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Nightmare starting from cold. When warm she runs lovely but seems to be choking only on the right hand cylinder. Carbs have been cleaned,compression is good and base gasket good. Any had this problem before before I go down the crankcase oil seal route. Previous owner did a complete rebuild which included a rebuilt crank and new seals but I am struggling to find a solution.Both coils are good so I can only put it down to carburation or crankcase oil seals? Any advice will be much appreciated
 

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Crankcase seals ?? Is it losing oil ?? I don't understand that.

Are you saying that it is hard to start and runs poorly when cold ?
But runs fine after warming up ?
That sounds like it's running lean when cold.

Are you using the choke AND not touching the throttle ?

Maybe a vacuum leak around the intake that closes up when hot.

Does it still have a stock air box and air filter ?

If yes, then I suggest a healthy dose of Berrymans B12 Chemtool in the gas.
And NO, SeaFoam is not good enough.
 

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Discussion Starter #3
Crankcase seals ?? Is it losing oil ?? I don't understand that.

Are you saying that it is hard to start and runs poorly when cold ?
But runs fine after warming up ?
That sounds like it's running lean when cold.

Are you using the choke AND not touching the throttle ?

Maybe a vacuum leak around the intake that closes up when hot.

Does it still have a stock air box and air filter ?

If yes, then I suggest a healthy dose of Berrymans B12 Chemtool in the gas.
And NO, SeaFoam is not good enough.
Hi many thanks,being an old school two stroke that works on a crankcase compression system I am thinking that I may have lost the crankcase vacuum that on the down stroke is not allowing the compressed air/fuel in the crankcase to to be pushed up to the cylinder. Possibly leaking air through a seal ? She is totally original (1981) including air box.1/4 choke and no throttle.I will check for air leaks around the inlets.
 

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Oops. Sorry I didn't realize that it is a 2 banger.
That can be a sign of weak reed valves too.
Why only 1/4 choke ?
If it doesn't want to start, full choke might help a lot.
And I'm not sure that "no throttle" applies in this case either.
 
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