KR Heads

Racing K Models

Re: KR Heads

Postby wz507 » Tue May 02, 2017 1:11 pm

starcain wrote:If the Competition Racer manual is circa 1959, and since it shows the final #7 head shelf schematic for a flat top piston (FTP) KR, it would follow that all the head development, relating to FTP KRs that the factory divulged, occurred between 1952 and 1959? Presumably the 60-R head incorporated all the learnings occurring up to that point in time and all 60-R heads are #7? And sometime from 1960 to 1969 the clearance specs you quoted were discovered?

wz507, For what it's worth, I have a set of 60-R heads that are # 6

Thanks again for that, as that's exactly why I asked! Your 60-R head #6 then leaves open the possibility that the #7 might have the higher valve to head clearance that Patrick recited, or perhaps it was even post head #7 development, i.e., the latest latest of the last Mohican. Do you have any idea what the valve to head clearance might be for your #6 head? If not, how deep are the head reliefs at the valve circumference near points A and B in your #6 combustion chamber? Thank you.

lr A-B.jpg
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Re: KR Heads

Postby EKHKHK56 » Tue May 02, 2017 1:42 pm

My 52 KR heads have stamped in numbers -52 with an X instead of 1-7#s
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Re: KR Heads

Postby EKHKHK56 » Tue May 02, 2017 1:45 pm

We should set up a std to see if heads have been milled at all before checking shelf heights. I suppose measuring bottom of head to deck should do it.
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Re: KR Heads

Postby EKHKHK56 » Tue May 02, 2017 3:24 pm

These 52 R heads have chamber depths of .500" to .560" above Intake Valve. Checked halfway between spark plug hole and head bolt holes. Going from #5 hole to #2 similar to A-B in line. The Exhaust shelf runs about .430" to .560" going through center of Ex shelf from top of #5 hole to top of #3. Like C-D
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Re: KR Heads

Postby starcain » Tue May 02, 2017 4:16 pm

wz507 wrote:
starcain wrote:If the Competition Racer manual is circa 1959, and since it shows the final #7 head shelf schematic for a flat top piston (FTP) KR, it would follow that all the head development, relating to FTP KRs that the factory divulged, occurred between 1952 and 1959? Presumably the 60-R head incorporated all the learnings occurring up to that point in time and all 60-R heads are #7? And sometime from 1960 to 1969 the clearance specs you quoted were discovered?

wz507, For what it's worth, I have a set of 60-R heads that are # 6

Thanks again for that, as that's exactly why I asked! Your 60-R head #6 then leaves open the possibility that the #7 might have the higher valve to head clearance that Patrick recited, or perhaps it was even post head #7 development, i.e., the latest latest of the last Mohican. Do you have any idea what the valve to head clearance might be for your #6 head? If not, how deep are the head reliefs at the valve circumference near points A and B in your #6 combustion chamber? Thank you.

The attachment lr A-B.jpg is no longer available

wz507, I have no idea what the valve to head clearance is. These heads are a bit unusual as they have had their lip ( or deck if that's the correct word ) the part that mates up to the cylinder, milled off. One head is completely flat, no lip left at all and the other has only a .015" lip left. If I had a standard height for the lip I could measure how deep the relief is and just add to what I get. I have a 52-R # 2 head that measures about .095" tall on the lip. Several standard K heads I have measure .120" tall. Not sure then if there is a standard. If you know of one let me know and I will measure. There must have been a reason why Bob would have done that to the heads as he was a very experienced long time racer. Maybe as the valve seats kept getting lower they kept lowering the heads to match? Way outside MY wheelhouse.
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Re: KR Heads

Postby wz507 » Tue May 02, 2017 6:56 pm

ambike wrote:The " hottest " Champion in that series is the N62-R, followed by the N60-R.

Some charts show the 60 Champion equivalent to an NGK 9, but the Champion could be a bit hotter.

Running Champion plugs on a half-mile track or less, I'd race a Harley V-twin or an Aermacchi CR or ER with no hotter than an N57-R.

The Sprints ( especially the short-stroke 250 ) with a tight squish require an R type gap.

It should be understood R means retracted, not racing.

AM, thanks for your input and clarification.

Interesting how we see the same thing and think different thoughts, thus perspective is everything. You are certainly correct that the N60R is the 2nd hottest plug in that series of retracted plugs. When I suggested it was a cool plug, I was thinking of it in the context of the standard series of plugs where it would be off-scale on the cool end of that world. I guess one persons cold is another persons hot. ;)

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Re: KR Heads

Postby EKHKHK56 » Tue May 02, 2017 7:03 pm

I was thinking it would be good to measure decks from another stand point than the cast fin. Maybe the machined top of spark plug hole to deck. Or :?:
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Re: KR Heads

Postby thefrenchowl » Thu May 04, 2017 12:32 pm

Warning! Contains obvious data!!!

As a KR head never works alone, it is worth also looking at the cylinders.

KR cylinders are clouded with deeper mystery since they have much less info available compared to the heads.

And they have no #...

Any KR head won't work with any KR cylinder.

Since most of the tuning happens on the cylinders, it is obvious that the recess the valves have, from the cylinder top deck, is becoming greater as the year passes.

The bigger the cylinders recesses, the less work required on the heads for achieving the 120 and 80 thou over the heads flow...

So head #7 might have appeared in mid KR life span, but work on the cylinders progressed still till 1969...

Taaa from France:

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Patrick
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Re: KR Heads

Postby wz507 » Sun Jun 25, 2017 8:22 pm

Just wanted to provide a link here to some info on a set of -52R heads that I posted in the K forum. Probably should have put it here, but ....

http://www.harleykmodel.com/phpBB3/viewtopic.php?f=3&t=601&start=30
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Re: KR Heads

Postby wz507 » Wed Aug 09, 2017 10:14 pm

Several weeks back I was attending a flat track race with a friend and he introduced me to several of his friends. As we were departing the race track walking back to our bikes, I over-heard a fellow utter the words “KR” something or another whereupon I inquired if he had a KR or any KR parts. He informed that he might be able to build a KR someday but was short several parts for his bike. But……… he just happened to have an NOS set of KR heads in factory boxes but couldn’t remember which specific heads they were, but volunteered to text me images of them. I awoke the next morning to the most unbelievable text images – his NOS KR heads just happened to be the rarest of rare – the 69R #8 for domed pistons. I inquired if by some remote possibility he would lend them to me to document and cast the combustion chambers and he simply said “if you are a friend of my friend you are welcome to take them”. I beat a hasty path to his house, retrieved the heads, thanked him profusely and returned home for casting and picture taking. Below are the images of the -69R heads and some comparative photos with the -52R heads. As always I wish it was easier to convey the 3D nuances in a 2D picture, but alas….

Aside from the obvious differences between the -52R and -69R heads, due to the flat top piston in the -52R and the domed piston in the -69R, there were a few other features that stood out.

• The -69 combustion chamber is fully sanded and blended whereas the -52 was employed as-cast.
• On the -69R head the circumferential clearance between valve head and side of combustion chamber has more top to bottom arc than the -52R head.
When you feel with your fingers it is a smooth radiused trough that you can easily fit your fingertips into.

The -69 heads and their respective boxes.
LR -69 heads and boxes.jpg
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Top view of -69R heads showing short window, fins fully encircling spark plug hole, the casting numbers between fins, and the #8 stamped on the lower edge of the heads.

LR-69R top view.jpg
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-69R casting numbers
LR -69R casting numbers.jpg
LR -69R casting numbers.jpg (196.22 KiB) Viewed 16826 times
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