Top 20 2005 Derbi GPR 125 Racing Questions & Answers

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The seals in the caliper flex when the brake is applied, and when released, they return to their original position. When they do this, they are suppose to pull the piston(s) back with them. As they age, they tend to harden, and not work as good. You could try replacing the piston seals, and insure the pistons and their bores do not have any corrosion or crud on them.

earth is a ground

Earth goes to ground. In this case the chassis

up,forward is offdown,backwards on

If you do that, all that may happen is if you have a fault, the wire loom will burn out instead of the fuse.
Tuning should be carried out by a trained technician.

the fuse idea is complete rubbish do not attempt !!!!

You can get a 150cc bore kit from derbi which is very easy to fit and cheap. It's on derbi.com and will give you a performance increase of about 5 HP bringing your total to about 20hp. Once you do that you can get a bigger exhaust also from derbi which should add another 3hp. I have the derbi gpr125 4t and I have done all the above, top speed is about 90mph and accelerates very very fast. Good luck.

YTX5L-BS Got mine from ebay.
http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=190434638024

GPR125 '05 model engines have a piston of 56mm diameter

Ride safe
Bike-Doc
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if you can get it off of the bike which should only be a couple of bolts and a wire harness...take it to a good locksmith. They might know a trick on how to get the broken piece out. good luck.

I can't find the a micro phish on but if i where to guess where to start it would be the start clutch or idler gear
Some bike use a sprag clutch it lets it engageone way and free spin the other works great but can get worn out.
Pull your starter out most bikes two bolts and a + wire that comes from your relay. after you have in your hot light hand take a battery and a set of jumper cables clip the groung (-) the body and the positive (+) the to the post. Now clip the ground to the battery and while holding the starter down touch the positive to the battery if you start is working right it should spin fast and want to jump off the table. if so check your starter clutch, or idler gear.

I too would head for the speedo cable, but if you say you have checked it let's move on. Did you try "removing" the speedo calbe yet? Might be worth a try. After that we're looking at brakes, wheel bearing, or an interferance issue. Have you tried setting the front end up on a tire stand and rotating the wheel by hand to see if you can replicate it without riding? I would start there.

put the bike in gear and go down a hill and let clutch out and see if it starts if it jams or skids or doesnt go get back to me

yh you have to select a certian mode and put in a code or something like that i got told in a shop i got mine from so if u have a booklet or a shop near you they would probly do it for free but i THINK you need a code

No kick start is availabe as an add-on. You will need to install a new battery.

It could be the sensor needs to be changed... In some cases it occurs cuz of the voltage drop of battery output... how old is your bike cuz if its a few yrs old it might be the battery

any competant shop should be able to remove disassemble and clean the brake calipers -replacement would be expensive

There is a video on youtube showing you how yo do this, you install a 15amp fuse under the seat...

The Gilera SC is the same as a Derbi GPR ,right? This is how I change the time on my Derbi Tap the button until it goes to the clock then hold it in until it starts flashing. Tap to change the hour then leave it for a second and it will move over to the minutes and cycle through, just tap it to stop on the right time. The batteries are **** though so don't expect it to keep the time, you'll find yourself having to set it nearly every time you start your bike.