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Carb issues

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Carb issues

Post  ScottT on Wed Jun 08, 2016 9:09 pm

30C engine, S16 carb.
The engine has had electronic ignition fitted and the carb was reconditioned by Villiers services, it starts 1st kick 98% of the time, 2nd kick the rest.

Looking at the spark plug it is running very rich and seems a bit down on power. After a test run and i'm looking at 30-35mph max on the flat, it should be better than that shouldnt it?

I've tried a colourtune on it and all i'm seeing is an orange flame (rich), no blue at all anywhere through the rev range.
The carb has had a new (size 80) main jet, the needle height is at the correct 2.015 and the air screw 1 1/2 turns out (as suggested by Piston 197 as the factory settings)

The bike will start without using the choke even after being sat for a couple of days, the only way i can get it to tick over is by adjusting the throttle cable, the air screw makes no difference to the tick over no matter how far or which way i turn it. And i'm running it at 40:1 using a modern synthetic two stroke oil.

Any suggestions as to what i can try to lean it off and what performance should i be looking at when it is running right.

If this helps i took it out and rode 12miles without any problems, stopped for 10-15mins set off again and 5 miles later it felt like it didnt want to rev, not wanting to risk anything i stopped had a fag break started it again and rode 7 miles back home with it feeling the same as it was when i started, it felt like it would rev but still felt down on power.

Bike is a Cadet 150.
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ScottT

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carb

Post  piston 197 on Thu Jun 09, 2016 6:07 am

I would try lowering the needle if you are running mix of oil weaker than 20 to 1 it will pass the jets quicker.
JH
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piston 197
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Re: Carb issues

Post  ScottT on Thu Jun 09, 2016 8:36 am

Thank you John, how far would you suggest lowering it?
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lowering the needle

Post  piston 197 on Thu Jun 09, 2016 10:25 am

would suggest set pilot air screw 1 1/2 turns out, then try lowering the needle one turn of the screw at a time and trying it up the road, the fact that it is so rich and the moving of the pilot airscrew makes no difference suggests it is getting fuel past the needle/needle jet when it should not i.e. the needle needs lowering ??
JH
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Re: Carb issues

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