KHK Fkywheels into XLCH

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KHK Fkywheels into XLCH

Postby Ferrous_Head » Mon Nov 19, 2018 4:25 pm

Hi Guys,

Forgive me if ths has been covered before - I can't find the info I need.

I have picked up a 1958 XLCH engine. The bike was bored and stroked many years ago. It came with Dytch cylinders and KHK flywheels. (minus minus cams as well - someone knew what they were doing)
I know the KH and XL shafts are different as well as the rods. But I don't know what the difference is between the KH shafts and the XL ones. I'm hoping it's just the taper. It probably needs a complete rebuild but the pin is the same. What I'm hoping here is that stock XL parts can be used to rebuild these wheels.

Anyone have any experience with these wheels in XL cases ?

I did consider putting everything back to stock - but only for a micro second. I won't race the engine and will do my level best to preserve what I have left. i only have the major engine parts - not the complete bike. So it will never be a 100% stock 58 XLCH. As a racing man myself I do believe that "as raced: can be just as nice to own as factory stock.
"I know only too well the evil that I propose, but my inclinations get the better of me."
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Re: KHK Fkywheels into XLCH

Postby Maxcapacity » Tue Nov 20, 2018 1:08 am

I have a 57XL with KHK wheels. The KHK wheels use the KH/KHK pin & shafts. From there out everything else XL will work, assuming the cases are already clearance.
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Re: KHK Fkywheels into XLCH

Postby xlh59 » Tue Nov 20, 2018 2:22 am

The KH and the KHK use the same flywheel assembly, so no difference there. The KH and the XL also use the same crankpin, meaning crankpin, rollers, cages and rods can be taken from the XL. The thrust washer is (to my memory) a bit smaller on the KH flywheels ... and its steel like on the early Xls.
The tapers in the flywheels are identical for all shafts, the only relevant difference I am aware of is the shoulder on the sprocket shaft on the XL ... the KH has no shoulder on it. Not sure from my memory now ... is the shoulder then on the flywheel? No matter what the situation is ... all very easy to fix. Not sure whats the difference on the pinion shaft though ... I can post a comparison picture, but not now (traveling) ...
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Re: KHK Fkywheels into XLCH

Postby Ferrous_Head » Tue Nov 20, 2018 8:22 am

I've had a good look at my -57 parts book can see where there are different part numbers used on the KH and XL. I did notice that the KH and XL have different rear rods. Don't know why,
Someone took the engine apart - don't know why but I think they thought they would get more for it if they sold off individual bits of the engine.I can't see any obvious damage to the parts I have. The flywheels were assembled and they do have wear on the crank pin/rollers. But it's not major and I may just clean them and put it back together. Very little wear in the bores and thinking a light hone might even suffice there.
There is a different number(s) for the pinion bearing sets between the KH and XL. Possibly the shoulder on the XL shaft necessitates a shorter pinion bearing ? There is also a different pinion shaft nut. So, I just need to determine if it has KH or XL pinion shaft on it. I'll ghave a look in the morning.

Were the KHK wheels polished from the factory ? These are but don't know if that was a factory thing or not.
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Re: KHK Fkywheels into XLCH

Postby wz507 » Tue Nov 20, 2018 9:46 am

Ferrous_Head wrote:Were the KHK wheels polished from the factory ? These are but don't know if that was a factory thing or not.

No polishing - standard finish like other HD flywheels of the era.
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Re: KHK Fkywheels into XLCH

Postby wz507 » Tue Nov 20, 2018 5:50 pm

Ferrous_Head wrote:I've had a good look at my -57 parts book can see where there are different part numbers used on the KH and XL. I did notice that the KH and XL have different rear rods. Don't know why.

There is a different number(s) for the pinion bearing sets between the KH and XL. Possibly the shoulder on the XL shaft necessitates a shorter pinion bearing ? There is also a different pinion shaft nut. So, I just need to determine if it has KH or XL pinion shaft on it. I'll have a look in the morning.

I'm presently in the process of converting my KHK to the Sportster PTO and pinion shafts, so some technical overlap with your project.

Regarding your query about the difference in rear rods between KH and XL (both are -52 casting numbers), I believe it is due to the longer stroke KH rear rod being clearanced/machined differently on the big end to provide clearance with the male rod at BDC. With the shorter stroke XL the extra clearance in the rod big end was not required so they left the rod sturdier with more material on the big end. The front rod remained the same for both KH and XL since it had nothing to do with BDC clearance.

Regarding differences in the KH and XL flywheel, as noted by others, the left KH flywheel has a shoulder (~0.060” proud) at the PTO shaft bore. The Timken bearing seats against this shoulder when the engine sprocket nut pulls the entire assembly together. This of course is also the Achilles heel of the shoulderless KH PTO shaft, i.e., the shaft is tightened into the flywheel taper, but when the engine sprocket nut is torqued to pull the entire assembly together, it pulls directly on the PTO shaft in the flywheel taper. Which end of the shaft do you think wins this tug-of-war for real estate, the daintier nut inside the flywheel or the bulkier ¾-16 sprocket nut?

Anyway, eliminating this tug-of-war was likely the reason the shouldered PTO shaft (item 13 in image below) was introduced for 1957. To install the shouldered PTO shaft in a KH flywheel requires that the shoulder on the flywheel be narrowed/removed to provide clearance between the flywheel and shoulder when the shaft is fully tightened into the flywheel. When this was done on my project it resulted in the flywheels shifting right in the KH cases ~ 0.125” because the PTO shoulder presents a new obstacle ~0.125” further to the left of the flywheel which in turn results in the Timken bearing seating on the new obstacle (previously seated on the 0.060” flywheel shoulder). Some creative whittling, shimming and a new custom seal retainer by my engine builder alleviated this misalignment issue. In your XL case the Timken bearing is located ~ 0.125” further to the left so you will not have this issue to deal with and everything should align perfectly. This leftward shift of the Timken was likely due to the combination of the shouldered PTO shaft and the bore growing from 2.75" in the KH to 3.0" in the XL, and the desire of the design team to leave the more complex pinion/cam chest side of things alone and instead alter only the PTO side of the world.

Shouldered XL PTO Shaft.jpg
Shouldered XL PTO Shaft.jpg (13.31 KiB) Viewed 233 times

Wish I could provide some insight on the -54 and -57 pinion shafts but have none. The shaft from my KHK flywheels and a new S&S -57 pinion were measured as carefully as possible and no difference could be found. Seems either the -54 and -57 pinion shafts are the same, or possibly the shafts I am measuring are not -54 and -57 parts. So if somebody knows the difference please enlighten all of us. I have queried other builders on the subject pinion shafts and nobody is aware of any differences and they routinely put the -57 pinion in KH engines with no issues.
Last edited by wz507 on Tue Nov 20, 2018 8:08 pm, edited 1 time in total.
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Re: KHK Fkywheels into XLCH

Postby Ferrous_Head » Tue Nov 20, 2018 6:08 pm

Mate ! Thank you very much for that info. The KH wheels into an XL was a common (sort of) thing back in the day and I always wondered how difficult it was. Apparently, not very.
I just need to source some base gaskets and head gaskets and I think I can put this one all back together. The polished wheels along with a few other minor things tell me this one was put together with a lot of care. I'm not touching the outside patina and it should wind up running and looking like the thing it is.
Cheers
Gene
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