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Help needed 300st won’t start

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1 hour ago, Erky181 said:

Sounds like this rear tank set up is rubbish no wonder they changed back to front tank 

Quite right 

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If you have a good spark, fuel and a clear airway and adequate compression the bike should start. Start again and work methodically.

No fuel in crankcase, drain (if drain plug fitted) or turn fuel off and leave to evaporate 

Choke operating correctly, on and off etc.

Good plug, cap as well.

Good compression.

Clear airway, air filter not blocked.

Kill switch working correctly, possibly by-pass to eliminate.

Fuel flowing to carb, float stooping fuel from flooding.

Carb overflow pipes routed correctly, not blocked/ kinked etc.

Throttle (handlebar) set up correctly.

Throttle cable fitted accurately and free movement.

DO NOT ATTEMPT to tow start this proves nothing and is dangerous to both you and your bikes engine.

With everything set/working correctly bike should start after second or third kick. 

Others have pointed to the woodruff key allowing the flywheel to move on the crankshaft, entirely possible and an area that should be inspected. If the woodruff key has sheared then a straight forward replacement is normally all that is needed. However if its happened a few times ( you won't know this as the bike is new to you) then the woodruff keyway in the crankshaft may be seriously compromised. Not an impossible repair if you are handy with a welder and Dremel type cutters. Glue is not a way to go it will not last the test of time. Hope this is helpful and you solve the issue??


Edited by section swept

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21 hours ago, Erky181 said:

No I’ve not laid it over at all 

If you've not laid it over and you are getting fuel in the crank/ exhaust then it has to be the the floats not stopping the fuel flow when the carb bowl is full. You say you have had the carb apart (are you sure you reassembled it correctly)?  Its floats sticking or wrong height, float needle valve not seating or incorrectly assembled. For me it all points to something wrong in the carb bowl area. You also say you also changed crank seal. What was the reason for that? Go over your work to confirm its correct before you take anything else apart or your only going to complicate matters

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I called the splatshop , and told him my symptoms and he advised changing crank seal , it’s running fine now , I think I’m going to replace the float valve and float as cheap parts hopefully it will be fine now 

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