[cigarjack]

The knowledge base on this forum is incredible. I rely on it a lot and know someone will have a wise (not wise ass) answer.
At 70 mph I'm turning about 5000 rpms. Above that it seems to be stressing the little motor some and the mpg drops off noticeably. 70 mph is plenty fast except on the slab where you'll get blown off the road if you're not doing at least 75 or closer to 80. At what point is the motor past its comfortable rpm range? At what point will long term, high rpm damage the motor? Thanks

 

[greywolf]

You aren't stressing the engine at all. MPGs drop off because of aerodynamic drag. Out West I'll do an indicated 82/actual 75mph at 6000rpm all day long day after day. The only issue is the bike starts misting oil through the breathers so I carry extra oil with me. The bike will do 8000rpm just as easily but that would be a bit fast.

 

[rconti]

I've cruised for extended periods at 7k. I wouldn't mind taller gearing for 'comfort' (ie, mental relaxation) but it sure doesn't seem hard on the engine; if anything it's right in the powerband.

 

[barryg]

Get a 16T front sprocket. Mine came with one and can't imagine having stock. Indicated 80mph is 5500rpm. Stock would be 6000rpm I've heard. Would that stress the engine? No. But do I wanna cruise around at 6K+ on the freeway for extended lengths of time? No.

 

[greywolf]

Now I found zero value in the difference between 5500 and 6000rpm when trying a 16T front sprocket. The thing bothered me greatly at lower speeds though. The bike didn't have the same zip. Different folks prefer anything from a 14T to a 17T. The Montrose CO police bike has a 13T according to its rider but I can't even find one.

 

[scrivens]

6000rpm seems to be the sweet spot, and it's still only a bit over half max revs. Around here with radar and so on it's a bit unwise to go much over the usual highway speed limit of 110kmh, which is 5500rpm in top (and on my bike, showing nearly 130kmh on the useless speedo.) Trouble is the bike wants to run at 6K and keeps edging up there. Very smooth at that speed and the usual Wee noises level out so it's very quiet. Fuel use goes up markedly though and long stretches at 6K will drop mine down to around 60mpg imperial compared to high 60's low 70's at 80-100kmh.

 

[farmerlou]

I don't like running below 5,000 and do 6, 7, and 8,000 in the twisties.

 

[bartron3030]

I agree with scrivens, 6000rpm seems to be the sweet spot with little or no engine vibs and plenty of power ready for overtaking, hills etc. but to answer your concern about long term engine damage IMO the engine is designed to be a high rpm V twin and operating around the bulk torque range 5000-8000rpm is not gong to damage your engine

 

[greywolf]

Once again, it's air resistance that uses fuel. I've run a 16T sprocket and the fuel economy was identical to the 15T.

 

[zt0117]

I agree with Greywolf. I've run a few tanks on my average commute at 3,000-4,000 RPM (DL1000) and then run a few where I kept the RPMs in the sweeter spot of 4-5,000 RPM with no real loss of fuel economy, but a big gain in zip/fun. In the 5-6,000 range, on the same route, I do see some loss of fuel economy. In the 4-5,000 RPM range, I get about 40-43 MPG. At 5-6,000 it looks to drop 2-3 MPG.

But then again, my usual commute is 7 miles with lots of lights, and I do hard engine breaking to save the breaks. Most of the time I ride my KLR650 which is the superior "urban commuter vehicle"

--Dave

 

[dtalk]

Once again, it's air resistance that uses fuel.

+1.

Worst economy I've ever seen was in west Texas: high speeds, high wind, 35mpg. If I'm going a steady 50mph, it doesn't matter what engine speed I use (within reason); I'll get about 50mpg.

It's not the engine, nor does weight make much difference. Riding style also matters not much at all. It's the barn-door attack angle of the bike. :biggrinjester:

 

[bartron3030]

Your correct Greywolf, the increase fuel consumption is due aerodynamic loads at higher speeds

 

[scrivens]

Faster spinning motor = more fuel used, higher speeds = more wind resistance. Comes down to the same thing - higher speeds use more fuel. I had a 16 tooth for a while and it made little difference in consumption on the highway. It really should be using more fuel as it is pushing against the same wind resistance and load but with lower hp and torque.

 

[greywolf]

The drag coefficient of a motorcycle is about the same as a truck. Air Drag Coefficients
Motorcycle Safety Site
Our bikes with tall profiles, wide handlebars and an upright seating position are on the high end of the scale.

 

[DrPaul47]

Not sure if this is a hijack or not. Original question was about engine wear life etc. I remember reading in a MC rag that engine braking is not a great idea or methode to use for braking. That it is best to use the brakes, they are easy to replace and not that costly. Any comments or knowledge about engine braking and engine life?

 

[greywolf]

Not sure if this is a hijack or not. Original question was about engine wear life etc. I remember reading in a MC rag that engine braking is not a great idea or methode to use for braking. That it is best to use the brakes, they are easy to replace and not that costly. Any comments or knowledge about engine braking and engine life?

Do whatever you like. It's not going to hurt the engine. I just don't see any advantage to engine braking.

 

[soderholmd]

Get a 16T front sprocket. Mine came with one and can't imagine having stock. Indicated 80mph is 5500rpm. Stock would be 6000rpm I've heard. Would that stress the engine? No. But do I wanna cruise around at 6K+ on the freeway for extended lengths of time? No.

I agree - I added a 16 tooth sprocket and it totally changed the character of the bike for highway / Freeway use - Highly Recommended!

 

[soderholmd]

Once again, it's air resistance that uses fuel. I've run a 16T sprocket and the fuel economy was identical to the 15T.

I almost never disagree with you greywolf, but..............

I gained 3-5 mpg consistently when running both sprockets at 80 mph indicated over a tank.

The rpm's do make a difference in fuel usage though. It has too.....running the engine 500 rpm's more over the course of a tank has to use more fuel to do that. Take it too extreme and run it in 3rd gear on the freeway over a tank and then use sixth over the same stretch:yikes:.

Air resistance also has a big affect on mileage with the Wee, but that variable is independent of the rpm at which the engine is run.

:thumbup:

 

[cigarjack]

Thanks for the info

All the replies were helpful, thanks. Knew I could count on ya. I'm already running the 16t and agree with Greywolf that wind resistance is a major factor. With the throttle lock have noticed it fighting wind gusts and the corresponding drop in speed. Will continue to ride hard and worry free.

 

[greywolf]

running the engine 500 rpm's more over the course of a tank has to use more fuel to do that. Take it too extreme and run it in 3rd gear on the freeway over a tank and then use sixth over the same stretch.

Air resistance also has a big affect on mileage with the Wee, but that variable is independent of the rpm at which the engine is run.

:thumbup:

I've seen a couple of other posters say their mileage improved with a 16T, but most say it stayed the same. 6000rpm is in the meatier part of the power band so the engine doesn't have to work as hard to overcome the air resistance as it does at 5500rpm. The engine makes about 48hp at 6000rpm but only about 43hp at 5500rpm. http://www.mcnews.com/mcn/model_eval/VStrom05B.pdf#search='dl650 060'
The power required to overcome air resistance is not independent of rpm. The idea of dropping to 3rd gear puts the engine past its power peak so is not applicable to this discussion. You're totally missing the most important part of the equation, the horsepower available at different rpms.

I have to wonder if your expectation that lower rpm means less fuel use may have affected your status as an observer and your mileage calculations. You might have done that just fine and actually do get better mileage over your observed time. However, so many conditions affect mileage it's hard to tell if longer periods of record keeping might result in closer figures. 3-5mpg can be within the margin of error.