Definative main bearing thread

[tourist]

Hey John

that's crazy stuff from them sending out bikes with no crank end float

one thing Ive not mentioned yet is that sometimes the bearing outers move inside the cases when the cases are hot and settle at zero end float as the bike cools down

then the next time you start the bike you have zero end float until the cases get at least as hot as they were when the bearing moved.

happened to my bike once.. at around 80 hrs I think .... i thought it was going to be stuffed for sure ... could not get the bearing to move back until it bike was really hot.. took 30 min easy riding before the bearing moved again and I got the end float back by tapping the end of the crank with a mallet.

so if you rev a "warm" engine that happens to have settled with zero end float....

Interesting Just to ask a stupid question, can you tell what the end float is without splitting the cases? I'm assuming it wasn't that you noticed at 80 hours that the bike was acting was funny, split the cases, saw the bearing had moved, put it back together and gently rode it back into place ..?

 

[bushmechanic]

just remove the ignition cover, put a dial gauge on the crank and measure the axial play.

 

[Lanttola]

Just out of curiosity, what is the downside if you have too much axial play in the crank?

Earlier in this thread was mentioned that setup where one side bearing was locked in the crank.
What are your opinions on doing that on this engine?
I mean if you make a spacer between the left side bearing and the gear so the crank stays locked in the left side and the right side is free to move on a roller bearing?

I did that to mine and it hasn't broken down yet...

 

[bushmechanic]

none that I know of

however there have been some failures of the inner race where the lip has broken off (with "normal" axial play")

i think these failures are due to crank spread and lack of support of the lip but in theory the crank can develop more inertia if it can move further in the axial direction

however most of the development and testing of different mains configurations we have access to comes from the RFS builders with 540 - 640cc builds (there are simply more RFS engines being big raced and tuned than bergs) and none have found any problems with the mains at crank end floats set up to 1mm.

I ran 1mm float on rollers for 100 hours in my 700 nothing went wrong.

the setup you use I think is great if it works for you, and I'd like to be crystal clear that I think anyone who has found a setup to work for them should be happy with it.

IMHO the NTN rollers are the best option they are cheaper than the SKF bearings and to date there is no record of them failing in 1000s of builds even with floats down to 0.15 - 0.2mm. Orangeberg noticed the KTM race team using them in the finke desert race here in aust as they were fitted as OEM parts to the ktms.. no failures in the RFS bikes... the bergs in the same race fitted with SKFs had issues at similar end floats.

 

[bushmechanic]

recap on ball/ roller

the advantage of ball on the drive side in theory is that it can handle misalignment + axial loading + radial loading all at the same time better than a roller

I wouldn't use the ball/roller personally for 3 reasons

1) because the ball bearing has a much lower load rating than the rollers around 22Kn for the ball, 44Kn for the roller and the spherical rollers I use are 84KN http://www.vxb.com/page/bearings/PROD/30mm/Kit10509.

Thomas of enginehardware found it was a good setup if changed every 100 hrs .. but generally people find the ball does not last as long as a roller

2) while the crank is locked to the ID of the bearing the outer of the bearing is not locked to the case and is only a very tight fit.. if it does move you have a problem .. potentially zero endfloat. (see pic in quote below)

3) the axial loading due to crank spread is shared between the 2 bearings so no matter what you put on the drive side, the ign side still gets the same axial loading.

the first one that was popular was the use of a KTM crate engine deep groove ball bearing on the drive side and an NJ 206 on the ignition side.

many jap bikes use this idea but they fasten the ball bearing to the cases and also to the crank so the crank cannot move.

they also have about 2mm room between the rollers on the roller bearing and the lip or.. no lip at all so the rollers never contact the lip in these bikes

in the husaberg the ball bearing is just a stupdly tight fit in the cases and on the crank but the crank is not actually locked in position and can move.. you wouldn't know about it though till the roller bearing failed.

it is also very difficult to measure the space between the ends of the rollers and the nj roller bearings lip... you still need the same amount of room for the crank to expand because the axial loading is shared by the 2 bearings and the NJ bearing still gets squashed into the lip

it has worked for some people but i have seen it fail in 20 hours

this shows the degree of force that is pulling the bearing out of the case

check how the bearings can be pulled inward out of the cases 8O

Interesting experiment i tried to retain the outer race of an Nj2206 with an alloy plate

you can see its cracked. the outer race of the bearing has been pulled
out of its bore by 1.5mm and with enough force to break the retainer.

I find this interesting as there is no easy way to apply a force to the outer race
in this direction. there is a lip but it can only push the bearing into its bore not
out

also I was running 0.8mm crank endfloat so for the outer race to move any
more than 0.8mm out of its bore means there is some extraordinary flexing
going on.

 

[bushmechanic]

Tech description of Types of Misalignment

if you enjoy reading technical stuff

this comes from The American Bearing Manufacturers Association standards and explains the different types of misalignment and how they affect the load capacity of roller bearings.

in short 2 main types of misalignment and 3 resulting less than ideal scenarios to explain how overloading occurs in the mains and causes the ends of the rollers to dig in

I posted it up in 2009 somewhere but it should go here as well.

ABMA standards state that optimum dynamic capacity C values refer to roller bearing mountings so designed and executed that uniform load distribution over the active roller length is assured. it is further stated that if misalignment is present a reduction in the capacity value should be made.

2 types of misalignment: A location misalignment, and B deflection misalignment.

location misalignment implies misalignment in a plane at right angles to the direction of the load. this type is assocoated with skewing of the rollers on the roller track and resultant distortion of the contact area. location misalignment may arise as a consequence of 2 bearing supports some distance apart being out of line. though very undesirable this type of misalignment is not as serious as deflection misalignment and does not result in large bearing capacity reduction.

Deflection misalignment misalignment in the same plane as the direction of the load. this type is ascocitaed with a tendancy toward digging in of the roller ends on the roller tracks with resultant high stresses at these points. with straight non crowned, cylindrical rollers this condition is much more exaggerated than in designs incorperating crowned cylindrical rollers.

deflection misalignment is encountered when moderate to heavy external radial loads exist on small diameter shafts and/or bearing supports are remote from the point of load application

 

[WArdogG]

This is one helluva thread, I'm very happy I read it before attempting any rebuilds.

I have seen it mentioned somewhere, as usual having difficulty finding it again, about the inner races spinning on the crank. Is this the same cause as the bearing failures, the rollers pinching the inner race and spinning it when the crank flexes, or would it be because the fit between crank and inner race is not tight enough? Or maybe a little bit of both.

Also, regarding the main bearing cages, what would be the best cage material, brass, poly or metal? I would say poly would be safest in case of a bearing failure, I can only imagine what damage a collapsed metal cage can cause...

 

[bushmechanic]

given how tight the fit on the crank is IMHO they can only spin if the bearing is refusing to do its job

both the crank and the inner race are steel so the interference fit can only really change if the bearing is the main heat source .. a ball or roller bearing overloaded axially.

if the bearing is a ball race or a spherical roller then there actually needs to be a slip fit to allow axial movement without damage

yes poly cage is going to cause the least damage but is more prone to embrittlement from heat, and not as good at maintaining alignment of the rollers, id also think that in these bearings the rollers and the inner races fail first not the cage.

Ive used brass caged "rollway" nj206s in C4 they were very good, the nachi 22206s have a steel cage

 

[WArdogG]

What would one do regarding the slipping inner race? should I change to a ball bearing setup in this case, or try rechroming that part of the crank and machine it back up to spec?

I noticed the Honda 450X inner race is a slip fit on the crank, it can rotate freely by hand, but then I suppose the crank was made to work like that, so having a slipping race on the BerG crank would not be ideal..

 

[bushmechanic]

I know the Honda engine.. the roller bearing never sees any axial loading because the ball bearing on the other side is fastened securely to the crank and also to the case, there is 2mm+ room between the end of the rollers and their "lip" so the inner race doesn't have a reason to slip and because its loose anyway there is no damage caused if it does slip.

I use a 1/2 thou slip fit for the spherical roller bearing this works very well

IMHO they only spin on the crank if there is something wrong so I run bigger axial play to reduce axial loading

after that you have 2 options .. make the inner race proper loose and let it slip = less damage to crank and bearing if overloaded axially

or make it tighter and try to stop it spinning which is just fighting with the problem, it will surely stop the race spinning and reduce the radial clearance in the bearing but its not really an elegant solution.

something to watch is the radial play, not sure if I put the specs above but the recommended radial clearance as installed is 0.04 to 0.07mm.

I tried to tighten up the inner race on one bearing by heating the inner slightly and dropping it over the crank with loctite,

radial play was 0.02mm .. this bearing was on the less loaded ignition side but wore out more quickly than its partner which had 0.05mm radial play.

from that I figured it is not possible to get enough crush to stop movement unless you go to a C4 bearing because the radial play is reduced when you increase the crush

 

[WArdogG]

Thanks Bushmechanic. So there isn't too much cause for concern, then. The slipping race is also on my ignition side. When the race is on the crank, I can turn it easy by hand, I was just concerned that it may be too loose on the crank.
I am thinking of using the 20mm wide roller on the drive side, with the c/b removed, and crank rebalanced. Or should I just stick to the 16mm NJ206? I intend to remove the c/b regardless.

 

[bushmechanic]

The 20mm wide bearings last longer than the 16s

I used Rollway NJ 2206 ema C4s, brass cage

if your crank has a oil squirt for the counterbalancer can close it up with a spotweld, big end will get more lube

also up to 1mm endfloat doesn't cause any issues in my engine

if weeds gallery was up I could show you a pic of a good spacer design, its important to give the inner race full support which means machining a funny lip

he had the inner race crack from lack of support

 

[WArdogG]

Ah, looking at the bearing now, I understand what you mean by making a support for the lip. Would you say it would help if I drilled a tiny, say 1mm hole in the inner race for lubrication, so that the slipping inner race wont generate excessive heat and damage the crank?

 

[bushmechanic]

interesting idea wardog

not sure how that would work out .. you'd think it would be better than no hole at all ..

it might be better to grind a shallow spiraled groove along the ID of the race with a 3mm diamond coated burr, say 2 thou deep

either way it creates a weak point

 

[WArdogG]

That's what I was afraid of, creating a weak point in the inner race.
I will test this, maybe run it with a hole drilled in the inner race, maybe check it out after 15hr or so...

Hopefully it will be less prone to making seize marks on the crank. I'm thinking the slipping race will generate heat, and any excess heat is bad in my book, so hopefully a lil' bit of lubrication may help.

 

[Taffy]

there is nothing wrong with the KTM OEM roller mains. they are a great product and shouldn't be slandered for no GOOD reason. finding fault and splitting hairs over a perfectly good product is unjustified.

the original very, very long main bearing thread where this was all sorted took a leap forwards when a member known as 'enginehardwear' explained how he (like me uses the OEM bearing) he races them, he tunes them, as do I.

the problem is in the axial float, if you don't have enough float - the engine will suffer. get enough axial float and they are fine.

the problem has always been when engines go wrong, rarely do people say: "it was my fault" and they blame something in the engine. the next rebuild is done better than the last and with another bearing and then a miracle cure is found!

stick to the OEM roller main and get the axial float right, check that the crank is 'true' using a vernier and a ruler.

ruler
us this across the ends of the flywheels. no daylight should appear underneath anywhere.

vernier
the width of the crank should be the same all the way around at 4 points = top, bottom, left and right.

if you are changing the balancer bearings then use the old ones to help you
put one on each end of the crank and make a pair of V-blocks or something akin to this. spin the crank and have something static near the crank axial ends to try and spot run out.

after over 100 engine rebuilds with original roller mains I have yet to have had a failure. Enginehardwear of Sweden was the same - no failures when using this bearing.

don't be mislead

Taffy

 

[bushmechanic]

?????

nothing is being slandered, just technical observations about 2 different bearings

NTNs are cheaper and IMHO better for many reasons

at the very least for arguments sake they are equal to the skf .. certainly they are not worse

you see they were fitted as OEM to some years of KTM 525s ... with no failures but the SKFs in the same bikes with the same setups failed all the time. believe it or not there have been thousands of rebuilds done in the US on the RFS engines , tuned raced ... 640cc +, the sample size comparing both types of bearings is much larger than ANY husaberg "specialists" opinion.

finding a way to make SKFs work with tunnel vision has nothing to do with making a valid comparison

even if they are only equal then the choice is still simple

don't waste your money

 

[Finnmats]

Main bearing radial clearance ok/nok?

Hi guys,

First post in this forum, I believe! I'm a KTM guy, but I couldn't resist a Husaberg FS650E with broken valve spring for a bargin, so I've joined the club of yours now! However, got the bike running with new parts, but without opening the cases. I felt some radial play in the flywheel bearing, but just that you could feel it. Engine has been running for 2 hours now, I got the famous leak from the weep hole and engine doesn't sound healthy at all now, as it did when I first started it. My question is; is it ok with ANY radial clearance in the main bearings or is that enough sign to consider them being lost and causing exessive noise?

Thanks!

Mats

 

[bushmechanic]

Hi Mats

if you can just feel a movement there it is usually 0.04mm but if you have access to a dial guage you can check it as close to the bearing as possible

the specification for radial play is 0.04 to 0.07mm

it is unlikely to be more than 0.07mm with the stock bearings, it is possible if someone used C4 bearings (very good idea) but if it were more than 0.1mm you should probably open it up and have a look.

the best indicator besides a rumbling noise is probably the magnetic drain plug, wash the oil off it ... the mains make hard shiny steel flakes about 0.5mm long

this is a pretty bad one... radial play so great it took out the stator

 

[bushmechanic]

these are some of the bearings I have tested

OEM SKF, Rollway C4 in 20mm wide, SKF C4 in 20mm wide, rollway emaC4 16mm wide and one of orangebergs NTNs

ign side SKF bearing, 0.75mm axial play, 0.05mm radial play, 105mm piston 28 hrs

Ign side NTN bearing 0.75mm axial play 0.04mm radial play, 105mm piston 50 hours

it looked the same at 120 hours, it even endured the debris from a rod big end failure

Rollway EMA C4 drive side bearing used with both the above bearings 150 + hrs

none have failed and all are good enough but it is clear to me which one is handling the situation with the least stress.

this is a sketch I did years ago to explain the difference

the surface speed at the contact point of the SKF roller with the inner race lip is higher than the other bearings because of its sharper roller radius, the axial load is also more concentrated.

I really don't care which bearings people use.. I just find this stuff extremely intriguing