Hi,When my sons 50 boy is warm I cant start it again when the engine stops. I have cleaned out the carb and there is a good spark.It use to start fine, I have messed about with the mixture but that hasnt helped ( does anyone know the correct settings for the mixture screw )i would be very grateful for any advice.

check reeds are sealing on the reed block and that reed block/carb manifold is sealed and you dont have an air leak have you changed the plug ? could be weak ingnition it may spark when earthed on the cylinder head but may not under compression good luck

Hi,When my sons 50 boy is warm I cant start it again when the engine stops. I have cleaned out the carb and there is a good spark.It use to start fine, I have messed about with the mixture but that hasnt helped ( does anyone know the correct settings for the mixture screw )i would be very grateful for any advice.

check reeds are sealing on the reed block and that reed block/carb manifold is sealed and you dont have an air leak have you changed the plug ? could be weak ingnition it may spark when earthed on the cylinder head but may not under compression good luck

Hi,Thanks a lot for your reply.Unfortunatly things have got worse, it wont start at all now. I took the reed block / carb manifold off today and checked the rubber for splits, all was ok. I have tried 3 different plugs and cleaned up any electrical connectors I could find,Im sure it must be the carb, I started it yesterday and messed arounnd with the mixture screw to try and get it running better, but have messed it up. I dont know what to do now, does anyone else have any ideas that i can try? thanks.

Hi, I'd test the stator. West Country Windings will test it and re-wind if req'd.

http://www.westcountrywindings.co.uk/

Best of luck, these bikes are notorious for not starting.

Hi,When my sons 50 boy is warm I cant start it again when the engine stops. I have cleaned out the carb and there is a good spark.It use to start fine, I have messed about with the mixture but that hasnt helped ( does anyone know the correct settings for the mixture screw )i would be very grateful for any advice.

There is really no single "correct" mixture screw setting. So for what it's worth, my air screw is 2 1/4 turns out from closed. The rest of my carb is set up as follows:

main jet: 70

pilot jet: 36

starter jet: 50

slide: #40

needle: type A2 with clip in 2-nd from top groove

My starting procedure when bike is cold:

1) choke ON, throttle completely closed

2) lazily push kickstarter several times until I start to feel occasional resistance

3) give it 1 or 2 swift kicks and it should start. But if it doesn't, then go back to step 2

4) turn off choke pretty much right after it fires up

My starting procedure when bike is hot:

1) choke off, throttle WIDE OPEN

2) several swift kicks gets the motor running

There is really no single "correct" mixture screw setting. So for what it's worth, my air screw is 2 1/4 turns out from closed. The rest of my carb is set up as follows:

main jet: 70

pilot jet: 36

starter jet: 50

slide: #40

needle: type A2 with clip in 2-nd from top groove

My starting procedure when bike is cold:

1) choke ON, throttle completely closed

2) lazily push kickstarter several times until I start to feel occasional resistance

3) give it 1 or 2 swift kicks and it should start. But if it doesn't, then go back to step 2

4) turn off choke pretty much right after it fires up

My starting procedure when bike is hot:

1) choke off, throttle WIDE OPEN

2) several swift kicks gets the motor running

Hi,

Thanks a lot, I will give it another try using your suggested method.

Hi,

Thanks to all who replied, I got the bike going today and it seems to be ok.Gas Gas UK recommended only putting 50ml of oil in 5ltrs of fuel, and setting the air screw at 2 3/4 turns out. Will give it a good blast at the weekend to blow all the muck out.