The Yamaha Super Tenere XT1200Z Big Thread

Would't that be a matter of centrpedal? forces though. If the 21 Inch front had more weight toward the inside would it really make that much difference?

Is it more a matter of light weight RRRace tyres Vs heavier tough ass off road tyres adding to the centrepedal force 25mm further from centre?

Inquiring minds want to know!

Cheers
Graham

Actually the spoked 21's are the same or lighter than a typical 17". I have both wheel sets for my DRZ and the 17's it is a crazy canyon slicer upper. Even when I had road oriented rubber on the 18-21 it wasn't even close. The motards have some qualities.

I have a heavily worked DRZ. I have gnarly offroad to medium grade adventure touring covered. I need/want something for lighter offroad greater distance. Unfortunately the there is no replacement for displacement.

BMW claims 85 HP for the 800 GS. So what mid 70"s? I don't gain much from the DRZ other than 6th gear. It doesn't strike me as enough oomph for easy miles. I still intend to test ride one though. Maybe a ride will be enough.

You mean zero inertial torque I guess.

Amazingly BMW have probably under claimed a bit here. Depending on the bike and Dyno they usually see somewhere between the mid 70's and a high of 92 horsepower at the back wheel. Typically they are between 80 and 85 RWHP.

It's a matter of mathematics I guess... I believe (guessing) that the weight of a GS Adventure is + 30/35 kg towards the 'standard' GS 1200.

The weight of an XL1000V Varadero ABS is + 30kg towards an carb-non-ABS Varadero.
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Which would bring the 'standard' S10 back to an - surprisingly! - <?xml:namespace prefix = st1 ns = "urn:schemas-microsoft-comffice:smarttags" /><st1:metricconverter w:st="on" ProductID="230 kg">230 kg</st1:metricconverter>. Which is exact the same figure as for a 'wet' XRV750 Africa Twin. <o></o>

Hmm. Must get some of that lightweight fuel.

Philosopher, heal thyself.


That aside, I do agree with your light = good argument.

Agree

You are unfamiliar with the 180&#176; crank... Fair enough, you did say you were no expert.

Advertising budget slashed by 90%? Good!
I accept that in a competitive market, it makes sense for any individual manufacturer to spend on advertising - it gives them an edge over the unadvertised competition. The only thing is of course, every manufacturer feels they have to advertise. So there is no net gain. The only outcome is that we all have to pay more for our bikes, because some of the price is being siphoned off into the pocket of the marketing man. Ban advertising! We'd all* be richer.

*Except of course, the marketing man

Isn't the 180° crank in-plane? I'm asking. And yes, I'm unfamiliar with it.

....and that's why everyone who is truly interested should contact Yamaha NA.

Worked for the FJR.

OTOH, if they play the "FJR game" where you order without acutally seeing or riding the bike it might not work so well.

Yes it's in-plane, but no it's neither 360&#176; or 270&#176;

Off the top of my head, I know of at least two twins with 180 cranks: The Suzuki GSX250 of 30 years ago, and the Norton Commando. Norton twins tended to be 180s while Triumphs were 360s. I'm sure there are other, more recent 180 bikes, but crank angle is not the sort of thing manufacturers include in their specs so I can't say.

As usual, wiki has some relevant info

Yup, that's what I said in post 1948, but let's not split hairs.

Stupid ass Yamaha :ruskie No friggin mention of side-car availability or anything else either :fyyff

Yes, I remember the Norton being 180 but could not think of a modern twin.
Thanks.

Almost all old Honda twins are 180-deg (e.g., CB350s) and I suspect bikes like the Ninja 250, Ninja 500, GS500, Europe's CB500, etc. are now although I don't know. So I actually suspect 180-deg is the most common parallel twin.

180-deg has better primary balance but a really nasty "rocking couple" secondary vibration. The 360-deg is more amenable to counter-balancing though, so that's why you generally see 180-deg in small/cheaper bikes that have acceptable vibration without counter-balancers, whereas 360- (or now 270-) tends to be in larger counter-balanced bikes. 180-deg also has better pumping loss characteristics - when you have both pistons go up and down together, the crankcase volume is changing pretty dramatically which requires more sophisticated baffling and breathers to have acceptable pumping losses. Most people think 180-deg crank twins sound pretty bad and 360- (or better yet 270-deg) sound better.

As always, lots of engineering tradeoffs.

- Mark

For some reason I had it in my head that Honda twins - at least those of 30 years ago, when I rode 250s, were 360&#176;

The 360 format offers other advantages:

1. You can use a single carb (you can't on 180s)
2. You can use a simpler ignition system - both sparks fire every 360° of crank rotation.

But as you say, it's about trade-offs

That's interesting.... and perhaps one reason why most of the british 360-twins offered single- and dual-carb models (e.g., Tiger vs. Bonny). I recall perhaps one single-carbed Honda twin that had a single carb, but don't recall the model. And I think Honda even tried dual-carb singles for a couple years.

I'm curious.... what's the issue with a single-carb on a 180-deg crank bike?

- Mark

I'm curious too - In fact, I'm convinced there is no problem with this and it has been done in the past (Honda Benly CD125 & CD200?).

I had a GPZ305 twin (180 degrees) in the eighties. Before it blew up for the second time, I had learnt a bit about that engine. Althoughit was twin-carbed, the manual listed a difference in one of the jet sizes between the left and the right. I cannot remember which exactly but it was not the main jet IIRC. When asking around my local biker pub as to why this might be, I was given the answer by the older & wiser Brit bikers. The intake stroke of the leading cylinder momentarily reduced pressure in the shared airbox which starved the trailing cylinder of air charge, thus requiring a different jet size to compensate. Of course, there would be a longer duration between the trailing & leading cylinder sucking so the air pressure would have a chance to regain itself.

Made sense at the time & still does. If Kawasaki found a way to get around that with twin carbs then there is nothing difficult about getting a single carb system to work.

Of course, this could have been a load of baloney if it was all down to a misprint in the Kawasaki manual!

Jon

If I understand it correctly, a 360-deg crank serviced by a single inlet tract would pull intake charge evenly every other half-rev of the crank like,

pull (cyl1) > wait > pull (cyl2) > wait > pull (cyl1) > wait > pull (cyl2) > wait....

while a 180-deg crank pulls two consecutive half-revs, then waits for two half-revs,

pull (cyl1) > pull (cyl2) > wait > wait > pull (cyl1) > pull (cyl2) > wait > wait ....

Of course, a single carb for a single cylinder is going to be even more uneven,

pull (cyl) > wait > wait > wait > pull (cyl) > wait > wait > wait ....

So I would think a single carb on a 360-deg crank would definitely see a more even pulsing in the inlet stream vs. a 180-deg crank. Whether this makes a single carb infeasible or significantly more difficult, for the 180, I don't know. I seem to recall that perhaps the little Honda training bikes used by many of the MSF contractors were single carb twins and I bet they had 180-deg cranks.

This whole discussion makes me wonder a little while one-carb per cylinder is such a performance advantage - it would almost seem better to have the carb see a more constant pull from multiple cylinders.

- Mark