Author Topic: CB400f steering head roller bearings  (Read 836 times)

Offline llessur

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CB400f steering head roller bearings
« on: November 26, 2017, 10:30:22 AM »
Just wondered if anyone could help out with my installation of a roller bearing kit. Whilst the bearing kit fits in the top nice and snug it looks like in the bottom of the head tube there ought to be a spacer or similar to stop the bearing going too far up the tube. The kit I bought (M&P) had the dust seals and bearings only, but scanning fleabay it looks like some are supplied with a washer. Do you think this is to use as a packer inside the tube. Your words of wisdom would be appreciated.

Offline K2-K6

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Re: CB400f steering head roller bearings
« Reply #1 on: November 26, 2017, 12:40:16 PM »
It'll be more help to you if someone looks in that's got a kit like this with specific parts detail.

But generally when doing this type of conversion the bottom bearing does go further into the frame tube than an equivalent ball race type,  just because they are more compact.

They are usually supplied / configured with a spacer that sits on the bottom yoke ( the very first thing you'd put onto the stem) this will allow the bearing itself to fit in the frame as is,  but then spaces the bottom triple clamp back where it would be if you had a ball bearing type in there. Hope that makes sense.

I feel it's one of the best things you can substitute on old bikes,  well worth the conversion.

Offline llessur

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Re: CB400f steering head roller bearings
« Reply #2 on: November 26, 2017, 01:14:48 PM »
Thank you that does make sense. I think I will fit it all together and tighten it all up to remove play, then strip it to see how far the lower bearing is up the tube and see if its contacting the shoulder that restricts how far it can travel upwards. If there is a gap still to the shoulder I will measure the gap and make a spacer so it cant pull the bottom yoke up too far.

Offline mike the bike

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Re: CB400f steering head roller bearings
« Reply #3 on: November 26, 2017, 01:37:38 PM »
Make sure there isn't a gap between the bearing cup and the shoulder,  otherwise the cup will gradually push itself in with use and the bearings will be too slack.  Use the old cup as a drift to knock the new ones in.  When it's fully inserted the sound will change.
Where's that 10mm socket got to?

Offline K2-K6

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Re: CB400f steering head roller bearings
« Reply #4 on: November 26, 2017, 03:11:24 PM »
As acknowledged,  you can't actually run it with a gap else the bikes weight on it in use will push it in further.

You may find a limit in how far it will tighten by the bottom yoke touching the frame first and preventing you going any further.

As you say though,  a spacer above will give you the clearance and correct geometry.

One of the advantages of a spacer on the yoke that I've seen, is to incorporate an O-ring on the outside diameter of it that will make an effective dust seal on the inside of the frame's headstock.

When tightening them you can use about 20lbs of torque while gently rotating the bearing to squeeze them into final seating position. When it's ok,  release the load and nip it tight again before the locking ring is secured.

Offline Rob62

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Re: CB400f steering head roller bearings
« Reply #5 on: November 26, 2017, 08:07:55 PM »
If you still have the old roller bearing, measure the thickness of the whole thing and compare it to the overall thickness of the new bearing assembly. Then you will see if a spacer is required.

Offline andut

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Re: CB400f steering head roller bearings
« Reply #6 on: November 26, 2017, 08:35:56 PM »
Ideally you should measure the height of the old bearing and compare with the new one to work out how thick a stem washer would need to be before you assemble.  If you assemble and trial fit, you'll have to remove the interference fit lower race from the stem to fit a washer.

Offline Integra99

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Re: CB400f steering head roller bearings
« Reply #7 on: November 27, 2017, 10:47:04 AM »

I had the same problem, the M&P bearing does not come with the lower washer.. without the washer the roller bearing locates too low on the the stem and it fouls when you tighten up.  So you need a spacer, from memory its a 3mm x 30 washer basically. Pop on the shaft followed by the bearing and it basically allows it to sit higher.




 

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