2005 Yamaha F40TLR Hard to Start

[Toltec]

I have a 2005 F40TLR that is very difficult to start and keep running until it gets warm enough to continue to run. There is no power to the electothermal alve with the key in the in position. And, I do have power to the 20-amp fuse inside the cowling. Anyone have any ideas on how to proceed to a repair? Thanks.

 

[99yam40]

power to the heater unit comes from the lighting coil before it hits the rectifier/regulator and is only there when the motor is running to heat it up and close off the extra fuel for a cold motor

 

[Toltec]

Thanks 99yam40 for your reply. I do fully understand the enrichment system. I can tell you this. If I take a shop towel and block the fresh air intake this motor starts immediately and idles great. Take the shop towel away and it will start and die, start and die until warm enough to run. I don’t get it?

 

[Toltec]

Sorry, should have said do not fully understand the enrichment system.

 

[99yam40]

something is not letting enough fuel thru.
I have read about some replacing the pilot jets in the F40s with larger ones to help if all is clean and working as it should be

 

[jakedaawg]

When I run into this issue I pop out the idle mix plugs and riches it up ever so slightly...probably illegal but no one will know...

I should amend this to state that is the last resort after everything else is proved functional and in spec

 

[boscoe99]

Sorry, should have said do not fully understand the enrichment system.

When the motor is cold the fuel enrichment valve is cold. When the enrichment valve is cold it allows more fuel to flow through to help a cold start. Once the motor is running electrical power is provided to the valve to warm the valve. As the valve warms it allows less extra fuel to flow. When the motor is fully warmed up (no more extra fuel needed) the valve is fully warmed up and stops allowing extra fuel to flow.

 

[boscoe99]

When I run into this issue I pop out the idle mix plugs and riches it up ever so slightly...probably illegal but no one will know...

I should amend this to state that is the last resort after everything else is proved functional and in spec

Many do this. Remove the EPA plugs and turn the idle mixture screws outwards a half turn to see if it starts more easily when cold. Some have gone so far as to install over sized idle mixture jets.

If you look at say a 2000 model years F40 they used a certain idle jet size. They then went down in idle jet size. Then the cold start problem got worse.