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i bought a js550 with a fully rebuilt motor had a broken starter so i didn't see it run. it started for 1 sec then died it sounds like it wants to start but doesn't. has great compression, spark, tried starter fluid no idea. any help or ideas would be great thanks
 

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three questions do you have spark? do you have fuel delivery? do you have compression? if you have these it will run its just a matter of tuning. once the starter is fixed crank it and check all the above and go from there
 

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have u tried priming the fuel circut? pull the return line off the carb lightly pressurize the fuel tank and gas should bleed out the return nipple on the carb hook it back up and then try it. I have to do this on my ski before every ride cause i am too cheap to buy the aftermarket pump primer. but it works. give it full choke till it pops then 1/4 choke.
 

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Check the vacuum pulse line from the crankcase, see if you've got a good bounce on your vacuum gauge. If it just sits there you've got a crankcase leak. Be very careful with the starter fluid and a leaky crankcase you can end up with a runaway engine
 

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Check the vacuum pulse line from the crankcase, see if you've got a good bounce on your vacuum gauge. If it just sits there you've got a crankcase leak. Be very careful with the starter fluid and a leaky crankcase you can end up with a runaway engine

Is the vacuum pulse from the crankcase what pulls the fuel from the gas tank?
 

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No, its the line from the crankcase to the carb. If you have a case leak there won't be a pulse. Hook up a vacuum gauge to the line and see if the needle bounces
 

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No, its the line from the crankcase to the carb. If you have a case leak there won't be a pulse. Hook up a vacuum gauge to the line and see if the needle bounces
ok but what is the purpose of the pulse? and if i dont have a vacumn gauge will i be able to feel it with my finger whilei turn the engine over?
 

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Sorry, yes the pulse pulls the fuel into the carb. It will also tell you if all the crank seals are good. Even if you have fuel, spark and compression, a piston port type motor (440 550) needs a good crank seal
 

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Sorry, yes the pulse pulls the fuel into the carb. It will also tell you if all the crank seals are good. Even if you have fuel, spark and compression, a piston port type motor (440 550) needs a good crank seal
Alright well im working on a 750ss and it has pulse vacumn to the touch but it is not pulling fuel in, but there is so many fuel lines and a whole fuel filter it needs to fill before it enters the carb, should i try to prime the fuel lines?
 
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