Rebuild crankshaft KR

Racing K Models

Rebuild crankshaft KR

Postby prostreetholland » Fri Nov 16, 2018 5:17 am

The crankshaft from my 1959 KR need rebuild. The bike was stored for a long time in wet circumstances. I need the crankpin, rollers and rod races. The crankpin is sell by Eastern Parts. The rollers and rod races are hard to find for me, because I'm living in Holland. Any suggestions?
Is there somebody who has experience with making a thinner crankpin (1,25 inch) and using XL connecting rods and bearings?
Dutch KR
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Re: Rebuild crankshaft KR

Postby 55panman » Fri Nov 16, 2018 11:20 am

Dutch, The crankpin and rod races are available, made new, from Drew Gatewood aka Gatewood Engineering. I'm not sure if he has the rollers available also. Google him and it will come up. He builds vintage race engines and is the Head Tech. Man at the Bonneville Motorcycle Meet. RL
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Re: Rebuild crankshaft KR

Postby prostreetholland » Sun Nov 18, 2018 7:44 am

Is there anybody who has experience with using a special (1-1/4 inch) crankpin and use XL connecting rods?
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Re: Rebuild crankshaft KR

Postby Ferrous_Head » Sun Nov 18, 2018 3:55 pm

Have you tried Jan W. Boon. The Netherlands and he has a LOT of NOS parts. He has them.

https://www.jwboon.com/
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Re: Rebuild crankshaft KR

Postby xlh59 » Mon Nov 19, 2018 2:20 am

If you want to mount a XL crankpin and rods to KR flywheels there are several aspects to consider ... generally the taper of the XL crankpin will fit into the KR flywheels and the width of the XL and KR rods are the same. One essential difference is the design of the roller cages, which are much wider on the KR. Therefore the KR flywheels do have a recess machined where the cages fit into. If you want to use XL rods you would have to fill that recess with a steel plate (like a thrust washer) and hope that no part of the XL rod will run on the "edge" of your "thrust washer. Ok, you could always machine a bigger thrust washer recess, so that anything fits nicely.
From my point of view you will run into a more relevant problem, which is the weight of the connecting rods. As the KR rods are much heavier than the XL ones, you would have to re-balance your flywheels. You might end up with a swiss cheese type of flywheels, but thats just an assumption.

As Ferrous already mentioned, the pin and the roller/cages set is available NOS from JWBoon. Not cheap though, but original (which should be a real aspect for a original 59KR) ... Boon also has the roller set available in 0.001 oversize, so with a set of suitable rod races from Drews you might be able to refurbish your original crankpin. Even your rod races might be suitable, if they have not come loose in the rods (which happens from overheating the engine). Crank pin / roller sets also pop up on Ebay from time to time. And as far as I know Drew even offers a complete rubuild of the flywheels including all parts. As you live in Holland, you are closer to OEM parts than anyone else!

Why dont you post pictures of the parts and we might be able to tell if refurbishing and using oversize rollers would do the trick?
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Re: Rebuild crankshaft KR

Postby prostreetholland » Mon Nov 19, 2018 9:20 am

I know Jan Willem Boon for around 45 years. We ride WLA models in that time. I found bigendpins from Eastern Parts. From the rod races I can't find any partnumber in the partsbook. At this time only the rollers are the problem. J W Boon have some sizes rollers but only complete with cages. The Engine is from a friend in England and he like to race with it. An other friend has also a KR that needs rebuild. That's the reason that I was thinking about XL connecting rods because the parts are easy to get.
Thanks for help, Ger
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Re: Rebuild crankshaft KR

Postby wz507 » Tue Nov 20, 2018 12:17 am

prostreetholland wrote:The crankshaft from my 1959 KR need rebuild. The bike was stored for a long time in wet circumstances. I need the crankpin, rollers and rod races. The crankpin is sell by Eastern Parts. The rollers and rod races are hard to find for me, because I'm living in Holland. Any suggestions?
Is there somebody who has experience with making a thinner crankpin (1,25 inch) and using XL connecting rods and bearings?
Dutch KR

IMHO you are on the right track seeking to use the common, easily accessible and robust XL components in your KR engine. These components make a superior bottom end that would trivially handle a 50HP KR since much higher HP Sportsters are routinely built making up to 2X that HP. For durability reasons the large-roller KR/XLR crankpin set-up was ultimately abandoned by Harley in favor of the smaller 5 mm rollers employed in XR engines.

I'm not positive, but believe the S&S flywheel set below in combination with their special crankpin would allow use of all XL rod/bearing components.

https://www.sscycle.com/products/3-thir ... d-engines/
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Re: Rebuild crankshaft KR

Postby 55panman » Tue Nov 20, 2018 12:44 am

wz507 I don't know if S&S still has the ball bearing shafts for KR's and XLR's to use on these flywheels. They used to supply them. If not I believe Eastern still has the pinion and motor sprocket shafts to use ball bearings. Also Larry Pettis in Wisconsin may have some information about these parts as he was the person who developed the replacement WR, KR and XLR wheels when he worked at S&S. If you were to go to the XR750 Facebook page and post a question for him, I imagine he would answer you. Ron
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Re: Rebuild crankshaft KR

Postby xlh59 » Tue Nov 20, 2018 2:09 am

If you want to use XL parts for crankpin and rods, I would not change any bearings or shafts. First of all, the XL shafts will not fit into the KR flywheels. Although the taper angle seems to be the same, the depth is somehow different. But the KR shafts do have another big benefit over XL shafts: The use metric bearings and the rollers do not run on the shaft, meaning wear on this shaft is rather not commen (unless a bearings starts spinning on the shaft). Even if a shaft has pitting, you can refurbish it for ball bearings, which is not possible if the rollers run on the shaft.

The early XL flywheels used steel thrust washers and I think T&O also used steel. All you need to do is machine thrust washers of the right depth and fill the recess in the flywheels that is supposed to give room for the KR roller cages. That is all mechanical change that is needed to use XL rods in KR wheels -- very simple. YOu can use steel or brass as material for the thrust washers. I just bought a connecting rod set (the japanese ones) for my XLH that came out of the dixie stock, whichj is all over Ebay now. I really like the quality, and the prices are very very competitive. YOu would not even get used KR roller cages for that price.

now talking about balancing:
I had to balance my KHR flywheels with a counterweight of 1101g using pistons with a total weight (including rings, pin, clips) of 430g which is propably close to a KR piston assembly. My current XLH had to be balanced with 1048g with the japanese rod set and piston weight of 560g -- you can imagine, that lighter pistons will even reduce the counterweight of 1048g. Both times I used the same balancing factor. As your KR flywheels have been balanced for the heavier rod setup, you would need to remove material from the flywheel.
To give a rough estimation: If you need to reduce the weight by 50g, we are talking about 2" in lenght of a 1/2" hole ... seems possible to me (depending on how many holes the flywheels have already).
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Re: Rebuild crankshaft KR

Postby Ferrous_Head » Tue Nov 20, 2018 8:35 am

What balance factor are you guys using ?
Ive been toying with the idea of re-balancing my race engine. Stock bore but 4 1/2 " stroke. (S&S rotating assembly).
It does vibrate. A LOT. From memory this one is at 60%. At 6 grand the handlebars grow to twice their diameter and my eyes start to shake. Originally I rubber mounted the engine but it destryed the rubber in the mounts in the first race meeting.
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