Derbi GPR 50CC 2007

Poor rear sprocket fitment - keeps coming loose

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VR46
10/09/2010 at 10:47
Hi All,

My Nephew has just got his first bike, a 50cc 2007 Derbi.

I check his bike regularly to make sure all is OK and I have noticed straight away that the rear sprocket bolts keep coming loose.

I have tried loctite thread lock but the bolts still work there way loose.

This could potentially be a big problem and could cause the rear wheel to lock up on him.

I am now looking to put a solution in place, Studs appear to be the best option. By using studs and nuts this would also protect the rear wheel threads from damage as a result of tightening up bolts repeatedly.

Anyone from here had a similar problem?

fastfitter
10/09/2010 at 17:00

You're not the first sadly - http://www.visordown.com/forum/forummessages/mps/dt/4/UTN/10029/

Studs would seem to be the way to go

VR46
10/09/2010 at 20:20

Thanks for your reply.

 I wonder if the Aprilia RS 50 of the same year has the same problem? Both bikes look exactly the same but possibly the aprilia may have improved sprocket fitment.

I would of thought that this fault would be widely known all over the Net but I have not found much info.

fastfitter
11/09/2010 at 06:42

I'm not well up on tiddlers I'm afraid. Is the Derbi just a badged Aprilla? If so it's probably the same set-up. Not that many Derbis on the roads over here so maybe there's no wide-spread info available.

The problem looks to be a lack of any sort of cush drive so any transmission shocks will go straight through the mounting bolts. Add a teenager with clumsy gearchanges and probably a bone-dry and loose chain ...... <img /><img />

axial basher
01/10/2010 at 16:59

Hi

My son has a 2008 Aprilia RS50, the back sprocket is held on by nuts screwed on to stud's. You can use Aprillia parts to change to stud's.

VR46
26/11/2010 at 09:37
Update for any other unfortunate Derbi GPR 50 '07 owners.

Repair job:

Aluminum swingarm removed and professionally welded.
New chain & sprocket kit - Steel rear sprocket chosen.
New high tensile sprocket bolts.
Sprocket bolts fitted and spot welded in place.

There is also a recall notice on this bike stating that the front area of the chassis may crack badly and break resulting in a crash.

Derbi design and quality is crap.
waspie
27/02/2011 at 11:40
hi my son has had a crash on his derbi 50cc 57 reg the front headstock tube was torn from the aluminium frame the front was held on by the wiring has anyone else had this happen ? please if someone has can they let me know as i want to take this further my son was so lucky he was not going fast and no other cars near him as could have been fatal
VR46
05/05/2011 at 11:34

Hi Waspie,

Glad you Son was OK after the accident. There is definately a big problem with the chassis and all models should have been recalled.

The frame can crack below headstock area, more info here:

http://www.bikechatforums.com/viewtopic.php?t=176680

Edited: 05/05/2011 at 11:37
marra176
31/08/2011 at 22:14
Ive rebuilt my 2005 engine, now i cant get my gears, any ideas what ive done to the gear box, i didnt touch it only put crank and bearings in.
shoppy
05/10/2011 at 07:40

hello, i have recently brought a derbi GPR 50cc, im loving the bike and the way it rides, one slight problem it seems to smoke alot out of the exhaust when i take it past 700rpm?

can any one tell me why this would be?

please let me know would be much appreciated

matthew gill
17/08/2012 at 16:40

hi im putting a derbi gpr 50cc racing together and was wondering if anyone has a wiring diagram or know were i can get one from thanks

tappy
18/08/2012 at 19:02

There are quite a few wiring diagrams here, and I think this is the Derbi GPR50 Racing here.

arrrf.
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