V-twin (Guzzi) vs Flat-twin (BMW)

[Triple Jim]

The XRs' 750 flat tracker has a 45/675 firing order.

Wow, thanks for that Kirby.  Even with my ex-flat-track-racing buddy around, I had no idea anyone was doing that.  In fact I would have assumed that it created an unusably vibrating engine!

[kirby1923]

Wow, thanks for that Kirby.  Even with my ex-flat-track-racing buddy around, I had no idea anyone was doing that.  In fact I would have assumed that it created an unusably vibrating engine!

Believe me it does!!! Not really sutable for the street!! Ha!

[oldbike54]

Wow, thanks for that Kirby.  Even with my ex-flat-track-racing buddy around, I had no idea anyone was doing that.  In fact I would have assumed that it created an unusably vibrating engine!

 

Believe me it does!!! Not really sutable for the street!! Ha!

 When the iron head XR race bikes came out in 1970 some of the racers complained that the engine shook worse than the old KR , and much worse than the vert twin Brit motors , a lot of which were either converted to fire both cylinders at once , or a couple that were really trick with cranks converted to 90 degree pin spacing . Yeah , flat trackers are simple 

 Dusty

[Triple Jim]

I tried to find a video somewhere, showing startup and running, but I struck out.  I bet it's an odd sound.

[oldbike54]

I tried to find a video somewhere, showing startup and running, but I struck out.  I bet it's an odd sound.

 Especially at the almost 10,000 RPM 's a good XR motor is capable of on mile tracks . They look a little like a Sportster motor , but absolutely nothing is the same . Another reason the XR is good on dirt , they have a falling torque curve . Their dyno graph looks weird compared to almost every other motor.

 Dusty

[sturgeon]

Aretha Franklin has soul. Otis Redding and Amy Winehouse and Etta James have soul. To my ears, they all sound nice too.
Motorcycles and other machines do not have soul.

I tend to sit forward of the noise emitters on my motorcycles and can't really hear exactly what they sound like while wearing earplugs, so I don't much care, as long as said noise doesn't p**s off my neighours too much.

As for V vs Flat, I have one of each and I like 'em both. Mine have different uses and get sort of equal billing.

In the end, the old-man Flat 108 hp and 79 lb-ft wins out when I want to go somewhere in a hurry or show off at stoplights. Sometimes I strap a walking cane to the seat, for effect.

[jas67]

"
A narrow angle V-twin such as the 45° Harley-Davidson naturally has slightly unevenly spaced power strokes. By changing the ignition timing on one of the cylinders by 360° the power strokes are very closely spaced. This will cause uneven fuel distribution in an engine with a single carburettor. The Harley-Davidson XR-750 with twin carburettors was a popular bike to twingle. It had great success in flattrack racing.[citation "

Better change the valve timing of that cylinder by 360 degrees too,or that won't work.

[Triple Jim]

Better change the valve timing of that cylinder by 360 degrees too,or that won't work.

Actually, I read that it's only the valve timing that has to be changed, since the ignition system is a wasted spark type that fires each cylinder every turn of the engine anyway.

[Tom]

I'll be honest, I don't really care what my bike "sounds" like.   I've had V-twin Harleys, a BMW airhead, multiple British twins and singles, single and twin two-strokes, and two triples.

I have no idea what kind of "character" and "soul" a bike has until it has:

1) Started up for me on a freezing morning.

2) Started up after marinating in rainwater for three days.

3)  Carried me over dark mountains in foul conditions without missing a beat.

4)  Carried me in the flow of traffic at 70 MPH in the fast lane, boxed in between three trucks and a bridge guardrail.

5)  Carried on after hitting an unexpected pothole, leaned way over on a guardrail-less mountain road.

6)  Gotten me home with a big load on blazing hot day through the hills.

A bike that will do that for me (and there have been many) has CHARACTER and SOUL, I don't care how many pistons it has, how big they are, or what order it fires them in.

Lannis

 :1:

[oldbike54]

Actually, I read that it's only the valve timing that has to be changed, since the ignition system is a wasted spark type that fires each cylinder every turn of the engine anyway.

 The XR has become the small block Chevrolet of motorbike engines . The original aluminum head versions introduced in 1972 made 70 HP at 7500 RPM's with a slightly oversquare bore/stroke ratios,
the latest versions make over 100 HP at 9600 RPM's . Of course the really hot ones have become a bit fragile in mile tune , in fact Jared Mees lost the GNC championship this year because his very hot XR went boom at the Springfield mile 2 .
 As for being 'twingled' , in the past they ran that configuration on 1/2 mile tracks , still running standard boom chuff chuff boom chuff chuff chuff chuff chuff on mile tracks . Wait , is that the right number of chuffs ? 

 Dusty

[LowRyter]

Aretha Franklin has soul. Otis Redding and Amy Winehouse and Etta James have soul. To my ears, they all sound nice too.
Motorcycles and other machines do not have soul.

I tend to sit forward of the noise emitters on my motorcycles and can't really hear exactly what they sound like while wearing earplugs, so I don't much care, as long as said noise doesn't p**s off my neighours too much.

As for V vs Flat, I have one of each and I like 'em both. Mine have different uses and get sort of equal billing.

In the end, the old-man Flat 108 hp and 79 lb-ft wins out when I want to go somewhere in a hurry or show off at stoplights. Sometimes I strap a walking cane to the seat, for effect.

water boxer 

[webmost]

I'll be honest, I don't really care what my bike "sounds" like.   I've had V-twin Harleys, a BMW airhead, multiple British twins and singles, single and twin two-strokes, and two triples.

I have no idea what kind of "character" and "soul" a bike has until it has:

1) Started up for me on a freezing morning.

2) Started up after marinating in rainwater for three days.

3)  Carried me over dark mountains in foul conditions without missing a beat.

4)  Carried me in the flow of traffic at 70 MPH in the fast lane, boxed in between three trucks and a bridge guardrail.

5)  Carried on after hitting an unexpected pothole, leaned way over on a guardrail-less mountain road.

6)  Gotten me home with a big load on blazing hot day through the hills.

A bike that will do that for me (and there have been many) has CHARACTER and SOUL, I don't care how many pistons it has, how big they are, or what order it fires them in.

Lannis

Pretty accurate description of an old Honda UJM, right there. Dead on description of my KLR650. But... In a thread that claims to be about moving the soul? You're talking tangibles in the intangible zone.

The old airheads had a nice purr. Uglier'n turd on a stick. The little bricks make a fascinating whish, go like bandits, and you can't kill 'em with a sledge hammer. But the engine looks like --- a brick. Uglier'n even an airhead. The early oilheads make a hypnotic thrum. Styling was better. But by the time they began making the R12s, they were so stupid over-engineered it's just frustrating. My R12CLC chromehead rumbles down the road making a sweet sound, chewing up asphalt and spitting out miles. Many a time we have ridden eight hours to a distant B&B, and arrived wishing there were more. Then the ABS went south. The part costs $2,800, can't be rebuilt, and is six months backordered. Eff that. Meanwhile, no one I know got good service oit of their K12. Best oilhead I had was an R11R. Shoulda stopped there.

Guzzi soul? Haven't had mine long enough to say.

[oldbike54]

 Hey Kirbster , tell 'em how great my old R60 sounds turning 5K RPM's from a perspective of 50 feet behind .

 Dusty

[OlDogface]

You ask this in a Guzzi Forum? 

 :1:

[Huzo]

I'll be honest, I don't really care what my bike "sounds" like.   I've had V-twin Harleys, a BMW airhead, multiple British twins and singles, single and twin two-strokes, and two triples.

I have no idea what kind of "character" and "soul" a bike has until it has:

1) Started up for me on a freezing morning.

2) Started up after marinating in rainwater for three days.

3)  Carried me over dark mountains in foul conditions without missing a beat.

4)  Carried me in the flow of traffic at 70 MPH in the fast lane, boxed in between three trucks and a bridge guardrail.

5)  Carried on after hitting an unexpected pothole, leaned way over on a guardrail-less mountain road.

6)  Gotten me home with a big load on blazing hot day through the hills.

A bike that will do that for me (and there have been many) has CHARACTER and SOUL, I don't care how many pistons it has, how big they are, or what order it fires them in.

Lannis

I reckon most of us here don't "care" what order they fire in or any of the other things you mention Lannis, however some of us are interested. Would you prefer we talked about something else ?

[kirby1923]

Hey Kirbster , tell 'em how great my old R60 sounds turning 5K RPM's from a perspective of 50 feet behind .

 Dusty

Ah!
The airheads make sweet music, the 4 valve oil head just doesn't have the deep tone of the 2 valve, harmonics I guess..donoh,,,

:-)

[oldbike54]

I reckon most of us here don't "care" what order they fire in or any of the other things you mention Lannis, however some of us are interested. Would you prefer we talked about something else ?

 Huzo ol buddy , I do believe it important that they do fire 

 Yeah , these types of threads always interest me , always fun to ferret out details and read what some of our smart guys have to say .

 Dusty

[Lannis]

I reckon most of us here don't "care" what order they fire in or any of the other things you mention Lannis, however some of us are interested. Would you prefer we talked about something else ?

You'll notice (if you'll actually read my post; people tend not to read them, just to react to something in their own heads), that I only say what "I" think, and what "I" like, and what "I" think it means.   That's all I'm really qualified to comment on.

I haven't said one word about what "YOU" should think, or about what "YOU" should write about or discuss.   That's over my pay grade, and would be useless anyway.

So if you've had your little sarcastic, snarky comment, carry on.

Lannis 

[oldbike54]

Ah!
The airheads make sweet music, the 4 valve oil head just doesn't have the deep tone of the 2 valve, harmonics I guess..donoh,,,

:-)

 An airhead on an airhead ??? 

 Dusty

[arveno]

I have had few airheads and loved them all. ( 75/5 lwb , R100R , R100 gs )
I think they are even simpler than guzzi to work on ... replacing the clutch it's a little bit less time consuming.
Setting points it is a breeze ( easier that twin point and are more accessible )
My favorite airhead is a R100GS , it is a war horse and never let me down .
I can take both wheels off with the bike on center stand.
Not enough power ? they just have different way to deliver the power ,airhead deliver the power like electric motor , yes i agreed guzzi have more "punch" but in the end a r100 does to 0/60 mph in the same time a 1000cc guzzi does.
Handling ?
Guzzi are sturdier ,they feel like a train on rails ,airheads feel more "buttery" but i have never had problem with a beemer at high speed. they are straight as arrow.
two up riding ?
very comfortable .
MPG : i thing they are same.
I love guzzi more, maybe because i am Italian and i want to ride something made were i was born and raised.
both machine will run forever and ever with basic maintenance .
 i do not "hate" beemers and i like them.
guzzi and BMW are both wonderful machine.... ride what you like.
I am lucky enough to be able to ride them both.

ciao

I do not ride any modern guzzi or bmw ,i am not interested so i cannot compare or express an opinion.

[Carlo DeSantis]

Aretha Franklin has soul. Otis Redding and Amy Winehouse and Etta James have soul. To my ears, they all sound nice too.
Motorcycles and other machines do not have soul.

I tend to sit forward of the noise emitters on my motorcycles and can't really hear exactly what they sound like while wearing earplugs, so I don't much care, as long as said noise doesn't p**s off my neighours too much.

As for V vs Flat, I have one of each and I like 'em both. Mine have different uses and get sort of equal billing.

In the end, the old-man Flat 108 hp and 79 lb-ft wins out when I want to go somewhere in a hurry or show off at stoplights. Sometimes I strap a walking cane to the seat, for effect.

Sounds a lot like my situation.  R1200R and T3 that I enjoy equally -- for different reasons.  I wouldn't want to part with either of them.

I really like both marques and feel there is a place for both in my garage and my riding style.

Best,

Carlo

[wirespokes]

It's an emotional topic, isn't it? But that's understandable - I know these bikes certainly stir up emotions in me.

I do love my airheads. They're subtle and much more capable than they appear. They go much faster than it feels they're going. They just calmly go about their business. I like being stealth and slipping past before anyone knows I've been there. I'm sure many an LEO didn't wake up in time to point the radar because he didn't hear me coming.

I've ridden in some pretty rotten conditions - rain, cold, fog, middle of nowhere - and afterwards thought how awful it could have been had the bike broken down. Seems funny to think that being broken down is worse than riding in fog, but it is, though it's hard to explain why.

I'd been riding for 25 years when I got my first airhead. It took me a while to figure out the way IT wanted to be treated and handled. It behaved differently than anything I'd ridden before. Once that was sorted out, it was almost magical - the bike became an extension of myself.

The Guzzi is similar in many respects and totally different in others. I love the looks, always have, but I know someone who finds the engines ugly. To each his own, I guess. I used to think the BMWs were pretty damn ugly, but at some point my perception turned around and I now find them beautiful. Funny how that goes. At the time I got my first BMW in 1990, I'd thought they were ugly and expensive. I swapped my old Volvo 122 wagon for the 1976 R90, and have been riding them ever since. At the time, I'd gotten tired of the bikes I'd had and decided it just wasn't practical having a bike here in rainy old Portland Oregon. Now I ride year round and rarely drive the PU. Yes, the parts are more expensive, but it all evens out in the end.

I think also, one of the differences between my airheads and this 77 T3 I just got, is the compression ratio. The Guzzi bark with each firing makes more of a boom than the airhead with it's lower compression and quieter mufflers.

As for the differences in crank angle and the reasons why, I thought it was a trade off between torque and vibration. Singles have a lot of torque and two cylinders firing close together are more like a single. Both kicking the flywheel close together gives it a stronger push. I could be all wrong here, but that's how it seems to me.
 
And even though the airhead has a power stroke every 360 degrees, they have a fair amount of torque and a fairly flat torque curve. Like the Guzzis, it's not a good idea to make them work below 3500RPM.

I'm still trying to understand how a 90 degree V twin can run so smooth, especially at 4K and above.

I like what you said arveno. And I agree.

[oldbike54]

 WS , 90 degree V twins actually have pretty good primary and secondary balance . At the moment of TDC or BDC the opposite piston is near max piston speed , therefor providing a natural balance factor.

 Dusty

[wirespokes]

WS , 90 degree V twins actually have pretty good primary and secondary balance . At the moment of TDC or BDC the opposite piston is near max piston speed , therefor providing a natural balance factor.  Dusty

I've heard that, but can't picture it. It makes no sense to me how a motion at 90 degrees to something that's stopped can cancel vibration forces.

[Triple Jim]

Picture a rotating counterbalance weight trying to make up for the linear movement of a piston.  It can't, because it has a sideways movement that's not in line with the piston.  But put another one 90 degrees to that, and now the unneeded sideways movement is in line with the first one.  If you cleverly adjust the counterbalance weight to minimize imbalance for both pistons, you're better off than you would have been with just one.

Then there's what Dusty and I said, that stopping two pistons at the same time introduces a rotational vibration, so putting one piston 90 degrees out of phase from the other negates that.

[oldbike54]

 Thanks for that Jim , you have a good way of explaining things . Damn , I do love these types of discussions 

 Dusty

[Huzo]

Thanks for that Jim , you have a good way of explaining things . Damn , I do love these types of discussions 

 Dusty

Yeah that's the closest I've come to understanding the concept, but it's still over my head.

[Huzo]

You'll notice (if you'll actually read my post; people tend not to read them, just to react to something in their own heads), that I only say what "I" think, and what "I" like, and what "I" think it means.   That's all I'm really qualified to comment on.

I haven't said one word about what "YOU" should think, or about what "YOU" should write about or discuss.   That's over my pay grade, and would be useless anyway.

So if you've had your little sarcastic, snarky comment, carry on.

Lannis

C'mon Lannis it wasn't that bad was it ? I've seen worse on this forum from down here, but yeah, it was a bit sarcastic, but harmless. Anyway, thanks for the offer, I'll carry on.

[oldbike54]

Yeah that's the closest I've come to understanding the concept, but it's still over my head.

 Jim can expand on this , but picture a 360 degree twin cylinder configuration . Now , rotate one of the crank pins 90 degrees , effectively creating a 90 degree V twin . If you start from that configuration , and can picture how the piston at TDC or BDC is being balanced by by the other piston moving up or down at close to maximum piston speed , then transfer that to a 90 degree V angle in your mind , it might become clear . A crank with throws at 90 degrees also creates less rocking couple than a flat twin or a 180 degree layout , although I understand the rocking couple forces are fairly small , every little bit helps . Dang , does this help ?

 Dusty

[Huzo]

I do try Dusty, I really do, but I'm becoming mentally lazy, so when something like this comes along I just defer to those that have it covered and busy myself with something within my capability. One day it might "click" for me, but I'll probably die wondering, but jeez it's a good thread, something for everyone, don't you agree ??!