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Increasing Size.. 45 to 74 ?

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George Greer

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Location: Markt Einersheim, Germany

Post Tue Feb 01, 2011 12:05 pm

Re: Size Increase

:D :D :D
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irishbaker

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Location: Cork ,Republic of Ireland

Post Tue Feb 01, 2011 2:52 pm

Re: Size Increase

was that another reference to "Size Increase" hehe :mrgreen:
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WZ507

Posts: 84

Joined: Tue Aug 09, 2005 12:01 pm

Post Tue Feb 01, 2011 10:59 pm

Re: Size Increase

OK, so to ease back on to topic, let's assume that we have this generously proportioned female commanding DD's Frankie up a very steep grade under excessively aggressive throttle, and we're worried about melt down as the hog is bellowing for it's life. I want to add my $0.02 of speculation on the survival of poor Frankie.

Previously 45Brit expressed his concern, rightfully so, about melt down, but acknowledged that Frankie's survival is the proof.

"I take your point about the actual power output but I would be more concerned about local heat build-up in what must be very short piston skirts and very thin castings, and lubrication issues. The 74" and 80" flatheads suffered from this, and my old M20 used to produce temperatures that I've never seen on any ohv engine, even a Squariel; the oil in the tank would be like tar at the bottom and yellow froth at the top after an hour or so, assuming the exhaust valve hadn't stuck that is.

However if you have a bike that's been running reliably in that state of tune for a fair few years, that's the proof of the proposition"


My take on the survival of Frankie is that perhaps the primary factor breathing life into him as he is being flogged (DD openly admits to the floggings!) is the piston squirters, which should do wonders to cool the pistons. Unlike a stock engine, where the underside of the piston head looks like you just had a barbecue on it, I'll bet the underside of Frankie's pistons look like they're right out of the box. This is certainly true for late style Hogs with pistons squirters, where the underside of the pistons look virgin for 10's of thousands of miles. In my opinion there really is nothing more important than keeping the piston dimensions under control in such a scenario, which helps keep the entire situation under control. I'm sure having it cammed generously doesn't hurt either as this tends to minimize EGR as it has a least a fighting chance to expell more bad breath at overlap, which in turn facilitates the combustion event occuring quicker and cleaner, which is highly desired over the long slow combustion of a stocker full of bad breath. My $0.02.
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45Brit

Posts: 1364

Joined: Tue Nov 27, 2007 2:29 am

Post Wed Feb 02, 2011 3:03 am

Re: Size Increase

I'd go with that last comment, overall.

AJS produced an ohv sporting model known as the "Big Port" in the 1920s. It was a very successful machine, and the name came from the oversized exhaust valve. There are a few around the vintage racing scene, and even by 1950s standards they are quite nippy.

However the oversized exhaust valve was dropped on later models. The original design was influenced by then-current sidevalve orthodoxy, whereby the restricted breathing gives low compression ratios, low inlet depression, poor cylinder filling and consequent constraints on exhaust gas expulsion. Ohv engines are different, anything that finds its way IN will find its way out again with few problems.

Also, exhaust gas dynamics were little understood. Comments about the desirability or otherwise of oversized exhaust pipe diameters apply here.
Shoot, a man could have a good weekend in Dallas with all that stuff...
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45Brit

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Joined: Tue Nov 27, 2007 2:29 am

Post Wed Feb 02, 2011 3:15 am

Re: Size Increase

I'm less convinced about the piston oilers. Quite a lot of vintage racers over here don't have them. The usual system is for the piston to overshoot the base of the cylinder by about 2mm to provide lubrication from oil fling from the flywheels. That said, the typical Brit design of having the barrel spigotted into the crankcase makes it easy to do this, and stroked engines are rare ( oversize barrels producing short-stroke variants within established capacity classes are more usual ) so most of the time, piston skirts can be as long as you like

I'd certainly agree that the undersides of 45 pistons are often pretty gross, and removing this has to be worthwhile in itself.
Shoot, a man could have a good weekend in Dallas with all that stuff...
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Cotten

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Post Wed Feb 02, 2011 8:55 am

Re: Size Increase

45Brit,

Your notion that Big Twin flatties were inherent overheaters is based upon prejudice, hearsay, and faulty modern reconstructions.

When new, they were worthy match for the OHVs, as noted in Wagner's Harley-Davidson 1930-1941: Revolutionary Motorcycles & Those Who Rode Them.
My suspicion is that if fresh manifold assemblies had always been applied, the machines would have outlived the OHVs in service, and probably have survived in production for decades.

There are plenty of Big Twin Flatties in service today operating at higher average speeds than they were designed for, without overheating, and without skirt oilers. The manifold problem has been solved.

....Cotten
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Chris Haynes

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Location: Los Angeles, CA

Post Wed Feb 02, 2011 3:11 pm

Re: Size Increase

According to John Nowak, the Dean of the H-D Service School, the reason production on the UL ceased was because no matter how many cylinder designs they tried they could not build an engine that wouldn't get .001 of taper every 1,000 miles it was ridden.
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Cotten

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Post Wed Feb 02, 2011 5:52 pm

Re: Size Increase

Chris Haynes wrote:According to John Nowak, the Dean of the H-D Service School, the reason production on the UL ceased was because no matter how many cylinder designs they tried they could not build an engine that wouldn't get .001 of taper every 1,000 miles it was ridden.


Chris!

Too bad the MOCO never figured out how to test for a manifold leak. (Duh.)

It would not surprise me if they still haven't!

...Cotten
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jib

Posts: 570

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Location: devon,england

Post Wed Feb 02, 2011 6:15 pm

Re: Size Increase

i thought the ohv's had the same sealing method on the manifold as the sv's had, so did the ohv's have the same rate of bore wear?
Dude, check out that jibhead, he's crazy. Hasn't been sober for 40 years
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Cotten

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Location: Central Illinois, USA

Post Wed Feb 02, 2011 8:43 pm

Re: Size Increase

jib wrote:i thought the ohv's had the same sealing method on the manifold as the sv's had, so did the ohv's have the same rate of bore wear?


Jib!

Heat is the critical cause of wear, and any vacuum leak raises temperatures dramatically.
Flattys run at an optimum temperature that is about 100F higher than the optimum temperature of OHVs, thus OHV are more forgiving in that respect.

....Cotten
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45Brit

Posts: 1364

Joined: Tue Nov 27, 2007 2:29 am

Post Thu Feb 03, 2011 2:42 am

Re: Size Increase

UL and ULH models are pretty much unknown in the UK, but we did once have various comparable home-produced machines. I once had a 1000cc Matchless Model X which was a surprisingly fast machine - comparable to a 500cc BSA A7 - but the fuel and oil consumption was far higher, which suggests top end wear. BSA service data for the G14 ( a big side-valve twin much used for commercial applications of various sorts in the 20s and 30s ) indicates frequent and quite major top-end servicing. I know an 1150cc Royal Enfield - one of the last ones from 1939 - at our local VMCC section which has severe top-end wear including marked heat corrosion of the fins, but relatively light bottom-end wear.

I remain of my previous opinion that 750cc is about the optimum size for bikes of this sort, as demonstrated by the WL and Indian Scout.
Shoot, a man could have a good weekend in Dallas with all that stuff...
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Frankenstein

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Location: Interlaken, NY USA

Post Thu Feb 03, 2011 4:25 am

Re: Size Increase

O.K. Pa, I told you we should have changed the topic name!! I've got two emails in my inbox this morning, from a "jlorraine@sscycle.com topic reply notification-'size increase' ", which I have not opened. Unless there's a new webmaster at s&s, some web bot caught our topic and is now bombarding me with another way to "stroke my engine" :lol: :lol:
Now I'm here, I would like to mention that I believe the U series had an issue with top end wear, not exclusively tied to leaky manifolds. I think it probably has been aggravated by modern combustion, maybe due to lack of lead, or whatever gas is made of these days, whatever. I'm hopeful using oil to cool the piston crown from the inside will help.
I would like to point out an owner's manual that tells you to briefly close the throttle to bring up lubricant to the top end, points to an acknowledged engineering shortcoming somewhere. Your model A owner's manual didn't give the same advice.
Further, 45Brit may have something about the size thing. I don't know that a 45 has the same issues the "U"'s have. They surely have a better longevity reputation.
Now I know we're all crotchety old farts, and I won't change anyone's mind, :D but I feel better for beating my drum one more time!
Now, I'm going to open one of jlorraine's emails and see what she's got to offer :lol: :lol: It will probably crash my computer and you may not hear from me for months!
DD
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Cotten

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Location: Central Illinois, USA

Post Thu Feb 03, 2011 6:44 am

Re: Size Increase

DD!

Tetraethyl lead was added to fuels for one reason only: To raise the octane rating.
This meant that motors would run cooler at higher compressions.
This is critical for an OHV, but pointless for a sidevalve which needed the higher temperatures for efficiency.

Extra octane just goes out the exhaust pipe.

And the instructions for rapid de-acceleration was in the Knuckle instructions as well!
(It was critical for draining the heads.)

....Cotten
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45Brit

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Joined: Tue Nov 27, 2007 2:29 am

Post Thu Feb 03, 2011 8:04 am

Re: Size Increase

I'm not convinced by any means that sidevalves "need" higher temperatures; I don't believe they can get rid of it the extra heat by virtue of the shape and mass of their main castings. Certainly a VMCC friend who has a fast 16H Norton tells me that he just pours as much dope into it as it will stand for the sake of extra cooling, and has made no attempt to relieve the barrel fins for the same reason, although he HAS trimmed the head fins.

regarding the shutting-off thing, I remember a comment in Bike magazine in the early 70s. Two contributors travelled to the US to ride the then-new Super Glide and the Sportster. They quoted a then well-known journalist and bike builder called Larry Richardson to the effect that the non-return throttles fitted at the time meant that you needed to back off occasionally for the same reason ( the spring-return European throttles do this automatically, sooner or later, as you ride and shift your grip, fidget about or whatever )
Shoot, a man could have a good weekend in Dallas with all that stuff...
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Pa

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Location: Ohio USA

Post Thu Feb 03, 2011 8:39 am

Re: Increasing Size.. 45 to 74 ?

OK DD.... I edited the topic wording just to make sure your concerns were addressed. I contacted webmaster as to why you received that email also. Sent you a PM to boot. Pa
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Chris Haynes

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Location: Los Angeles, CA

Post Thu Feb 03, 2011 5:33 pm

Re: Size Increase

45Brit wrote:I remember a comment in Bike magazine in the early 70s. Two contributors travelled to the US to ride the then-new Super Glide and the Sportster. They quoted a then well-known journalist and bike builder called Larry Richardson to the effect that the non-return throttles fitted at the time meant that you needed to back off occasionally for the same reason ( the spring-return European throttles do this automatically, sooner or later, as you ride and shift your grip, fidget about or whatever )



WOW! That brings back memories. Larry K. Richardson. I haven't thought of him in decades. Back in 1970 when Larry first came to CA from Chicago he came to my shop and bought a used CHP Shovelhead. Larry was new to bikes and this was his first bike. Larry spent a good deal of time hanging out at my shop. He built his bike in the back. We got to be good friends and he moved into the same apt building I lived in. He had a gift of gab and could tell stories and make anyone laugh. Eventually he got hired as a magazine editor. He was on a weekend run in the CA mountains when someone shot him as he was riding down the road. I never heard if it was the shot or the wreck that killed him.
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Frankenstein

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Location: Interlaken, NY USA

Post Thu Feb 03, 2011 7:06 pm

Re: Increasing Size.. 45 to 74 ?

Cotten, I was theorizing the Tetra ethyl raised octane by damping combustion temperatures, preventing pinging. Don't really know. I'm obviously just making some guesses as to changes in operating temperatures over the years.
I know the knuckle had the same roll off thing, but after they drained the heads to the piston skirts on the panheads, guess OHV's didn't need to bring up oil to the pistons with combustion chamber vacuum.
I would loved to be a fly on the wall back in the day, to listen in on some conversations!
DD
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45Brit

Posts: 1364

Joined: Tue Nov 27, 2007 2:29 am

Post Fri Feb 04, 2011 3:51 am

Re: Size Increase

Chris Haynes wrote:
45Brit wrote:I remember a comment in Bike magazine in the early 70s. Two contributors travelled to the US to ride the then-new Super Glide and the Sportster. They quoted a then well-known journalist and bike builder called Larry Richardson to the effect that the non-return throttles fitted at the time meant that you needed to back off occasionally for the same reason ( the spring-return European throttles do this automatically, sooner or later, as you ride and shift your grip, fidget about or whatever )



WOW! That brings back memories. Larry K. Richardson. I haven't thought of him in decades. Back in 1970 when Larry first came to CA from Chicago he came to my shop and bought a used CHP Shovelhead. Larry was new to bikes and this was his first bike. Larry spent a good deal of time hanging out at my shop. He built his bike in the back. We got to be good friends and he moved into the same apt building I lived in. He had a gift of gab and could tell stories and make anyone laugh. Eventually he got hired as a magazine editor. He was on a weekend run in the CA mountains when someone shot him as he was riding down the road. I never heard if it was the shot or the wreck that killed him.


foraging through my loft, the article in Bike is dated 1972. Richardson is referred to as "LDR" He is described as a "Harley veteran" and also as an associate of an editor called Chris Bunch. Bunch's name was at least, known in the UK as editor of "Choppers" magazine which was distributed through W H Smith's at the time, although I haven't seen it in years. I do recall "Choppers" having a project bike built around an old Harley Big twin, could this be the same shovelhead you are referring to?
Shoot, a man could have a good weekend in Dallas with all that stuff...
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Cotten

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Location: Central Illinois, USA

Post Fri Feb 04, 2011 8:48 am

Re: Size Increase

45Brit wrote:I'm not convinced by any means that sidevalves "need" higher temperatures; I don't believe they can get rid of it the extra heat by virtue of the shape and mass of their main castings.


Lest anyone else has forgotten the basics of motor design, let me remind everyone that a motor's efficiency is a matter of how much power it derives from its fuel.

Compression and heat are synonymous when breaking down fuels and extracting as much work force from their combustion as possible. "Cracking" the chemical bonds of the large molecules provides the energies that move the pistons. The pistons are rebounding "hammers", and the heads are the "anvils".

Flatties use residual heat more than compression to achieve this. Thus they can use lower octane fuels.
OHVs rely on compression, so that they can reduce residual heat for the benefit of hardware, however much cooler-burning fuels must be used.

If either is not up to its optimum temperature, its efficiency is compromised.
If these temperatures spike, the hardware is compromised.

Needless to say, many have tried to maximize the compression of Flatties beyond their capacities to cool themselves.
This is like training Clydesdales to run like an Arabian. It isn't in their genes.

But this is by no means a valid reason to condemn them, as 45Brit is so often eager to do;
Instead, their strengths should exploited, especially in these times of poor fuels.

...Cotten
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jib

Posts: 570

Joined: Sat Dec 10, 2005 3:36 pm

Location: devon,england

Post Sat Feb 05, 2011 6:45 pm

Re: Increasing Size.. 45 to 74 ?

hi pa, i have been getting the same email as DD about size increase 45 to 74 from jlorraine@sscycle.com , but its seems like spam , inthat it tthe link wont work
Dude, check out that jibhead, he's crazy. Hasn't been sober for 40 years
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