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Discussion Starter #1 (Edited)
All those years I spent in the engine well of a cage, taught me a good deal about how engines go together; how they run, etc..

When "motorcycles" came into my life, I knew that the basic combustion and drive principles were the same, but that the design principles varied (much like as in cages as well of course).

What I'm looking at a bit more closely these days, since it is vividly apparent on a HD Motor, is the design of the Lifters (that's what those external vertically angled rods are, outside the motor, right?).

I'm trying to wrap my head around a couple of questions that you "Professional" Service guys would know the answers to:

1. Why are there "external Pushrods" as opposed to internal Pushrods
on my HD Motor, even on my 2004?
2. Was/is this design a proprietary HD thing?
3. What, in your opinion are the disadvantages or advantages of this design?


This video (at the beginning of the video) was helpful, in seeing the differences between types or designs of the combustion process:


The way THIS guy removes the pushrods, was interesting!!



-Soupy
 

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1. Why are there "external Pushrods" as opposed to internal Pushrods
on my HD Motor, even on my 2004?

-There's not enough room to put them inside.

2. Was/is this design a proprietary HD thing?

-Nope. Although some brands have added something on their bikes which sort of looks like a push rod tube to give them a more classic appearance.

3. What, in your opinion are the disadvantages or advantages of this design?

-There are many less moving parts as opposed to an OHC design, so there's less to wear out and less to break. Also, Harley's use a hydraulic lifter to move the push rod so they never need adjustment or service. There is no valve adjustment that needs to be done as part of the routine maintenance, ever.

-A disadvantage would be that they would needed to be upgraded if you wanted to build a very high revving engine for racing or something, but that's not a concern any street legal bike would likely ever have.
 

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The overhead cam gives advantages as far as performance goes, but is more complex.

The VRod has OHC, I believe. You don't want to know how much they cost to do an adjustment.
 

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Push rod

Do a search on old JAP motors. They had external push rods, and valve springs and the stem of the valve.

Push rod motors used to max out at about 6000 revs. The Honda 500 sideways V twin ran a bit over 10,000. The push rods were very thick to prevent flexing. But that adds mass, which robs a bit of power.
NASCAR is now running around 9,500 for 500 miles with push rods.

But all the high horsepower engines usually run twin overhead cams. That allows them to rev high enough to make the extra power.
But in reality most of the extra power is not needed. 100 hp and 80 pounds of torque will propel a bike plenty fast enough. That might describe a Vrod, and is a bit more than my 79 XS11.

Unkle Crusty*
 

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The overhead cam gives advantages as far as performance goes, but is more complex.

The VRod has OHC, I believe. You don't want to know how much they cost to do an adjustment.
I'm curious. Do they have to remove the engine to adjust them though or something nearly as obscene?
 

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I'm curious. Do they have to remove the engine to adjust them though or something nearly as obscene?
When I was in Harley school they said it was easier to remove the engine to check and adjust the valves, but some of the experienced V-Rod master techs said they could do it in-frame in slightly less time. What little we did on V-rod engines was all done on engines on stands. I'm pretty sure that for any rocker arm work or for any repairs to the cam chain upper sprockets the engine would have to be out.
 

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I'm curious. Do they have to remove the engine to adjust them though or something nearly as obscene?
From what I understand, the engine needs to be unbolted and rotated down to get at the valve adjustments. I think the valves use shims as well, making it more difficult.

I think the book time on a valve adjustment is about 2.5 hours.
 

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Discussion Starter #8 (Edited)
Given what Uncle Crusty has said.......... "Harley Davidson" was not the first to do an External Push Rod set up?

-Soupy
 

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The first.

Given what Uncle Crusty has said.......... "Harley Davidson" was not the first to do an External Push Rod set up?

-Soupy
Same with hemi heads and liquid cooling, overhead cams and so on. All used in the early part of 1900. Airplane engines and bike engines shared a lot of common mechanical issues to resolve. Big end bearings was one. An interesting read is the design of the Moto Guzzi V8.
Simply put, more horsepower means more heat, and more stress on everything. The metallurgy has improved dramatically over the last 50 years.

We used to get pistons expanding in dime sized bumps and seizing. Sand down the bumps, or fit the piston with more clearance. 1 1/2 thou down the side might be fine for the dirt, but run it WOT down a long straight and ease off, new back brake connected to the engine. So we would get several pistons, all standard and put the one in that gave us 2 1/2 thou of clearance.

While on the same theme. The reason the British 3 cylinder 750s all blew up at Daytona was the lousy placement of the oil coolers. The reason my 750 Norton made the maximum power, and stayed together, was the size and placement of the oil cooler, and the venting ( breathing ) of the oil tank and engine.

Unkle Crusty*
 

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Back in the day the push rods were not even enclosed. Ships back in the early 1900's had open engines where all the moving parts were out in the open with big open pans under them to collect the oil. That's why they used to have 'oilers' who went around with oil cans to squirt on all moving parts. Only combustion champers were enclosed.
 

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The Curtis Jenny was another. I always wondered how oily the pilots got in the cockpit.

 

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Discussion Starter #13
Nope.

Most IC engines in the early part of the last century used pushrods.
Yeah, but I'm discussing "external" push rods.......


How cool is THAT, Hog!! Thanks for the video!! I'm a big "aircraft" buff. Clearly the rocker arms were visible, and yet the push rods were not quite the same setup.

Didn't the old WASP engine have external push rods, if I recall correctly?

-Soupy
 

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Yeah, but I'm discussing "external" push rods.......


How cool is THAT, Hog!! Thanks for the video!! I'm a big "aircraft" buff. Clearly the rocker arms were visible, and yet the push rods were not quite the same setup.

Didn't the old WASP engine have external push rods, if I recall correctly?

-Soupy
Okay, let me re-phrase that:

Most IC engines in the early part of the last century used external pushrods.
 

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Back in the day the push rods were not even enclosed. Ships back in the early 1900's had open engines where all the moving parts were out in the open with big open pans under them to collect the oil. That's why they used to have 'oilers' who went around with oil cans to squirt on all moving parts. Only combustion champers were enclosed.
Aircraft too. Just about all of the WWI aero engines used a "total loss" lubrication system, and pilots would frequently land back at thier bases covered in a film of castor oil blown back from the engine.
 

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WW1 pilots used to suffer from major diarrhea ( believe it or not) from all the castor oil they ingested behind those engines. They would sometimes have to land and make a brief pit stop because of this. The solution..Blackberry brandy would supposedly somehow combat the laxative effect of castor oil, so many pilots carried a flask of it with them when flying!

Aircraft too. Just about all of the WWI aero engines used a "total loss" lubrication system, and pilots would frequently land back at thier bases covered in a film of castor oil blown back from the engine.
 

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WW1 pilots used to suffer from major diarrhea ( believe it or not) from all the castor oil they ingested behind those engines. They would sometimes have to land and make a brief pit stop because of this. The solution..Blackberry brandy would supposedly somehow combat the laxative effect of castor oil, so many pilots carried a flask of it with them when flying!
Might work. But what happens when you drink too much brandy. Double trouble? Maybe that's where the term got the runs came from. When you think you're cured then one swig to much, boom, and you have to run fast.
 

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Oh darn.

Darn Hog you ruined it for me. I read the post from Mike and was thinking: what I need is a flask of blackberry brandy to offset the effect of all the cage fumes.
Now you tell me I could be in for double trouble.
Excitement, despondent, excitement, despondent.

Unkle Crusty*
 

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WW1 pilots used to suffer from major diarrhea ( believe it or not) from all the castor oil they ingested behind those engines. They would sometimes have to land and make a brief pit stop because of this. The solution..Blackberry brandy would supposedly somehow combat the laxative effect of castor oil, so many pilots carried a flask of it with them when flying!
Very interesting! I'd never heard that before. (I'm a bit of a WWI history buff.)

On the other hand, diarrhea was the least most pilots had to worry about...

But castor oil was some pretty amazing stuff in it's day. Come to think of it, it still be a rather amazing lubricant today.
 

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Very interesting! I'd never heard that before. (I'm a bit of a WWI history buff.)

On the other hand, diarrhea was the least most pilots had to worry about...

But castor oil was some pretty amazing stuff in it's day. Come to think of it, it still be a rather amazing lubricant today.
It is still my favourite thinh to oil knives with.
 
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