55 K fork tube lengths

Production K Models

Re: 55 K fork tube lengths

Postby Bubbalowe » Thu Apr 12, 2018 9:29 am

Apologies if seen as a hijack. Found some parkerized 21 7/8" tubes in basement of local shop for $150 pair, look new. 56 KH would these be correct or is chrome? Sticking a finger in the bottom some had pronounced edge and some seemed smooth. Because tubes are hidden is using newer valves/ tubes a better choice? Thanks for clearing up 21 7/8" length as correct for L5 frame.
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Re: 55 K fork tube lengths

Postby Mark.A » Fri Apr 13, 2018 12:27 pm

Hey Bubbalowe Looking at my parts book tells me that 45953-52 fork tubes are probably 227/8 and 45953-55 are the 217/8 tubes. But also there is a different # for springs and shock absorbers are they 1 inch short two. Also if your forks still together you need to look at the bottom of the slider is there a nut or a bolt. If there is a bolt you have a 68 and up shock absorber that needs a snap ring in the bottom of the tubes.The early ones are smooth.I think I would take apart what you have you said they are 6 inches over.You should have a 6 inch plug in there to make up the 6 inches. measure your tubes and subtract 6 inches that would tell you what you have
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Re: 55 K fork tube lengths

Postby hennesse » Fri Apr 13, 2018 1:14 pm

oneinch.jpg
Sept 1954 Enthusiast
oneinch.jpg (92.88 KiB) Viewed 13607 times


For 1955, the factory changed from the "raked" triple trees to the parallel ones. Actually, this occurred in late 1954. The change in angle pushed the front of the frame up, so to keep the bike level, they shortened the fork tubes. Unfortunately, I don't know the actual measurements - the advertising "one inch" might not be an actual 1.000". There are only two tubes for 1952-1969

49953-52 Fork slider tube 1952-1954 K and KH; 1958-1969 XLCH; special 1" more road clearance 1957-1969 XL and XLH
49953-55 Fork slider tube 1955-1969 KH, XL, XLH

BTW - more trail means more high-speed stability (chopper). Less trail means it's easier to turn the wheel (via handlebars or bumps in the road - motocross). It's confusing - raking the frame causes an increase in trail. "Raking" the triple trees causes a DEcrease in trail.
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Re: 55 K fork tube lengths

Postby Ferrous_Head » Fri Apr 13, 2018 5:47 pm

While I agree that the change in trail would have altered the ride height I suspect the real problem with tube lengths became apparent with the option to use 18" wheels instead of 19. They offered 1" more clearance on the front and AND the back end to compensate for this.
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Re: 55 K fork tube lengths

Postby Bubbalowe » Sat Apr 14, 2018 4:36 pm

So the plan is assemble an original type front end, wheel, fender and change over and offer up the early Sportster front end to offset cost. So far have set of lower sliders out for chrome and new bushings. Opinion here is 21 7/8" is correct length tube so looking for those and "de-raked" triple trees. The frame is L5 which doesn't have a raised neck, only as high as backbone. Going to Oley with a side trip past Bill's Custom Cycle, thanks for the help and hope to run in to some forum members.
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Re: 55 K fork tube lengths

Postby JerrryR » Sat Apr 14, 2018 4:46 pm

Can you post some pictures of your frame? Your description of an L5 date code with the neck even with the backbone doesn't sound right?
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Re: 55 K fork tube lengths

Postby curiousgeorge » Sat Apr 14, 2018 7:25 pm

When was the transition from low neck frames, just wondering, and why. Was it in anticipation of the xl or what?
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Re: 55 K fork tube lengths

Postby JerrryR » Sun Apr 15, 2018 12:12 am

To the best of my knowledge the neck to backbone height change took place with the 56 model year bikes. The first picture shown below is of a -55 neck casting. I have only seen these with D5 & E5 date codes. I believe it to be the last of the 55 model year neck castings. The second picture shows the -56 neck casting which I believe was introduced for the 56 model year. This is the "smooth " neck casting without a "ridge". This 56 neck casting is on a A6 frame just one month after your L5 that you indicate has the neck even with the backbone? The -56 neck casting changed slightly sometime between January, A6, and April, D6. By April the 56 neck had added the "ridge that all the sportster frames had through 69. If your frame truly is a L5 frame and has the low neck to backbone configuration, is it possible it is a racing frame? The last picture shows a -57R frame with its low neck to backbone relationship. Can you post some pictures?

55 K Model Neck Casting Optimized.jpg
55 K Model Neck Casting Optimized.jpg (316.07 KiB) Viewed 13578 times


56K Neck Casting Optimized 1.jpg
56K Neck Casting Optimized 1.jpg (196.81 KiB) Viewed 13578 times


57R Frame 2.JPG
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Oley Swap Meet

Postby hennesse » Sun Apr 15, 2018 8:42 am

Bubbalowe wrote: Going to Oley with a side trip past Bill's Custom Cycle, thanks for the help and hope to run in to some forum members.


If you stop by the "Multi-Purpose Gathering Place", you're likely to find me. To gain entrance to the M.P.G.P., you'll need to give the secret password. This year's password is "Give Me A Cold Beer". Try that at other vendor spaces and see what you get.

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Re: 55 K fork tube lengths

Postby Nightrain00 » Mon Apr 16, 2018 6:27 pm

Here is the L5 frame Bubbalowe was referring to.


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