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Old 03-28-2013, 06:19 PM   #646
Plaka
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Quote:
Originally Posted by disston View Post
It would seem then that you bought the wrong bike. Instead of trying to make the under powered R65 do something it was not designed to do you may consider getting an R100 of sorts.

If you are one of those that have an R65 because of height restrictions this may be more involved than I fancy. But there are things that can be done to the larger bikes.

You may even have the wrong brand of motorcycle. Harleys have a nice low rpm cruising vibe. They in general go much slower than an Airheads I'm around but that's another story. The Harley does fit many riders I think.
The Harley has a long stroke motor, runs at lower RPM and makes lower frequency vibrations and a deeper exhaust note. The R65, in particular, has a short stroke motor, runs at a higher rpm, has higher frequency vibrations and sounds like a sewing machine.

The shorter cylinders of the R65 helps
cornering clearance.

All airheads have perfect primary balance but a small rocking couple (noticeable at idle) due to the cylinder offset.

This is one of those situations where intuition leads you astray. All Airheads want to be run over 3800 -4000 rpm (charging) and a new rider often isn't used to this. The R65 gets run even higher, more like an inline 4 short stroke sport bike with the top end limited by the valve train.

You get harmonic nodes at particular RPMs. The early K100s had one right where you didn't want it. Unfixable and you got the "they all do that" from the factory. It was a basic flaw in the motor. You can move the node around some with balancing games but it remains somewhere.

I would do all the other anti-vibe stuff before I went to the expense of changing gearing. It all will help, costs little and no matter what one does with gearing, it will be a smoother bike.

Plaka screwed with this post 03-28-2013 at 06:24 PM
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Old 03-29-2013, 08:30 AM   #647
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Quote:
Originally Posted by Plaka View Post
The Harley has a long stroke motor, runs at lower RPM and makes lower frequency vibrations and a deeper exhaust note. The R65, in particular, has a short stroke motor, runs at a higher rpm, has higher frequency vibrations and sounds like a sewing machine.

The shorter cylinders of the R65 helps
cornering clearance.

All airheads have perfect primary balance but a small rocking couple (noticeable at idle) due to the cylinder offset.

This is one of those situations where intuition leads you astray. All Airheads want to be run over 3800 -4000 rpm (charging) and a new rider often isn't used to this. The R65 gets run even higher, more like an inline 4 short stroke sport bike with the top end limited by the valve train.

You get harmonic nodes at particular RPMs. The early K100s had one right where you didn't want it. Unfixable and you got the "they all do that" from the factory. It was a basic flaw in the motor. You can move the node around some with balancing games but it remains somewhere.

I would do all the other anti-vibe stuff before I went to the expense of changing gearing. It all will help, costs little and no matter what one does with gearing, it will be a smoother bike.

Thanks for all the points guys! You've all been a great help.
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Old 03-29-2013, 02:55 PM   #648
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Harley's have a long stroke engine? Not nearly as much as they use to. R65's have a short stroke engine but it isn't any shorter than a R100. R65: 82mm x 61.5mm bore and stroke. R100: 94mm x 70.6mm bore and stroke. Do the arithmetic. The both have the EXACT same bore to stroke ratio. 1.33:1. For many a year 1.33:1 was about as short of a stroke as most dared go. The R65 has the same 'stroke' as a R100. Well, if the R100 and the R65 are the same engines 'stroke' wise and they are, why does a R65 rev higher? Because it has to for all power that it is lacking compared to a R100.

I would do none of the Luftmeister type mods to a R65. They don't work. Besides, the airhead chassis is absolutely dependent of the engine as a stressed member. Rubber mount the engine and talk about a rubber cow!

Torque the engine mounts and maybe modify the engine spacers like my dad use to do. That's all you can do chassis wise.

supershaft screwed with this post 03-29-2013 at 05:57 PM
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Old 03-29-2013, 03:12 PM   #649
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The ratio may be the same but the stroke is shorter. Two different things.

Stroker motors used to be much more popular with the Harley crowd. It could be done with OEM parts but I think today it would involve after market flywheels. The Harley guys don't seem to be the same these days as they were back in the "mark your spot" days.
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Old 03-29-2013, 05:26 PM   #650
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Quote:
Originally Posted by disston View Post
The ratio may be the same but the stroke is shorter. Two different things.

Stroker motors used to be much more popular with the Harley crowd. It could be done with OEM parts but I think today it would involve after market flywheels. The Harley guys don't seem to be the same these days as they were back in the "mark your spot" days.
Two different things? The stoke is different but as far as the engine being a short stroke engine or a long stroke engine, it is the same as the R100. The term 'stoke' is relative to the bore when you are talking about long and short stroke engines. Harley's aren't short stroke engines because they have a shorter stroke than a marine diesel. The are long stroke engines because their stroke is longer than their bore. The R100 is a short stroke engine because its stroke is a lot shorter than its bore. Same story with a R65. Proportionately, exactly the same.
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Old 03-29-2013, 05:45 PM   #651
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Originally Posted by supershaft View Post
Two different things? The stoke is different but as far as the engine being a short stroke engine or a long stroke engine, it is the same as the R100. The term 'stoke' is relative to the bore when you are talking about long and short stroke engines. Harley's aren't short stroke engines because they have a shorter stroke than a marine diesel. The are long stroke engines because their stroke is longer than their bore. The R100 is a short stroke engine because its stroke is a lot shorter than its bore. Same story with a R65. Proportionately, exactly the same.
+1

And small engines buzz more, and generally rev more. Mass, physics, etc.
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Old 03-29-2013, 06:03 PM   #652
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Originally Posted by disston View Post
The ratio may be the same but the stroke is shorter. Two different things.

Stroker motors used to be much more popular with the Harley crowd. It could be done with OEM parts but I think today it would involve after market flywheels. The Harley guys don't seem to be the same these days as they were back in the "mark your spot" days.
The airheads had the same stroke from the /5 on---except the R65. It has a shorter stroke...same crank I believe but shorter connecting rods.
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Old 03-29-2013, 06:24 PM   #653
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The airheads had the same stroke from the /5 on---except the R65. It has a shorter stroke...same crank I believe but shorter connecting rods.
That would not make a shorter stroke. A different crank with shorter throws is required to have less of a swept volume. Shorter rods might be used too but they don't determine the amount of stroke.
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Old 03-29-2013, 06:55 PM   #654
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That would not make a shorter stroke. A different crank with shorter throws is required to have less of a swept volume. Shorter rods might be used too but they don't determine the amount of stroke.
I see what you mean.
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Old 03-29-2013, 09:50 PM   #655
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The airheads had the same stroke from the /5 on---except the R65. It has a shorter stroke...same crank I believe but shorter connecting rods.
Excepting the R65 they all have the same stroke but they all have different bores hence they are different stroke engines. They are all varying degrees of a short stroke engine except the R50. It's a long stroke engine. The R100 is a very short stroke engine. The R750 is what I would call a regular short stroke engine.
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Old 03-30-2013, 05:42 PM   #656
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Whatever happened to the Old School terms: over-square; undersquare; square bore to stroke ratios?

Can we get this to oil-thread level?

Just kidding. However there are some fine-point differences when discussing bore/stroke ratios, actual stroke, and rod length/stroke ratios within one family of engines. For a while the rod length paradigm reigned high & mighty among automotive engine builders. So called long-rod motors saw some benefits that led to a lot of work on shorter stroke and longer rod configurations. I got out the hot rod scene when I got back into riding, so haven't really followed where that all went.

Just some food for thought and discussion if anyone is so inclined.
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Old 03-30-2013, 06:00 PM   #657
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The R65 Mono has a bit more lower end torque and pulls a 37/11, or 3.36:1. We don't do mph, but it's doing about 4,100rpm at 100kph, that's 60mph. Riding 650 2 valve twins most of my life, that feels just right to me.
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Old 03-30-2013, 06:33 PM   #658
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The R65 Mono has a bit more lower end torque and pulls a 37/11, or 3.36:1. We don't do mph, but it's doing about 4,100rpm at 100kph, that's 60mph. Riding 650 2 valve twins most of my life, that feels just right to me.
That is as tall as I would go and you are never going to come close to pulling top gear with a 37/11. Third gear but the next to are doubtful?
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Old 03-30-2013, 08:45 PM   #659
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Last sunday testing a new exhaust mod it pulled 8,000rpm in 3rd, and 7,500rpm in 4th, was still climbing in 4th, but proved it could still pull max revs so that was it. Like the old British 650's, you don't get to top speed in top gear, red line in the lower gears gets you there. It's sluggish to get over 160kph in top, but 7,500 in 4th is over 165kph and gets there pretty quick.
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Old 03-30-2013, 09:49 PM   #660
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Originally Posted by mark1305 View Post
Whatever happened to the Old School terms: over-square; undersquare; square bore to stroke ratios?

Can we get this to oil-thread level?

Just kidding. However there are some fine-point differences when discussing bore/stroke ratios, actual stroke, and rod length/stroke ratios within one family of engines. For a while the rod length paradigm reigned high & mighty among automotive engine builders. So called long-rod motors saw some benefits that led to a lot of work on shorter stroke and longer rod configurations. I got out the hot rod scene when I got back into riding, so haven't really followed where that all went.

Just some food for thought and discussion if anyone is so inclined.
The shorter rod is lighter but for a given crank throw, works through a greater angle which costs mechanical efficiency. The hevier longer rod works through less angle, but makes the cylinder a lot longer. Steam engines use very long rods and run them externally to the cylinder. So the cylinders can be short and they are just located a couple feet behind the crank/flywheel. The rods are sometimes double jointed (like a gas engine but externally). Other times the entire cylinder swings. look at some pics of old trains to see the various layouts.

I'm working on a new choke linkage for my carbs at the moment. I need to change a pure linear movement into a rotational one with a very short rod. I had been using brass rods and just letting them flex. I want to go to heavier stainless rods which will require some sort of link. mostly a fabrication problem.
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