Derbi gpr50

[Turborange]

Hello

I have a 2005 gpr50 which isn't running right by any stretch of the imagination.

When I got it it had an arrow exhaust fitted what else I am unsure. There was a flat spot between 6-7k. The idle was a bit rough and sometimes didn't idle at all. A quick spray of carb cleaner on the body of the carb and the was an idle. But when it came to riding it you had to have the choke on a bit. I took it and a so called bike specialist who had the bike for 7 days and charged me £70 for the privilege. The bike then would not start at all. I called the aa out who on removing the plug show petrol dripping off the plug. They semi got me running again no choke at idle but choke to ride and still have flat spot.


Do you think that the carb is knackerd or is it just the jet needs doing.

Does anyone have a setting to go by on these carbs? I am now reluctant to take it to another bike shop to have my pants pulled down again. I am fine with spanners so doing. The work myself isn't to much of a issue. Based in Sheffield all help would be appreciated

[N cee thirty]

get a new plug,is it jetted correctly to suit the exhaust ?

maybe the compression is being lost

clean the carb aswell
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'00 Aprilia RS50 > '92 Honda CG > '99 Yamaha Fazer > '91 Yamaha RXS > '79 Suzuki X5 > 01' Honda Cg > 07' Honda Cg > 82' Kawasaki Z200 > suzuki gsxr 400 gk73a > honda vfr 400 NC30 Mod 2 Passed 09/06/2011

Jewlio Iglesias wrote: I actually did vote BNP once

[Turborange]

Don't know if it's been jetted what size should it be and where would I get one

[N cee thirty]

well you'd have to do a plug chop

ride down the road and get to full revs and then cut the ignition and roll to a stop.check the plug colour then,if its dark and sooty then its running rich and you need to go down about 5 jet sizes,if its looking whiteish go up 5 jet sizes until there looking a tea colour

you should be able to get a pack of jets off ebay or somewhere like that.

check the airbox aswell to see if the foam is good.

get a haynes manual for your bike and it should have the settings for the carb
____________________
'00 Aprilia RS50 > '92 Honda CG > '99 Yamaha Fazer > '91 Yamaha RXS > '79 Suzuki X5 > 01' Honda Cg > 07' Honda Cg > 82' Kawasaki Z200 > suzuki gsxr 400 gk73a > honda vfr 400 NC30 Mod 2 Passed 09/06/2011

Jewlio Iglesias wrote: I actually did vote BNP once

[Frost]

Sounds like it's running richer than a rich thing that's just won the lottery.
New plug, find a manual online somewhere and find out the following:

Mixture screw position
Jet size
Needle height

Someone compotent with the spanners could remove, strip, clean check, rebuild and refit the carb in half an hour or so. You could probably do it in a few hours with the following tools:

Screwdrivers, flat and cross head of various sizes
Spanners, 8mm, 10mm, 12mm
And thats about all you need to do most jobs on most bikes, well worth buying!

The bike needs the following to run right:
Compression
Fuel
Spark
Air

In this case it sounds like fuel is probably the issue from someones past attempts at tuning. But don't forget the others! Check the airbox fits properly and seals onto the carb. Make sure it has no water in it and that the air filter is clean.
Put the spark plug against the engine and press the starter and see if it sparks
Compression is a bit more of an issue to check an requires a special compression tester and a rebuild to fix. So it's best to rule out everything else first.

[Turborange]

I have thought all along that it is fuel that is the issue here. I have already done the spark which is spot on. I have a compression tester so it's just a case of finding a manual for the correct compression and carb settings. I didn't see a filter element in the box. Would a k&n be ok or similar filter. I have a small one kicking around off one of my old cars oil breather system

[N cee thirty]

anything over 120psi is ok compression


it would be best to find some foam and cut it in the shape of the airbox to put it to standard

the k&n would just be cheating the mixture without making it right

https://cgi.ebay.co.uk/AIR-FILTER-GREY-FOAM-12-X-12-x-1-2-cut-shape-/130434650884?pt=UK_Motorcycle_Parts&hash=item1e5e82d304

i put that in my mates rs50,to come to think of it he had the same problems as you,all i did was change the plug and replace the air filter foam and it ran nicely
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'00 Aprilia RS50 > '92 Honda CG > '99 Yamaha Fazer > '91 Yamaha RXS > '79 Suzuki X5 > 01' Honda Cg > 07' Honda Cg > 82' Kawasaki Z200 > suzuki gsxr 400 gk73a > honda vfr 400 NC30 Mod 2 Passed 09/06/2011

Jewlio Iglesias wrote: I actually did vote BNP once