Definative main bearing thread

[bushmechanic]

Kye this a drain plug after 1 main failed in a 550

Whoa! Yep, well I reckon that is what my drain plug would look like if I had a magnetic one (must throw one of those on the shopping list).

I had no idea these cranks flexed so much!

yes its a bit shocking really.... and the forces required to flex that far are about 4 tons in the 628 engine.

if you take a crank that has spread and come out measuring 0.15mm out and then try to correct that spread in a press it takes about 4.5 ton on the webs to get it straightened back up. at the bearings this is going to be about 6 tons ! its no wonder you need a lot of axial play

 

[tourist]

Fascinating. Thank you all for this incredibly deep and useful information. This thread has already linked what tatters of knowledge I had previously accumulated, and will help in learning more.

 

[Kye]

Glad to have you back by the way Bushie. 8)

 

[bushmechanic]

this is the better pic showing the flex I mentioned in the first post

its a print from a KTM FEA analysis used in marketing for the models that replaced the RFS engines (similar to ours)

"improved main bearing situation"

"balancer removed from crank housing"

I asked on KTMtalk if anyone had seem a picture of a failed NTN NJ206 .. nobody has and that covers at least 1000 builds between the main builders there.

All the pictures of failures are with the SKF bearings.. AFAIK Orangeberg hasn't had any of his NTNs fail either that is not to say that the NTN Nj206 is indestructible just that it is substantially better than the SKF.

 

[berglsmerg]

Improved bearing situation = 207's, eliminating the balancer removes two joins and a "sleeve"

I would like to know what an "FE-optimised" crank amounts to. I really need to measure my crank now that it is back in the cases Bugger.... Wouldn't take long to dig it out.

I think my rod is 132mm ? Is this right, I sent you the specs sometime.

Stiffer chain guide was offset by weaker adjuster.

Wow you guys have been getting around on cast pistons is that correct ?

Was it the aim to stiffen up the drive side ? I know nothing about the last generation of motors, the primary gear on the 570 is a very tight 120 nm torque setting, ( left hand thread) taper fit with added factory loctite. I guess the cycling of drive, coast and engine braking would really set things off as well. I see that you have added extra stuff to the drive side of your Frankenmotor. Is tolerance to axial and angular forces the drive ( pardon the pun ) running a ball roller combinaton.
As an act of faith my fancy pants ldc has gone back together on the tightest .09 mm axial clearance. I hate to compare apples to oranges, I just would really like to quantify the changes that have been claimed by ktm.

 

[edelweiss]

Interesting. could somebody insert the conrod dimensions (lenght C to C, width, diameters of upper and lower eye) of most common models e.g.: 400, 501, 600, 450, 550, 650? So one could have better idea about the stiffness fighting the spreading forces. thanks in advance. one cant find all this info in tunning section.

 

[plumbbob]

if you take a crank that has spread and come out measuring 0.15mm out and then try to correct that spread in a press it takes about 4.5 ton on the webs to get it straightened back up. at the bearings this is going to be about 6 tons ! its no wonder you need a lot of axial play

Hey Bushie,

sounds like i've had this happen to my 650 engine, the flywheel side is 0.05mm out just outside the woodruff slot.
That side bearing is a pretty tight push fit on the crank but the balancer side needs a bit of a knock.
I've stripped the engine as it had developed a bad vibration between 4-5000 rpm (on the street with sm tyres) it does seem to smooth out over 5000.

Is it pretty straightforward for a good engineering shop to straighten it back up?

6206 bearings used and pretty sure the axial float was 0.4mm.

Chhers Carl

 

[bushmechanic]

Improved bearing situation = 207's, eliminating the balancer removes two joins and a "sleeve"

I would like to know what an "FE-optimised" crank amounts to. I really need to measure my crank now that it is back in the cases Bugger.... Wouldn't take long to dig it out.

I think my rod is 132mm ? Is this right, I sent you the specs sometime.

Stiffer chain guide was offset by weaker adjuster.

Wow you guys have been getting around on cast pistons is that correct ?

Was it the aim to stiffen up the drive side ? I know nothing about the last generation of motors, the primary gear on the 570 is a very tight 120 nm torque setting, ( left hand thread) taper fit with added factory loctite. I guess the cycling of drive, coast and engine braking would really set things off as well. I see that you have added extra stuff to the drive side of your Frankenmotor. Is tolerance to axial and angular forces the drive ( pardon the pun ) running a ball roller combinaton.
As an act of faith my fancy pants ldc has gone back together on the tightest .09 mm axial clearance. I hate to compare apples to oranges, I just would really like to quantify the changes that have been claimed by ktm.

Hi bergsmlerg

yes the info you sent me on the 570 rod is .... centre to center is 120.8 **edit is that right ? seems very short**** and small end is 20mm the big end pin is 35 od and 62.7 long weighs 394g the big end is 42mm id and 19.90 thick with a 19.70 thick bearing cage.

the NJ207 has a 35mm ID vs the 30mm of the old engines so the idea behind the change Is to stiffen the crank and put both mainbearings closer to the webs reducing deflection even more. your axial play is very tight but if the crank is stiff enough the axial loads on the rollers isn't very high .... obviously it works.

what is the factory axial crank play spec for the 570 ?

i put the fancy spherical roller on the drive side simply because the drive side roller always showed more signs of wear than the ignition side. the ignition side NTN Nj206 bearing i got off Orangeberg years ago still looks brand new so i left it but still run 0.8mm axial play since half the axial loading is taken by each bearing.

the drive side obviously has more radial loading than the ignition side and i noticed more wear when i went to the 105mm bore so I think radial load plus axial load plus misalignment from flex are the reasons the drive side bearing cops more abuse.

cast pistons no all the 100mm pistons are forged

 

[bushmechanic]

Interesting. could somebody insert the conrod dimensions (lenght C to C, width, diameters of upper and lower eye) of most common models e.g.: 400, 501, 600, 450, 550, 650? So one could have better idea about the stiffness fighting the spreading forces. thanks in advance. one cant find all this info in tunning section.

I don't think the rod itself has anything to do with the main forces responsible for crank spread which are due to the weight of the crank itself, the pin diameter and the crank mass defiantly do

550 crank and rod 4.75 kg 32mm pin rod length 123mm

628 crank and rod 4.5kgs 35mm pin, rod length 136.2mm

I can dig up some more numbers after work but the main thing is crank mass vs stiffness

 

[bushmechanic]

if you take a crank that has spread and come out measuring 0.15mm out and then try to correct that spread in a press it takes about 4.5 ton on the webs to get it straightened back up. at the bearings this is going to be about 6 tons ! its no wonder you need a lot of axial play

Hey Bushie,

sounds like i've had this happen to my 650 engine, the flywheel side is 0.05mm out just outside the woodruff slot.
That side bearing is a pretty tight push fit on the crank but the balancer side needs a bit of a knock.
I've stripped the engine as it had developed a bad vibration between 4-5000 rpm (on the street with sm tyres) it does seem to smooth out over 5000.

Is it pretty straightforward for a good engineering shop to straighten it back up?

6206 bearings used and pretty sure the axial float was 0.4mm.

Chhers Carl

Hi Carl

with 0.05 measured like that you would probably see 0.1 runout between centers which is really not bad at all .. most cranks would measure that after the first time you rev the bike out. it might be twisted on the pin slightly which doesn't show up as the same kind of run out.

if theres been a change in the engine vibes though I would open it up and check everything

yes its a straightforward thing to correct the crank they only need measuring gear a mid sized press and a soft hammer

 

[berglsmerg]

The factory spec is 0.25mm to 0.35mm or 0.0098" to 0.0138". I have set up the 0.0098" clearance and erroneously referred to it as 0.9 mm in my above post, so even tighter again.

The cast piston question was my attempt at humour.... I see that work really well.

I'll measure my rod rod for you again

 

[bushmechanic]

ha sorry no humour today, i have 3D design crap and FE simulations running a muck on 2 computers .. my head is full of matrices and constraints that won't spin around according to their own rules in e space

if the rod still comes up short I recommend using a fluffer

 

[plumbbob]

Thanks Bushie,

it's already spread over the garage so i'll check start looking for other causes.

Could counterbalancer bearing harmonics show up as vibes? Only ask as i fitted a new pair, tight on the crank but only a push fit in the balancer...........saw the loctite tip too late!

Carl

 

[bushmechanic]

sure it could but I don't know much about the idiosyncrasy's of the counterbalancer, I removed mine early on and loved the change with a 75% Balance factor, now I run 58% and its better again .. 62.5% is supposed to be the sweet spot.

mine had more vibes through the pegs below 3000 but much much smoother above 4000 rpm

with your 82mm crank it might be the CB doing a funky dance, weed and others noted removing the CB without re balancing the 82mm crank though is not a good idea

 

[tourist]

sure it could but I don't know much about the idiosyncrasy's of the counterbalancer, I removed mine early on and loved the change with a 75% Balance factor, now I run 58% and its better again .. 62.5% is supposed to be the sweet spot.

Is the 62.5% figure applicable to all the engine types? I.e. the 550 also?

 

[bushmechanic]

I would say yes but Ive not tested it personally

all the RFS builders are at about 62% on all their different builds and the RMZ450 which does not run a Counterbalancer is at 62%

since the majority of rmz owners don't even notice it has no balancer you have to assume its a pretty good place to start

 

[ORANGEBERG]

Interesting tech stuff Bushie, i stumbled across the right NTN bearing years ago and worked out it was good because it eliminated the problem and my warranty issues. Never studied enough to see the extra taper on the roller of an NTN, Not enough crank end float was the main problem and we had bulletins sent to us back in 2002 to open it up to at least .50mm on the KTM RFS motors. In 2005 we had to check every Husaberg bike as some had Zero from the factory I had to strip a couple and fix before i sold them. (Austrians on the piss again). Ive Been quiet lately but still get the odd rebuild sent to me.
My Husaberg weephole kit still sells around the world and if every Husaberg owner has there own CNC lathe at home in there shed im happy to share the specifications, if you dont have a lathe you just buy it off me.
Dont want be seen as making money from the site.
John ORANGEBERG

 

[ORANGEBERG]

My old thread on the main bearings was done in about 2007 but we had trouble in 2005 back then i was silenced by the powers above (KTM HUSABERG AUST) it went on to be one of the biggest ever on the UHE, it did get a bit off the track towards the end and we had no proof what was going on inside the engine, we were blaming oils, bad fuel, the position of the sun and moon etc but this latest post by you is very informative.
Im rebuilding my 07 650 which had NTN put in immediately off the floor and its done 10.000 hard KMs without a problem i just feel sorry for it so its getting a birthday and i have a few long distance rides coming up.
Like you said the 550 was by far the worst an the 450 occasionally, the 650 with the forged crank didnt have such a big problem.
My biggest problem lately is the primary drive nut coming loose and destroying the crank keyway and splitting the gear, must have been another Austrian factory worker who engaged in way to much AM drinking and didnt torque them up.
John ORANGEBERG

 

[bushmechanic]

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....

 

[bushmechanic]

reduction in axial play after rebuild

its probably worth mentioning that after a new build with a new crank or big end rebuild the axial play often reduces by about 0.1mm

so if you had 0.5mm on a new 650 build it will most likely end up a bit less say 0.4mm