Cam group 56R

Production K Models

Cam group 56R

Postby starcain » Fri Feb 08, 2019 9:27 am

I just recently noticed this cam group on the back page of the 1959 Competition Models Spare Parts Catalog. Does anyone happen to know what the 25501-56R and 25502-56R cams are or what they look like? They are both just intake cams but shows they are for 52 to 56 K,KH & KHK. These are new to me!
Stan
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Re: Cam group 56R

Postby thefrenchowl » Fri Feb 08, 2019 11:39 am

Most likely 25499-55R KR grinds fitted with K/KH shafts...

Patrick
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Re: Cam group 56R

Postby starcain » Fri Feb 08, 2019 12:28 pm

Patrick, sounds like a reasonable assumption with the shafts. I can't lay my hands on the lift spec for the 55R right now, do you happen to know off hand what it is? Being a hobbyist I sometimes struggle with fully understanding how things work in the motor but I try. If the 55R cam lift is close to the J,H or other KR cams it would be quite a bit higher lift then the low lift K or KH cam lift. .030"+ What kind of end result would you end up with having high lift intake cams with long duration and exhaust cams with low lift and short duration? Always wondering!
Stan
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Re: Cam group 56R

Postby thefrenchowl » Fri Feb 08, 2019 3:16 pm

It's all been here for the last 13 years...!!!

https://web.archive.org/web/20160504093424/http://harleykrxlrtt.com/technical_info_on_kr_cams.htm

You'll have to machine the heads with these lifts on std K or KH.

Tool to do that is just a 2mm (exhaust or 3mm (inlet) high cutting tool brazed on a spare valve:

Image

Fit head on cylinder and rotate valve in cylinder with a drill and sink it 10mm towards the head. Clearance of .80 on exhaust and .120 on Inlet is then achieved

Patrick
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Re: Cam group 56R

Postby starcain » Fri Feb 08, 2019 3:43 pm

I suppose it's natural for when someone asks a question about something that people would assume you are working on a project. I am not. I just came across the 56R cams and wondered what the heck they are. I am well aware of head machining required for higher lift cams. If your getting on me for not having the 55R lift spec at the tips of my fingers,sorry. I was just curious what the difference would be between 55R intake cam and a K exhaust cam. No big deal. I just have a lot of time right now to sit around and think about nonsensical and meaningless stuff. I wonder a lot!
Stan
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Re: Cam group 56R

Postby thefrenchowl » Fri Feb 08, 2019 6:56 pm

I wasn't being facetious...!!! Just showing you where these specs have been sitting...

Knowing Harley from my gut feeling and experience, the 25 500-56R is a full set of 4 cams, not just 2 inlets as nobody in his right mind would use a mix or K exhaust and KR inlet cams in the same motor.

Std K cam set runs out of steam at 5000 rpm, just above average WL cam set... And a decent KR inlet cam will breathe till 7500 rpm...

So they had a few 25 500-56R full sets for sale and then for some reason a few inlet cams as well.

Patrick
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Re: Cam group 56R

Postby starcain » Fri Feb 08, 2019 7:51 pm

Patrick, that makes sense and follows the parts book part numbers for the KK & KHK cam group. 25500-53 is for a complete 4 piece cam set. 25501-53 is a front intake cam and 25502-53 is the rear intake cam. Since the listing is under " Miscellaneous Parts Available " maybe as you say, they had some extra intake cams left over that became available for sale.
Thanks for your thoughts,
Stan
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Re: Cam group 56R

Postby thefrenchowl » Sat Feb 09, 2019 5:23 am

Yep, one can find all sort of stuff listed over the years in this miscellaneous section!!!
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