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Author Topic: 550 F2 Steering Head lower bearing loose  (Read 535 times)

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Offline bbrian66

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550 F2 Steering Head lower bearing loose
« on: February 15, 2026, 07:34:13 AM »
Hi  - I'm trying to install new head bearings in my 550 F2 project - sticking with the original ball bearing set up. I have a new bearing kit from Dave Silver. All looks good except that the lower inner race is a loose fit on the steering shaft. I thought this should be a slight interference fit.
I'm amazed at how much slop there is. I'm guessing this is not correct. Can anyone advise what i can safely do?
Thanks in advance.
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Offline bryanj

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Re: 550 F2 Steering Head lower bearing loose
« Reply #1 on: February 15, 2026, 08:44:12 AM »
It should be a tight fit, trouble is you dont know if somebody has changed the lower yoke
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Semi Geriatric ex-Honda mechanic and MOT tester (UK version of annual inspection). Garage full of "projects" mostly 500/4 from pre 73 (no road tax in UK).

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Offline bbrian66

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Re: 550 F2 Steering Head lower bearing loose
« Reply #2 on: February 15, 2026, 09:14:56 AM »
That's exactly what I was thinking. I guess it's possible I have a yoke of a different model.
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Offline Little_Phil

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Re: 550 F2 Steering Head lower bearing loose
« Reply #3 on: February 15, 2026, 09:20:05 AM »
Is it possible that you are trying the upper bearing and not the lower? It may be a dumb question, can't remember if that is possible.
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Offline bbrian66

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Re: 550 F2 Steering Head lower bearing loose
« Reply #4 on: February 15, 2026, 09:56:36 AM »
Luckily, even I can't get that wrong as they are clearly different sizes - top is noticeably smaller.
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Offline bryanj

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Re: 550 F2 Steering Head lower bearing loose
« Reply #5 on: February 15, 2026, 10:29:06 AM »
Thing is i know the headrace sets are same for all the sohc fours but there was a time people were fitting the 400 twin forks with twin sisk and comstars, maybe its a yoke from one of those as i think fork tubes are same diameter.
Can you put up a pic of the lower yoke?

I think the K3 is the same but not the earlier K or 500 as steering lock is different
« Last Edit: February 15, 2026, 10:35:50 AM by bryanj »
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Semi Geriatric ex-Honda mechanic and MOT tester (UK version of annual inspection). Garage full of "projects" mostly 500/4 from pre 73 (no road tax in UK).

Remember "Its always in the last place you look" COURSE IT IS YOU STOP LOOKIN THEN!

Online scottly

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Re: 550 F2 Steering Head lower bearing loose
« Reply #6 on: February 15, 2026, 11:26:42 AM »
Quote from: bryanj on February 15, 2026, 10:29:06 AM
Thing is i know the headrace sets are same for all the sohc fours but there was a time people were fitting the 400 twin forks with twin sisk and comstars, maybe its a yoke from one of those as i think fork tubes are same diameter.

The 400 twins and fours had smaller 33mm fork tubes.
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Online scottly

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Re: 550 F2 Steering Head lower bearing loose
« Reply #7 on: February 15, 2026, 11:29:48 AM »
Quote from: bbrian66 on February 15, 2026, 07:34:13 AM
Hi  - I'm trying to install new head bearings in my 550 F2 project - sticking with the original ball bearing set up. I have a new bearing kit from Dave Silver. All looks good except that the lower inner race is a loose fit on the steering shaft. I thought this should be a slight interference fit.
I'm amazed at how much slop there is. I'm guessing this is not correct. Can anyone advise what i can safely do?
Thanks in advance.
Can you measure the diameter of the steering stem where the bearing fits, and the ID of the replacement race vs the original race?
EDIT: The stem OD/race ID should be 30mm.
« Last Edit: February 15, 2026, 11:50:54 AM by scottly »
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Offline bbrian66

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Re: 550 F2 Steering Head lower bearing loose
« Reply #8 on: February 16, 2026, 02:19:41 AM »
Hi Guys - many thanks for these replies. The bike came as a completely dismantled project with lots of bits missing,  so there is nothing to say that the parts i have are correct to the bike,  so I like your thinking here.
I've hopefully attached an image of the yolk - I have a 400/4 and the good news is this does not look like the yolk on that bike. The dimensions also stack up ok, except the steering stemm seems undersize:
Steering stem dia: 29.7mm
ID of new race: 30.0mm
Fork tube dia: 35.0mm
I've also just noticed (now I've had it powder- coated!) that the thread at the top is in very poor state so I'm thinking this may be a scrap yolk - photo attached.
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Offline bryanj

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Re: 550 F2 Steering Head lower bearing loose
« Reply #9 on: February 16, 2026, 03:25:54 AM »
That stem does not look right to me, the mark would suggest a slight bend
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Semi Geriatric ex-Honda mechanic and MOT tester (UK version of annual inspection). Garage full of "projects" mostly 500/4 from pre 73 (no road tax in UK).

Remember "Its always in the last place you look" COURSE IT IS YOU STOP LOOKIN THEN!

Offline bbrian66

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Re: 550 F2 Steering Head lower bearing loose
« Reply #10 on: February 16, 2026, 04:41:31 AM »
The image of the base of the stem is odd as it makes it look like the stem tube bows out just above the bottom. In reality this is not the case - it just gets a bit fatter near the bottom. However I'm not convinced this yoke has a future...
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Offline seanbarney41

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Re: 550 F2 Steering Head lower bearing loose
« Reply #11 on: February 16, 2026, 07:54:34 AM »
I agree.  That stem looks like was bent/crushed.  I have seen ones damaged like this before.  Sucks you did such a nice job painting it.
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Offline Nurse Julie

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Re: 550 F2 Steering Head lower bearing loose
« Reply #12 on: February 16, 2026, 11:17:13 AM »
Hi Brian.
If you haven't done so already, maybe consider joining the UK forum as you're in UK.
Julie
www.sohc.co.uk
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Offline Tim2005

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Re: 550 F2 Steering Head lower bearing loose
« Reply #13 on: February 16, 2026, 02:13:37 PM »
It looks like there's enough wear/damage on the left side of it in the photo to create a lip, perhaps that's the missing 0.3mm that the bearing needs. Looks like 550 bottom yokes only make £30 here (UK ebay) so I'd go for a replacement
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Offline bryanj

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Re: 550 F2 Steering Head lower bearing loose
« Reply #14 on: February 16, 2026, 03:30:52 PM »
Just be sure its an F or K3 part
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Semi Geriatric ex-Honda mechanic and MOT tester (UK version of annual inspection). Garage full of "projects" mostly 500/4 from pre 73 (no road tax in UK).

Remember "Its always in the last place you look" COURSE IT IS YOU STOP LOOKIN THEN!

Offline bbrian66

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Re: 550 F2 Steering Head lower bearing loose
« Reply #15 on: February 16, 2026, 03:59:45 PM »
Hi Julie - I've already joined,  I just need to get into the habit of using it more. A great resource!

Guys - huge thanks for your responses. It's really annoying to get to this point,  but it's good to know what i need to do next.
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Offline bbrian66

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Re: 550 F2 Steering Head lower bearing loose
« Reply #16 on: February 16, 2026, 04:20:23 PM »
Are the F and K yokes the same item? It looks so from the parts list.
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Offline jonda500

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Re: 550 F2 Steering Head lower bearing loose
« Reply #17 on: February 16, 2026, 05:58:55 PM »
yes, same as the 500
John
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Offline bryanj

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Re: 550 F2 Steering Head lower bearing loose
« Reply #18 on: February 16, 2026, 10:31:02 PM »
NO  the 500 and early 550 are NOT the same, steering lock is different
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Semi Geriatric ex-Honda mechanic and MOT tester (UK version of annual inspection). Garage full of "projects" mostly 500/4 from pre 73 (no road tax in UK).

Remember "Its always in the last place you look" COURSE IT IS YOU STOP LOOKIN THEN!

Offline bbrian66

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Re: 550 F2 Steering Head lower bearing loose
« Reply #19 on: February 17, 2026, 03:54:10 AM »
That's good to know - thanks!
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