 It's a Yamaha XS650, but...
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Joined: Jan 2005
Posts: 3,734
Loquacious
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OP
Loquacious
Joined: Jan 2005
Posts: 3,734 |
...it relates to our bikes. I've been down with this cold so it gives me time to surf around on the net. I've always liked the street tracker look so that's what I typed into Google as I sit here with a bloated sinus. I eventually came across this article from a guy who is building a street tracker out of a 1977 Yamaha XS650. It's a popular project for that bike, and there's some nice examples out there. What got my interest about this particular article was that this guy is/was converting the normally 360 firing interval of the stock engine, into a 277 degree firing motor. He goes with 277 instead of 270 because it's cheaper. Now his reasoning for doing this is because he claims this allows for a freer revving motor and produces less vibration. Now I've ridden a 2001 Bonnie, and didn't notice it vibrating anymore than our bikes, but that could be compensated for in some of the part of the engine design for all I know. Anyway, not being a gearhead myself, I was wondering if his logic is correct? If any of this makes sense, maybe Triumph had something more in mind than just a more cruiser-like exhaust notes for our bikes. Another possible reason is for slightly better rideability, which could also be tied into Bill Gately's flat track racer. After trying the regular Bonnie configuration, his team went to a 270 crank. I don't know the exact reasons why, but speculation is that it hooks up better on the dirt, and might give an edge in the midrange department.
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Re: It's a Yamaha XS650, but...
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Joined: Jan 2005
Posts: 5,537
Check Pants
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Check Pants
Joined: Jan 2005
Posts: 5,537 |
I don't know much about firing orders but I rode a buddy's XS650 Special a good bit in the early 80's and that thing was a real shaker. If left running, on the centerstand that thing would walk across the parking lot!
Al
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Re: It's a Yamaha XS650, but...
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Joined: Jan 2005
Posts: 8,639 Likes: 3
Old Hand
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Old Hand
Joined: Jan 2005
Posts: 8,639 Likes: 3 |
All this time, I thought those had a 180 degree crank like most jap twins.
Let's hope there's intelligent life somewhere in space 'cause it's buggar all down here. -- Monte Python
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Re: It's a Yamaha XS650, but...
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Joined: Jan 2005
Posts: 134
Adjunct
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Adjunct
Joined: Jan 2005
Posts: 134 |
>I don't know the exact reasons why, but speculation is >that it hooks up better on the dirt,
This is the reason I've heard this firing order is often used for dirt trackers. The idea is that the uneven power stokes give the rear wheel a little more time to hook-up.
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Re: It's a Yamaha XS650, but...
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Joined: Feb 2005
Posts: 78
Member
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Member
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Posts: 78 |
I've said that a 1200 Trophy would be my next choice, but this weekend I got to ride an '04 Speed Triple....what a gas! I didn't know those hooligan bikes had so much torque...and enough HP to get you in serious trouble. That ride made me re-think the whole don't-go-fast common sense that age brings. The best thing about the bike was it's unbelievable handling. It has been a long time since I have ridden anything that felt as good. All the ergo's seem to fit right. I recommend a test ride anytime you get the chance.
....whew!!!
miles & miles of Texas...
TM
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Re: It's a Yamaha XS650, but...
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Joined: Jan 2005
Posts: 5,537
Check Pants
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Check Pants
Joined: Jan 2005
Posts: 5,537 |
Rode a Speed Triple at last years Triumph Truck in VA, awesome! The '05 version is even hotter and looks A LOT sharper. My brother has a Kaw ZRX1200R, same philosophy as the Speed Triple, nearly identical performance stats. Not quite the same class & panache as the Triumph though.
Al
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Re: It's a Yamaha XS650, but...
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Joined: Mar 2005
Posts: 5
Complete Newb
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Complete Newb
Joined: Mar 2005
Posts: 5 |
Quote:
...it relates to our bikes. I've been down with this cold so it gives me time to surf around on the net. I've always liked the street tracker look so that's what I typed into Google as I sit here with a bloated sinus. I eventually came across this article from a guy who is building a street tracker out of a 1977 Yamaha XS650. It's a popular project for that bike, and there's some nice examples out there. What got my interest about this particular article was that this guy is/was converting the normally 360 firing interval of the stock engine, into a 277 degree firing motor. He goes with 277 instead of 270 because it's cheaper.
Now his reasoning for doing this is because he claims this allows for a freer revving motor and produces less vibration. Now I've ridden a 2001 Bonnie, and didn't notice it vibrating anymore than our bikes, but that could be compensated for in some of the part of the engine design for all I know. Anyway, not being a gearhead myself, I was wondering if his logic is correct? If any of this makes sense, maybe Triumph had something more in mind than just a more cruiser-like exhaust notes for our bikes.
Another possible reason is for slightly better rideability, which could also be tied into Bill Gately's flat track racer. After trying the regular Bonnie configuration, his team went to a 270 crank. I don't know the exact reasons why, but speculation is that it hooks up better on the dirt, and might give an edge in the midrange department.
Hi, this is my first post here. I'm an XS650 owner, and I just recently discovered the Bonneville America and Speedmaster--cool bikes! I see them as being what my 650 would/should/could have developed into.
Re: the 270* crank: as I understand it there are several advantages. The XS650 has both pistons rising and falling together. Since a 4 stroke cycle engine fires once every other revolution this results in perfectly spaced power strokes. This might be a "good" result, but there are problems. One of the downsides is that the crankcase is pressurized by the change in volume that is the direct result of both pistons moving in unison. This results in some power loss, and a greater potential for oil leaks. Another, more significant, issue is that both pistons are moving at their top speeds and then reversing themselves simultaneously. The 270* orientation means that one piston is essentially "sitting still" at TDC while the other is moving at max speed halfway through its stroke. The vibration is greatly reduced! Your Triumph motor is more sophisticated in that it has auxialliary balance shaft(s) (I believe) in addition to the 270* orientation. The XS650 does not have any such innovation. Switching to the 270* orientation provides a marked improvement because it vibrates so much worse to start with.
Add your oil cooling, larger displacement and cruiser style, and you've definitely got a new fan! These are the EXACT mods that many are doing on their 650s. My bike is pretty much stock, and I enjoy it in that form. If/when I go shopping for another bike, the Bonneville America/Speedmaster will be on my short list.
Cruiser
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Re: It's a Yamaha XS650, but...
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Joined: Jan 2005
Posts: 106
Adjunct
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Adjunct
Joined: Jan 2005
Posts: 106 |
welcome james -
where are you located? i'm about 15 miles north of the dells.
jeff
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Re: It's a Yamaha XS650, but...
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Joined: Mar 2005
Posts: 5
Complete Newb
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Complete Newb
Joined: Mar 2005
Posts: 5 |
Hey Jeff,
I'm down here by Madison. . . . Thanks for the welcome! This site has lots of good information.
Cruiser
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Re: It's a Yamaha XS650, but...
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Joined: Jan 2005
Posts: 106
Adjunct
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Adjunct
Joined: Jan 2005
Posts: 106 |
cruiser -
check out Sharer cycle in verona. pretty nice people. they have the whole line up right now plus a good selection of used bikes as well as a couple vintage.
jeff
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