 360 - 270 - 180
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As it goes, our motors are 270 degree firing motors. Rumor has it that Triumph did it for teh sound, but we get a little bit more torque over the 360º motors. So, would we get an even better thump and more torque if our motors were 180º firing?
Soren
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Interesting thought. I'd bet a 180 would thump, but why stop there? How about something closer to 90 degrees to give you a real "lope". I bet the counter-balancers would eat up a lot of power though.
Along the same lines; a conversion done on Yamaha XS650 for racing is to convert into 277 degree motors. Originally they're 360 motors. The racers are looking for the smoothest power pulse which would be where the firing cylinder at TDC, while the alternate piston is accelerating upward and at the point of maximum speed. It works out to 277 on those engines. The actual degrees has to do with the stroke length & the length of the rod.
'05 America - Tec 2-1 (from a Thruxton)/ 4 pot caliper/ Kurt's Rearsets /
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Bar Shake
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Quote:
How about something closer to 90 degrees to give you a real "lope".
A 270 degree is a 90 degree.
360-270=90.
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Fe Butt
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I learned all I need to know about life by killing smart people and eating their brains.
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Bar Shake
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Quote:
beat me to it Bill! LOL
I seem to be good at that lately 
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Quote:
Quote:
How about something closer to 90 degrees to give you a real "lope".
A 270 degree is a 90 degree.
360-270=90.
360-270=90 ?? hmmm. That would be okay if we're riding two-strokes. A four-stroke cylinder takes 720° crankshaft angle (i.e., 2 revolutions) to complete 1 cycle of 4-stroke operation. In other words, it fires once every 2 crankshaft revolutions. The standard Bonnie 360 engine has both cylinders traveling in the same direction, but they aren't on the same phase. One cylinder fires every 360 degrees. This results in the even cadence you hear when it runs.
Follow me here:
360 DEGREE ENGINE
a piston fires
the next piston fires at 360 degrees
there is a 360 degree gap
a piston fires
the next piston fires at 360 degrees
there is a 360 degree gap
and so on...
270 DEGREE ENGINE
a piston fires
the next piston fires at 270 degrees
there is a 450 degree gap
a piston fires
the next piston fires at 270 degrees
there is a 450 degree gap
and so on...
HARLEY DAVIDSON ENGINE
a piston fires
the next piston fires at 315 degrees
there is a 405 degree gap
a piston fires
the next piston fires at 315 degrees
there is a 405 degree gap
and so on...
180 DEGREE ENGINE
a piston fires
the next piston fires at 180 degrees
there is a 540 degree gap
a piston fires
the next piston fires at 180 degrees
there is a 540 degree gap
and so on...
90 DEGREE ENGINE
a piston fires
the next piston fires at 90 degrees
there is a 630 degree gap
a piston fires
the next piston fires at 90 degrees
there is a 630 degree gap
and so on...
'05 America - Tec 2-1 (from a Thruxton)/ 4 pot caliper/ Kurt's Rearsets /
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I got this shirt at the gap
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Loquacious
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Quote:
As it goes, our motors are 270 degree firing motors. Rumor has it that Triumph did it for teh sound, but we get a little bit more torque over the 360º motors. So, would we get an even better thump and more torque if our motors were 180º firing?
Soren
As I understand it, we get better torque because as one piston is dead stopped at TDC or BDC, the other is halfway through it's stroke and at top speed. Helps to conserve momentum. A 360 or 180 degree crank has both pistons stopped at the same time.
Steelheart- '03 Speedmaster Black/Yellow
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Brian T - I'd guess our engines are pretty close. Like I said in an earlier post, the XS650 is perfect at 277 degrees, but each engine is a little different depending on the length of the connecting rod & its stroke. I have no idea how to do the math, but maybe 270 is right on the money for our bikes.
'05 America - Tec 2-1 (from a Thruxton)/ 4 pot caliper/ Kurt's Rearsets /
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Fe Butt
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Looking up the stats on the official Triumph website, I noticed that in fact the BA and the SM have 1 ft lb LESS torque than the T100 has, and so Soren, your premise here isn't factual.
The best way I know of to increase torque figures is to increase the stroke of engines.
The advantage that I see in our 270 designed cranks are that they do, as you infer, make a vertical(parallel) twin sound a bit more like a V-Twin, which I believe was the impetus for Triumph designing these bikes this way, as they ARE "cruisers", and V-twins dominate this particular niche of motorcycling.
The other advantage to this 270 crank is that in Flattrack racing especially, and seeing as how the Harley XR750 racers have dominated that sport for years(whatever, unfortunately, is left of that great sport today, anyway)...the theory is that the power pulses of a basically "un-sychronized" firing-order helps "dig-in" the rear tire for more traction during that type of race.(I read this theory put forward by Kevin Cameron, the tech-writer for "Cycle World" a few years ago)
Last edited by Dwight; 06/12/2007 1:44 PM.
Yep! Just like a good Single Malt Scotch, you might call me "an acquired taste" TOO.(among the many OTHER things you may care to call me, of course)
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Kurt, Mathematically, I understand what you're saying. This might be a dumb question, but what are the differences (besides exhaust cadence) in the 270 and 360 engines, as far as what you would feel when riding? I guess what I'm asking is how the 270/360 firing translates to the way the bike rides. Hhmm, maybe a good excuse to go test ride a Bonnie...it's for research purposes, right?  Will
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I thought the 270 reduced the vibration aspect as well.
Bob
2005 America, 904cc - sold. 2014 Trophy SE.
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Fe Butt
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In theory, understand it does a bit, Bob, at least in "primany-imbalance" supposedly. But of course, with the Hinckley Triumphs all having balance-shafts, it would be difficult to notice any difference in vibration between the "Modern Classics"(as Triumph calls their standard Bonneville line) and their "Crusiers".
As you probably know, the less the angle from 180 degrees(as in a "Boxer" BMW) the two pistons are moving, the more primary vibration a twin will have(without a balance-shaft, of course), thus causing the old "Triumph front wheel bogie" often seen when older Meriden Triumphs were started while setting on their centerstands, and why the engines of Harley's Dynaglide rubber-mounted models to their own version of this dance inside their frames while sitting at a stoplight.
It would be interesting to remove the balance-shafts of both Triumph models and see which would actually vibrate less, wouldn't it?!
Last edited by Dwight; 06/12/2007 2:26 PM.
Yep! Just like a good Single Malt Scotch, you might call me "an acquired taste" TOO.(among the many OTHER things you may care to call me, of course)
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Re: 360 - 270 - 180
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Bar Shake
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Kurt. There are 360 degrees in a circle. We have two cylinders. The crank pins are offset 270 degrees. If you look at it from the side there is a 90 degree difference between the pins. Each cylinder fires once every two rotations. The only difference between a 90 degree and a 270 degree is the relationship between #1 and #2 cylinder. Your explanations are wrong as you seem to be forgetting that there are two cylinders involved. Hence your 720 degrees must be divided by two..720/2=360 So: Quote:
a piston fires
the next piston fires at 360 degrees
there is a 360 degree gap
a piston fires
is BS. One cylinder fires each revolution (360 degrees). There is no 360 degree gap.
Your other examples are equally flawed.
maybe this will help:
web page
Last edited by bigbill; 06/12/2007 10:35 PM.
Contra todo mal, mezcal; contra todo bien, también
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Bill, I am quite sure I accounted for both cylinders: In each example I wrote "a piston fires" and "the next piston fires". That would account for both cylinders.
On a four stroke engine, the crankshaft must travel 720 degrees between power strokes (up & down twice). Your quote: "One cylinder fires each revolution (360 degrees)" is exactly correct for the Bonnie's 360 engine. And that is exactly what I was saying earlier. There are 360 degrees between the time the cylinder #1 fires and the time the cylinder #2 fires. One rotation later, the sequence starts again. If I reword it:
360 DEGREE ENGINE
Cyl #1 fires
the crank rotates 360 degrees
Cyl #2 fires
the crank rotates 360 degrees (720-360=360)
Cyl #1 fires, etc...
Our bikes have a 270 degree crank, but the crankshaft still has to travel 720 degrees, so the time between power strokes is not equal like the 360 engine:
Cyl #1 fires
the crank rotates 270 degrees
Cyl #2 fires
the crank rotates 450 degrees (720-270=450)
Cyl #1 fires, etc...
A 90 degree engine would not be the same as a 270. Cyl #1 would fire and the crankshaft would move only 90 degrees before Cyl #2 fired. Our crank is a 270 crank (measured in the direction of rotation from TDC of the #1 cylinder. Visually, they would be 90 degrees apart, but it is not the same thing.
If there is no gap (as I worded it in the first example) there would be no time for the crankshaft to rotate.
Each of the examples above are valid.
'05 America - Tec 2-1 (from a Thruxton)/ 4 pot caliper/ Kurt's Rearsets /
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Re: 360 - 270 - 180
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Should be Riding
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Bill, I think Kurt is right. On a four stroke motor there is also the exhaust stroke. Four Stroke Engine  Two Stroke Engine  Wankel Engine  Soren
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Bar Shake
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Well Kurt. Of course you are correct. I seem to have fixated on the 90 degree offset of the crank journals and the similarity to a 90 degree V-twin (which can or does also use a 270 degree firing angle). Mea culpa. Thank you for a simple explanation that got through this thick skull. 
Contra todo mal, mezcal; contra todo bien, también
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Learned Hand
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Thanks Soren I could watch those animations for hours they are strangely fascinating.
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Loquacious
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yeah but I suddenly have the urge to but a t-shirt...did you "lace" those with sublimital advertizing 
THE VOICE OF REASON
per: Stewart
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Re: 360 - 270 - 180
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Bar Shake
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Yeah Soren, I figured it out after Kurt's explaination last night, but it was late. It wasn't the difference between 2 and 4 stroke that had me, it was, well............see above post . I just didn't do the math  .
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I think sometimes the confusion may come because many 4 stroke ignition systems fire (unnecessarily) during the exhaust stroke just before the intake stroke--as well as normally near the end of the compression stroke, just before the power stroke. This is to simplify the ignitions components design, and the extra firing at the 360 degree interval (during the exhaust stroke) does not hurt anything.
--Tom
02 TBA; 130 mains; TBS; Nology Coils&Wires;Unifilter/opened Airbox; -AI/snorkels; -2 baffles;Progressive 440s & Springs
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Re: 360 - 270 - 180
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Fe Butt
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all I can say is oops! LOL I had the same train of thought.
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Eat right ,Exercise ,Stay fit, Die Anyway!
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Bill, it took me months to understand this once I had it figured out. I couldn't put it all together until I worked it out on a Single cylinder bike. It wasn't until then that the 720 degree thing made perfect sense. One cycle every two crank rotations.
Then twins were easy to figure after that. Of course, nothing is simple, because I was then hung up on how to count rpm's on a single because I didn't know about the wasted spark. Arhhgg!
'05 America - Tec 2-1 (from a Thruxton)/ 4 pot caliper/ Kurt's Rearsets /
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he theory is that the power pulses of a basically "un-sychronized" firing-order helps "dig-in" the rear tire for more traction during that type of race.(I read this theory put forward by Kevin Cameron, the tech-writer for "Cycle World" a few years ago)
--------------------I have an o6' triumph manual,the stats aren't the same as the new specs.(Max Torque,Max. power) But we can achieve greater torque with less RPM than the T-100. I think I understand the 360,270,180 deal now. I have to remember 4- stroke. So what can one do in our case 270 speedmaster to weed out more horsepower since they don't usually occur at the same time. Displacement? Compression ratio? Ignition timing? Valve Timing? Actual conversion of 07 specs on Max. Torque-nm to ft.lbf Speedmaster 50.8 ft.lbf @4800 RPM....T-100- 52.3 ft.lbf @ 6000 RPM
Last edited by speedblastr; 07/25/2007 8:21 PM.
sometimes ya' gotta hold a candle to the devil.-06' Blk Spdmastr,TBpipes,Plrs-Blmth,3Trns,AI Out, ,UNI,130/40,1shm-Ea.,TBS ndls.
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Re: 360 - 270 - 180
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Should be Riding
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but offsetting the pulses doesnt create more pulses... still one per revolution, just not at the same point in that revolution.
Benny
Black & Silver '02
Too many mods to list
Not enough miles ridden
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Benny what about the 360? Doesn't it have slower ignition pulses than ours, we all know about the H.P. & Torque values of....could it be created to pulse more quickly? Just wondering. Trying to learn all I can.
sometimes ya' gotta hold a candle to the devil.-06' Blk Spdmastr,TBpipes,Plrs-Blmth,3Trns,AI Out, ,UNI,130/40,1shm-Ea.,TBS ndls.
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Re: 360 - 270 - 180
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I know i'm a bit slow but can anyone explain this , in the official Triumph Motorcycles Brochure the Firing Interval for the America/Speedmaster is 270 Degrees reading further on the firing interval for the Bonneville/ T100 & Thruxton is 360 degrees and the Scrambler is 270 Degrees - they all have the same capacity, bore & stroke & compression ratio. I thought the were all exactly the same motor. It seems to me that Triumph has done this 270 degree firing interval to eliminate vibrations.
Whats your thoughts
Hoffo
2x Norton Commando Roadsters
08 Triumph America
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Re: 360 - 270 - 180
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Worn Saddle
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Quote:
It seems to me that Triumph has done this 270 degree firing interval to eliminate vibrations.
Whats your thoughts
Hoffo
Yes, at the expense of horsepower they've gone for long distance comfort by reducing the vibration to extend the rider's duration stamina.
A positive attitude may not solve all your problems, but it will annoy enough people to make it worth the effort. Herm Albright (1876 - 1944)
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Re: 360 - 270 - 180
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Loquacious
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does not seem they lost hp going to the 270
Frank
(Former)05 BA tbike pipes, ai removed, Freak, mikuni hsr 42's, 904, ported/polished head, 1mm oversized valves
NOW-2010 silver and black tbird
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Re: 360 - 270 - 180
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Bar Shake
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Quote:
I know i'm a bit slow but can anyone explain this , in the official Triumph Motorcycles Brochure the Firing Interval for the America/Speedmaster is 270 Degrees reading further on the firing interval for the Bonneville/ T100 & Thruxton is 360 degrees and the Scrambler is 270 Degrees - they all have the same capacity, bore & stroke & compression ratio. I thought the were all exactly the same motor. It seems to me that Triumph has done this 270 degree firing interval to eliminate vibrations.
Whats your thoughts
Hoffo
I think it's more for the exhaust note. The lesser vibration was a side benefit.
Contra todo mal, mezcal; contra todo bien, también
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Re: 360 - 270 - 180
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Worn Saddle
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Quote:
does not seem they lost hp going to the 270
Frank
It's hard to misread Triumph's published specs: America max HP is rated at 54hp@6750rpm, Bonneville max at 66hp@7200rpm. It also implies the 360 is designed to rev higher. There are a lot of us America/Speedmaster owners doing aftermarket work to achieve that extra 12hp! Of course, we won't really know until some money-boy drops a stock 360 into an America and dynos it...
Anyway, This quote from T595.com fleshes out this discussion:
"The reason for the 270 degree crank is that, being 90 degrees apart, one piston is always at maximum velocity down (or up) the bore at the exact same time as the other piston is at minimum velocity at TDC or BDC.
This means that the potential energy in the high speed piston is released as kinetic energy against the drag of the stopped piston and eases the piston through this period and assists with accelerating the piston back towards its maximum velocity.
It is supposed to be smoother that a 360 degree crank with its primary balance forces acting together whilst not suffering the high frequency secondary vibrations.
I think it was Phil Irvine (assisted with the design of the Vinnie twins) that actually calculated that 72 degrees difference was the best angle to have between parallel bore motors for this exact reason."
And there you have it.
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Oil Expert
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What animations?
Am I missing something?
Keith
Houston
Ridin'Texas
'04 Speedmaster
AI removed, Pingle, UNI Filter, 1 shim, straight-through slash-cut TORs, Stage 1 DynaJet, 140 mains, 3 turns, 16/42 final drive, 115K
2020 T120 Black
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Worn Saddle
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Quote:
What animations?
Am I missing something?
Yes, Soren's post on page 2 takes a little while to load.
A positive attitude may not solve all your problems, but it will annoy enough people to make it worth the effort. Herm Albright (1876 - 1944)
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Old Hand
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Well, truth is, both engines were originally rated at the same power and torque. BUT, the 270 engine did it with milder valve timing, so it would have done better if they both had the same cam profile.
Let's hope there's intelligent life somewhere in space 'cause it's buggar all down here. -- Monte Python
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Bar Shake
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Bar Shake
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Quote:
What animations?
Am I missing something?
Right here, Keith:
Animations
If you're using dial-up it may take a while.
Contra todo mal, mezcal; contra todo bien, también
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Re: 360 - 270 - 180
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Bar Shake
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Quote:
It's hard to misread Triumph's published specs: America max HP is rated at [Email]54hp@6750rpm[/Email], Bonneville max at [Email]66hp@7200rpm.[/Email] It also implies the 360 is designed to rev higher.
There may be other differences too Ed.
Perhaps cam profiles?
The earlier versions, when all had 790cc engines, before the 865, the 270 and 360 degree engines had the same power specs.
The 270 firing order is essentially the same as that in a 90 degree v-twin.
Seems to work for Ducati, among others 
My daughter's a physics major (4th year, switched from engineering), I'll see if she can figure it out.
Contra todo mal, mezcal; contra todo bien, también
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Re: 360 - 270 - 180
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Worn Saddle
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Quote:
There may be other differences too Ed.
Perhaps cam profiles?
The earlier versions, when all had 790cc engines, before the 865, the 270 and 360 degree engines had the same power specs.
The 270 firing order is essentially the same as that in a 90 degree v-twin.
Seems to work for Ducati, among others
My daughter's a physics major (4th year, switched from engineering), I'll see if she can figure it out.
Agreed, the cam profiles coupled with the firing order makes a lot of sense, especially if the lift and duration is aimed at the higher RPM range.
A positive attitude may not solve all your problems, but it will annoy enough people to make it worth the effort. Herm Albright (1876 - 1944)
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Re: 360 - 270 - 180
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Loquacious
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theres more differences than just 270 and 360. like greybeard said the cams are one of those big differences. and from what i hear from many racers the 270 makes the same power, but lays down the tq a bit better
Frank
(Former)05 BA tbike pipes, ai removed, Freak, mikuni hsr 42's, 904, ported/polished head, 1mm oversized valves
NOW-2010 silver and black tbird
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I got it. Thanks for the animations! So one piston TDC and the other for sake of argument (above) ABDC So the pistons don't dead stop,(less inertia)Releases kinetic energy against drag, Less vibration, Exhaust sounds like a Harley...Potato chip..Potato chip. And we can achieve better Torque values at a lower RPM than the 360.So then ultimately it's about the cams or part of it,at least that's what I Read that's different about the 270 & 360 or one of the things narrowed out besides the crank.
Last edited by speedblastr; 07/29/2007 5:53 PM.
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