be huge and the bearing outer would surley move and close up the float. even if it doesn't move the crank would especially if it was stationary or at low RPM, can't be good for the ends of the rollers.

regards

wildman said:

The SKF bearing rep that now works for us says that you should only have a press fit on either the outer or inner race but not both

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i have put figures up for this before in this (long) thread but you're forgiven for not spotting it! :lol: :lol:

the bearing should be a non-interference fit into the cases whereas the crank should be a press fit into the bearing. it was about 10 microns interference as i recall. i had called SKF uk for the details and spoke to their technical rep.

regards

Taffy

If you are using ball bearings you do want an interference fit in the cases!

As for rollers I'm not sure I would accept no interference fit between engine cases and bearing housing - I would want something there - at least a tap in.

Remember, part of the reason for the bearing internal clearance (C3 or C4 designation etc.) is there to "soak up" a reduction in running clearance of the bearing from the tightness of fit to begin with.

As I've said before if the tolerances of fit in cases/crankshaft are incorrect, it will cause a closing up of the internal bearing clearance and may be a cause of premature bearing failure as on expansion there will be no clearance left.

In my mind therefore, if there is a really tight fit, it may call for installing C4 bearings instead of C3 as everyone strangely seems to stick with.

All the best,
Simon

Mains bearings

Just to let you know i am at the moment rebuilding my mates ktm 380 exc it did the bottom end bearing stuffed the main bearings ,tap danced all the needles in the head scratched the bore lucky it has a cast sleeve in it from a previous rebuild so just a re-bore and new piston and so forth, i can usually get all the bearings myself but one i couldn,t get was one of the mains L/H/S so he went and got it from ktm when he gave it to me i thought he was joking ,the bearing was so loose in the race it was unbelievable it had side to side movement up and down movement i thought it was second hand it also had a plastic cage suffice to say am not using told him to take it back and tell them its rubbish and should not be selling it.has anyone ever encountered this before,it was a ktm bearing made in Portugal? on a Friday i think.

RE: Mains bearings

i was told - a 'no clearance' fit simon. if you know better that's good.

regards

Taffy

Most of the thermal expansion the skf rep spoke about was the bearing itself but even the crank must expand when hot. He has miced up a bearing on a timber mill shaft & got 5mm of thermal expansion on a bearing which to me is rediculous. 8O As he has no knowledge ( like me ) of the Husaberg I have been trying to explain where the problems are occuring & getting theories from him on a fix. he suggested the c4 bearing but warned about the warmup as it would have extra play until thermal expansion took up.

I want to see a slight interference fit at operating temperature, otherwise the outer race can start to migrate in the case. Once some movement begins, it can only loosen more. The way I look at it is: interference fit at 100*C operating temp and slip fit at 150*C case temp for bearing removal. I would install the outer race with loctite if I had a case with a worn bearing seat.

Neil_E. said:

I want to see a slight interference fit at operating temperature, otherwise the outer race can start to migrate in the case. Once some movement begins, it can only loosen more. The way I look at it is: interference fit at 100*C operating temp and slip fit at 150*C case temp for bearing removal. I would install the outer race with loctite if I had a case with a worn bearing seat.

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When I rebuilt my engine last year I fitted C4 ball bearings on both sides, the outer race was shunk fit in the cases where as the inner were just over interfirence fit over the crank.
I am also running the crank modification that is done by DCR's in the UK. Over 3000 miles and going on 70 hours sweet as a nut.
I know it doesn't get the hammer an enduro gets but it's had some lenghty spells on the motorway sat at aruond 75 80 mph but mainly twisty mountain road stuff up and down the gear box like a fiddlers elbow.


Regards

Sparks.

When I rebuilt my 02 FX470E I used Fafnir C4 bearings on the crank & cam. So far so good. When I rebuild air handlers rotating assembles I always have a fixed end on the spinning assembly" (sheave side) so the thermal expansion makes the shaft grow one way and I keep alignment on drive components. How this would apply to a piston crank assemble I don’t know but I’m sure there's a large amount of thermal expansion!

sparks said:

Neil_E. said:

I want to see a slight interference fit at operating temperature, otherwise the outer race can start to migrate in the case. Once some movement begins, it can only loosen more. The way I look at it is: interference fit at 100*C operating temp and slip fit at 150*C case temp for bearing removal. I would install the outer race with loctite if I had a case with a worn bearing seat.

Click to expand...

When I rebuilt my engine last year I fitted C4 ball bearings on both sides, the outer race was shunk fit in the cases where as the inner were just over interfirence fit over the crank.
I am also running the crank modification that is done by DCR's in the UK. Over 3000 miles and going on 70 hours sweet as a nut.
I know it doesn't get the hammer an enduro gets but it's had some lenghty spells on the motorway sat at aruond 75 80 mph but mainly twisty mountain road stuff up and down the gear box like a fiddlers elbow.


Regards

Sparks.

Click to expand...

And what modification do DCR recommend??

Regards

swedishsteel said:

sparks said:

Neil_E. said:

I want to see a slight interference fit at operating temperature, otherwise the outer race can start to migrate in the case. Once some movement begins, it can only loosen more. The way I look at it is: interference fit at 100*C operating temp and slip fit at 150*C case temp for bearing removal. I would install the outer race with loctite if I had a case with a worn bearing seat.

Click to expand...

When I rebuilt my engine last year I fitted C4 ball bearings on both sides, the outer race was shunk fit in the cases where as the inner were just over interfirence fit over the crank.
I am also running the crank modification that is done by DCR's in the UK. Over 3000 miles and going on 70 hours sweet as a nut.
I know it doesn't get the hammer an enduro gets but it's had some lenghty spells on the motorway sat at aruond 75 80 mph but mainly twisty mountain road stuff up and down the gear box like a fiddlers elbow.


Regards

Sparks.

Click to expand...

And what modification do DCR recommend??

Regards

Click to expand...

On the drive side of the crank they fit the inner of a roller bearing over the crank up to the inner of the ball bearing on the crank, this in turn now needs a larger diameter oil seal, now when the crank nut is done up it pulls and secures the crank to one side so it is in a totally fixed position.
With the engine now on balls there is not the need for end float unlike with the rollers that need it.
Since they have done this mod they havn't had any problems that I know of, I had people say it is not good engineering but I can see why they have done this and the end result seems that it works.
I thought this mod was a well know thing.

Regards

Sparks.

sparks said:

now when the crank nut is done up it pulls and secures the crank to one side so it is in a totally fixed position.
With the engine now on balls there is not the need for end float unlike with the rollers that need it.
Since they have done this mod they havn't had any problems that I know of, I had people say it is not good engineering but I can see why they have done this and the end result seems that it works.
I thought this mod was a well know thing.

Regards

Sparks.

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Thank you sparks. I wrote about using a spacer that pulls the crank up to the drive side some time ago and I think it is even in this thread somewhere, which is something I used on my 2001 engine. I got flamed about that too.

I understand that this technique has historically not been uncommon in other engines.

To me the reason people say the DCR mod is not good engineering is the zero crank end float. The ball bearings can tolerate some radial load but not a lot so you don't want things too tight in there. However, I've never know the crank to fit flush with the bearings on assembly with these engines anyway - unless the bearing isn't seated properly - it usually has a good margin of float off the production floor.

Taffy said:

i was told - a 'no clearance' fit simon. if you know better that's good.

regards

Taffy

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As I'm here it's worth clarifying this point.

With the utmost respect Taffy, some of the things you've stated about bearings and stated they have come from the skf guys conflicts with the technical bearing data that skf themselves publish regarding their bearings.

This means that there is some interpretation and generalisation, or even misunderstanding, going on that muddies the water.

As for other items, I think it would be really helpful if when writing about bearings and their installation people would specify which bearings they are talking about - i.e. ball or roller or whatever else because this topic is confused enough as it is. Installation procedures are not always the same.

All the best,
Simon

sparks said:

When I rebuilt my engine last year I fitted C4 ball bearings on both sides, the outer race was shunk fit in the cases where as the inner were just over interfirence fit over the crank.

Regards

Sparks.

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the above is how it was explained to me it should be.

Simon said:

"I got flamed about that too."

All the best,
Simon

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you take it too personally simon.

i'll take back what i said about the crank being locked at one end because i realise now that it isn't!

nothing stops the crank assembly c/w inner races from expanding, going left or right etc.

regards

Taffy

Interesting thread over on KTMTalk discussing the stroked RFS motors which also damage the roller mains. They use ball bearings and polish the crank so that it can move inside the bearing inner race when the crank spreads.
http://ktmtalk.com/index.php?showtopic=276750