harleyKmodel

The flat tappet (WR) operates like many automotive solid tappets: it always follows the highest point on the cam lobe, whether directly above it or not. The tappet must be wide enough to act on any part of the lobe (or it will be destroyed), but the tappet length does not affect the cam duration.
The H-D roller tappet operates similarly to an automotive roller tappet: it follows the closest point on the cam lobe (tangency) beginning with the approaching side of the lobe. However, the motion is not symmetrical w/r/t opening and closing rates (even with symmetrical lobes) due to the tappet offset: the roller is always closer to the opening ramp. This is why the center-to-center distance of the 4-cam (45, K, XL, UL) intake and exhaust tappets is different than the c-c distance between the intake and exhaust cam lobes. H-D roller tappets 1929-83 are .855" OD.
There is another (non-H-D) variant: a solid (not rolling) tappet with a radiused contact surface such as Triumph "B" series. The tappet motion matches the roller (except for the friction element). Triumph tappets were produced in 3/4", 1-1/8" and 3" radius (among others).
In both of these cases, the tappet radius (or roller radius) greatly affects the events: a larger diameter radius makes contact earlier and acts differently during both opening and closing events. Obviously, a flat tappet has infinite radius.

The WR style hi performance cam kit for the K model (52R) is unique in being offered only in 1952
These are not WR cams, tappets, or lifters only WR style.
The flat tappet cam kit was replaced with the roller tappet hi performance cam kit for the K model (53R) in 1953
According to long time Harley dealer Eddie Boomhower the K model flat tappet kit was a failure and replaced by the roller tappet kit in 1953.

EKHKHK56 wrote:Hi folks, Stan that KK cyl w WR set up may have a Date casting. The -56 Spare Parts lists the most KK, and 54KHK parts! As well as 55, 56KHK etc...Erik

Erik, I think in my earlier post I mentioned I had seen several cylinders with the WR valve setup. Actually it was only one and that was a couple of years ago. I should have looked at the date code as you said but didn't think of it at the time. Thinking about it now, would that actually reflect anything about the WR valve setup? I am going to have to go back and look how that cylinder date code thing works. Someone please correct me if I'm wrong but wouldn't the date code just tell you when the cylinder was made and not refer to the valve setup in it?

Stan

The date codes for the most part are provided by the foundry and establish the date when the item was cast. When the casting is finish machined and transfered to P&A inventory or sold as a part or used in assembling a motor or motorcycle is a matter of conjecture.

hugoct wrote:The WR style hi performance cam kit for the K model (52R) is unique in being offered only in 1952
These are not WR cams, tappets, or lifters only WR style.
The flat tappet cam kit was replaced with the roller tappet hi performance cam kit for the K model (53R) in 1953
According to long time Harley dealer Eddie Boomhower the K model flat tappet kit was a failure and replaced by the roller tappet kit in 1953.

Although none of the cam-related parts of the flat tappet cam kit are specifically WR, presumably the end result would be WR valve action. Since the K was basically a unitized W with the same cam chest lay-out, I suspect all the factory had to do to develop the kit was to angle-grind the WR profile on cam blanks to compliment the K Model valve geometry and machine the tappet guides to receive the modified flat-shoe lifter. This must have been the KR cam fitment for 1952? If not what else would they have used, since the roller tappet kit didn’t come out for another year?

Regarding the comment about the failure of the flat tappet kit, I too have heard a similar story from a friend that worked at a local HD dealership circa 1973. He explained that there was a 3 lb coffee can full of angle-ground cams and flat-shoe lifters in the basement and when he inquired of the owner what they were for, he was told they were failed parts from a flat tappet cam kit for a K Model that didn’t work. My friend further commented that the square corners leading to the nose of the cam lobe were worn round and that the flat-show lifters were no longer flat, but rather were hollowed out across their face from wear.

This may be an unrelated observation, but Indian won the flat track championship in ’51, ’52 and ’53 and makes me wonder if these winning seasons were the result of HD working to sort out the necessary valve motion required for the KR as well as addressing the reliability issue associated with the flat tappet cam?

hollowed out across their face from wear
This is the first place the Triumph tappets show wear - a thin line across the center of the pad.

I think it's more than coincidence that the H-D success rate improved when the 1/4-speed pump (1954) and big rod set (1955) were introduced.

The AMA Grand National Championships for 1951, 1952, and 1953 were won by Indian.
The Championship was based on the Springfield Mile.
One race, winner take all.
As far as reliability the KRTT won the Daytona 200 mile race in 1953 it's second year in competition
.

I have seen one of these 1952 kits offered NOS on eBay many moons ago. I'll dig around to see if I can find any saved pics, but it will take some time.

Simon, That would be great and very much appreciated. Would love to get a better understanding of the kit compared to the 53R kit that became available in 1953. Would specifically love to get a closer look at the tappet guides and cams.

Stan

I had one early KK cam and Boot lifter set up. It had WR grind, but K axles for bushings, no oil drive #1 cam, etc. Bob Wells purchased the kit from me. Obviously the near frictionless roller wins the best set up award. Some of the first roller cam V8 one offs Ive seen used Harley lifters -29