1954 KHRM

Racing K Models

1954 KHRM

Postby Rubone » Thu Mar 16, 2023 1:57 pm

Here is a copy of a factory letter to dealers about the 54 Competition models, including the KHRM. And a copy of the 54 brochure.

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Re: 1954 KHRM

Postby panic » Thu Mar 16, 2023 6:07 pm

Thanks.
Was the 26203-54R ¼-speed pump used immediately, or later?
Is there any difference between the breather timing (generally referenced by the opening point in degrees) between KR and KHR with this same pump?
[url="http://victorylibrary.com/L-BK.htm"]The Linkert Book[/url]
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Re: 1954 KHRM

Postby Rubone » Thu Mar 16, 2023 9:00 pm

From the "Specifications and Instructions for Racing Models, 1954"

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Re: 1954 KHRM

Postby hugoct » Fri Mar 17, 2023 10:52 am

Can one acquire a copy of the rest of that document?
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Re: 1954 KHRM

Postby panic » Fri Mar 17, 2023 12:58 pm

Thanks.
I'm surprised at the 32° spark timing; Branch used 36° for the KR in 1965 (the Cycle World interview). Was this modified in later years?

The breather timing events are confusing (omitting the +/- 10°).
Opens 36° ATDC is much later than the KR (and S&S Sportster instructions) use. The total of -36 + 180 + 70 = 214° (about the same duration as KR), but the entire range is later, KR is about 25°.
Later opening means higher pressure before the breather opens.

Ideas?
[url="http://victorylibrary.com/L-BK.htm"]The Linkert Book[/url]
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Re: 1954 KHRM

Postby Rubone » Fri Mar 17, 2023 2:24 pm

hugoct wrote:Can one acquire a copy of the rest of that document?

I'll scan it and send it to Dave, he'll put it in the competition section. Send me your email Bill and I'll send you one.
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Re: 1954 KHRM

Postby hugoct » Fri Mar 17, 2023 3:13 pm

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Re: 1954 KHRM

Postby wz507 » Fri Mar 17, 2023 3:36 pm

panic wrote:I'm surprised at the 32° spark timing; Branch used 36° for the KR in 1965 (the Cycle World interview). Was this modified in later years? Ideas?

I suspect the answer to your question is YES, since the later competition manuals I’ve seen call out KR valve timing of 36 deg at 7/16” BTDC. The 11/32” value was a familiar value called out for KK, KH, and KHK engines of that era, when I believe the only performance cam available was the KK/KR/KHK cam set 25499-53R. Ignition timing for the K/KH engines trended with cam duration, i.e., the engines with shorter duration cams employed later ignition timing, and the larger cammed engines employed earlier ignition timing, and there were only short duration cams available circa 1954. With the evolution over time of higher duration cams leading to higher engine speeds, I suspect the MoCo increased ignition timing to 36 deg BTDC for KRs.

There are certainly ignition timing discrepancies in the HD literature, e.g., in the early competition manual the KR ignition timing is shown pictorially and stated to be 36 BTDC which was 7/16” BTDC piston position. In the later competition manual, the text portion of the specification (up front in the manual) gives ignition timing as 38° BTDC, whereas in the image of the “timing mark in hole” the same image as used in the older manual shows 36° BTDC. In both instances (old and new manual) they quote 7/16” as piston position for ignition timing.

Likewise, there are examples of KHK cam timing given as both 11/32” (1955 KH Riders Hand Book) and 13/32” BTDC (MoCo factory timing chart).

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Re: 1954 KHRM

Postby 44UL » Mon Mar 20, 2023 7:24 pm

I just have to say I love this thread! Can't wait to get my KHRM sorted and back out in the dirt. Keep it coming!
62 KR, 54 KHRM, ‘61 XLR, ‘68 XLR, original paint ‘59 CH, several 60 and 61 CH’s, two original ‘47 Servicars, 44 UL, 48 UL, 48 WL race bike(40 rwhp) 51 WR, original 68 XLCH, 65 Topper, Japanese Rikuo. Always interested in buying KR, KHRM, and XLR parts
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Re: 1954 KHRM

Postby panic » Mon Mar 20, 2023 10:01 pm

The 45, K, iron Sportster, etc. engines and KH engines will have its piston at different positions at the same crank rotation, due to both stroke increase (3.8125" vs. 4.5625")and rod ratio decrease (1.95:1 vs. 1.63:1).
At 36°, the 45, K etc. piston is .449" below deck @ TDC.
The KH at the same crank rotation is .558".
Important: the shape of piston motion is not merely changed, but differently shaped. The KH spends less time near TDC, and more time near BDC. Trigonometry is needed for this!
[url="http://victorylibrary.com/L-BK.htm"]The Linkert Book[/url]
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