Heads Up – K Model Head Quandary?

Production K Models

Re: Heads Up – K Model Head Quandary?

Postby wz507 » Thu Apr 27, 2017 6:56 pm

thefrenchowl wrote:PS: The head in the middle of the above photo is a KK or a KHK head and looks factory, The K and KH heads are never machined for inlet clearance by the factory.

Since the KK and the KHK have different diameter inlet valves, it could be that the KK don't require as much work as the KHK head to fit THE SAME early KR grind cam in it

A question about combustion chambers for KK or KHK heads. The image below shows the late “circle E” casting on the right with a fully machined combustion chamber, i.e., the chamber shown in the image was machined vertically toward the top of the head around the valve circumference with the machining ending “square” at the top of the head, that is, in a sharp 90 deg angle where the vertical wall intersects the top of the head. In contrast the left head, early style “underscore 1”, has a “raw”, as cast combustion chamber.

Has anyone seen this “square machining” on their factory KK or KHK heads, do all the KHK heads look identical to this, or is this the work of some privateer after the fact? Thank you.
low res combustion chambers.jpg
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Re: Heads Up – K Model Head Quandary?

Postby sportsterpaul » Fri Apr 28, 2017 12:31 am

Patrick, great observation on how the fin on top will cause a stress riser that cracks the head at the spark plug. I wonder if they did a heat treat after casting if it would have stressed-relieved the head enough so they don't crack. It may have nothing to do with casting stresses, but how thermal expansion is just ripping the metal apart. Thanks for the explanation, too bad you were not at Harley back in the day to show them how to fix these things.

Dr. Dick, sorry I am not trying to be argumentative or a know-it-all. Especially to you, who I gladly acknowledge as the best K and Iron Sportster guy out there. When you explained how to put the mainshaft rollers in from the outside I about fell off my chair. That is when I decided you are not Dr. Dick, you are Saint Dick.

Even if K-Models were a low-volume semi-failure, Harley Davidson was a high-volume manufacturing company, and the methods and procedures would have been the same for the K as the Panhead or other big bike. I suspect that Harley was closer to being a tractor manufacturer than Chevrolet, but it could not have been that far from modern manufacturing methods. And modern means pre-WWII. Look at the Chevrolet company film about making 1936 cars.

To have two different castings with the same casting numbers molded into them is just a stunning case of blatant incompetence. They probably had a square box on the drawing that said "Casting number and foundry code here". But the pattern shop did not realize they were supposed to use the new numbers, or just had a brain fart. One question was if Harley used their own pattern shop or just sent drawings to the foundry and each foundry made its own patterns. This would make sense since they could use their own code when the engraved the part number and code in the head.

You just can't assign old numbers to a new part, that is the cardinal sin of manufacturing, just ask the idiot at GM that did that exact thing to the fix for the faulty ignition switch. I really doubt Harley made a drawing revision this major and left the same number on it. What is far more likely is that they just forgot to change the number on the pattern, and once they caught the mistake, they changed the pattern to show the right casting number, the number on the drawing that the pattern shop based the pattern on.

Its tempting to think that an old iconic manufacturing company is like a big high-school shop class. Everybody gets together every day and sits around jawboning until someone says, "Hey, lets build up a new pattern for the cylinder heads." "Yeah, that would be fun, I was getting bored!" Like it or not, management manages. This is a business. They decide to make a new cylinder head, not the pattern shop. They authorize an ECO (engineering change order). That orders new drawings, and describes when the change will happen, and what to do with old parts (run them out, put them in service parts, or scrap them). The new cylinder heads were so different that would have to make a new pattern.

Now maybe, just maybe they figured they were just changing the fins, so this was just a revision to the original casting, and so they kept the same number. This would mesh with what Dave and you have observed on how tight money was for Harley in the early 1950s. So rather than a new pattern, they did a revision to the original drawing. This would be a bit of a mess, since they would have to erase the fins on the drawing (we all used pencil back then), and then draw over the new pattern. I doubt it would be cheaper than a whole new drawing with a new part number. They they get the patterns back from the foundry and machine off all the fins that are changing. Then they glue up the new fins. But the thing is, look at the side view in the picture on the original post. Its not just a few fins changing. The base is thicker, the mezzanine deck is different, this is a whole new part.

So its based on that side view that I maintain that it was a simple mistake. I new part from a new drawing that got the old number put on it. Please don't think that when I criticizes the Motor Company or the designs I am criticizing the people that like them. Heck, I am one of those people. I accept that a broke company like Harley in 1953 might cut corners, but you have to have drawings to make a pattern. You have to. It doesn't make things more expensive, it makes them cheaper. When I helped Vance Breese with his Bonneville streamliner he had the attitude that "blueprints are for sissies." So then he had his welder make a change to the oil tank, and we spent a couple hours trying to get it back into the bike, it just didn't fit anymore. I asked him, "See why people make blueprints?"
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Re: Heads Up – K Model Head Quandary?

Postby thefrenchowl » Fri Apr 28, 2017 8:06 am

At the time, the H-D engineers would have had meetings at the foundry to discuss patterns and how to mod their drgs to economically make patterns, cores and castings. Then bits of to and fro to smooth the conflicting angles.

Once a definite drg is done and issued with a casting number, that's not the end of it, the foundry has now to decide where the parting lines will be, where to inject for an improved flow and spread of the liquid, locations of chimneys and reserves if needed.

The foundry would be in charge of making the patterns and cores. Few cast trials to see problems, mod the patterns and cores...

The H-D shop would not be involved in any of the pattern/core making, that's an expert job well left at the foundry door!!!

As for different parts made from different moulds, there's an easy answer...

If the moded part will fit without mods on the old set up, both on the bike or on the machine tool etc, well, H-D kept the same number.

As long as the foundry moded the original to do the new part, the old one is gone forever and nobody's the wiser!!!

If you work in a factory environment, you will know that any extra time spent filling bits of paper costs a lot and goes against your profit margin. So, the less of it the better...

Patrick
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Re: Heads Up – K Model Head Quandary?

Postby ambike » Fri Apr 28, 2017 9:01 am

Fully agree with the above.

We run a modest-sized tool co. About the time Tricky Dick resigned, we changed sand castings to investment castings.

Detail improvements were made, but there was no reason to change any part numbers. Same Alpha-Numeric codes continued, and KISS.
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Re: Heads Up – K Model Head Quandary?

Postby sportsterpaul » Fri Apr 28, 2017 12:44 pm

Wow, then I guess Dr. Dick was right (yet again), I have been "spoiled" by working for two high-volume auto companies around Detroit. My feeling was always that these concepts of part number discipline and configuration management came about due to contracts with the military in WWII. I guess not.

I know disciplined manufacturing was not just confined to GM and Ford. I worked with a guy that was at Boeing in the 707 era. He said to look at the door jamb plate as you walk into a plane. The serial number and build date are stamped on the plate. He said Boeing had a record of every single part number and revision in that exact plane. More impressively, they also had a record of every field change and replacement part that was done to the plane to today's date. They did not change anything on a part, including the procedure to make, it without bumping the revision letter or cutting a new part number.

He told me about this in context to the machinery company we worked for, that did not even have schematics or drawings for the wire harnesses used in the machines. The brainiac scientists would build a harness on the prototype machine and send it to a contract shop to copy off a few sets. The contract shop was the only people that knew how the harness went together. We finally had a guy crawl around a machine and buzz out all the connections to draw schematics. That's when we finally could understand why upgrading one circuit board from a rev A to a rev B out in the field would break some completely separate function that should have nothing to do with that board. The brainiacs decided there was an unused pin on two of the connectors and they used that to route the unrelated wire. They forgot about that on the rev B board.

You gents have convinced me I was dead wrong. Harley did not have some oversight by assigning the same part number to two different parts. No, they did it on purpose. Enough said, you draw your conclusions and I will draw mine.
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Re: Heads Up – K Model Head Quandary?

Postby thefrenchowl » Fri Apr 28, 2017 4:19 pm

Paul,

Yes, I had a friend in France who worked on the Concorde... 100 safety features on a door alone...

But if a plane crashes, it will cost a lot in lives lost, family pains and insurance handouts...

You could loose 1/2 a K or Iron Head Sporty on the road to somewhere and it will still plod along nicely, do the rally and then, bring you back home like nothing happened...

My front brake broke on the way to a rally... Did not crashed, pulled the inners out and continued on my way... Later on a head gasket blew out!!! Not the best day out!!!

Image

Image

Hence one can be a bit sloppy without any consequences in MC manufacturing!!!

Patrick
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Re: Heads Up – K Model Head Quandary?

Postby sportsterpaul » Fri Apr 28, 2017 9:20 pm

Wow, that is some brake drum! Glad you lived to tell about it. Glad we all lived to tell our stories, yours are pretty amazing.
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Re: Heads Up – K Model Head Quandary?

Postby ambike » Sat Apr 29, 2017 4:57 am

You guys should know why the Harley brake drum broke.....

Buyer Beware. Below is copied & pasted directly from Buchanan's site :

Spoke kits for 1964-1972 BIG ALUMINUM DRUM hubs

NOTE !!! Please thoroughly inspect for cracks around spoke hole area.
This is a very fragile hub. High zinc content cast aluminum alloy. Hub is all inside laced.

_______________

But that's not all....Harley's " R-code " SPOOL HUBS were made with a similar aluminum, if not the exact alloy.

Sometime in the 1990's ( yeah, 20 + years ago ! ) a bulletin was issued from the race dept.

" Do not use the alloy hubs. "

______________

Many here will be familiar with the " R " hub's geometry. Originally the hubs were steel and those are not a problem.

BILLET rear hubs using Harley's sprockets / sprocket carriers were produced by another outfit(s) such as Kosman ( ? ). Those hubs were made with a larger spoke flange.

In the past, Buchanan's has had an upgraded hub available. Right now, I'm not seeing it on their site.

The problem with the weak hubs was discovered in the early 1970's.

The AMA kicked off each new season at Houston's Astrodome. In conjunction with the races there was also a trade show. " Everybody " was there.

I met Frank Buchanan, chatted, and liked his work. This was early 1973.

In Spring ' 72 I'd purchased a Sprint CR from a local amateur upstart much like myself. ( He burned out quickly & could no longer race. ) The Aermacchis were no longer the hot set-up, but hey, I was already a Harley diehard. I was also building up a modern cycle ( Yam motor in a Trackmaster ) and after meeting Mr. Buchanan sent two of the Sprint's spare hubs to be built with new rims and his SS spokes.

The rear hub was a Barnes knock-off but the front was genuine H-D. A few weeks later I rec'd the rear wheel. Included was a Dear John note stating the front hub broke when they were truing the assembly. I'd already built & trued many wheels myself and inquired with a typical WTH. There was no argument - all was cool - and we decided the used hub had been over-stressed from a wreck. Sounded logical, and for the time being, that was that.

But, as time rolled on I encountered several front XL / FX brake drums with cracks around their flanges. Hmmmm...more wrecks ? Years later, I'd built-up an H-D R spool hub wheel ( alum. rear ) to be used on a display bike. That hub & rim was polished and Buchanan's SS spokes were laced to it. One night I was working and heard something pop. Sounded like something fell from my shop's display wall. Guess where the wheel was hanging ? Second guess is easy : Yep, a chunk from the spoke flange broke off. KNOWING what I knew, I'd not over-torqued anything and had thoroughly inspected the hub. It " rang true ". OK, stay with me here....

A few years later I bought an XR-TT that had been tarted-up for display. It uses some re-pop items but the rear hub is one of the genuine, now infamous types. It's a good-looking machine and no, it was NOT Cal Rayborn's back-up bike. Anyway, it's been sitting in my shop, holding down the fort until I make its motor right, and suddenly I find a shiny piece of aluminum about 20 feet away. I recognized what it was immediately. Walked to the bike and sure enough, aprox three spokes had pulled themselves from the hub.

At that point I've determined : Yes, the original hub material is weak, but all of the KNOWN broken or cracked items have been pro-polished. I believe a chemical reaction occurs, and certainly if the part has been acid-dipped for cleaning. I know my own rear hub ( for the display bike ) was not acidized before being polished, but it's entirely possible the XR-TT hub was. Who knows, it might have come from a dirttracker's mess of dogged-out junk.

I own a 1980 XR-750 which I purchased new. ( Just for grins, the price for each was 5995.00 USD ) I've raced the bike many times. It's all original except : Before I ran the machine, I went thru the motor and the rear wheel was re-laced with Buchanan's SS spokes. Now, the machine has never been abused nor crashed, and the rear hub has its original finish. I have another XR from the same batch. It too has an OEM hub, unpolished, and uses Buchanan's SS spokes. No polish, still holding, and that motor is pumped-up. I've never raced it, but I know it was. On my back roads, I've run the bike as hard as it will go and I'm thinking I'd better quit pushing my luck.

One of the front brake drums observed with several cracks was on a 1971 FX Boat Tail. The owner wasn't happy when I pointed-out the reality. Indignant really, so the situation became take a hike man. For all he knows, I saved his punk-ass from an " event ". Another man who owns an XR-750 made street legal was warned / advised of H-D's Race Dept. hub bulletin. It is a Pride & Joy type possession. Later on I asked IF he upgraded his rear wheel and he acted offended. Don't shoot the messenger ! lol
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Re: Heads Up – K Model Head Quandary?

Postby thefrenchowl » Sat Apr 29, 2017 5:22 am

Mine did not brake on its own...

Mounted on left so I made a new torque arm.

That was a bit thin and after some time, the eye opened when I hit the brakes at 80mph. Back plate went round until torque bit and bolt hit the back of the forks, back plate exploded and went sideways in the hub, it said I've had enough!!!

I also believe in not tightening spokes like if they were a crank pin...

I do my own wheels and never had an issue with a full hub, that is apart from the fact it's twice as useless as a brake compared to the previous steel 1/2 hub...

I'm also of the opinion that my brain has a function and can decide for meself where the limits are, both on what I ride, how far can I mod and and what I can acheive...

What amazed me most with that breakage is the gap. That gap is actually the release of all the internal stresses from the cast iron liner versus the alloy outer.

Yes, that alloy is what we call monkey metal or in french "cochonium" (piginum if you like!), but not as bad as most carbs of the period I've seen and certainly better than what they pass as alloy these days to pressure cast Evo crankcases, cylinders and heads...

Cheers

Patrick
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Re: Heads Up – K Model Head Quandary?

Postby ambike » Sun Apr 30, 2017 11:48 am

You don't think the backing plate was the first to crack, break, and brake ! ?
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