harleyKmodel

The attached image shows the wide range of K/XL gearing possible by altering the engine, transmission and rear wheel sprocket sizes. Of particular note might be how judiciously altering the tranny sprocket and rear wheel sprocket sizes can provide nearly identical 4th gear ratios.

Your first post states that you have a 49t sprocket that has only a few rivets left keeping it attached to the drum. If it is the original factory drum, you should use that for your 49t sprocket. From my preliminary research, it should have a raised casting number on the outer surface, 41407-52, and no casting lugs (cogs). The lugs didn't appear until 1957 along with the return of the 51t sprocket and the casting number was etched on the inside of the drum. As stated in earlier posts, I don't think there is an aftermarket K-model rear brake drum with 49t reproduced currently. There's a very good tutorial on how to rivet your rear sprocket by Dr. Dick on the XL forum http://xlforum.net/forums/showthread.php?t=1526811

regarding rear sprockets that rivet to brake drums, there are 3.
1st and most common:
41471-30 (sprocket only) 51t
or
41470-70 (includes 41471-30 plus 16) pn 8486 rivets and 4) 41485-30 dowels)
used 52-53 and 57-78.

very rare are the 41473-54. 49t used 54 to 56.

rarer yet is the 41472-55r 50 tooth.

any of the above will rivet to any brake drum 52-78

It appears that all K & KH models use the same rear brake drum and that none of those drums have "cogs" (whatever they are). Is this correct?
I appreciate all the input I have received. I just want to make sure I understand. We will probably find the rear drum I want on eBay or at a swap meet. The V Twin / J&P / Sporty's new drum comes with a 51T sprocket on it that I do not need now because I already bought one. If anyone finds fault with my reasoning, please let me know. Just be gentle!

Coolbreeze, That is INCORRECT on the cogs. For whatever it's worth, my 1956 Original Paint KHK has the cogs or as you say ( whatever they are ) The parts books show the same brake drum without sprocket for all K Models. What purpose the cogs have and when they first appeared is beyond me. My '53 KK does not have them. Maybe someone with an original '54 or '55 could chime in on the subject.

Here's a very original 56 KHK with the raised casting number on the outside of the drum and no visible casting lugs. So the drum with lugs could be a running change in 56?

Good one strong. That would certainly lead a person to believe that the cogs were a running change in 1956. That also means there shouldn't be any brake drums on any '54's or '55's. If anyone has a brake drum on an original '54 or '55 that has the cogs it would be nice to hear from you. I wonder if we couldn't possibly narrow it down even more by comparing vin #'s. My vin # is 2268 with a F6 frame date code. If your vin # is earlier it would make sense that somewhere between those two numbers the cogs appeared? I'm not that knowledgeable on early Sportsters so do they all have the cogs on the drum?

BTW strong, very nice original or at the very least period correct dimpled chain. I just reluctantly replaced my dimpled chain as it was just shot. A dimpled chain is a pretty good indicator that the bike is pretty dog gone original.



Stan

Good spot on the Duckworth chain. I hadn't picked up on that. The picture is from an auction a few years ago of what the seller listed as an original paint 56KHK. Unfortunately there was no picture of the vin number or info on the frame date. The exhaust system is the one made by Corso so is not original but a lot of the details on the bike are correct for 1956 based on a series of 17 pictures I have of it. Perhaps it is owned by a member of this website and they could tell us what the numbers are. If you look at the pictures of Jim Garret's 54KH in the gallery section it has the raised casting numbers on the drum. Dave Larkin's 1955 clearly has the casting lugs as seen in one of the pictures which I didn't pick up before. I believe that the drums with the raised casting numbers where restricted to K-models but my theory of when they changed to the lugs was wrong. I would recommend to Coolbreeze to restore and use the one that came with his bike.

Can I ask what constitutes a “dimpled” chain ?
Thanks.

Tim The Grim wrote:Can I ask what constitutes a “dimpled” chain ?
Thanks.

Dimpled refers to the depressions (dimples) left in the ends of the pins from the setting operation. Some are smooth and rounded after setting (see the chain image above in Starcains 1st post) and the Duckworth chain pins have a depression in the end of the pin (as shown in the chain image directly above).