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Discussion Starter · #1 ·
I was riding my GL on the freeway yesterday and the damn thing pulls so hard. Even at 90mph, it seems to have so much more throttle. I wimped out going any faster. Maybe after I shake it down with a bit more miles, I'll open her up and see what she can do. I only have about 200 miles on it since the rebuild.
I'm just so surprised at how much power it seems to have, even near the ton. Anyone know where it tops out?

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1978 CX500 "The Grub", 1983 GL650I "Nimbus"
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Spec'd top speed is 108mph at redline.
 

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Discussion Starter · #3 · (Edited)
Spec'd top speed is 108mph at redline.
Interesting, only 108. At 90, I felt like the bike was still pulling extremely hard, much more than another 18mph. Maybe the bike now being much lighter combined with my tuning (pods, jets, open exhaust) has more in it. I'll have to remember to weigh it one of these days. Regardless, all of it is fast enough and a thrill getting there!
 

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You'll have to tell us the indicated top speed once you get there!!! Have you ever tried comparing the bike speedo to a GPS or GPS app?
 

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Have you ever tried comparing the bike speedo to a GPS or GPS app?
The Grub shows about 4% high, consistent with all the cars I've had (since owning a GPS), with the exception of my wife's 2017 Sienna.
 
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At 90 mph, you're already spinning over 9000rpm. Redline is 9800. (Or is it 9600?)
With the smaller 16" rear, spec for the GL500 might be a little less, unless the higher profile tire makes up all the difference.
 

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108mph is pretty good.......(remember that)
the late 1970s, 750cc of the time were bout 120mph if no gearing changes...

The big ticket items in the ol' showrooms were the Kwaka 900s and new Bmws of the early 1980s that were good for 150to160mph.....😀

Worth noting that many period tests showed results for rider seated and rider prone....usually a difference of up to 5 to 8mph....
 

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I tap out before the bike tops out.
 

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I found 104mph on MotoFaction, citing Cycle World. I don't know if those were long UK miles or short US miles.
 

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Worth noting that many period tests showed results for rider seated and rider prone....usually a difference of up to 5 to 8mph....
Absolute top speed is a function of gearing and rev limiter. Drag is a secondary factor that varies.
 

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Fwiw...theres also reference to earlier 500 engines having a higher power output....
Dunno if this is the methodology used or real life differences....


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So, if you run it past redline, it will continue to accelerate until the valves float or something goes boom in the crankcase. The top speed is limited by gearing for this bike. You can swap the 650 clutch and primary gear into the 500 and get higher gearing for theoretical higher top speed, but I don't know if the engine has enough power to reach redline in 5th with that gearing setup. Someone here probably does though.

Charles.
 

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I assume the testing was on the early CX models....inline/close to the 116mph I linked to.
The 750s did about 125 even for the later DOHC....except for the Auto that topped out at 97mph...:confused:
 

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I would take this with a grain of salt although the figures aren't far off the mark simply because it begins with the 'factoid' about the CX engine originally being designed for a car. I don't think this is true but given Hondas micro engined cars of the 60s and 70s I wouldn't entirely rule out a kernel of truth.

I'm thinking the power loss refers to US modlels after the venturi size was dropped and accel pump fitted to compensate.

For the rest of the world though, likely no change.
 

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They do make a shitasston more power with Murray's carbs, so I wouldn't doubt it. I also remember riding a customer's 78 with a MAC 2-into-1 and a properly rejetted carb, and the thing was a ROCKET compared to my 82 CX500. I thought it was just the mac, but putting a mac on my 82 didn't give me the same results.

Hrm, I'm working on a 1980 CX with 82 wiring harness right now. I need to check what carbs I've got on it, and see if I have the earlier model carbs in my parts stash somewhere...

Charles.
 

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I was riding my GL on the freeway yesterday and the damn thing pulls so hard. Even at 90mph, it seems to have so much more throttle. I wimped out going any faster. Maybe after I shake it down with a bit more miles, I'll open her up and see what she can do. I only have about 200 miles on it since the rebuild.
I'm just so surprised at how much power it seems to have, even near the ton. Anyone know where it tops out?

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The lighter weight has zero impact on top speed, but it will impact how quickly you get there. Top speed is going to be a function of engine rpm and what you can do to either cause less drag, or to raise the engine rpm. As said earlier, a tire change may have altered your theoretical top speed. From my experience racing the CX650 turbo, the factory speedo is off by six or seven mph when you are at top speed.
 

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Don't worry about it. Top sped doesn't matter unless you are on a track with a long enough straight (or maybe a deserted highway in the desert). Even a 250 will go fast enough to send you to jail if you do it on public roadways.

What really matters is how quickly it will accelerate to the sped you can drive at......

At 90 mph, you're already spinning over 9000rpm. Redline is 9800. (Or is it 9600?)
With the smaller 16" rear, spec for the GL500 might be a little less, unless the higher profile tire makes up all the difference.
It is the diameter/circumference of the tire that matters, not the wheel and the stock tire sizes for the 16" & 18" are close enough to identical that it won't make any difference.
 
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