Introduction

Production K Models

Re: Introduction

Postby panic » Sat Dec 31, 2022 2:33 pm

W/r/t "Will a later K motor fit in an earlier frame? I.E. a 52 - 53 frame?"
Yes, the KH is .346" taller than the K.
The earlier frame has a smaller rake angle, less high speed stability.
Last edited by panic on Sun Jan 01, 2023 9:26 am, edited 1 time in total.
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Re: Introduction

Postby Rubone » Sat Dec 31, 2022 7:23 pm

yard man wrote:
panic wrote:Hi, welcome to the site.
The cams are easily identified as "K" etc. (but exactly which is more complicated, there are many different grinds, this site has the best information): they all have tapered lobes, taller facing you and smaller facing the engine.
The cylinders and heads you're looking for have casting numbers ending in "-54" (not "-52").
If original isn't important, you can use any frame after 1954(?) including iron Sportster through 1969.

Keep us posted as the build goes along.

Happy New Year!


Thanks! Will do. Will a later K motor fit in an earlier frame? I.E. a 52 - 53 frame?

Hi there Yardman,
Any K series engine will fit any K or Sportster frame.
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Re: Introduction

Postby Coolbreeze » Sat Dec 31, 2022 8:06 pm

At the Davenport Swap Meet this year, I ran across a buddy whose friend was parting out a '56 KH. Do you want me to help you get in touch with "Buzzard"?
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Re: Introduction

Postby yard man » Sat Dec 31, 2022 8:17 pm

Yes if you wouldn’t mind, I would appreciate it. Just let me know how and where I can reach him
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Re: Introduction

Postby Ferrous_Head » Sat Dec 31, 2022 11:18 pm

panic wrote:W/r/t
The earlier frame has a smaller rake angle, less high speed stability.


Something I have wondered about. The early tree casting -52 has legs that are not parallel to the steering stem. This was modified in 54 (?) withe the 52A casting. On those forks the legs are parallel to the stem.
The effect of "raking" the trees out changes the trail which did indeed affect the handling.

But I wonder why it was designed that way to begin with. My thinking was there may have been an earlier "development" version that didn't handle as they wanted it to and rather than change the frame they modified the triple trees ?

Or were the front forks from some earlier incantation of Harley's line up ? Just modified to suit the K Model ?
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Re: Introduction

Postby Coolbreeze » Sun Jan 01, 2023 1:39 am

yard man wrote:Yes if you wouldn’t mind, I would appreciate it. Just let me know how and where I can reach him

I just sent a PM with the name and phone number.
Good luck and Happy New Year!
'56 KHK
'60 XLCH
'48 Chief
'42 Indian 841
'64 BMW R69S
'84 Moto Guzzi V65Sp
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Re: Introduction

Postby panic » Sun Jan 01, 2023 8:47 am

Tony Foale has written some interesting findings on the net.
His opinion: trail is far more important to stability than rake. He built a test bike with vertical forks and enough tree offset to get 3-4" of trail, and could be ridden with no hands.
Rake is still needed to cope with road surfaces.
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Re: Introduction

Postby chuckthebeatertruck » Sun Jan 01, 2023 8:50 am

To frames

I run an early k frame, circa 1953, with a sportster motor. It fits, but removing the rear head in frame requires turning it 90 degrees. I’ve also shoved a 76” stroker in a k frame. This frame is before hd reworked the neck angle.

I have ridden this early k frame, a couple of 54-55 k with the “corrected” geometry, a true 56 k frame, a ton of 1957-71 frames and several 79-82 frames. Hands down the 53 frame is my very favorite. With the correct sized tires, it cuts a VERY tight line and turns in very easily. It’s almost too quick into turns and feels twitchy to riders who don’t know how to drag the rear brake. I replace my foot peg rubbers every few years cause I deck them and my muffler has grind marks on it too. I run a 67 front fork and progressive rear shocks on that bike with 19/18 wheels. It surprises a lot of people by how well it turns and how little I slow down.

As for high speed stability, I got pulled over several years ago doing a true 94 mph sitting bolt upright with the bubble bags filled with groceries, it was perfectly stable. I’ve also routinely taken my short and long frame strokers well over 110-120 mph with the same solid feeling.

My “opinion” is based on 15,000 miles of riding the early k frame with a sportster motor. I adore the bike because it handles and rolls so much better than my other sportsters.

Contact Jerry R if you need a frame. I bought a 56k frame from him in 2021, which was used for a stroker.
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Re: Introduction

Postby panic » Sun Jan 01, 2023 9:25 am

W/r/t engine height:
The KH cylinder is .375" taller than the K (50% of the stroke increase from 3.8125" to 4.5625"), to use a piston* with the same compression distance).
* the K piston ends in -52, the universal replacement (both K and KH) ends in -52A when the skirt was shortened for flywheel clearance with the big stroke.
To calculate the vertical change in engine height: it's the cosine of the "V"-angle ÷ 2 (22.5°) × the cylinder height change. The cosine is .9239, so for a KH the engine height is +.346".

I wrote an Excel to automatically calculate this, along with bore & stroke, static CR, DCR, CCP (absolute and gauge), stroker plate thickness for more stroke, chamber volume, intake closing effect on CCP, more. e-mail (not PM) me for a free copy.
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Re: Introduction

Postby Ferrous_Head » Sun Jan 01, 2023 5:58 pm

panic wrote:Tony Foale has written some interesting findings on the net.
His opinion: trail is far more important to stability than rake. He built a test bike with vertical forks and enough tree offset to get 3-4" of trail, and could be ridden with no hands.
Rake is still needed to cope with road surfaces.


Tony wrote a whole book on motorcycle suspension and design. He was scathing of telescopic forks. With good reason. I have experimented with everything from 5" down to 1" of trail and finally settled on 40mm. But that's with leading link forks. Telescopic s are dangerous and useless on a racing sidecar. Too much stress. The difference in steering effort between 5 inches and 1 inch is huge. But at 1 inch it was just a little "sensitive" at speed.

19 inch wheels ill handle better than 18 inch. The biggest problem with 19 inch wheels has always been tires. Manufacturers make what they can sell. Precession forces are going to be higher with 19 inch wheels. Meaning they will be easier to turn and steadier when they do.

But I am still curious as to the odd early tripe trees. They were clearly playing with the trail. Minor rake changes have little effect in themselves. The frame wasn't a derivative from earlier bikes. A whole new design I think. But were the forks "borrowed" from something else ?
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