Author Topic: Front forks  (Read 3567 times)

Offline Trigger

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Re: Front forks
« Reply #30 on: November 22, 2019, 07:10:43 AM »
Thanks Trigger, So next question, is it the fork bottoms are longer?? Fork tubes shorter, springs the same rate. All I can tell you that it certainly feels very funny on the front end and not the sort of thing you would chuck into a corner.  Tube are straight and forks not twisted, but quite hard and not much movement. Springs are far longer than the manual states, nearly 480mm. Changed the oil  to 10w and waiting for progressive spring. 550 and 500 spring lengths are the same according to the manual. Time will tell!!

Short cases come with longer stanchions ( tubes ) and the springs are different. On the 550K they are different than the 550 F2 / K3.
I am trying to help another member that is local to me but, he has the short cases on a 550K3, which are bottoming out  ;)

The original 500 for cases came with only one case that you could mount a caliper (left side) and a lot of riders removed the early forks so they could fit a double disc and caliper set up.

Offline oldboy

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Re: Front forks
« Reply #31 on: November 22, 2019, 08:48:37 AM »
Getting more and more complicated, (think I'll fit a set of Ohlins  ;D ) They do have gaiters fitted and at least now I'm beginning to now what I'm looking at, confusingly!!

Offline Trigger

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Re: Front forks
« Reply #32 on: November 22, 2019, 09:07:54 AM »
Getting more and more complicated, (think I'll fit a set of Ohlins  ;D ) They do have gaiters fitted and at least now I'm beginning to now what I'm looking at, confusingly!!

I have mentioned to the member who has the bottoming out problem that, I maybe a good idea to swap lower cases and springs with you or at least compare spring length  ;)

Offline oldboy

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Re: Front forks
« Reply #33 on: November 22, 2019, 01:18:26 PM »
Thanks

Offline Erny

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Re: Front forks
« Reply #34 on: November 23, 2019, 10:44:07 PM »
If you allow me, I have one question about correct spring length for 550K1.

I measured mine that has now 462mm.

Looking into service manual, it says 451,7mm as standard for both, 500 (page 140) and 550K1 (page 142).
But forks for 500 and 550K1 are different so I suspect there is mistake in service manual.

Does anyone know proper standard length of 550K1 fork spring and its service limit?
CB750K7 US model (1977)
CB550K1 US model (1975)

Offline Trigger

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Re: Front forks
« Reply #35 on: November 23, 2019, 11:11:42 PM »
If you allow me, I have one question about correct spring length for 550K1.

I measured mine that has now 462mm.

Looking into service manual, it says 451,7mm as standard for both, 500 (page 140) and 550K1 (page 142).
But forks for 500 and 550K1 are different so I suspect there is mistake in service manual.

Does anyone know proper standard length of 550K1 fork spring and its service limit?

475 mm on K0,K1,K2 and the spring in the picture is not oem  ;)

Offline Erny

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Re: Front forks
« Reply #36 on: November 23, 2019, 11:38:52 PM »
Trig, thanks!
so I suppose OEM are not progressive, right?

Any idea where to buy OEM like or other recommended alternative?

I need to do something to avoid horrible bouncing I have...
CB750K7 US model (1977)
CB550K1 US model (1975)

Offline Trigger

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Re: Front forks
« Reply #37 on: November 23, 2019, 11:59:08 PM »
not progressive ! Are you sure it is the forks and not the wheel ?

Offline Erny

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Re: Front forks
« Reply #38 on: November 24, 2019, 12:05:38 AM »
typical as many others has - forks does not react on small bumps - looks as too high striction.
Worst it is at stable speed around 40mph
But I want to start with full rebuild. Springs are definitely on the list. But where to get them?  :-\
CB750K7 US model (1977)
CB550K1 US model (1975)

Offline deltarider

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Re: Front forks
« Reply #39 on: November 24, 2019, 06:58:23 AM »
Not so fast, those are the progressive springs I have in my CB500K2-ED and they are definitely OEM. These springs were also on: the C550K, CB550K!, CB550K2 and the CB500T. They measure the same as mine and should be fine. I have best results with max 140-145 cc of 7,5 weight fork oil.

Offline deltarider

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Re: Front forks
« Reply #40 on: November 24, 2019, 07:19:47 AM »
typical as many others has - forks does not react on small bumps - looks as too high striction.
Worst it is at stable speed around 40mph
That's the typical speed where many bikes of that era show let us say a less than ideal behaviour.
Quote
But I want to start with full rebuild.
Why? What starting point is that? What is your diagnosis? What you could do however, is loosen bolts and then tighten them again in the right order. I'm sure others will chime in to tell the right procedure, that gave them best results.
Quote
Springs are definitely on the list. But where to get them?
I have no indication yours are the wrong type or have passed the servicable limit. Mine have the same length, have done 135.000 km and are still OK. You may also want to read this: http://forums.sohc4.net/index.php/topic,151936.msg1736598.html#msg1736598
But if you must... parts number is: 51401-374-003.
https://www.cmsnl.com/products/springfrontcush_51401374003/#.Xdovgq_vJVc
I wouldn't be surprised that after ordering, you will find they will have exact the same length as yours.
As I said before: the Shop Manual CB500-550 has some errors. In my experience the parts lists have none, be it that the depiction of the springs is not very accurate but... who can blame that poor Japanese schlemiel that had to draw all those windings...  ;)
« Last Edit: November 24, 2019, 07:56:46 AM by deltarider »

Offline Trigger

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Re: Front forks
« Reply #41 on: November 24, 2019, 08:18:03 AM »
Not so fast, those are the progressive springs I have in my CB500K2-ED and they are definitely OEM. These springs were also on: the C550K, CB550K!, CB550K2 and the CB500T. They measure the same as mine and should be fine. I have best results with max 140-145 cc of 7,5 weight fork oil.

You do make me chuckle in the morning with your ignorance to parts and you just quote what you have read or heard, without having any real hands on experience of all SOHC units  ;)

The measurement i gave was from a NOS 374 spring out of the packet with numbers ending in 000. Todays listed spring is ending in 003, that means it has been superseded or it comes from another supplier meaning, it will be a different spring. Boing goes Zebedee  ;D

Parts lists have many errors to them and, I would not go on CMSNL. As a good example this week is that I sold off a load of  500 air box brackets (323) and everyone that ordered them by part number said, that they had received the wrong bracket as CMS had the wrong picture of the bracket against the wrong part number. But, the ones I sent out were correct  ::) ::)
« Last Edit: November 24, 2019, 08:22:11 AM by Trigger »

Offline Bryanj

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Re: Front forks
« Reply #42 on: November 24, 2019, 08:30:21 AM »
Parts books correct! Check the gearbox page and explain to me where the forth selector in the quantity list fits.

Offline Trigger

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Re: Front forks
« Reply #43 on: November 24, 2019, 08:34:21 AM »
Parts books correct! Check the gearbox page and explain to me where the forth selector in the quantity list fits.

That's the part you order for your spares box mate  ;D ;D ;D

Offline Bryanj

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Re: Front forks
« Reply #44 on: November 24, 2019, 08:53:17 AM »
I did! But the one they say you need 2 of is not the centre one that wears!!!!

 

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