Slow top speed? Or not?

[tonyfan70]

I have searched this forum and can't seem to find the answer.
My 98 runs great, I have shims and the pilot tool to do some fine tuning this winter for the common surge, but otherwise it's great.
I was curious and did some high speed riding to get some gear/rpm numbers and got the following at redline:
1st=50 mph
2nd=75 mph
3rd=102 mph
4th=125 mph...but I felt a "skip" every so often over 9000rpm, like in 1st when the tire spins over cracks in the road.
5th=128 or so...not redlined just wouldn't go any faster..

This is stock gearing, muffler mod, 180 Metz on the rear. I do have a Hondaline windshield on her too. Am I running out of guts at 125 in 5th and can't overcome the wind resistance or is there a problem? I thought I had read the top speed was 140 on these, but I was somewhat disbelieving of that...thats alot for a 750, even a Magna.

Like I said, I have no other issues that make me think I have any problems, but I was suprised that was it for the top speed. It's probably best, my girlfriend hates me when I do this kinda of thing anyway!

[Greg Cothern]

Those #'s seem appropriate.  This is the limitations of a smaller cc engine.  Just simple reached the end of its power.

[dc112675]

I reckon when the white stripes on the road appear to be solid, you're going too fast.  I have seen triple digits but have no desire to go beyond the century mark.  The ithought of my body skipping across the pavement for a 1/4 mile is not as exciting as it once was.  

As for the top speed, I believe I read on a forum that one guy had it in the 30's . . . either 132 or 137 as I recall.  My guess is that a few factors come into play as you hurl your body at such speeds.  

1)  Are you daring (read: do you have guts)?
2)  How much do you weigh (read: do you have a gut)?
3)  How much does your passenger weigh (just kidding . . . i hope)?
4)  What accessories do you have?  This effects weight and aerodynamics.
5)  How much gas is in the tank?  Probably not a big deal, but a full tank weighs almost 30 lbs.
6)  Are you going downhill?
7)  Is the wind at your back?
8 )  How many teeth do you have (on your sprockets, not in your mouth)?
9)  What tire size are you running?

I can't figure out if the tire makes any difference.  Either you have a smaller tire that needs higher RPM, or you have a bigger tire that needs more torque.  I suspect the wind would be a bigger factor.  My Magna hits 45 mph at 3k rpm & 60 at 4k rpm.  So using simple math, it should hit red line around 145.  Either way, you are going to have to do the real life testing.  But good luck.  

BTW, at what speed do you think you can get the optimal mpg?

[tonyfan70]

Thanks guys. This isn't an everyday thing by any means. Just curiousity. Truth be told, when I'm feeling frisky and ride fast, once in a while, it's not nearly as scary as riding in town at 40 and under with every tard on the road trying to pull out in front of me!
Usually I ride about 70 mph on the interstate with some brisk riding on the back roads. I haven't checked for optimum mpg's but I alway get 110 or so when hitting reserve, from what I've read this is about average.
I was thinking...Usually vehicles with OD will go as fast, if not faster in the 2nd to highest (read non OD gear) than in top gear. EX: 5 spd Mustangs have a better top end in 4th. If this is the case, and given the range in 1st being 0-50, I could drop down a tooth on the countershaft and improve my acceleration times. Would this also bring the rpm's up in 5th, maybe bringing the engine into more of the powerband? I realize that in theory my top end would be lower, but since 4th and 5th give me about the same, would the gear change enable 5th to give me a few more miles per hour on the top end?
BTW...this was alone, 3/4 tank of gas, accesories as pictured, I weigh 170, stock gears (16/40 IIRC), level ground, calm wind. Rear is a 180/70 Metz which I think is 1/2 different..taller or shorter I don't remember.

[swader]

well i know i was trying to get from north Richland hills to lower Greenville. and was on a stretch of highway and twisted back and i know i was well into 140 i just held the throttle allthe way back till i was where i needed to exit... there weren't any... well.. many cars on the road at the time but yeah i was scootin pretty good... lol it blew off my side covr and didnt know it till a couple days later...  but yeah they will get up there!!!