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Lugging the Boxer


doc47

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I just saw this comment in a post. Opinions?

 

"Don't ever lug a boxer twin, ride em hard, hit the limiter as often as possible, even if its in 1st or 2nd.

You gotta run these bikes hard or they don't last as long."

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Paul Mihalka

A little bit exagerated, but close to truth. You don't have to hit the rev. limiter, but running it to 6 or 7 thousand rpm is good. Riding under 3000rpm is lugging, unless you are just accelerating through first gear. You definitely can't hurt them by running full power at high rpm.

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"Don't ever lug a boxer twin, ride em hard, hit the limiter as often as possible, even if its in 1st or 2nd.

You gotta run these bikes hard or they don't last as long."

lmao.gif

The 'ride em hard' style totally clashes with the profile of a typical boxer rider. I really don't see us charging around town over 6000 rpm.

 

IMHO, I'd say myth, especially since 50K miles on a boxer seems low mileage.

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The 'ride em hard' style totally clashes with the profile of a typical boxer rider. I really don't see us charging around town over 6000 rpm.
Does the typical boxer owner, especially one who has 50K on his bike, spend much time charging around town at all?

 

I don't believe they will last longer if you thrash them, I don't think they will last any less either. If you never run the boxer motor hard it will without doubt carbon up and that will affect its performance considerably. There is no doubt that this motor likes to be run hard, I've proven it with mine time after time, it runs much better after a hard charge (now have 117K on mine).

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Steve_Witmer
Riding under 3000rpm is lugging, unless you are just accelerating through first gear.

 

Sorry to disagree. Lugging generally involves running under a high load/low rpm condition, the danger of which is that because of the low RPM the oil pump is delivering insufficient oil to the lubricated parts under load. This is obviously bad for a motor.

 

I agree that the motor is very happy to run at higher RPM, and in fact runs smoother up in the powerband, but I can putt down the street towards my house at the end of a ride at 1500 rpm in second gear and it's not lugging the engine, because there is hardly any load.

 

If I fail to downshift before a steep uphill grade and the motor is straining to pull the bike uphill at 1500-2000 RPM in the wrong gear, I may be lugging the motor because it is under load.

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I dunno, I wish BMW had put another gear in the 1150RT to use between 60-75 mph. 6th gear seems too low and 5th seems too hi.

 

But... Boy oh boy does she run nicely at 85 mph...

 

clap.gif

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Lugging generally involves running under a high load/low rpm condition, the danger of which is that because of the low RPM the oil pump is delivering insufficient oil to the lubricated parts under load. This is obviously bad for a motor.
I believe the real problem with lugging an engine is the load on the bearings, not lack of oil circulation. Compare it to pushing a child on a swing. At the start it takes a lot of effort to move the swing. Once it is moving a very small push at the right time is sufficient to keep it swinging and even to increase the amplitude.
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ShovelStrokeEd

No problems with the oil pump delivering sufficient oil, or even oil pressure to protect the bearings. In the case Steve mentioned, since there is no load on the motor, the bearings are not at risk. Will is closer.

 

Part of the ability to protect the bearings with the oil film comes from the relative speeds of the components. At higher speeds, and dependent on the viscosity of the oil, the oil forms a wedge between the journal and the bearings and it is this wedge that protects the assembly from metal to metal contact. At lower rotational speeds the wedge is not present, or very small, and the pounding load, particularly on the connecting rod big end, can do some damage.

 

There is also, during lugging, the risk of detonation which can damage both the pistons and the bearings.

 

I'm in the higher RPM is better camp for a couple of reasons. I just don't spend any time, other than 1st gear acceleration, under 3K RPM.

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I find this discussion very interesting. Being fairly new to BMW and coming from HD, I always hesitated to run the engine at real high RPM. Since reading more on this subject on this firum, I have started to use lower gears and run at 4k to 5k. Usually do not run below 3k except up my drive way. Above 5k the vibration increases and it just doesn't feel right to me. At top end she really is singing, but I will try to overcome my fear of the engine blowing to pieces and attempt to run higher RPMs based on what I read here.

 

I am not a real high speed rider, mainly because I don't want to get caught. So, I hardly ever get into 5th gear now. dopeslap.gif

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Joe Frickin' Friday
Part of the ability to protect the bearings with the oil film comes from the relative speeds of the components. At higher speeds, and dependent on the viscosity of the oil, the oil forms a wedge between the journal and the bearings and it is this wedge that protects the assembly from metal to metal contact. At lower rotational speeds the wedge is not present, or very small, and the pounding load, particularly on the connecting rod big end, can do some damage.

 

There is also, during lugging, the risk of detonation which can damage both the pistons and the bearings.

 

The other problem, especially on an engine with only a couple of cylinders, is the large fluctuations in speed that occur through the course of a combustion cycle. During the compression stroke, the engine slows down a bit, and during the expansion/power stroke, the engine speeds up a bit. Obviously this speed variation will be more extreme during high load; less obvious is the fact that this speed variation will also be more extreme at low RPM's. Put the two together, and those speed variations will beat the daylights out of your whole driveline.

 

We get this at work sometimes when a dyno malfunctions. Instead of briskly pulling the engine down to zero RPM at shutdown, it lets the engine coast down to zero. The problem is that we're talking about the rotational momentum of a 350-horsepower electric motor attached to the back of the engine, so it ends up taking about thirty seconds to spin down from 1500 to zero RPM. When it gets below about a thousand RPM, things start to get ugly: the engine writhes and shudders in its mounts like a dying buffalo. We really, really try to avoid that if at all possible.

 

You can idle across a parking lot at idle RPM in first gear, no problem (light load, remember?). While doing this, you can even roll on the throttle hard and launch; yes, the load is high, but the engine will only go a few revs before it's up to decent RPM, so no harm no foul. But a sustained cruise at low RPM (especially at higher speeds, where load is higher) is not going to be good for the engine.

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So how low do most people consider the minimum crusing speed of the motor under load. On mine, in it's current state of tune, it feels like 2500RPM. So 6th gear can only be used over about 52mph. Anyting lower causes pronounced vibration under load. On the other hand, at higher RPM's and very low loads such as 2nd gear at 30mph, the drive train lash causes a surging. This might be lean surging people talk about from the engine, but it feels more like a rubber band action from the drivetrain.

 

The point about low oil pressure and crankshaft velocity is interesting. A motorcycle has a wider operating range than a car, so the oil pump is likely geared taller. Another factor is that this motor still has a relatively short stroke (oversquare) and high compression, which is not as typical for a OHV design.

 

However, compare the ability ot run this motor at 2500 RPM compared to my 900cc I-4 ZX9R motor, that was unhappy under 3000RPM. Of course that motor was smoother, and happily crusised at 5000-7000RPM... where it just started making the real power. That motor hower lacked character.

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my 900cc I-4 ZX9R motor, that was unhappy under 3000RPM ... happily crusised at 5000-7000RPM... where it just started making the real power.
To me that describes the boxer motor perfectly, although it will cruise at 4000 just fine too, but no real power down there.

 

I never run mine under 3000rpm and don't use 6th gear until I'm over 70mph and cruising, it's a tall overdrive as far as I'm concerned (and I'm not alone in this opinion)

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to overcome my fear of the engine blowing to pieces and attempt to run higher RPMs based on what I read here.
Fear not. Bottom end problems from over reving are virtually unheard of with the boxer.

 

I have to temper all this talk of flogging the boxer to death in the upper RPM ranges (I'm talking 7 - 8K here) with the severe impact it has on economy. At least in day-to-day type riding. To me the 5 - 6K range is a better compromise.

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Cruising on my 03 RT is 75/80mph which is a very comfortable 4k(80) in 6th and I wouldn't let the motor drop below 3k in 5th or, especially!, 6th.

Hooning around here on our 70mph roads generally keeps me in 4th and 5th grin.gif.

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ShovelStrokeEd

Used to be, that BMW posted 2 different recommended maximum RPM's. Something like maximum engine RPM, 7200. Maximum sustained RPM 6800. I think they have stopped that.

 

To me, unless I am engaged in a contest of speed with someone, running the engine up to red line is stupid, wasteful and unnecessary, to be redundant. Beating the crap out of your motor for no good reason. This from a guy with a 45 year history of drag racing. Does this mean I don't advocate or like strong acceleration? Hardly. I enjoy a good burst through the gears as much as anyone, witness my primary ride. However, shifting at 4K in the city and around 6K if I'm in a hurry to merge with freeway traffic is much more the norm. I do believe in a little brisk acceleration to "clean it out" now and then although a good high speed freeway blast for a tankful or so probably does a better job at that.

 

Also, engaging in said contest of speed, on a BMW, with any modern 2 wheeled conveyance other than another BMW or a scooter, is likely to leave the rider with his feelings hurt. blush.gif The new K12S being the exception.

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I agree with Ed pretty much, I didn't mean to imply that I ran the engine to red line all the time. My point is just that you won't hurt and might well help the motor by running it to the rev limiter from time to time. There have been days when it has spent most of the time up there, when I'm riding with those well known hoons on their KGTs and FJRs, but as Ed says, even then there is no way to keep up with them if they are having fast fun.

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_______________________________________________________

I never run mine under 3000rpm and don't use 6th gear until I'm over 70mph and cruising, it's a tall overdrive as far as I'm concerned (and I'm not alone in this opinion)

_______________________________________________________

 

Can't agree more, I mentioned to someone that I did not care for the gearing of my 1150rt due to the fact that a lot of my riding is around 70-75 mph, so I never use my 6th gear. They thought I was should be getting into 6th around 65 mph. I know it's not exactly lugging at that speed in 6th, but sure lacks power.

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_______________________________________________________

I never run mine under 3000rpm and don't use 6th gear until I'm over 70mph and cruising, it's a tall overdrive as far as I'm concerned (and I'm not alone in this opinion)

_______________________________________________________

 

Can't agree more, I mentioned to someone that I did not care for the gearing of my 1150rt due to the fact that a lot of my riding is around 70-75 mph, so I never use my 6th gear. They thought I was should be getting into 6th around 65 mph. I know it's not exactly lugging at that speed in 6th, but sure lacks power.

 

I will cruise in 6th at 60mph but if I need to pass, or if there is a hill, I drop to 5th. 6th is just an overdrive on these. I wish BMW had kept the old 5 ratios and then put 6th on top - that way the bike would be more rideable but still have that economy gear.

 

Andy

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I just got back from a nice ride and tried to really ring her out. It went fine even up to red line and I feel more comfortable now running at higher revs. Today I never got out of 3rd gear and running in the 70s & 80 mph. I don't think I will do this all the time as the most comfortable range seems to be 4500 to 5k. I think, like Andy, cruising along in 4th or 5th will be fine except when needing to pass. I did notice the temp went up to 6 bars running like that and she seemed to use more fuel. It was only 55 deg. outside and I was surprised that the temp ran up.

 

I checked the oil when I got home and it was right where it was before I left. Don't know if it was the placebo effect or not, but she seems to run smoother now. Thanks for all the good info. smile.gif

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"Don't ever lug a boxer twin, ride em hard, hit the limiter as often as possible, even if its in 1st or 2nd.

You gotta run these bikes hard or they don't last as long."

lmao.gif

The 'ride em hard' style totally clashes with the profile of a typical boxer rider. I really don't see us charging around town over 6000 rpm.

 

IMHO, I'd say myth, especially since 50K miles on a boxer seems low mileage.

10-4; my sentiments as well!

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took me a while to get use to the RPM. I ride about 15 miles to work at about 55-60 and don't get out of third that's between 4-5K unless I'm passing. FUN!!!

 

Cheers

strat thumbsup.gif

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I know it's not exactly lugging at that speed in 6th, but sure lacks power.

 

I think this is an important point that is underlying this discussion but often not explicitly brought out. There is an RPM below which you should not ride unless asking for very little power, because the engine is lugging and it can cause damage if done consistently. Then there is an RPM below which the engine is not in the peak of the power curve. Lugging occurs below about 2500-3000. Don't put any load on the engine below that level. Power/torque kicks in about 4000-5000. Don't expect much performance below that level, but it won't hurt the engine.

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Stan Walker

Lugging occurs below about 2500-3000. Don't put any load on the engine below that level.

 

And this is based on what? A BMW spec? Some mathematical thing? Seat of the pants? Failure analysis? Quess?

 

Interested "luggers" need to know. My bike spends a great deal of it's time between 2800 and 3500 rpm. Heck, I sometimnes shift at 3500 hundred when riding in town.

 

Stan

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Lugging occurs below about 2500-3000. Don't put any load on the engine below that level.

 

And this is based on what? A BMW spec? Some mathematical thing? Seat of the pants? Failure analysis? Quess?

 

 

Seat of the pants, guess.

I figured if I put it out there, someone would disagree and we could come to an agreement about where the minimum speed should be. I spend a lot of time at those rpms too. Maybe the minimum should be lower.

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Joe Frickin' Friday
Seat of the pants, guess.

I figured if I put it out there, someone would disagree and we could come to an agreement about where the minimum speed should be. I spend a lot of time at those rpms too. Maybe the minimum should be lower.

 

"Minimum RPM" is gonna be fuzzy. The situation is less severe as the load decreases; under zero load, obviously, the engine can be safely run at 1000 RPM indefinitely. As the wear from harsh operating conditions is cumulative, the general policy for maximizing engine life (subject to the constraint of actually using and enjoying the bike's capabilities) can be stated:

 

"Try to avoid high-load operation at low RPM's for extended periods."

 

A practical implementation might include simply avoiding steady cruise and WOT acceleration below about 3K RPM.

 

Why 3K? I don't know. The limits of a machine are hard to define, and usually include a generous margin of safety. For example: The space shuttle's main engines have a maximum rated thrust level, "100%." And yet, shortly after liftoff, they run them at 104%, and they don't immediately go to pieces. (but they don't run them like that for very long...)

 

Likewise, even while generally abiding by that practical implementation above, I'm not averse, now and then, to going WOT shortly after getting the clutch fully engaged in first gear (at maybe 2K RPM?). As I described in an earlier post, the engine will only remain under 3K RPM for a fraction of a second under these conditions. However, in higher gears, the engine will spend more time at any given RPM; if you're puttering along at 55 in 5th gear, small increases in throttle are OK, but it might be wise to drop down a gear or two before getting on the gas hard.

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Stan Walker

Why 3K? I don't know. The limits of a machine are hard to define,

 

I think we are setting the bar too high. If their were problems caused by lugging the BMW engine we would see lots of engines failing with lower end problems. Instead, it's almost an unknown type of failure. I pronounce this an internet myth. Busted. grin.gif

 

Stan

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Paul Mihalka

A bit of summary: Low rpm and little throttle is good. High rpm and lots of throttle is (very) good. Low rpm and lots of throttle is not good.

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Joe Frickin' Friday
Why 3K? I don't know. The limits of a machine are hard to define,

 

I think we are setting the bar too high. If their were problems caused by lugging the BMW engine we would see lots of engines failing with lower end problems. Instead, it's almost an unknown type of failure.

 

If a lot of people were known to be disregarding that 3K limit and getting away with it, then yeah, we could say the 3K limit is unnecessarily conservative.

 

But we don't know that. And at the same time, you're right, I don't have any data that suggests 3K is a good cutoff point. This is why I don't mind violating it with the WOT roll-ons in first gear that I described.

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Is the gearing the same on the 1100 as the 1150?

Like temperature load is a relative term (so it seems).

 

That said, I keep my 1150 above 3k(ish).

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Also, engaging in said contest of speed, on a BMW, with any modern 2 wheeled conveyance other than another BMW or a scooter, is likely to leave the rider with his feelings hurt. blush.gif The new K12S being the exception.

Unless one is in the twisties and then experience and skill get the better of newbies on their rice burners. clap.gif And yes that priceless look when they think HTF did he do that. lmao.gif

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SAAB93driver
Is the gearing the same on the 1100 as the 1150?

Like temperature load is a relative term (so it seems).

 

That said, I keep my 1150 above 3k(ish).

 

1150RT has OD in 6th, 1100RT is a 5 speed, top gear is not an OD so it is running at higher rpm for given speed in top gear vs the 1150RT.

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Lugging occurs below about 2500-3000. Don't put any load on the engine below that level.

 

And this is based on what? A BMW spec? Some mathematical thing? Seat of the pants? Failure analysis? Quess?

 

Interested "luggers" need to know. My bike spends a great deal of it's time between 2800 and 3500 rpm. Heck, I sometimnes shift at 3500 hundred when riding in town.

 

Stan

 

+1. Where folks get the idea that this is a problem for the bottom end I will never know. Running under moderate load at low RPM will certainly separate the well tuned from the rough runners, but will not damage the bottom end. From the research into "Lugging" that I have done, the damage done is generally a ring bouncing problem in older style motors with thick rings, poor design.

All that said, as long as you open it up once in a while, the carbon thing is moot.

I have been known to leave it in 6th at 55 as long as there isn't a big hill.

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I pronounce this an internet myth. Busted. grin.gif

 

Stan

I don't think that lugging increases the loads on the low end because the combustion pressures are lower at low RPM than at max torque. I would think that lugging is nothing that the shaking of an engine block on its mounts. This happens when it is operated a low revs and the crankshaft angular speed varies too much. What damage does this cause? I don't know, but it is painful to my senses.

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In general terms, I think there is such thing as "lugging." I'm defining it as high loads at very low RPM's. But specific to the boxer, I've got to agree with Stan. Bottom end problems are virtually unheard of in the R engine and we can bet they are ridden under any RPM vs. load situation imaginable.

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+2 Being the incompetant rider I am I frequently shift up at 2500 and run 6th gear at 50mph. I don't feel like the engine is laboring, nor do I detect signs of detonation. DETONATION is about the only thing likely to hurt an engine at lower rpm. After running heavy equipment for years I just don't buy into the low rpm lugging myth. Most equipment is governed to no more than 2300 rpm.

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+2 Being the incompetant rider I am I frequently shift up at 2500 and run 6th gear at 50mph. I don't feel like the engine is laboring, nor do I detect signs of detonation. DETONATION is about the only thing likely to hurt an engine at lower rpm. After running heavy equipment for years I just don't buy into the low rpm lugging myth. Most equipment is governed to no more than 2300 rpm.
It's irrelevant what other types of motors are governed too, they are presumably designed that way. I am not a mechanical or auto engineer and I don't know anything about bottom end failures, what I do know is that if I cruise my RT around at 50mph in 6th gear it fairly quickly gets sluggish and starts to detonate under any load. This is apparently due to carbon buildup and seems to be a common experience with boxer owners.
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+2 Being the incompetant rider I am I frequently shift up at 2500 and run 6th gear at 50mph. I don't feel like the engine is laboring, nor do I detect signs of detonation. DETONATION is about the only thing likely to hurt an engine at lower rpm. After running heavy equipment for years I just don't buy into the low rpm lugging myth. Most equipment is governed to no more than 2300 rpm.
It's irrelevant what other types of motors are governed too, they are presumably designed that way. I am not a mechanical or auto engineer and I don't know anything about bottom end failures, what I do know is that if I cruise my RT around at 50mph in 6th gear it fairly quickly gets sluggish and starts to detonate under any load. This is apparently due to carbon buildup and seems to be a common experience with boxer owners.

 

I often wonder about the number of posts from the USA about carbon build-up. I regularly run my bike at 2500 in top and never have that problem - even after two or three days of tootling along on a tour. Mind you I also regularly run it to 7K. My point, I think, is that the fuel in the UK seems to burn cleaner judging by the lack of carbon build up on any of my bikes.

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Any minute now.....and we all are going to be entertained with a sound bite of Mitch.....errrr, I mean "Sanjaya" bursting out into a replay of "Mary Poppins"

 

GETREADYEVERYBODY!! lurker.giflmao.giflurker.giflmao.gif

 

Pat

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Lugging, what's that? 6th gear, what's that? I thought these bikes only had 3 gears. Wow, is it noisy on the interstate. lurker.gif

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ShovelStrokeEd

There actually is a useful piece of information available that can be used as a guideline for load applied to the engine. It is called the torque curve. Call the point just after it turns steeply up the minimum for application of full throttle, the point at which it is in a linear rise the 1/2 throttle and anything below that, only about 10% throttle, which, btw is adequate to sustain steady state cruise at around 50-60 mph on level ground with favorable winds.

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My owner's manual states that 3, 4, or 5th gear can be used for speeds of 50 mph or more. The engine sounds just fine in 5th at 50 but I shift down below that speed. If someone will post a torque and HP diagram that would be useful.

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Couchrocket

When I first got my RT I thought it was a little "doggy" on power. I was shifting at about 3k-3.4K and would be in 6th gear at about 60 mph. It just didn't "feel right" even though it wasn't "lugging" in absolute terms (as in bucking, and snorting, and pinging, etc.).

 

So, I decided to not "listen" to how it sounded, and only go by "feel" of how it responded to throttle inputs.

 

I now keep it somewhere between 3500-4500 as my "minimum" rpm unless I'm going down hill with a strong tail wind. And, it never sees 6th gear below about 75 mph, and is "happier" with 80+ as a starting place.

 

I continue to have this weird love / "what the hell?" relationship with this bike! And the fact that it is a big-bore twin that likes to rev like an inline 4 japanese bike (within its rpm range, of course) is just one more "character" thing about this wonderful and strange machine.

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I continue to have this weird love / "what the hell?" relationship with this bike! And the fact that it is a big-bore twin that likes to rev like an inline 4 japanese bike (within its rpm range, of course) is just one more "character" thing about this wonderful and strange machine.
I know exactly what you mean, I do feel better since I discovered that it likes to run hard, really hard. I have the opposite with my CRF, here is a thumper with a 14,000rpm red line! And it really really loves to rev.
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Lugging, what's that? 6th gear, what's that? I thought these bikes only had 3 gears. Wow, is it noisy on the interstate. lurker.gif

 

3rd gear 100+

not noisy at all

 

Oh, sorry wrong forum. smirk.gif

Dark Side

 

Last boxer, '96 RSL was a 5 speed.

I only used 5th above indicated 80mph in most cases

 

Hey Mitch/Joe/Sanjya,

What about the effect of speed on air/fuel mixture at higher/lower speeds and low/high rpm's? In other words, does lugging reduce rate/volume of air and impact air/fuel mixture negatively??

lurker.gif

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ShovelStrokeEd

Tim,

It shoudn't as, by definition, lugging would describe high throttle opening at low RPM. The Motronic doesn't actually measure air flow, only RPM and throttle position.

 

My Blackbird would automatically compensate as it also has a manifold pressure sensor.

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