fork spring lengths

Racing K Models

fork spring lengths

Postby No side stand » Tue Oct 09, 2018 10:14 pm

Hi.
I'm trying to find out some spring lengths as follows:
46056-68R Fork spring (short),
46057-68R fork spring (medium)
46058-68 Fork spring (long)
46057-52 (1" longer)
The spring length information isn’t listed in the KR, XLR, parts manuals or the Specification/Instructions manuals, but it may be in one of the racing dope booklets. I don’t have any of those so I am hoping that an inquiry here might garner some good information.
Thanks in advance.
No side stand
 
Posts: 12
Joined: Tue Oct 09, 2018 4:59 pm

Re: fork spring lengths

Postby No side stand » Thu Oct 11, 2018 10:36 pm

Nothing?
OK I’ll do some guessing:
The length of springs I have:
19” long. 0.162” wire diam.
19 ½” long. 0.163” wire diam.
20” long. 0.173” wire diam.
20 ½” long. 0.159” wire diam.
20 ¾” long. 0.161 wire diam.

I also have a range of original front shock absorbers:
NOS KR Short (Maybe 46095-54R) front shock absorber which is 19 15/16” long.
This may pair with the 19” and the 19 ½” springs. I guess it would give the racer a different feel.

Also have 22” long shock absorber.
These may pair with the longer springs listed above.

I would post pictures, but can’t haven't worked out how to enact that action.
Regards Steve.
No side stand
 
Posts: 12
Joined: Tue Oct 09, 2018 4:59 pm

Re: fork spring lengths

Postby Simon » Fri Oct 12, 2018 1:01 am

Hi Steve, I can't offer anything I'm afraid, but this is interesting stuff!
Simon
 
Posts: 127
Joined: Mon Oct 12, 2015 10:14 pm

Re: fork spring lengths

Postby Ferrous_Head » Fri Oct 12, 2018 8:59 pm

I just went through this when I discovered I had a set pf front forks that had been assembled incorrectly. One leg had the lobger shock assembly and one the short.
After getting one leg apart and then attempting to reassemble it I found it was next to impossible (I never managed it) to get it back together again.
What I had was a short shock assembled into a long spring/tube combination.
I now know that the only difference in the shocks is the piston rod length. The longer rods and springs are 1 inch longer. I would eexpect the fork tubes to differ by 1 inch also. Hard to tell when you have original fork tubes now so can't be sure as som many people have quoted different lengths it's not funny.
But here's what I worked out with these lengths.
The fork legs for the 52-53 clamps (less trail) use the shorter tubes.springs/shocks. These forks are also used on the KR's and XLR's (I believe)
The longer forks (1 inch longer) are used on everything else.
I think they also came out with the 18 inch wheel size around 1954 so that MIGHT play some part in the rational to use loner fork legs.

It actually makes sense to use longer fork legs on some race bikes. To get ground clearance for cornering you lift the bike up higher. So it's a;so possible the longer legs really were to help the KR's. But I don't know.

becuase there are so many aftermarket and worn, sagged springs as well as after market tubes out there it's hard to know what your holding in your hand sometimes.

What DOES amaze me is that the forks I took apart with the wrong length shock in one side had Obviously been used that way for many years.
Might have worked very well on tracks where you only turn left. But it would have been much cmarter to just offset lace the rims.
"I know only too well the evil that I propose, but my inclinations get the better of me."
User avatar
Ferrous_Head
 
Posts: 93
Joined: Tue Jun 06, 2017 5:36 pm
Location: Australia

Re: fork spring lengths

Postby No side stand » Sat Oct 13, 2018 12:39 am

Hi Ferrous and Simon. Thanks for getting in.
I was hoping for spring and front shock absorber lengths, but it seems the question may be untested in the forum. To get closer to the information I’m looking for I will try tackling it from a different direction. I had a quick peruse through the 1952- 1965 KRTT – XLRTT and the 1958-1968 XLRTT – KRTT parts manual. The information from both of these lists is written below:

52-65 parts manual.
45942-54R Fork side complete. Right. (Short) 52 to 65 KR, KRTT, XLRTT.
1965 cut off is because this info is from the 1952- 1965 parts catalogue.
*During the time period of this booklet, it only mentions a short front end.*
If someone has a 52-60 booklet the period may be confirmed of refined a bit more.

1958-68 parts manual.
45510-68R Front fork assembly. (Short) 1968 to * KR, KRTT: 1968 to * XLRTT (optional)
45511-68R Front fork assembly. (medium length) 68 to *-XLRTT (std). 68 to * KR, KRTT. (Optional)
45516-68R. Front fork assembly. (long) 1968-* XLRTT (optional)

The later part numbers suggest that the longer length springs and absorbers were brought in by the factory at a later date?
Confirm or reject this info as your investigations unfold.

Regards Steve
No side stand
 
Posts: 12
Joined: Tue Oct 09, 2018 4:59 pm

Re: fork spring lengths

Postby Ferrous_Head » Sat Oct 13, 2018 2:47 am

OK - found the pictures I took.
The short shock assembly is 21 " long and the long one is 22 " long.
I believe the springs that go with the long shocks are 20 ".
I can only presume the springs for the short shocks are 19".
My long shocks and springs are fitted to 23 " fork tubes.

The parts book and FSM refer only to 1 " more ground clearance. The change on fork length on it's own probably wouldn't give you another inch as the forks aren't perpendicular t the ground. But combined with19" wheels they probably would. I suspect you'd also need the longer rear shocks.
"I know only too well the evil that I propose, but my inclinations get the better of me."
User avatar
Ferrous_Head
 
Posts: 93
Joined: Tue Jun 06, 2017 5:36 pm
Location: Australia

Re: fork spring lengths

Postby No side stand » Sat Oct 13, 2018 8:08 pm

Hi Gene.
If the shockers you have listed are not modified, there is a chance you may have a medium and a long. I also have some original shocks at 22” but I can’t confirm if that is the length of the R numbered shocker. The medium length set which I have, has been modified to 20 ¾” so that can’t trusted either. Was yours exactly 21” and I should ask, do you know the history of the bike it came out of.
A friend lent me a couple of shock absorbers for reference, and there is a NOS shock which is 20” long. The information written on the tag: “KR Short”. If we can get a couple of confirmations on that length we might have one R shocker we can tick off.
Regards Steve
Last edited by No side stand on Sat Oct 13, 2018 8:12 pm, edited 1 time in total.
No side stand
 
Posts: 12
Joined: Tue Oct 09, 2018 4:59 pm

Re: fork spring lengths

Postby Ferrous_Head » Sun Oct 14, 2018 12:26 am

First image is the lengths of the two shock assembly's I had apart at the time. They appear to be exactly 21 and 22 inches in length.



Image


This shows the two assemblies side by side. At that time I was unaware there were 3 lengths of assemblies. I thought just the two.
Unfortunately these came from a bike of unknown history. I have no real idea why they had two different length shock assemblies in them. Based on the overall general condition I presume the forks had been put together like that many years before. So it\s anubofy'a guess as to what these assemblies originally came in.


Image
"I know only too well the evil that I propose, but my inclinations get the better of me."
User avatar
Ferrous_Head
 
Posts: 93
Joined: Tue Jun 06, 2017 5:36 pm
Location: Australia

Re: fork spring lengths

Postby Ferrous_Head » Sun Oct 14, 2018 12:58 am

So now, looking in my parts book I actually see 4 sets of forks.

45510-68R - SHORT - used on 68 KR . KRTT - optional on 68 XLRTT

45511-68R - MEDIUM - used on 68 XLRTT - optional on69 KR, KRTT

45515-52RA - used on 52 - 67 KR, KRTT and XLRTT

45516-68R - LONG - optional on 68 XLRTT.

So on the most common sets of forks, those used from 1952 to 1967 on the KR's, KRTT's and the XLRTT's appears to have no description as to the length of those forks. I can only guess they are the same length as stock K and XL forks ?

Hasn't that thrown a spanner into the works !
"I know only too well the evil that I propose, but my inclinations get the better of me."
User avatar
Ferrous_Head
 
Posts: 93
Joined: Tue Jun 06, 2017 5:36 pm
Location: Australia

Re: fork spring lengths

Postby No side stand » Sun Oct 14, 2018 8:01 pm

Hi Gene. Let’s keep this research area tidy, and spanners in their allotted draws. :D
My experience with original XLR parts (my main focus) is, if a part has an R number it is different in some way to general XL production parts. Aside from the short length of the KR short shock absorber in the picture, I noticed that the piston valve has the standard 1.5mm holes drilled through the bottom rim, but it has the added feature of a scallop cut in the leading edge. See close up picture. All the other piston valves that I have, only have 2 x 1.5mm holes drilled through the bottom rim.

PA150005.JPG
PA150005.JPG (363.21 KiB) Viewed 84 times


Another feature of the standard XL piston rod is that it has 2 X 3mm holes drilled through the upper section of the rod. I don’t know enough about these piston rods, but this hole-less feature may be a way to identify the race version.





Confirm or reject this information as your investigation unfolds.
Regards Steve
Attachments
PA150006.JPG
PA150006.JPG (368.26 KiB) Viewed 84 times
PA150009.JPG
PA150009.JPG (408.46 KiB) Viewed 84 times
No side stand
 
Posts: 12
Joined: Tue Oct 09, 2018 4:59 pm

Next

Return to KR, KRM, KRTT, KHR, KHRM, KHRTT

Who is online

Users browsing this forum: No registered users and 1 guest