Topic: 550K fork tubes

[emlupi]

I have been looking around at several of the usual parts suppliers and I see fork tubes for just about any Honda CB model except the 550K. I have a set of ‘76 550K forks and can’t find replacement tubes anywhere. I sent a message to Franks Forks but haven’t received a reply. What am I missing?

[Don R]

 Check the back side of the castings for a 341 number, if they are it's the same tube as a cb750, just a little shorter.  I haven't shopped lately but at one time there were three lengths for sale on ebay, 21 13/16", 22 13/16" and 23 13/16"
 I've used the shorter ones in former 550 castings (341) to make a lower 750 front end.

 The 550 rotor is smaller diameter than the 750 part, and the 550 caliper bracket angles down slightly. The brakes may also be swapped either way as long as the caliper, bracket and rotor match.

[emlupi]

Thanks Don, yes, they are the 341 lowers. I will check and see what is available.
Two questions:
1) What’s the difference between the F and K forks because tubes and lowers have different part #’s.
2) Why is it that nobody is making tubes for the 550K?

[Don R]

 I don't know the difference, I did what I did by accident and because I had both 550 and 750 341 lowers in case my tubes didn't fit. I didn't know they were 550 until a couple of the guys here educated me on the brakes that I noticed were different.
  I think I got Niche brand tubes. I bought several sets off of Ebay, maybe not as good as Franks but certainly better than any of my old tubes were.
  I was just looking at Partzilla, I noticed they don't list the "also fits" models anymore.
 Edit: Some of my older replacement tubes were Sudco brand, probably the same maker as Niche.

[Don R]

 I think they are making 550 tubes, they just don't know it. Just my opinion, I could be wrong, but I doubt it.  I've also mixed and matched tubes early F and later K forks that have the taller castings. 

[emlupi]

So, I remembered that I had an old set of 750 fork tubes and I did some investigating. The 341 fork bottoms are exactly the same between 550 and 750. They are the same length and all the lugs seem to be in the same place from one to the other. In the picture I am holding the 550 lower in my hand.
The tubes are identical other than length. The groove is in the same place and internal dimensions are the same. In the picture 750 tube is on the left.
Springs are also longer on the 750. I would imagine that spring rate and damping are different as the 750 is larger and heavier.
Essentially, it seems that the 550 internals and lowers will work in the 750 tubes, I will have to slide the tubes up in the clamps to compensate for the extra length or find a set of shorter length.

[calj737]

I thought Frank’s went out of business about 3-4 years back. Seem to recall Frank passed away and his wife and son sold the business. I could be wrong…

Emulpi, where are you? I have a set of Franks tubes in a ‘74 K that are in pretty darn good condition that might solve your issue. I’m on the East coast, about 150 miles south of DC.

[bryanj]

When talking about 750 you need to say the later 750, early 750 has a totaly different caliper bracket

[RAFster122s]

Apparently a group in Mississippi I think bought the business and are operating it there. Apparently still good quality products... I haven't heard otherwise...

[Don R]

  We specified the 341 forks, those being later 750. K3 through K6. Not including F's, K7 or K8.
  I've swapped the fork parts and am riding them when it's not snowing. I think the Rat Race bike has short (550) 21 13/16" tubes 750 F0 lower castings and 550 progressive springs.
 Note the late model dust boot swap over the fork seals.
 

[bryanj]

341 means nothing to UK, we only ever had the K2 759 until the K6 came along

[emlupi]

341 is the part number embossed on the lower fork sliders used on the ‘73-‘76 750’s. They are listed as different part numbers on the different models but they seem to be identical to my eyes. If there’s something I am missing please enlighten us.

[emlupi]

I thought Frank’s went out of business about 3-4 years back. Seem to recall Frank passed away and his wife and son sold the business. I could be wrong…

Emulpi, where are you? I have a set of Franks tubes in a ‘74 K that are in pretty darn good condition that might solve your issue. I’m on the East coast, about 150 miles south of DC.

Thanks, I am going to do a little more investigating. I’ll let you know if I can use them.
As to Franks Forks, I can’t get a straight answer whether they are still around or not. Their website and Facebook page are still active but so far nobody has responded to my emails.

[newday777]

I thought Frank’s went out of business about 3-4 years back. Seem to recall Frank passed away and his wife and son sold the business. I could be wrong…

Emulpi, where are you? I have a set of Franks tubes in a ‘74 K that are in pretty darn good condition that might solve your issue. I’m on the East coast, about 150 miles south of DC.

Thanks, I am going to do a little more investigating. I’ll let you know if I can use them.
As to Franks Forks, I can’t get a straight answer whether they are still around or not. Their website and Facebook page are still active but so far nobody has responded to my emails.

Frank's moved a few years ago, after Frank passed. I don't know who owns it now or if they are still in business.
Did you try calling them?

[emlupi]

I sent a message to the email in your screenshot, no reply.

[calj737]

I sent a message to the email in your screenshot, no reply.

Who are you referring to?

[jlh3rd]

I sent a message to the email in your screenshot, no reply.

I just called this #.....had a conversation.....says the email valid.....
call him.

[PeWe]

My CB750 K6 has 341lowers.
My K2 got them too. It is  a CB750 K2 -75.
These lowers were introduced in K2 according to CMSNL. When looking for front fender they have a from serial number. Fender and brake caliper holder follow these lowers.

[HondaMan]

While the 550's damper is different (actually better) than those in the 750 forks, they fit into those 750 lowers OK. The fork tubes were shorter by a bit, but the 550 could benefit from a bit more trail, and the 750 tubes might just be the ticket!
I have some extra-long 750 tubes (forks, actually) of the -341- type, taken off a chopper that wanted to become a bike again. I think they are 4" oversize for the 750.

[emlupi]

Thanks for all the replies. I can use 750 tubes in the 341 lowers with 550 internal parts. No need to hunt down tubes specifically for the 550K.