20 MPH speedo error?????

[Toe Dragger]

Was riding with another rider last week.

At one point my speedo said 135, he said his only got up to 115. I bought my bike used and it has several modifications so is not far fetched to think the sprokets may be different.

Question is....how can I tell?

Will more or less teeth front/rear cause it to read to high? Would this result in more actual top end speed or more low end acceleration?

I'd like to gear it for more acceleration when I replace the chain soon.

Thanks for any info you can offer.

[~Barn~]

Was riding with another rider last week.

At one point my speedo said 135, he said his only got up to 115. I bought my bike used and it has several modifications so is not far fetched to think the sprokets may be different.

Question is....how can I tell?

Will more or less teeth front/rear cause it to read to high? Would this result in more actual top end speed or more low end acceleration?

I'd like to gear it for more acceleration when I replace the chain soon.

Thanks for any info you can offer.

Any gearing change will affect your speedo and odometer. Gearing down (read: less teeth up front OR/and more teeth out back) will result in lower top end speed but increase low-end.

Also, that setup will cause more miles to be put on the ODO and a higher-than-actual speed displayed.

That being said, a reverse of the above will result a opposite results.

[badassbusa]

looks like you have 1 tooth down on the front sproket. you can buy a speedo healer & you can fix that problem.

[~Barn~]

Hope that helps. And to answer your other question about "how to tell"...

Go out on a HW, and find a milemarker. Reset your ODO and ride out the HW out as far as you can/want. 1 or 2 or 100 miles.

When you stop. Hopefully you stop at the completion of X mile you're on... Compare the ODO reading to how far you actually went.

Do the required math, and you can figure out what % your readings are off.

HW Milemarkers are very accurate and they are placed by engineers and such. That is your best bet.

Other school of thought is to pace a friend in a car and have them tell you what their SPEEDO says when yours says 50/60/100mph... Whatever... Obviously you have to have a signal worked out, whatever.

In my opinion, that school sucks. Go to my school.

[1000RR]

Or borrow someone's GPS

[~Barn~]

Or borrow someone's GPS

And then let me have it after tellin them you lost it.

[King Nothing]

when bertha's bike is working, i just ride up next to him and look at his speedo, it's dead on....

[Toe Dragger]

Hey thanks for the suggestions!

I just had an idea!

I have a watch for runners that has a GPS unit you wear on your arm. It talks to the watch and tells your exact speed and distance.

I think I'll take a little trip.

I don't think I'll go back to the stock setup...my bike already pretty weak in the acceleration dept. Just doesn't pull like I think a 750 should. Ridden 600's with more ass kick it seems.

Thanks fellas.

[bill]

You can use a bicycle computer. I put one on my Superhawk about 8000 miles ago and have had no problems with it. It is very acurate, I can ride for 20 or 30 miles and still be hitting the mile markers right on the money. It also gives you a clock, trip odometer, ride time, max speed, and odometer. I bought mine for about $30 and put it on a small bracket i built and attached to one of the instrument cluster bolts.