air leak?

[‘AAA Dummy]

Hi All. I have a TS-1 which was running fine until two weeks ago. Tried to start it one day and it behaved as though it had fuel starvation – fired and ran for a few seconds then died. The points, condenser, coil, HT lead, plug cap and plug are all new.The points gap is correct and the timing is correct as checked with a dial gauge and ohm-meter. I have thoroughly cleaned the carb and very carefully set the float height in both directions. The fuel level when I take off the bowl looks right. I have replace the gaskets on the inlet manifold. If I crank the engine with the choke on and a paper towel in the plug hole, there does not seem to be any sign of wetness. I drained the transmission oil but found no trace of petrol. The oil-seal on the dynamo side looks perfect. I am presuming that there must be some air leak that is not giving vacuum to pull fuel from the carb. Is there anything else I can try or is an engine strip the next step? Many thanks

[Richard Smith]

Hi Joe,
before tearing the engine apart,there are a couple of checks you could do. Move the air inlet tube out of the way,and put your hand over the carb inlet while kicking it over,you may need someone else to kick it over,but you will feel if it is sucking.
Check the pilot jet carefully and also the passage it screws into,it takes very little muck to block it.

[‘AAA Dummy]

Terry, very many thanks for your reply. I just took the air filter off and got my son to put his hand on the end of the intake hose. Plenty of suction. Just for the sake of it I switched on the ignition and to my astonishment it fired up – after weeks of not even getting a single bang from it. I will put the filter back later and try again.

[‘AAA Dummy]

Back to square one. The bike would only start with a push (still minus air filter) and then ran for around 75 meters before dying again and refusing to restart (with and without air filter).

[Nicholas Perry]

I had a problem with my Simson similar to yours and thought it was the carb. A friend suggested I fit a spark plug tester to the HT lead. Then you have visual confirmation that there is a spark. Fitting this showed tyhat it was in fact a spark problem and the new coil I had fitted was only working intermittently.

[‘AAA Dummy]

Nicholas, thanks for the reply – it looks you have hit the nail on the head. I had swapped the carb from a working bike with no result. Following your post, I put my old coil back on and the bike fired right up. Looks like the new coils are not of the best quality. Thanks again, delighted to be back on the road.

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