my alpi na is driving me round the bend,it wasnt running when i got it,i had the motoplat checked by bradford ignitions and everything is ok,ten got it running,but running very flat and smoking,and wont idle,so i renewed the engine seals,still running flat and smoking,so rebored with new piston,still flat and smoking, what now ? ive cleaned the carb out everytime so far,ignition is at 2,6mm btdc,looking like a complete strip down now,when i spun the flywheels i noticed there was some oil at the bottom of the crankcase,which came round when i spun them,could this be the gearbox leaking ?anyone got any ideas cheers andy

I would try cleaning the exhaust out. The Bultaco exhausts do clog up after a while. One way is to throw both parts on a fire and leave them there until they get very hot or use an oxy/acetylene torch and burn them out. It would also help to repack them but see if that works first. The slide on the Bing carbs also wear very quickly so check that as well.

Oil on the crank wheels is natural, excess of oil not good.

You didn't say what mixture, 50/1 is good.

Try another carb before going deeper (center gasket).

Good Luck

Larry

Carb is good slide is good,my next move was to empty the petrol and try some fresher fuel,I put extra oil in before,just to oil it up a bit,the exhaust system is new one so I wouldn't suspect that cheers andy

Andy, When you cleaned the air filter did you by chance over oil it?

Good luck

Larry

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ive tried it with and without the filter,ill check the timing again today,does anyone have any info on timing with a motoplat ?is it as ive done ?lining up the tiny holes when 2.6 btdc cheers andy

That's good timing should be between 2.5 to 2.7mm BTDC.

After the first running in procedure I would take out the bike and go for a longer ride on the street, starting carefully, going around 20km/h then advancing up to 50, going down again to 20km/h gearing up and down btw. and just drive in different rpm and under different loads just for let's say 15 Min so everything gets warmed up proper and any eccesive oil from mounting the new piston ... is really burned away.

When you start the engine just outside the workshop/garge and let the motor idle there this might not handle all exessive oil the rebuild.

If the bike is then still smoking a lot and you have changed the petrol then you might have an issue with the main seals at the crank again...

Cheers for the replays,this is where I'm at now,I drained the fuel and fresh fuel put in,reset the timing with dial indicter,started her up without the tank on,knowing it would cut out,and it was still the same,but A lot of fuel coming out of the intake ,and as the fuel started to run out it picked up to what it should be like,which makes me think that it's a fuel problem,ie,to much fuel is bogging it down ,and to much fuel making it smoke,so I change the float, and needle ,and adjusted the float level to different settings ,but no change,today I'll change the main jet,to see if that changes anything,but no strip down as yet cheers Andy

Try a known good carb if possible.

Is there anyone in the wolverhampton area with a bing 28 I could borrow ? I changed the jets not a lot of difference and took the rear silencer off to see if it made a difference but nothing so it's looking like a trip soon and start from scratch

That almost sounds like the needle and needle jet are very worn. The Bings are known for this. Also you have to check the timing with a multi meter or a powered light to check when the points start to open. They have to start to open at 2.5 to 2.7 mm BTDC. You can use any timing from 2.4mm to 3.0mm BTDC Take the wire off the coil under the tank and put one lead off your multi meter in it and the other in a screw hole beside the ignition. Use the Ohmns measurement. That is how to do the timing on a Motoplat points ignition.

just replaced my slide needel and needel jet on my bing

Is there anyone in the wolverhampton area with a bing 28 I could borrow ? I changed the jets not a lot of difference and took the rear silencer off to see if it made a difference but nothing so it's looking like a trip soon and start from scratch

Try and borrow a back box at the same time, as said, a blocked exhaust will kill performance.

If you decide to buy a new carb, think about a dellorto.

Edited November 15, 201411 yr by b40rt

i also cleaned my back box out as above. and it.s a good idea to have the down pipe repacked but you mentioned it was a new exhaust. so as mentioned could be the carb.

Please don't tear into things before trying a different carb.

PS it doesn't have to be a Bing.

Larry