 270 vs 360 firing
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OP
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Can anyone explain how the 270 dregee firing of our bikes compares to the 360 dregees on the other Bonnevilles ?
Last months Cycle World had a review of the new Triumph Scrambler, said it had broader Troque, than the 360 Bonnies.
Blue '03 TBA, Made in England. (50+ mpg).
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 Re: 270 vs 360 firing
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270 = No vibration. That's all I needed. Little or no vibration felt in the handle bars. My old Kawi, after 2 or 3 hours on the road my hands would be numb and tingling. Very technical term huh guys?
Steve
Where's my $6 million??
05 TR America;2010 T-Bird
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Re: 270 vs 360 firing
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Joined: Jun 2005
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Oil Expert
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Oil Expert
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360 = Thump-thump-thump
270 = Thumpathumpathumpa
(Note: The actual sound made may vary depending on pipes...)
JB
"Long live the Duck Force!"
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Re: 270 vs 360 firing
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Joined: Jan 2005
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Loquacious
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Loquacious
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On the 360 degree engines the pistons go up and down at the same time which means it fires every 360 degrees of crankshaft rotation, but the 270 degree crankshaft is slightly offset where # 2 piston fires slightly after #1
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Re: 270 vs 360 firing
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Learned Hand
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Learned Hand
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Often, I would like to have the pop...pop...pop...pop sound of the 360 Bonnie then the lumpity lump lump sound of the 270.....
Warren
04 Caspian Blue and Silver America
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Re: 270 vs 360 firing
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Learned Hand
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Learned Hand
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I was kinda disappointed that the BA and SM were 270 as compared to the Retro Bonnies 360 till we brought home the BA. MUCH smoother idle and ride, great power band.
Don't tell Nancy but the BA WILL burn rubber from first to second gear EASY!! Can't wait for my SpeedMaster to come home!!!
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Re: 270 vs 360 firing
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Loquacious
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Loquacious
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JPR, it was simply a marketing thing, to give the America/Speedmaster a "lumpier" idle, in order to make it sound more like a cruiser, i.e. more like a v-twin. A "true" Bonnie has a 360 or Parallel (since both pistons rise and fall together) twin.
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Re: 270 vs 360 firing
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Joined: Dec 2005
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Learned Hand
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Learned Hand
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FALSE!!! They do not rise and fall together!!
They are 360 degrees off set!!!
1 is up the other is down.
I suppose from here on we have to dig up the engineering
specs on off-set cranks. Pros and Cons. 
Last edited by privateer; 05/11/2006 8:51 PM.
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Re: 270 vs 360 firing
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Joined: Jan 2005
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Should be Riding
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Should be Riding
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No he was right, it's true. A 4 stroke motor goes around TWICE for every spark, so while one cylinder is firing, the other is sucking in gas. If one was up and one was down that would be 180 offset.
Benny
Black & Silver '02
Too many mods to list
Not enough miles ridden
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Re: 270 vs 360 firing
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Joined: Dec 2005
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Learned Hand
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Learned Hand
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Dang. Ya got me on the quick post!  Ment to post one up one down 180 degrees off-set BETWEEN pistons. But they do not rise and fall together! DANG! That would make HD a smooth engine if BOTH pistons were in the same plane! (NOT airplane)
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Re: 270 vs 360 firing
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Should be Riding
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uh... yeah they do rise and fall together.... it's just one is sucking while the other is banging (suck, squeeze, bang, blow).
Benny
Black & Silver '02
Too many mods to list
Not enough miles ridden
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Re: 270 vs 360 firing
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Joined: Dec 2005
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Learned Hand
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Learned Hand
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You wanna look at it that way, OK.
But 1 piston will be up one down.
Offsets weight.
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Re: 270 vs 360 firing
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Should be Riding
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Sorry dude, didn't mean to come off snooty or anything, and I agree that it WOULD offset the weight/vibration, but if it was like that it would be called a 180 motor, not a 360. I'll see if I can find a web page or something that shows it. Again, I honestly didn't mean to be a doof, just layin it out there 
Benny
Black & Silver '02
Too many mods to list
Not enough miles ridden
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Re: 270 vs 360 firing
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hey found a little info...
Check this out. It's about a Kawasaki, but it does mention brit bikes and 360's in general. Like this...
Quote:
The pistons rise and fall together (with a 360-degree crank) like some of the British bikes of yore.
OK found some more here and it's about the america!
One thing I forgot to mention before is that there's a bunch of counterbalancers inside to smooth out the vibrations and such caused by the pistions moving up and down...
Last edited by bennybmn; 05/11/2006 9:36 PM.
Benny
Black & Silver '02
Too many mods to list
Not enough miles ridden
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Re: 270 vs 360 firing
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Joined: Dec 2005
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Learned Hand
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Learned Hand
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Never took it as snooty As I said earlier, time to whip out the engineering specs! If the question is asked and we can't agree then lets pull up the true info so as to avoid "THE HAMMER"  We may have the same thought in mind but state it differently. My main concern now is not to confuss. Agreed?
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Re: 270 vs 360 firing
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Joined: Aug 2005
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3/4 Throttle
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3/4 Throttle
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To be old and wise, you must first be young and stupid.
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Re: 270 vs 360 firing
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Joined: Dec 2005
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Learned Hand
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Learned Hand
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After going into the basement to dig out an old crank, dropping a ton o crap on my foot, swearing to the Gods, limping upstairs for another beer to ease the pain, falling down the steps after said beer, (spilling the extra), all I can say is, DOOH!! In the words of Rosanna Rosanna Danna! Never Mind! Now where's that other beer? See? Didn't have to SMITE ME!!! I admit I'm wrong! (DO NOT TELL NANCY I SAID THAT!)
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Re: 270 vs 360 firing
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Loquacious
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Loquacious
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I'm no expert, but, I think the older Triumphs, and the new
Bonnies, are a true 360, and the pistons fire at the same
time. Bump, bump, bump, bump. Maybe the 270 degree timing
is an attempt to make it sound more like the V-twins,
ba-dump, ba-dump, ba-dump. What the heck do I know anyway?
I have the BUB's, and like the way my bike sounds.
Charlie
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Re: 270 vs 360 firing
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Joined: Dec 2005
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Learned Hand
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Learned Hand
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Well, they are side by side, just FIRE 360 degrees off. In other words, one fires the other is pushin out spent gases. On the original egnition system they did not fire on the exhaust stroke. Add a Boyer Branson system they DID fire on the exhaust stroke. Or am I wrong? AGAIN! 
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Re: 270 vs 360 firing
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Quote:
On the 360 degree engines the pistons go up and down at the same time which means it fires every 360 degrees of crankshaft rotation, but the 270 degree crankshaft is slightly offset where # 2 piston fires slightly after #1
This one is the correct answer. On the 360 the pistons rise and fall together, but fire on opposite strokes. THe 270 while following the same idea one piston is 90 behind.
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Re: 270 vs 360 firing
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Bar Shake
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Bar Shake
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Quote:
Well, they are side by side, just FIRE 360 degrees off.
In other words, one fires the other is pushin out spent gases. On the original egnition system they did not fire on the exhaust stroke. Add a Boyer Branson system they DID fire
on the exhaust stroke. Or am I wrong? AGAIN!
As one is firing (power stroke), two is sucking (intake stroke).
RE the 270 degree offset. Crank journals are offset 90 degrees. 360 minus 270= 90. Just adding a little more confusion  .
Contra todo mal, mezcal; contra todo bien, también
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Re: 270 vs 360 firing
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Should be Riding
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When I first figured out how a 360 motor worked I was kinda surprised too. I mean it seems like an awefull lot of reciprocating mass to be jumping around together! But that's how it is... There is a separate coutnerbalance shaft rotating (opposite direction I believe...) with some offset mass on it to quell the vibs. Check out the old bonnies and nortons at idle that didn't have that! The front wheel almost hopped off the ground
Benny
Black & Silver '02
Too many mods to list
Not enough miles ridden
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Re: 270 vs 360 firing
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Learned Hand
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Learned Hand
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All I know is that it goes when I turn the throttle
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Re: 270 vs 360 firing
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Loquacious
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Loquacious
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Quote:
FALSE!!! They do not rise and fall together!!
They are 360 degrees off set!!!
will you allow me the pleasure at least of one "nanny, nanny boo boo to you!!" (as my 6 year old would say!)
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Re: 270 vs 360 firing
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OP
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Thanks everyone, I get it now, 270 degree firing = less vibration. Because of the 90 degree offset the two pistons are 90 degree out of phase with each other.
Blue '03 TBA, Made in England. (50+ mpg).
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Re: 270 vs 360 firing
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Loquacious
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It can also mean better power delivery/traction at the rear wheel. That's one of the things Bonneville Performance found out when they made their AMA Flat Track bike....the 270 motor was better than the 360 motor when it came to getting the rear wheel to hook up on the dirt.
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Re: 270 vs 360 firing
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Loquacious
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Loquacious
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Quote:
270 degree firing = less vibration
Mmmmm, not necessarily. Now I haven't ridden a new 360 Motor to compare, but to me, it would be much easier to balance out the 360 Motor than the 270 Motor, since I would think primary and secondary vibration would be MUCH more complex than an engine with both Pistons moving in parallel. I would think balancing a 360 would require a larger counterbalance, to mimic the balance of say a boxer motor (BMW) than a 270, but I would think any weight you used to balance out #1 or #2 Cylinders primary mass would add to secondary vibration for the other cylinder. Any gurus want to step in an smash me to bits or pick up where I left off?
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Re: 270 vs 360 firing
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Complete Newb
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Complete Newb
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Once the rotating mass is balanced, whether 270 deg. or 360 deg., the main source of vibration becomes the power applied from the radial force of the explosion acting on the crankshaft. This is why the more cylinders in an engine, the smoother it runs (ex: an 8 cyl engine will apply force every 45 deg. of rotation - a four cylinder ever 90 deg.) The 270 deg. crank spreads the radial force out a little than the 360 deg. crank over full rotation, making it run smoother.
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Re: 270 vs 360 firing
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Joined: Jan 2005
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Bar Shake
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Bar Shake
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On another, related note. Three cylinders is the minimum number of cylinders in a four stroke engine that can be perfectly balanced, with 120 degree offset.
An inline four cylinder is actually two 180 degree twins side by each.
Contra todo mal, mezcal; contra todo bien, también
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Re: 270 vs 360 firing
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Loquacious
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Loquacious
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Don't know about you, but I'm getting seasick just watching that thing...
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Re: 270 vs 360 firing
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Joined: Jan 2005
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Should be Riding
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Should be Riding
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Dude!! Sweet Can you toss one up for a 360?
Benny
Black & Silver '02
Too many mods to list
Not enough miles ridden
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Re: 270 vs 360 firing
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Bar Shake
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Bar Shake
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Very cool site Soren, Thanks.
Benny, on the site, the 0 degree is the same as 360.
Contra todo mal, mezcal; contra todo bien, también
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Re: 270 vs 360 firing
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Loquacious
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Loquacious
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That is pretty cool Soren.... good find.
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Re: 270 vs 360 firing
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Should be Riding
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I guess the only difference would be showing when each sparks, which it doesn't show anyway...
Benny
Black & Silver '02
Too many mods to list
Not enough miles ridden
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Re: 270 vs 360 firing
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Joined: May 2006
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Complete Newb
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Complete Newb
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Quote:
uh... yeah they do rise and fall together.... it's just one is sucking while the other is banging (suck, squeeze, bang, blow).
Hey, I think I know those girls...
"Little old lady got mutilated late last night...AAOOOO."
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Re: 270 vs 360 firing
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Quote:
Mmmmm, not necessarily. Now I haven't ridden a new 360 Motor to compare, but to me, it would be much easier to balance out the 360 Motor than the 270 Motor, since I would think primary and secondary vibration would be MUCH more complex than an engine with both Pistons moving in parallel. I would think balancing a 360 would require a larger counterbalance...
Hi guys - not strictly true - the 270 degree motor has much better primary balance - see the explanation below - basically, its to do with the forces generated when the pistons reaching the end of their throw not reinforcing each other as they do in the 360 degree motor. Lotsa guys in Australia have done this mod to the Yammy XS650 which has a 360 degree crank - it is splined and can be dismantled and rebuilt as a 270. Needs new cams, of course and ignition mods, but is apparently worth the hassle. This was originally done to a Meriden Triumph motor by Phil Irving.
Have fun
Jan
270 degree timing explanation
Never whistle while you're ******....!
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