RPM's - then and now. - Kawasaki KLR 650 Forum
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post #1 of 10 Old 04-04-2013, 05:30 AM Thread Starter
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RPM's - then and now.

I don't know if I have this right nor do I understand what is happening.

During the break-in period of my 2012 KLR I never brought the RPMs above 4,000. I also noticed that going from 4 th. to 5 th. gear the tachometer would be at 4,000 RPMs at 60 MPH.

Now, 5,500 miles later, I notice that when the tachometer is reading 4,000 RPMs on 4 th. gear the speed is only 55 MPH and I can travel up to 70 MPH just under 5,000 RPMs.

This doesn't make sense to me. I thought that once the engine is "brocken-in" the engine should be operating smoother. So, according to my frame of mind, smoother engine should be lower RPMs per MPH. Does that make any sense????
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post #2 of 10 Old 04-04-2013, 07:49 AM
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Have you always had the same front tire on it? I was thinking maybe your noted rpm/mph disparity could be caused by a wearing tire, but reason tells me a tire with a slightly smaller diameter due to wear would make more rotations per mile than a larger tire, resulting in a higher mph reading compared to engine rpm's, so that can't be it since you're now seeing a lower mph reading compared with the same engine rpm. That was probably the worst sentence I've ever written, by the way.

Did you maybe put a new/different front tire on it?

Engine rpm's are engine rpm's and I would imagine the disparity is caused by something associated with your front tire/speedometer drive/speedometer. The KLR speedometer isn't exactly a high-tech piece of engineering.



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post #3 of 10 Old 04-04-2013, 08:03 AM Thread Starter
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Planalp

These are the original tires (front & back).

I think I am going to go with your statement that these speedometers are not the best in quality...:-)
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post #4 of 10 Old 04-04-2013, 10:08 AM
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As planalp says, engine RPMs are engine RPMs.

With the exception of a very minor change in speed due to the rear tire wearing, your bike is going exactly the same speed at 4000 RPM as it was when new.

Had you been measuring the speed with a GPS that would have been apparent. Something else has changed in the bikes measurement of the speed.

The only thing that will materially affect the speed at a given RPM is a change in gearing, such as changing from a 15 tooth sprocket to a 16 tooth sprocket.

T

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post #5 of 10 Old 04-04-2013, 10:58 AM
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The only thing that changes in RPMs other than what Tom has said is that after time when the engine is worn in well it will spool up easier, or RPM up quicker. It will feel quicker in this respect, not saying the bike will be that much quicker just that it may feel less sluggish.
Gearing or some sort of restriction is the only way to make the RPMs alter but the engine will always be the same rpm wise it physically can't change.

The speedo is notorious for being 10% out on some bikes on average. I run a Vapor and a GPS and they are within 1.5 kms difference at 100kph which is good imho. It can be spot on if I were to sit and calibrate it better but that works off front tire dia. and that will change as the tire wears, so I'm happy with what it's reading.

Hope this not to clear explanation helps.....

Willys
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post #6 of 10 Old 04-04-2013, 02:55 PM Thread Starter
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Thanks guys. I think I will try someone's GPS if I get a chance. I don't have one of my own yet.
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post #7 of 10 Old 04-04-2013, 02:58 PM
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Do you have a smart phone that you can get a low-cost GPS app for?

T

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“She went out slowly. The way she did it hadn’t been learned at business college.” -Philip Marlowe

“'Why' and 'How' are words so important they cannot be too often used.” -Napoleon Bonaparte


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post #8 of 10 Old 04-04-2013, 03:17 PM Thread Starter
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No smart phone...yet.
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post #9 of 10 Old 04-04-2013, 03:24 PM
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Me neither.

I'm a dumb-phone kinda guy.

T

Tom [email protected]

“She went out slowly. The way she did it hadn’t been learned at business college.” -Philip Marlowe

“'Why' and 'How' are words so important they cannot be too often used.” -Napoleon Bonaparte


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post #10 of 10 Old 04-04-2013, 04:44 PM
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If you can wait for boxing day sales the nuvi 550 comes on sale for the $200 range and is motorcycle friendly It is the cheapest GPS that is motorcycle friendly. You can buy much cheaper used GPS's but if they are just for cars etc the rear plug isn't made to deal with the vibrations of a bike and will sooner or later die.....ask me how I know.

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