No power and stalling when accelerating

[nhewitt]

I have a 2002 Derbi Senda 50.

The bike was due to be sold today and when I started it up to give it a quick run about it just wouldn't move.

It starts first time and idles but when I put it into gear and let the clutch out it sounds very boggy and travels at about 1mph and when i stop it just cuts out.

Brand new spark plug, reg/rec, battery etc, the carb has the correct main jet inside.

I have played around with the idle screw and air mixture screw but its no better.

I have taken the air filter off in my garage and started it up and the revs went very high but again no power on acceleration.

[frostage]

Compression?
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2000 Gixxer 750
1995 RM 250

[wots]

Carb off and clean float bowl etc.

Worked with two scoots I've had recently with exact same issue, one was a 50cc 2 stroke and another a 250 4 stroke.

Carb off, can of carb cleaner and go to town it. Float bowl off and make sure there is no nastiness in there. Make sure you get a carb cleaner with the long pipe on and stick it in every orifice!
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Currently: Yamaha DT 125 LC2,Repsol Fireblade, and Bumblebee MSX 125

[nhewitt]

I will give the carb a good clean tomorrow. the float bowl seemed fine this morning when i changed the jet.

Would a clogged air filter stop the bike from moving at all?
i took the filter off and it ran the same just alot higher revs when at idle.

[bradh511]

Have you tried a new plug or cleaned old one up
Most 2t will oil plugs up ... Are you running it premixed?
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Theory 11-10-12 lets hope i get mod 1 and 2 done by the 18th of jan 2013

[bradh511]

Also check all the jets sent blocked
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Theory 11-10-12 lets hope i get mod 1 and 2 done by the 18th of jan 2013

[J.M.]

[nhewitt]

seperate oil tank and i changed the plug last week and the old one was brownish so a good plug. took the new one out today and its a little bit sooty.

The kicks over every single time its just when i go into first gear and accelerate there is literally nothing there, and then it cuts out when i take the revs off.

it idles perfectly fine and when i took the air filter off there was no power at all again, but the revs were alot higher and it didnt cut out when i took the revs off.

[nhewitt]

I upjetted the carb this morning as the previous owner didn't do this after putting a new exhaust on there.

I started the bike and took the fuel pipe off the carb and fuel was coming out with a good free flow

[nhewitt]

[J.M.]

[bradh511]

Do you have to bump start the bike ? Also I'm wondering about a csi fault... But that a cdi and coil pack all in one I would check reads are in correctly I have seen them put in upside down before but can't remember if here's any thing stopping u doing this ... I would comp test the bike also just pull reads out and look for piston scoring if I remember right just look in reed inlet to barrell also is there any cracks in carb rubber and the sitting right it will not rev if u do not have air filter use a pair of tights folded a fewtimes to restrict air if when it's running and u rev it goes burrr then your in need of a filter the reason say to check piston is any marks or scores the bike may have been heat seized
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Theory 11-10-12 lets hope i get mod 1 and 2 done by the 18th of jan 2013

[nhewitt]

took the plug out last week a brownish colour indicating a good plug. replaced with a new one and today it is a bit sooty.

[nhewitt]

[Rogerborg]

[nhewitt]

The jet was too small as it had the original jet and it has been derestricted, with an aftermarket air filter and exhaust so I fit the new one earlier.

The bike was running like this the other morning also, I just haven't had time to look at it due to bad weather outside!