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Old 08-22-2012, 10:35 AM   #1
paulisnofun
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My GZ 's top speed seems low

After a short amount of time practice riding in my neighborhood, I decided to actually taker her (2002 GZ250. 4500 miles) in to the real world. Yesterday was the second time I rode to work, and noticed that the bike doesn't seem to have the (for lack of a better word) balls that I thought it would. Reading on the forums, I saw that people had a top spead of around 70 miles per hour, and I am not close to that. I have about a half an our comute to work, no highway, just plain old suburban roads (mostly flat). The max speed limit on my route is 45, so I am not looking to go 75, but feel like maxing out at around 50 isn't right. That is 50 in fifth gear, with the throttle totally open.
Now, I am a bigger dude. I am six feet tall and weigh about 245 or so without my helmet and laptop bag. Would the fact that I am about as many pounds as my bike has CCs lower my top spead by that much? If not, where would be a good place to start looking to see where the lack of power comes from? I believe the person I bought the bike from said that a tune up had been done shortly before he sold it to me. Any help/advice would be great.
Thanks.



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Old 08-22-2012, 01:05 PM   #2
northsidegz
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Re: My GZ 's top speed seems low

Even at your height and weight and laptop load, you should be able to reach 70 I would think (based on what I know from riding my GZ at my height of 5'10" and weight of 225). You're definitely taller and heavier, but you should still be able to go 65 still without too much struggle. Certainly much faster than 50 on an open throttle! It's going over 65 when other factors come into play (such as height, weight, wind resistance, road levelness, load, etc).

I don't know where the lack of power could be coming from, so I'll let the others chime in and try to help out there.
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Old 08-22-2012, 01:26 PM   #3
paulisnofun
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Re: My GZ 's top speed seems low

Thanks Northside. I knew something didn't feel right. I something similiar in another post, but it turned out the rider was reading the speedometer wrong. I did check that I was reading it right before posting.
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Old 08-22-2012, 02:17 PM   #4
dentheman
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Re: My GZ 's top speed seems low

I'm curious about what you mean by reading the speedometer wrong or right. Are you considering the speedometer inaccuracy? They generally read a higher speed than you are actually going. For example: When my Shadow's speedo is reading 70 mph I am actually going 66 per my GPS. This same inaccuracy also shows on my odometer and trip meters vs GPS mileage.
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Old 08-22-2012, 02:31 PM   #5
paulisnofun
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Re: My GZ 's top speed seems low

I don't want to throw anyone under the bus, but when searching for anything similiar I found this. viewtopic.php?f=7&t=6063&hilit=speedometer
I thought that maybe I was doing the same thing as that poster, but I am not. I have not yet rode with a gps to see how accurate the speedometer is, but in fifth gear at full throttle (I even tried to upshift to make sure I was in fifth gear), the needle tops out at betweek 50 and 55 (actually it hit 55 when I was going down a decent sized hill).
I am new to riding, and don't know much (anything) about engine, and don't know where to start. I'm just looking for some suggestions on where to start looking.
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Old 08-22-2012, 03:22 PM   #6
jonathan180iq
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Re: My GZ 's top speed seems low

Put the bike in neutral and blip the throttle.
If the revs hang up before coming back down, you have an air or vacuum leak somewhere that is limiting your overall power delivery.

Check the air filter for leaves or something similar glogging up the port.

There luckily aren't too many things that it could be, so we'll get through this.

Just by chance, have you checked your chain tension? A very tight chain will limit you there as well.
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Old 08-22-2012, 04:48 PM   #7
paulisnofun
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Re: My GZ 's top speed seems low

Thanks for the advice Jonathan. I will take a look when I get home.
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Old 08-22-2012, 08:34 PM   #8
paulisnofun
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Re: My GZ 's top speed seems low

The air filter was clean, and it didn't sound like the revs hung around. The chain is not too tight either.
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Old 08-22-2012, 10:52 PM   #9
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Re: My GZ 's top speed seems low

I wonder if the bike has ever had the valves adjusted. Do you have a history of the bike? You just may need to spend some TLC on the bike to make it happier on the road.
Tire pressures up, check for rear brake dragging, all controls lubed and working.
Oh, you said the air filter looked good. Did you take it out for inspection? The air filter has a reverse flow so you must look at it from the inside.
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Old 08-22-2012, 10:58 PM   #10
5th_bike
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Re: My GZ 's top speed seems low

Mine goes up to 60 no problem, after that it's a matter of slope, wind and time. Maxing out at 50 is a bit low indeed.
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