Steering shaft/top yoke centre nut - torque?

[tedthebudgie]

Hello. Just started tinkering with my Mastiff.

Crown/centre nut torque?

I see that someone else has asked this question but didn't post the actual figure.

I had a tiny little bit of up/down play in the steering set up so changed the head bearings. When it comes to the crown nut, manuals for the XT660 and SZR660 state 110NM but, unlike the Mastiff, they are fitted with steering ring locking nuts which might make a difference. Other bikes go as low as 20NM and seem to rely on the fork pinch bolts to hold everything together. So I went for 110NM with with my 1/2 wrench but couldn't achieve this without skewing the yokes and forks off centre. I checked that my torque wrench was working on the rear axle of my X11 and it worked fine. Loosened things off and went for a lower setting (tried 18NM as per a KTM manual I was looking at), out for a ride this morning and the play is worse than before the bearings were changed.

Any ideas? Do I just need to man up and go for the full 110NM and find a way not to skew the forks?

Cheers

Tim

[tedthebudgie]

No luck here then. I guess nobody torques up their centre nut!

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[DAVID THOMPSON]

i hang bike from frame on a chain hoist and remove front wheel
then replace axle this makes a hand holder at the end of forks
i pack and install new bearing then tighten them till no free play front to rear at the axle

to little the road bumps will pound impact marks into the bearings .. to tight will make it steer funny

like a friction steering damper that's adjusted too tight

if its a tapered bearing there may be a factory recommend TQ on its spec sheet

i have done bicycles this way for years and a bunch of 55 to current BMW

research your bike with care falling OFF is not fun!

the older BMW bikes handle much better with a tapered roller 55 to 69
below site lists bulk of 10 need to ask about each
inquire at
https://www.cycleworks.net/

[tedthebudgie]

Many thanks for the responses. Much appreciated.

I ordered new steering head bearings from Grahams and was surprised to receive 2 x KOYO 62052RSC3 which are rubber sealed bearings which I'm more familiar with for wheel bearings. I checked and I'd got the right ones and they were the same as the ones I removed from the Mastiff. However, although they seem to work fine, they are not tight in the head stock and they will come out without any struggle whatsoever and I still have a little bit of clunking from the front end picked up in the MOT. I'm going to try adding spacers to the assembly to snug things up a bit. If that doesn't work, I've got 2 x KOYO 30205 taper roller bearings waiting in the wings which are the same inner and outer diameters (25mm x 52mm) but are 1.25mm deeper. If they don't work, I'll try the YZ bearings which another user has mentioned as being possibles.

I'm getting lots of practice removing the front end which is more of a ball ache than normal as I think the forks are slightly bent. Once you've slid one through the top and bottom yokes, the other fork will slide through the bottom yoke ok but then misses the top yoke opening by about 4mm and needs prying in with flat screwdriver working on the fork nut and the yoke. I've then got to rubber mallet it in from the bottom. I think that it is this which is then skewing things a little at the top and putting the bars off straight.

BA Bikes has some forks in but they're not cheap. I'll be exhausting all options before splashing out and will spend another few weekends taking the front end on and off with my trusty box of Helicoils by my side!

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[tedthebudgie]

The difficulty getting the second fork leg into the top yoke I think is a different issue to the play in the head stock/bearings.

As I said, they were normal deep groove ball bearings which came out of the head stock and, with just 8,000 miles on the clock, I don't think they would have been changed unless a previous wheelie mad owner knackered them! They looked original when I removed them and were the same as the Koyo ones I received from Grahams.

With the help of Google translate, I've also been on the German forums and the "Order number: 9017620000 Deep groove ball bearing 6205.2RS" is confirmed, from the forum...."I had bearings sealed on one side. The lower one had started to rust from the inside out, despite plenty of grease filling. I have now installed bearings sealed on both sides (6205 2RS). However, I had not ordered them as original spare parts. They come from my dealer from the large excavation box for standard parts."

By the way, if anyone is as sad as me and wants to have a look themselves, Lenkoppflager is, I believe, German for steering bearing but I am happy to be corrected.

There is also an interesting discussion with a clunky Google translation which sort of explains why standard ball bearings rather than tapered ones were used by MZ...

"Has anyone ever tried angular contact ball bearings as a steering head bearing?"

"Be glad that at MZ around forty years ago someone had the pretty brilliant idea of ​​using normal ball bearings as steering head bearings - just insert the bearings and you're done. The other manufacturers are still practicing the ... adjustment of their tapered roller bearing construction and always have problems. Everything that can / has to be set can also be set incorrectly, which, if the setting is too narrow, results in the two bearings destroying each other due to overload. You can then sell expensive spare parts."

"In the past, tapered roller bearings were used almost everywhere, but you got away from it. I guess she's wearing a KeRoLa even more than an angular contact ball bearing. The second thing I don't know for sure: Angular contact ball bearings must be braced, to my knowledge. The construction of the Baghi does not give it away. A support sleeve is installed and the torque for the head tube nut is 80Nm. No possibility to counter the screw connection."

No idea what KeRola is! And there's more from our German MZers...

"huh, steering head bearings not adjustable ?? What is the fat hex screw on the upper triple clamp that goes directly through the steering head? So I think that my steering head bearing also had play and by tightening the screw did that happen ?!"

"The fat nut only holds the one under the triple clamp together with the upper one. Normal ball bearings are installed as bearings (like the wheel bearings only larger). You definitely cannot readjust them."

I couldn't figure why the Mastiff set up had the steering stem protecting tube (part no. 9014696000) when other bikes didn't but the use of standard bearings seems to be the explanation. Anyway, I've got the answer to my original question: crown nut is torqued to 80 Nm...woohoo!! Although another German contributor gives it as 90. I'll tighten to 85 and rest peacefully until I strip another thread.

Happy riding.

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