The Poor Old Thing

Production K Models

The Poor Old Thing

Postby wz507 » Wed Jan 18, 2017 11:36 am

I was cleaning/prepping the cases of my 56 KHK basket for a rebuild, and while drying the cam cover with compressed air, got curious as to why no air could be detected exiting the top oil pressure hole that feeds back to the main case and ultimately feeds the piston oilers. Performing a quick and dirty inspection of this horizontal top hole by probing it with a small screwdriver showed that it was quite deep and likely intersected the vertical galley. However, upon closer inspection with a bright light l could see what appeared to be cast aluminum at the bottom of the horizontal hole! Getting more aggressive with a pick and pushing hard at the bottom of the hole I thought I felt something move, and low and behold I had pushed through an aluminum “skin” at the bottom of the hole, and gained access to the vertical galley. Thus the hole never connected to the vertical galley and the piston oilers never oiled.

So, the poor old thing never got a drop of oil fed to the piston skirt its entire life. As I look at the 0.050” OS cylinder bores I wish the engine could talk and tell me how it got to 0.050” OS – was it one catastrophic event, or 4 slow, hot, dry, incremental deaths?

Hopefully better times lie ahead for this old girl. Anyone ever observed seen anything similar?

annotated cam cover oil flow.jpg
annotated cam cover oil flow.jpg (78.76 KiB) Viewed 14250 times


low res 56 KHK cam chest.jpg
low res 56 KHK cam chest.jpg (114.96 KiB) Viewed 14250 times


low res 56 KHK case inside.jpg
low res 56 KHK case inside.jpg (113.24 KiB) Viewed 14250 times
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Re: The Poor Old Thing

Postby EKHKHK56 » Wed Jan 18, 2017 1:43 pm

Hmm that's interesting. The hole checker must have been sleeping that day at the factory. :D Well some people don't run the direct skirt oilers. I believe they should be used especially with the long 4.56" stroke and modern oil scraper rings which pass less oil. Nice work checking everything carefully and leaving nothing to chance. The oil "cups" machined in to the cam bushings are the way to go to help lube cam axles for all bushed K XL engines.
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Re: The Poor Old Thing

Postby Simon » Thu Jan 19, 2017 1:20 am

Do you mean the "lines" opposite the pins for the bushings?
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Re: The Poor Old Thing

Postby EKHKHK56 » Thu Jan 19, 2017 2:12 am

The lines are more like 'drains' to keep fresh oil flowing. On the crankcase side you can see the almost 90° cut out on the lip to help funnel oil to the inboard bushing.
Last edited by EKHKHK56 on Thu Jan 19, 2017 2:17 am, edited 2 times in total.
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Re: The Poor Old Thing

Postby EKHKHK56 » Thu Jan 19, 2017 2:15 am

Since the cams are angled there is no direct thrust on the inboard bushings so these cutouts don't hurt bushing life in any way. To shim use only the thick
007" ones and place inboard. A little extra side play is OK.
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Re: The Poor Old Thing

Postby sportsterpaul » Thu Jan 19, 2017 2:10 pm

Wow, very diligent and excellent eye. Thanks so much for posting this and the great pictures. Like Bruce at HP Express told me, you have to think of why any part ended up on the pile, and whether it is a junk pile or a pile of cherry stuff taken off during the chopper years.

No direct situation, but I did go through two cylinder rebuilds on my 1979 before realizing that the gasket around the same transfer hole (its a slot by 1979, had broken off a chunk on the inside, so no oil was getting to the top end, it was pouring into the gearcase. There was some oil blowing out the breather pipe, and I should have thought why and pulled the gearcase cover. That two-dollar gasket cost me hundreds of dollars and weeks of misery.
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Re: The Poor Old Thing

Postby Noot » Fri Jan 27, 2017 4:13 pm

I shut off my piston oilers on my '52K and reduced my pinion size hole to .060 and the rings seal better, and it runs better without over oiling.
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Re: The Poor Old Thing

Postby sportsterpaul » Sat Jan 28, 2017 6:52 am

Yeah, I heard flat-track racers used to reduce the pinion shaft hole as well. The consensus seems to be early models have a little too much oil whipping around the bottom end, while 1977 and later cases have way too much oil in the bottom end, since the gearcase drains into the flywheel cavity.

When Vance Breese campaigned his road-race Sportster (in AFM I think it was,) he reduced the pinion hole, welded on a sump, and added an extra scavenge pump driven off the #2 Cam. All the experts told him he was crazy to do that, and double crazy to not run an oil cooler. They promised he would burn up the engine on the 5th lap. Thing is, without all that extra oil down there, he didn't need an oil cooler and told me his oil temps dropped 20 degrees. He never did have wear or oiling problems with the bike.

I worked with a guy, Dale Ransom, that was a tech at the GE electric motor plant in San Jose. He confirmed this "too much oil" theory, when he described a test he did on big roller bearing used in power plant generators. He said they would run hot dry, and a little bit of oil would cool them. Then more oil would cool them a tiny bit more. Then even more oil and they would run hotter again. All that oil gets whipped around and heated, and I wonder if too much oil does not make the bearing skate a bit as well.

I am surprised that you could block the piston oilers, if that is the same as a Sportster-- holes in the lower part of the cylinder to drain oil from the top end. Anybody that has pulled a timing plug while the engine runs know how much oil spray is flying around down there. I just assumed the factory was using crankcase vacuum to suck down the oil drain holes, but my 79 sure seemed to need the side oilers, as evidenced by the two scuffed pistons I got when there was no oil to the top end. I didn't see any horrid wear to the valve tips or guide or rocker arms, but the pistons seem to scuff in a hundred miles. Lesson learned was to fix any problem, even if it did not seem relevant. If I had investigated why oil was dripping out the breather tube I would have seen the blown gearcase gasket, maybe before either front piston scuffed.

BTW, I think the front cylinder and head runs hotter because the exhaust port is wrapped back with more surface area to transfer heat into the head. Other people say its because more oil gets whipped up into the back cylinder by the flywheel. Some people even say the rear runs cooler since the mixture to the back is richer. Curious as to your thoughts. I guess all I have to do is mount a rear head and cylinder on the front and see if it runs cooler. Hmmm, I am pretty sure people have done this already.
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Re: The Poor Old Thing

Postby wz507 » Sat Jan 28, 2017 9:47 am

sportsterpaul wrote:Yeah, I heard flat-track racers used to reduce the pinion shaft hole as well. The consensus seems to be early models have a little too much oil whipping around the bottom end, while 1977 and later cases have way too much oil in the bottom end, since the gearcase drains into the flywheel cavity.

I am surprised that you could block the piston oilers, if that is the same as a Sportster-- holes in the lower part of the cylinder to drain oil from the top end.

Of course on a K model since there is not much up top, just a cylinder head, there is no oil to drain back. Instead, the K models had a 0.040” (1mm) hole in the cylinder base flange, under full oil pump pressure, that squirted straight across the bore. Item 17 in the picture below, is the plug that provides access to the subject oiling hole. This is the hole that Noot blocked off. And yes, at 5-10 psi oil pressure a 0.040” or 0.060” hole flows a surprisingly large amount of oil. So with the 0.060” pinion pill installed there would still be a generous amount of oil going to the rods and bottom end.

K model cylinder.jpg
K model cylinder.jpg (284.72 KiB) Viewed 14027 times

The early oil pumps fit on K’s also had smaller scavenge gears than later engines in the pedigree, so K models were certainly not scavenged as efficiently as some of the later engines. As you note extra oil in the bottom end is not good (can result in serious over heating), and can present a particular problem for a single piece oil ring, and in general ring packs of this era, as were used on K pistons. If a person fits a piston with a modern ring pack (3-piece oil ring and different design 2nd ring) to a K model I think most of the oil issues they had would go away.
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Re: The Poor Old Thing

Postby EKHKHK56 » Sat Jan 28, 2017 2:19 pm

Due to the 45° layout the rear cylinder gets a larger intake charge than the front even with same cams. This has to do with front piston dwelling more during the intake charge than the rear. This is why Sifton KR cams have different profiles on the intakes. Tom Sifton tuned each cylinder for maximum efficiency and torque. Front cylinder cam received less duration but earlier timing. Balance was achieved and max torque to send Joe Leonard rocketing to the next checkered flag! 1954....etc. My 56KHKR has KR valves, .420" E cams and Linkert. With the Linkert properly adjusted I decided to sniff it on my emission testing machine. Sure enough with all things equal between the two cylinders the rear ran 1.5% CO and the front was only .75% indicating more charge going to the rear. That's why the front cylinder also runs hotter, with everything else equal. Erik K
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