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KR crank options?

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slindo

Posts: 66

Joined: Tue Jan 08, 2008 7:25 pm

Post Wed Jan 09, 2008 9:10 am

KR crank options?

Can anyone give me a rundown on the options for putting together a crank assembly for my KR? Mine has no crank at all.
I gather from older posts here that it is possible to use WR bits, or S&S flywheels and Sportster rods. Is it possible to use Sportster flywheels? Are the shafts unique to the KR or standard bits? I won't be racing the machine, so for now keeping the price down is more important to me than having the ultimate setup.

Oh and can anyone point me to any good part sources for these machines, new or used. I have been able to find very little on the net.
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37ULH

Posts: 681

Joined: Mon Nov 25, 2002 1:01 am

Location: somerset, oh usa

Post Wed Jan 09, 2008 7:01 pm

Re: KR crank options?

WR, S&S wheels will work. Also sporty rods. So will sportster wheels if you don't mind the necessary plates under your cylinders.
Yes shafts are unique.
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slindo

Posts: 66

Joined: Tue Jan 08, 2008 7:25 pm

Post Wed Jan 09, 2008 7:52 pm

Re: KR crank options?

Thanks, but can you elaborate? If the shafts are unique, do they fit the different flywheels mentioned here without modification, or will they need remachining?

My understanding is that the KR rods and crankpin were also unique, so I assume the WR flywheels would have to be used with stock WR rods, and the others with sporty rods?

Why would sportster flywheels require plates? Don't the KR and the Sportster have the same stroke and rod length?

Oh and what S&S flywheels are we talking about.

37ULH wrote:WR, S&S wheels will work. Also sporty rods. So will sportster wheels if you don't mind the necessary plates under your cylinders.
Yes shafts are unique.
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45Brit

Posts: 1360

Joined: Tue Nov 27, 2007 2:29 am

Post Thu Jan 10, 2008 12:07 am

Re: KR crank options?

T&O also do crank parts which can be made to fit. You might start asking there, bacause they will know what works, they will have done it at some time
Shoot, a man could have a good weekend in Dallas with all that stuff...
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XLH59

Posts: 4

Joined: Sat Nov 10, 2007 12:45 pm

Post Thu Jan 10, 2008 6:44 am

Re: KR crank options?

to understand which rods fit to what kind of flywheels this link is quite helpful:

http://victorylibrary.com/tech/pin.htm

If you don´t want to spend big money KR flywheels and rods are not the way to go (they are quite rare). I do not really know wether you will need plates for Sportster flywheels or not (although I don't think so) this would be the best way to go. The problem here is the shafts. KR shafts will fit to sportster flywheels -- but sportster shafts will not fit to ball bearing KR cases.

I think using KR shafts with sportster flywheels and rods would be the best way to go .... the heavier sportster flywheels will keep your idle speed down and make the thing better for street use. You could machine them down for optimal flywheel weight.

The left KR shaft is tapered compared to k-model or sportster shaft which is splined. For KR you have the choice of 4 motor sprockets (20T, 25T, 30T, 34T) -- sportster has 34T and KH has 30T ...

Hope this helps
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panic

Post Thu Jan 10, 2008 12:18 pm

Re: KR crank options?

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Last edited by panic on Sat Jan 12, 2008 6:21 pm, edited 2 times in total.
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thefrenchowl

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Posts: 584

Joined: Fri Mar 10, 2006 3:18 pm

Location: Crewe, Great Britain

Post Thu Jan 10, 2008 12:41 pm

Re: KR crank options?

Do what I did on my KHK when I machined the cases to KR specs,

Grind down std KH or Sporty shafts to KR spec ( 1" down to 25mm, not a lot of grinding) and use single lip roller bearing on drive side (25 x 52 x 15, same dimms as KR ball bearing) and no lip roller bearing on timing side (25 x 47 x 12, same dimm again as KR ball bearing) a few spacers are required to make it work, see post
http://www.flatheadpower.com/tech/viewtopic.php?f=19&t=9480
where they are shown...

Patrick
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timf937

Posts: 9

Joined: Wed Oct 11, 2006 3:33 pm

Post Thu Jan 10, 2008 8:50 pm

Re: KR crank options?

Just make sure you find a set-up that fits in the cases.This forum wasn't around 20 plus years ago when I built mine.I new guys in machine shops but not many that built bikes.I found a set of matching krk cases and cam cover and cams for 150 dollars,at a swap meet.What do you think the chances are of finding something like that now?.Don't know why the second k but the cams have it too.Maybe one someone made special.Nobody else seems to have heard of either. Anyway,I thought they were all 750cc and bought some other khk parts and had to make everything fit.A buddy of mine knew Elmer Trett,may he rest in piece,and only after I talked to him did I find out I was putting a 55 inch crank in.At the time I think it was him that told me ,but I can't be sure,kr shafts and flywheel halves were one piece and you couldn't buy just the shafts.It may be wrong info that I got back then ,I don't know.Anyway,after having the shafts ground to fit the ball bearings,went to set the assembly in the cases and the cases wouldn't go all the way together.I want to say they liked about 1/8th of an inch or more from touching.So the kr crank cases aren't as deep as the 55 inch kh.I do know that much.But like an idiot I had that perfct set of cases milled .100 on each side and made it work. It runs great but I still think back and wish I never did that to the cases. Just listen to these guys and I'm sure you'll have it up in no time.
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panic

Post Fri Jan 11, 2008 9:33 am

Re: KR crank options?

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Last edited by panic on Sat Jan 12, 2008 6:21 pm, edited 1 time in total.
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thefrenchowl

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Posts: 584

Joined: Fri Mar 10, 2006 3:18 pm

Location: Crewe, Great Britain

Post Fri Jan 11, 2008 12:20 pm

Re: KR crank options?

KR crankcases were certainly different than K cases due to the fact the K followed the W in having cam shafts/cast bosses that protude inside the crank cavity (that's the reason why K have pressed in shaft/pin on the timing side, wider than W crank assembly and no room for crank pin nuts...)

But KR should be the same width as KH since they got rid of the longer K bosses on the KH and used shorter cam shafts and crank pin nut thereafter.

Patrick
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slindo

Posts: 66

Joined: Tue Jan 08, 2008 7:25 pm

Post Fri Jan 11, 2008 2:10 pm

Re: KR crank options?

I called T&O and got suprisingly little info. They said they'd never made any KR wheels, and were under the impression that all I had to do is use K flywheels, which they said were different from XL. They did say that they would be happy to do a custom job, if it could be done with any of their standard wheels, for $500 with an 8 month turnaround, but I would have to supply the specs.

So I'd like to try to confirm a few points made here. Am I correct in concluding that:

- KR shafts will fit 45 flywheels without modification?

- KR shafts will not and cannot be made to fit K and XL flywheels.

- 45 crankpin and rods could be used in a KR with 45 wheels but are too small for best results.

- K and XL cranks cannot be used without modification in a KR.

- KR, K and XL crankpins are interchangeable as long as they are used with the appropriate rods and bearings.

- K and XL cranks can be modified to work in a KR by slightly grinding down the shafts and using some spacers.

If that is all correct, it would seem that a modified XL crank is the most cost effective way to go, and having T&O make up some custom 45-based flywheels probably the best if price was no concern.
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thefrenchowl

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Posts: 584

Joined: Fri Mar 10, 2006 3:18 pm

Location: Crewe, Great Britain

Post Fri Jan 11, 2008 2:29 pm

Re: KR crank options?

- KR shafts will fit 45 flywheels without modification?

52/53 KR crankpin is the WR crankpin but wheels/shafts are different

- KR shafts will not and cannot be made to fit K and XL flywheels.

slight difference in the tapers, but anything is possible in a good machine shop...

- 45 crankpin and rods could be used in a KR with 45 wheels but are too small for best results.

- K and XL cranks cannot be used without modification in a KR.

right

- KR, K and XL crankpins are interchangeable as long as they are used with the appropriate rods and bearings.

yes, sort of...

- K and XL cranks can be modified to work in a KR by slightly grinding down the shafts and using some spacers.

yes

it would seem that a modified XL crank is the most cost effective way to go

yes, you've got it in one!!! and probably the best way as well...

Patrick
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panic

Post Fri Jan 11, 2008 5:56 pm

Re: KR crank options?

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Last edited by panic on Sat Jan 12, 2008 6:22 pm, edited 1 time in total.
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panic

Post Fri Jan 11, 2008 6:03 pm

Re: KR crank options?

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Last edited by panic on Sat Jan 12, 2008 6:22 pm, edited 1 time in total.
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slindo

Posts: 66

Joined: Tue Jan 08, 2008 7:25 pm

Post Fri Jan 11, 2008 7:37 pm

Re: KR crank options?

Sounds good, but I am still confused as to the details.
You seem to be saying that the two shaft are the same size, since the 25x52x15 bearing and the 25x47x12 both have the same I.D., and you say they are both the same size as the orignal KR ball bearings. But Panic says that the Sporty sprocket shaft is 1-1/4", and while I don't have dimensions the schematic in my KR manual shows it as noticably larger than the timing size. So I am confused as to just how much modification the shafts will need.

Also,
Will the Sporty sprocket shaft require a Sporty sprocket, or can I use a KR one?

Are the spacers you discuss in the other thread required for the KR, or just the KHK you converted.

Anyone know what the various flywheel options weigh - the 45s, the KRs, and the Sportys?

Oh and are you currently running the Sporty crank conversion in your K(HK)?

It's incredibly frustrating trying to figure these things out "hands off", without being able to handle and measure the items in question. Thanks to everyone who has contributed for the help!


thefrenchowl wrote:Do what I did on my KHK when I machined the cases to KR specs,

Grind down std KH or Sporty shafts to KR spec ( 1" down to 25mm, not a lot of grinding) and use single lip roller bearing on drive side (25 x 52 x 15, same dimms as KR ball bearing) and no lip roller bearing on timing side (25 x 47 x 12, same dimm again as KR ball bearing) a few spacers are required to make it work, see post
http://www.flatheadpower.com/tech/viewtopic.php?f=19&t=9480
where they are shown...

Patrick
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panic

Post Fri Jan 11, 2008 7:50 pm

Re: KR crank options?

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Last edited by panic on Sat Jan 12, 2008 6:22 pm, edited 1 time in total.
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panic

Post Fri Jan 11, 2008 7:56 pm

Re: KR crank options?

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Last edited by panic on Sat Jan 12, 2008 6:23 pm, edited 1 time in total.
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panic

Post Fri Jan 11, 2008 7:58 pm

Re: KR crank options?

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Last edited by panic on Sat Jan 12, 2008 6:23 pm, edited 1 time in total.
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thefrenchowl

User avatar

Posts: 584

Joined: Fri Mar 10, 2006 3:18 pm

Location: Crewe, Great Britain

Post Sat Jan 12, 2008 6:54 am

Re: KR crank options?

- most KR, XLR and XR were always fitted with metric bearings, hence 25mm shafts. Early KR, 52/53, might have had a smaller timing shaft since they were derived from WR

- K, KH and iron XL shafts are 1" on both sides, I should know, I've got probably 10 in various boxes...

- my spacers, running the std KHK crank, are to adapt KH or XL crank inside KR cases or street cases machined to KR specs. KR, XLR and XR were made from the start for metric and have their own expensive bits beside crank for end float, oil seal, sprockets etc...

- you cannot mix KH bits with XL bits on the crank, ie you have to use KH shafts with KH crank, XL shafts with XL crank, specially on the drive side.

- I know there's a diff between street and race tapers because Jim Haubert told me, he should know, he used to machine for the race shop at the time he was there, 1970/72...

If you really need a crank, as I said, easiest, less painful, less cost is to go for a 57/70 CH complete crank, I mean rods, flywheels, shafts, sprocket... Panic's right in saying there is a street 30 teeth one, but it's the K/KH, and to use that, you'll have to weld it on its holder and get rid of the cush drive. 34 teeth CH ones have not this problem, they are one piece, without cush drive.

34 teeth XL ones also have a cush drive. I run a 34 teeth CH on my KHK, no sweat, it feels as torquey as it should despite the higher gearing.

Get the bits together, then it'll be easier for you to visualize it all...

Patrick
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slindo

Posts: 66

Joined: Tue Jan 08, 2008 7:25 pm

Post Sat Jan 12, 2008 10:33 am

Re: KR crank options?

It's all starting to make sense. Like you say, it'll make a lot more sense when I actually have the parts, but I have the ol' chicken-and-egg problem, if that I have to know just which ones they should be before I can buy them!

One thing that will probably make more sense then, that it would help a great deal if you could elaborate on , is which bits of all the odd little bits that go between crank and crankcase are retained, and which are unecessary with your setup. Things like the spring ring, shaft collars and seal ring.

Thanks again! You have been terrifically helpful.

thefrenchowl wrote:- most KR, XLR and XR were always fitted with metric bearings, hence 25mm shafts. Early KR, 52/53, might have had a smaller timing shaft since they were derived from WR

- K, KH and iron XL shafts are 1" on both sides, I should know, I've got probably 10 in various boxes...

- my spacers, running the std KHK crank, are to adapt KH or XL crank inside KR cases or street cases machined to KR specs. KR, XLR and XR were made from the start for metric and have their own expensive bits beside crank for end float, oil seal, sprockets etc...

- you cannot mix KH bits with XL bits on the crank, ie you have to use KH shafts with KH crank, XL shafts with XL crank, specially on the drive side.

- I know there's a diff between street and race tapers because Jim Haubert told me, he should know, he used to machine for the race shop at the time he was there, 1970/72...

If you really need a crank, as I said, easiest, less painful, less cost is to go for a 57/70 CH complete crank, I mean rods, flywheels, shafts, sprocket... Panic's right in saying there is a street 30 teeth one, but it's the K/KH, and to use that, you'll have to weld it on its holder and get rid of the cush drive. 34 teeth CH ones have not this problem, they are one piece, without cush drive.

34 teeth XL ones also have a cush drive. I run a 34 teeth CH on my KHK, no sweat, it feels as torquey as it should despite the higher gearing.

Get the bits together, then it'll be easier for you to visualize it all...

Patrick
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