Gsf 400 starting issues

[homer]

Few years ago we bought a little bandit for my wife. It was quite badly keeped so it was a cheap buy. Cheap indeed, airbox cover was missing, every bearing was fucked and there was very badly made "modifications" here and there.

Started to overhaul it last year and did the worst faults first. One very odd and annoying is still there. It is very hard to start when the engine is cold.

Done so far: 

New plugs

New coils

Ultrasonic clean for the carbs

New seals and misc parts for the carbs

Relay mod for the coils

Stock setup for the carbs

Fuel tap checked

Compression tested the cylinders

Valve clearances

Spark is very strong and plugs are wet after cranking. It starts if I jump start it and after it is warm it starts right away. Any ideas what to check next?

 

[Captain Chaos]

do these carbs have the plastic float holder things? If yes there should be a small jet pressed in each of them, this is for the choke circuit. They tend to come loose and fall out, which makes cold starting a bitch.

[Fula28]

I had one of these, did same a CC states , they fall off ,orings shrink too, (ethanol) Tiny air correctors and pilots , double check those with strand of wire from wire brush. There ace bike when carbs are good! I loved it little revvy motor. 

[homer]

Yes, float assembly is completely plastic. Have to check if there is a jet. Did not notice them when they were open earlier.

They are indeed very nice bikes. Even with so little power you could have such fun time especially in the cities.

Edited January 14, 2018 by homer

[Fula28]

There's a small o ring that holds float plastic cage/  inside carb body too, myn were so loose they fell off when turned over, If hard startin cold the slow running circuit is to blame usually, so floats, pilot jets air correctors, and mixture screw settings. 

 

Edited January 14, 2018 by Fula28

[homer]

Those tiny o-rings are new and hold nicely. Have to double check everything.

[El Gringo]

The other thing to check is if the emulsion tubes are ovalled

Mine was exhibiting exactly the same symptoms - new emulsion tubes cured it

[homer]

Fuuuuck... I did not check emulsion tubes when washed the carbs

Have to check them also

[homer]

Emulsion tubes seems to be ok. Visually checked them so not 100% sure. Few needles got some surface imperfections but I have had worse in working carbs. Float cage jets where there.

[richyrich]

I'm having a similar issue with hard starting.   I think my float valve isn't sealing,  cos gas drips from overflow, that is flooding it at startup. That's my theory. 

Good info to check jets and o rings on float plastic cage thingy. 

Is your overflow pipe visible or pointing at the rear tyre like mine was... 

Edited January 22, 2018 by richyrich
Safety ha

[homer]

After two ultrasonic treatment, several new o-rings, honing every hole with wire and blowing them with cleaner/air it finally starts nicely