Skull, Thanks for the link! As anyone can see, I'm in territory over my head here and I appreciate all the input I can get before I get into this. That goes for all of you.
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XS650 Single
- Thread starter ReycleBill
- Start date
Ranger
XS650 Addict
Just stumbled across this thread and am very intrigued by the idea...any updates?
Newagerocker
XS650 Addict
Newagerocker, Does he also have a 16" wheel on the front? It certainly looks as if he does.
Newagerocker
XS650 Addict
I've had this picture on my computer for more than 15 years. I'm sorry I don't remember any of the particulars. He was featured in XS650 Society Newsletter years ago. A 16" rear or perhaps any 18" front from a 400 Special.
Tomterrific
XS650 Junkie
I had a twingled Big Bear Scrambler in 1973/74. AWFUL! Way too much vibration but the crank was turned 180 on the 2-stroke. Ride around with a plug wire off to get a hint of the increase in vibration. A 180 crank will have bad rocking couple vibration. The lowest rpm smoothness and pull will be the stock firing set up.
That's a belt driven cam not an SC drive.
Tom
That's a belt driven cam not an SC drive.
Tom
Newagerocker
XS650 Addict
Was a fooler, you are correct. I found some further info after all these years.
When my other bike won it's class at Bike Week, they announced "Best Asian Custom goes to David Rayner with his supercharged Yamaha 650". I couldn't believe show judges could make a mistake like that. I went up to collect my trophy and when I returned to where I'd been standing, a small crowd was waiting for me. They all wanted to know if my bike was indeed blown. Here's why.
The belt simply runs the cam. OK, it looks like a blower belt and I put it there purely for the looks but I never thought anyone could mistake a belt driven cam for a blower. On the 10 hour drive home I was so elated to have won my class in Australia's biggest custom bike show and I kept thinking "If you think that was good, wait till you see my trike".
It also occured to me that since so many people thought she was blown, why not supercharge the trike just for good measure. I think that three belts running on the left and an open clutch on the right should look alright. I started making enqiries to Magnacharger and Sprintex but then remembered an ad I'd seen in a magazine back in the '70s.
Added pic you can see much better there isn't a blower in there.
Attachments
Well look what I finally found after all these years:
"ODD-FIRE V-12 ENGINE
Certain examples of odd-fire engines exhibit an unexpected characteristic: when one cylinder follows its predecessor very closely, the successor pulse combines with its predecessor pulse to produce a single larger torque pulse, and the output waveform changes to the order of an engine with half the number of cylinders. Therefore the excitation frequency is half what an evenly-spaced engine with the same number of cylinders produces, and the amplitude is considerably greater.
A specific example of that phenomenon is the 90° V-12 engine being used in a certain warbird (P-51) replica kitplane. That odd-fire engine is, in essence, a pair of in-line six-cylinder engines, physically separated 90° from each other, sharing a common 120° crankshaft. It has a 90°-30°-90°-30° firing impulse spacing, which produces the output waveform shown in Figure 7.
Notice how the cylinder which follows its predecessor by only 30° combines with the predecessor to produce a 3rd order wave-form instead of the clean 6th order of an even-fire V-12.
The torque peaks of this engine are roughly 140% of the mean torque instead of the 40% commonly expected from an even-fire V-12 (Allison, Merlyn, etc. as shown in Figure 6), and the valleys extend below zero (roughly -120% of mean torque). Also notice that the pulse shape looks less like a sine wave and more like a sawtooth wave. This shape suggests that there are some complex harmonic components in the excitation.
The substantial difference between this engine and an even-fire V-12 could lead to some very unpleasant surprises if the PSRU system was not designed with the torque signature of this specific engine in mind. The saving graces, in this case, might be the fact that (a) the PSRU on this particular engine is a knockoff of the Orenda™ PSRU, which is extremely hefty, but has begun to exhibit vibration-induced problems in service above 150 hours, and (b) the V-12 powerplant package described here is delivered with an MT 4-blade composite prop, which is quite forgiving of large amounts of torsional excitation. Only accumulated service will show whether this PSRU is up to the job.
UPDATE
Recently, we have seen several of these PSRU's apart for inspection and repairs after approximately 100-125 hours of in-flight service.. As a result of those inspections, the builders group contracted with EPI todevise a solution to these engine-driven vibrations. EPI designed an implementation of its very successful drive isolation system for that powerplant, but the proper solution was deemed "too expensive".
Instead, EPI was asked to design a retrofittable band-aid fix to prevent the catastrophic departure of the propshaft from the gearbox in flight. That fix was installed (as far as we know) in all the remaining examples of that aircraft.. The real solution to the vibration problem remains designed but not implemented." http://www.epi-eng.com/piston_engine_technology/torsional_excitation_from_piston_engines.htm
I've believed for years that the theory about big bang engines hooking up better in corners didn't make sense. Airplanes don't have tires to hook up in corners so if a V-12 Odd Fire (Big Bang) engine can make 140% of the power of the same V-12 with even fire then it must have something to do with the firing order.
So if one wanted to build a Big Bang XS650 for the street I'm thinking it would be best to run the engine at a lower redline with taller gears.
"ODD-FIRE V-12 ENGINE
Certain examples of odd-fire engines exhibit an unexpected characteristic: when one cylinder follows its predecessor very closely, the successor pulse combines with its predecessor pulse to produce a single larger torque pulse, and the output waveform changes to the order of an engine with half the number of cylinders. Therefore the excitation frequency is half what an evenly-spaced engine with the same number of cylinders produces, and the amplitude is considerably greater.
A specific example of that phenomenon is the 90° V-12 engine being used in a certain warbird (P-51) replica kitplane. That odd-fire engine is, in essence, a pair of in-line six-cylinder engines, physically separated 90° from each other, sharing a common 120° crankshaft. It has a 90°-30°-90°-30° firing impulse spacing, which produces the output waveform shown in Figure 7.
Notice how the cylinder which follows its predecessor by only 30° combines with the predecessor to produce a 3rd order wave-form instead of the clean 6th order of an even-fire V-12.
The torque peaks of this engine are roughly 140% of the mean torque instead of the 40% commonly expected from an even-fire V-12 (Allison, Merlyn, etc. as shown in Figure 6), and the valleys extend below zero (roughly -120% of mean torque). Also notice that the pulse shape looks less like a sine wave and more like a sawtooth wave. This shape suggests that there are some complex harmonic components in the excitation.
The substantial difference between this engine and an even-fire V-12 could lead to some very unpleasant surprises if the PSRU system was not designed with the torque signature of this specific engine in mind. The saving graces, in this case, might be the fact that (a) the PSRU on this particular engine is a knockoff of the Orenda™ PSRU, which is extremely hefty, but has begun to exhibit vibration-induced problems in service above 150 hours, and (b) the V-12 powerplant package described here is delivered with an MT 4-blade composite prop, which is quite forgiving of large amounts of torsional excitation. Only accumulated service will show whether this PSRU is up to the job.
UPDATE
Recently, we have seen several of these PSRU's apart for inspection and repairs after approximately 100-125 hours of in-flight service.. As a result of those inspections, the builders group contracted with EPI todevise a solution to these engine-driven vibrations. EPI designed an implementation of its very successful drive isolation system for that powerplant, but the proper solution was deemed "too expensive".
Instead, EPI was asked to design a retrofittable band-aid fix to prevent the catastrophic departure of the propshaft from the gearbox in flight. That fix was installed (as far as we know) in all the remaining examples of that aircraft.. The real solution to the vibration problem remains designed but not implemented." http://www.epi-eng.com/piston_engine_technology/torsional_excitation_from_piston_engines.htm
I've believed for years that the theory about big bang engines hooking up better in corners didn't make sense. Airplanes don't have tires to hook up in corners so if a V-12 Odd Fire (Big Bang) engine can make 140% of the power of the same V-12 with even fire then it must have something to do with the firing order.
So if one wanted to build a Big Bang XS650 for the street I'm thinking it would be best to run the engine at a lower redline with taller gears.
And look what else I found in Wikipedia:
"The Versys is based on the same platform as Kawasaki's other 650cc twin motorcycles, the Ninja 650R and the ER-6n. It shares the same electronics, engine, wheels, brakes and main frame as its siblings. Where it differs is in riding position, rear sub frame, suspension components, and engine tuning.[2]
The Versys' 650 cc liquid cooled, four-stroke, parallel-twin engine has been retuned for more bottom-end and mid-range torque. This is achieved with different camshafts and fuel injection mapping. These changes cause peak torque to occur at a lower engine speed and provide better throttle response in the 3,000 to 6,000 rpm range. In addition a balance tube has been added between the exhaust headers to smooth out power delivery. Power is 68 hp (51 kW) at 8,500 rpm, compared with the Ninja's 67 hp (50 kW) at 8,000 rpm.[1] Torque is 47.2 lb⋅ft (64.0 N⋅m), compared with the Ninja's 48.45 lb⋅ft (65.69 N⋅m).[1] Improving the engine's low and mid range response comes at the expense of a slight reduction in peak power however. A similar approach was recently deployed by Honda with their CBF1000 model. The engine uses a 180 degree crankshaft. This in turn requires an uneven firing interval (180 degrees, 540 degrees) which gives the engine note a distinctive "throbbing" sound at idle"
https://en.wikipedia.org/wiki/Kawasaki_Versys_650#Technical_details
"The Versys is based on the same platform as Kawasaki's other 650cc twin motorcycles, the Ninja 650R and the ER-6n. It shares the same electronics, engine, wheels, brakes and main frame as its siblings. Where it differs is in riding position, rear sub frame, suspension components, and engine tuning.[2]
The Versys' 650 cc liquid cooled, four-stroke, parallel-twin engine has been retuned for more bottom-end and mid-range torque. This is achieved with different camshafts and fuel injection mapping. These changes cause peak torque to occur at a lower engine speed and provide better throttle response in the 3,000 to 6,000 rpm range. In addition a balance tube has been added between the exhaust headers to smooth out power delivery. Power is 68 hp (51 kW) at 8,500 rpm, compared with the Ninja's 67 hp (50 kW) at 8,000 rpm.[1] Torque is 47.2 lb⋅ft (64.0 N⋅m), compared with the Ninja's 48.45 lb⋅ft (65.69 N⋅m).[1] Improving the engine's low and mid range response comes at the expense of a slight reduction in peak power however. A similar approach was recently deployed by Honda with their CBF1000 model. The engine uses a 180 degree crankshaft. This in turn requires an uneven firing interval (180 degrees, 540 degrees) which gives the engine note a distinctive "throbbing" sound at idle"
https://en.wikipedia.org/wiki/Kawasaki_Versys_650#Technical_details
