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KHK Flywheels and Trans

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cody-b

Posts: 15

Joined: Sat Apr 19, 2008 11:40 am

Location: SoCal USA

Post Mon Apr 28, 2008 5:09 pm

KHK Flywheels and Trans

I am hoping some of you seasoned K Model enthusiasts can point me in the right direction. I want to go through the motor of my 1956 KHK and improve some things. There are two items I'm still considering.

1. Does anyone make a set of 4 9/16" forged and lightened flywheels? I'd prefer not to modify the cast stock ones. Stock stroke is important too.

2. Also, the reach from 3rd gear to 4th gear is a real stretch. The current ratios are all "standard". A full close ratio setup would be great, but I'd settle for a 3rd gear ratio that was litte closer to 4th than to 2nd. Any ideas on this you can share?

Thanx for any suggestions,
Cody
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thefrenchowl

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Posts: 584

Joined: Fri Mar 10, 2006 3:18 pm

Location: Crewe, Great Britain

Post Tue Apr 29, 2008 12:52 am

Re: KHK Flywheels and Trans

Hi, Cody,

My guess is you won't find a modern KH replacement crank anywhere these days.

However, you can buy Sportster strocker at S&S or other places. They will fit in the KH cases as long as you use a Sportster mainshaft with them.

The diff between KH and Sportster crank is that the "spacer" for the timken is part of the flywheel on the KH, but is part of the mainshaft on the Sportster. Apart from that, the dimms/tapers are the same.

Patrick
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panic

Post Tue Apr 29, 2008 9:32 am

Re: KHK Flywheels and Trans

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greybeard52

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Posts: 1050

Joined: Tue Dec 05, 2000 1:01 am

Location: Chatham, NJ, USA

Post Tue Apr 29, 2008 4:44 pm

Re: KHK Flywheels and Trans

Panic is pointing in the right direction. Early XL's (up to at least 69) gears should fit your '56 no-problemo. Not like my '54.
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cody-b

Posts: 15

Joined: Sat Apr 19, 2008 11:40 am

Location: SoCal USA

Post Tue Apr 29, 2008 5:40 pm

Re: KHK Flywheels and Trans

Panic,
Thanx for the reference. This is a great source.
Cody
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panic

Post Wed Apr 30, 2008 11:09 am

Re: KHK Flywheels and Trans

The hardest parts are:
1. too many choices
2. where to get the parts?

If you just need a closer 3-4 shift using the original ratios (2.52, 1.83, 1.38, 1.00), move 3 closer to 2 using the 1.32:1 24/20 3rd gear (instead of your 23/20).
That's all that can be done using a single pair of gears, and it's not much.
To get it any closer, you need a closer high-gear pair like the 26/18 "C" ratio, which is available from Andrews.
However, this closes up all the gears in 1 shot, leaving you with a weaker 1st gear:
1. 2.29
2. 1.66
3. 1.26
4. 1.00
More changes = more parts = more $$$
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cody-b

Posts: 15

Joined: Sat Apr 19, 2008 11:40 am

Location: SoCal USA

Post Wed Apr 30, 2008 12:49 pm

Re: KHK Flywheels and Trans

I spent several hours reviewing the Victory Library trans info. Great reading. Nearly wore out my calculator figuring the possibilities and RPM losses. I arrived at the same conclusion as you.....too many choices and where to get the parts.

I am leaning toward the C Ratio fourth gear set. The reach from standard 3rd to standard 4th means I am never in the right gear in the mountains at altitude. That low compression motor just gasps and can't pull fourth going uphill and third is too slow. Maybe adding a W ratio first gear set would help with intown stop light driving. C plus W gives 2.44, 1.66, 1.26, 1.00.
First to second would be a reach, but tolerable.

So, the next question is where to get parts. The Andrews website lists the C Ratio main drive set (26/18) for 1971 and later. It lists the wide ratio first gear set for 1973 and later. I'll give them a call. Are these 4 gears compatible with a 1956 trans?

Finally, does anyone manufacture a 4 9/16" stroke forged flywheel for the K's? Truett and Osbourne's looks close but not exact.l

Panic, thanx again for the suggestions.

Cody
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thefrenchowl

User avatar

Posts: 584

Joined: Fri Mar 10, 2006 3:18 pm

Location: Crewe, Great Britain

Post Wed Apr 30, 2008 1:48 pm

Re: KHK Flywheels and Trans

Cody,

In the Sixties, guys put the KH flywheels/mainshaft in Sportsters to get an instant boost of stroke, no mods required in the bottom end.

Hence the reverse will work as well, fit a widely available Sportster 4" 9/16 stroker crank/mainshaft in your KHK without any mods.

It'll be a lot cheaper than having a KH type special crank made just to suit your KH mainshaft............

If you really want a lightened set of wheels, the race guys did it in the past by skimming about 1/4" off the wheels diameter (1/8th on the radius) That kept the oil from rubbing too much and still kept the weight within the amount needed for smoothness/tractability. The more you lighten them, the more untractable the engine will be...

The close C ratio is the only one to go for a street bike, just raises 3rd gear a bit to close the awful later gap. I was lucky, my KHK had it from new inside there... At the time, it was a std gear box, both for K, KH and early Sportsters... Why did they change it, gawd only knows...

When I was younger, I did make the chart with ALL the H-D race gears combinations, that's actually 48 different gear boxes out of the 20 or so available gears... The factory recommended 12 of them

Patrick
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greybeard52

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Posts: 1050

Joined: Tue Dec 05, 2000 1:01 am

Location: Chatham, NJ, USA

Post Wed Apr 30, 2008 3:54 pm

Re: KHK Flywheels and Trans

Cody, Sporty transmissions show up in the flea markets all the time, cheap. Probably more sporty transmissions than any other item. The only thing you probably couldn't use out of them is the trap door itself. G
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panic

Post Thu May 01, 2008 8:58 am

Re: KHK Flywheels and Trans

I'm not sure if it's possible to use the W gear; the next best is the 35277-54R/35760-54R (28/17) 1st gear, but it wasn't used in any stock bike so must be found.
1. 2.38
2. 1.66
3. 1.26
4. 1.00

Just remember that the RPM change between the original 3-4 shift (72.4% recovery) and the C 3-4 shift (79.6% recovery) is only 10%.
Original shift at 4,000 = 2,896
C shift at 4,000 = 3,184
That's a lot of work to get another 3 or 400 RPM.
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panic

Post Sat May 03, 2008 7:37 am

Re: KHK Flywheels and Trans

If anyone is actually racing one of these things, this saves a lot of work:

http://victorylibrary.com/GEARS.htm
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Lee W

Posts: 138

Joined: Sat Sep 23, 2006 8:58 pm

Location: Carver, MN

Post Sun May 04, 2008 6:57 pm

Re: KHK Flywheels and Trans

remember, whether you put the xl flywheels in a khk or visa versa, the timing marks will be in the wrong place. No big deal as long as you don't forget....
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panic

Post Mon May 05, 2008 10:05 am

Re: KHK Flywheels and Trans

Very important: full advance on the XL wheel is about 45°!!!
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panic

Post Sat Jun 14, 2008 4:26 pm

Re: KHK Flywheels and Trans

To give you some idea how much data and analysis goes into this, here's a screenshot from one of the spreadsheets; click for a full-size view:

Image

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