yamaha 25

[johnjo]

IM struggling to start a 25 horse Yamaha
Got the spark but no fuel coming to plugs
The pump is ok and the float chamber has plenty of fuel
So why no gas going through
I opened and closed jets among other things.
Any ideas from anybody?

Cheers,

John

 

[99yam40]

Re: yamaha 25

not sure how you open and close jets,
but carbs need to be completely taken apart and cleaned properly.
Then adjusted as the service manual calls for after reinstalling

Something I have found is that if there is not good suction do to leaks to crankcase then the motor will not suck in the fuel even if carbs a clean.

 

[johnjo]

Re: yamaha 25

Thanks for that,
will seal the gasket better with solution and see what happens

 

[johnjo]

Re: yamaha 25

Thanks for that,
Haven't touched the engine since as Im away, but one thing I found in this engine is that when you pull the starter you get just one 'kick' so to speak, ie one compression at the start of the pull and you are left with a lot of useless cord left over. You cant pull the cord continuously to get several compressions like the smaller engine.
Is this a feature of the big engine or a fault, and therefore a reason why the fuel isn't getting sucked in?
Hope you understand this?

Cheers,

John.

 

[99yam40]

Re: yamaha 25

is the motor locking up?
Or is there some other reason you cannot pull the cord farther

 

[johnjo]

Re: yamaha 25

No, the recoil is free enough when taken off, but when turning the engine you will not pull past the first compression.
However, when you take out the plugs you can pull the cord right through the full cycle.
So, if the engine doesn't fire on the first compression it will not fire at all.
Hope this is clear.

John

 

[99yam40]

Re: yamaha 25

if it is able to turn over easily with plugs out but not with them in, then maybe piston is hitting plug and physically binding up motor or you are getting a hydro lock due to liquid fuel or water in cylinder