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post #1 of 24 (permalink) Old 07-07-2008, 03:37 PM Thread Starter
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Lightbulb Why Rev So High?

Hello all. This is totally speculation, but it's been asked many times why our bike revs so high at highway speeds. I got thinking about that and did a little looking around. Back in 85' when the bike was intoduced the speed limit was 55mph. Now, just a few years after that it was raised up from the 55mph limit to 65 in most states. In 74 it was lowered because of the "gas problems". I could go on and on about that. But here's my though. The bike was designed to be a 55mph cruiser. Being that Kaw never modified the bike. Just a couple of years after it was introduced, tha average highway speed went up. The bikes gearing didn't. What do you think?


Quote:
1987 and 1988 65 mph limit
In the April 2, 1987 Surface Transportation and Uniform Relocation Assistance Act, Congress permitted states to raise speed limits to 65 mph (105 km/h) on rural Interstate highways,[12] and in 1988 Congress extended the same 65 mph limit to any rural roads built to Interstate standards even if they were not signed as Interstates (although states had to apply for this privilege).
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post #2 of 24 (permalink) Old 07-07-2008, 04:00 PM
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Sounds reasonable.
Also, the fact that the engine was first designed for the Ninja, which is high reving due to the nature of the knee scraper bikes.


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post #3 of 24 (permalink) Old 07-07-2008, 04:12 PM
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An intresting theory, but only good if they only made the bike to sell in the United States. They didn't. The Vulcan sold in Europe, Africa, Asia , South America and Canada....all which have diffrent speed limits on their major roads.

This thinking would also mean that from it's inseption , the designers/engineers wanted to build a bike that "worked best" at a specific speed...and I kinda doubt they do that, except for perhaps scooters.

My FJR is turning about 3500 rpms at 75 mph, at 5000 rpms it would be around 110mph..no where near red line yet.....and many other bikes are comparable here.

Harleys run diffrent, sportbikes, goldwings, etc..I doubt any bike is desgined with national speed limits in mind.........


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post #4 of 24 (permalink) Old 07-07-2008, 04:14 PM
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Your arguement would be sound except for the fact that the bike was exported as is to other countries whose speed limits were higher with no modification at all except the 700 limit in 85.
I think that the engine likes it up there in the high rev area and was designed for it. I think Kaw saw that the speed limits were going to go up anyway and released the bike accordingly. Just my thoughts.

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post #5 of 24 (permalink) Old 07-07-2008, 04:51 PM
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As a rule, DOHC engines come alive with higher rpm's, perhaps that why these were geared that way.

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post #6 of 24 (permalink) Old 07-07-2008, 09:45 PM
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I'm with Jon above. Mine runs so much smoother and is noticeably more responsive after riding at 6000 RPMs in 5th gear for a while. It's as if she wants to be ridden in that range. It seems to clean her out, and there's none of that small backfiring when decelerating or going slow, after a high RPM ride.

Still, I really wish she had a 6th gear for highway cruising. Seems it would save on gas and perhaps gain a longer engine life.

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post #7 of 24 (permalink) Old 07-07-2008, 10:17 PM
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I've said it before. My Vulcan seems to prefer to be running at around 5500 - 6000 rpm. I have to work at keeping it under 5200. 6000 rpm is still 2500 under the red line. I'm trying to keep it mostly around 5200 on the hi-way however. My concerned is fuel consumption.

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Last edited by kay; 07-07-2008 at 10:30 PM.
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post #8 of 24 (permalink) Old 07-07-2008, 10:47 PM Thread Starter
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post #9 of 24 (permalink) Old 07-08-2008, 01:07 AM
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There is some logic to speed/RPM/gearing discussion. My GL500, also a high rev v twin built in the 80's has a red line on the speedo at 55 and beyond. 60 mph turns 6200 rpms (with a 10k tach redline). As for the willingness for engines to 'want to run faster' at higher rpms is also true. Every combustion engine has a power curve where everything (valves, combustion, intake, exhaust, jetting) come together for maximum efficiency. Most of us old two stroker's called this 'coming on the pipe'.

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post #10 of 24 (permalink) Old 07-08-2008, 09:02 AM
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Quote:
Originally Posted by dirtrack650 View Post
Most of us old two stroker's called this 'coming on the pipe'.
Ah, yes 2 smokes.......
Give it gas.....start going fast...... then.........all of the sudden..... H O L D - O N.....there ya go >>>>>>> ZOOM ZOOM...............


AKA: Tim & 'The Adventure Cycle' VROC #24567, NEVROC, SteelCity VROC


"When life throws you curves,
Aim for the apex."

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