Yamaha F25 Four Stroke starting problems

[ROCKER63]

So.... I took the carb off and cleaned it cleaned every orifice with CRC carb cleaner. Runs good but have to use a little starter fluid to get started. What could be the hold up, The primer?

 

[Inducted]

Re: Yamaha F25 Four Stroke starting problems

I'm pretty sure that carb has prime start for its enriching choke system. When the engine is cold the needle valve is "open" this ollows for a prime circuit to be open. this prime circuit has a fuel supply and an air supply. Your Prime start valve could be defective but most likely your carb is still dirty. These carbs can be very tricky.

I would clean again Remove the prime start valve clean these circuits. Remove accelerator plunger and clean these circuits. Good luck

 

[ROCKER63]

Re: Yamaha F25 Four Stroke starting problems

thanks, is there a way of doing a bench test on the prime? I will assume that when working properly, it should start very quickly.

 

[Inducted]

Re: Yamaha F25 Four Stroke starting problems

If you put 12v directly to the connections the needle should move as the unit warms up. Should expand maybe 1/8 or 1/4 inch. if it moves its probably ok.

When you try to start the engine the throttle plate is basically closed. Some how fuel has to get behind the throttle plate this is your prime start circuit. when fuel can flow the engine should fire right up. Prime start electrothermal valve could be defective or the circuit is dirty.

 

[ROCKER63]

Re: Yamaha F25 Four Stroke starting problems

Just in case you feel like answering another question. Is the temp sensor separate or part of the prime valve? IF I remove the valve and put my thumb over the opening, can I bypass it and get it to start? Thank you for your time

 

[Inducted]

Re: Yamaha F25 Four Stroke starting problems

The temp sensor gives inputs to the ecu. The ecu makes adjustments accordingly.

The prime start electrothermal valve is the device with wires that is part of the carb. It just opens and closes. If you bypass ( remove) the carb should not operate properly.

 

[ROCKER63]

Re: Yamaha F25 Four Stroke starting problems

Thank you. A friend of mine was telling me about the fittings and bulb for the fuel. I think I am going to eliminate the fuel supply by replacing the Yamaha fittings with the Honda quick disconnect system and change the bulb and pick up tube with ethanol friendly replacements this weekend and ensure that the line is not sucking air trying while trying to draw the fuel from so far away through a worn out o ring. I am not losing anything by replacing them because I would do it anyway. I am certain that I had flow going through all the passages and ports on the carb when I cleaned it, so I believe that this would at least eliminate the supply as a possible problem to the unit. Once again you have been very considerate with the response. I know that you at least a technician and as a Diesel tech, I know how many questions are probably coming your way on a normal basis. Thank you for your time. I hope that I can post the success story this weekend with credit to you.

 

[Pas Bon]

Re: Yamaha F25 Four Stroke starting problems

I had trouble with mine recently I tried the carb cleaner route and it didn't work...it took a kit and a 24 hour soak in berry's chem dip to fix it. but it did fix the issue.

 

[ROCKER63]

Re: Yamaha F25 Four Stroke starting problems

I took the carb off and cleaned it properly this time and freed the plunger that was stuck and now the carb the unit runs like a new motor. Starts before it gets a full turn. Thank ya'll for your help.

 

[robert graham]

Re: Yamaha F25 Four Stroke starting problems

Continuous use of a fuel stabilizer like Stabil or Seafoam should help prevent these fuel related problems. Also a good idea to drain your carbs now and then to help remove water, debris, whatever from float chambers. A fuel/water separator type canister filter(Walmart/Attwood $27) mounted on your transom is another great preventive maintenance item. Plugged carb jets are a pain! Good Luck!

 

[junkyardwarrior]

Re: Yamaha F25 Four Stroke starting problems

JUST went through this on a customer's engine.

The F25 uses a prime starter of thermal type. When the primestart is cold, the plunger is "up", therefore opening a fuel and air passage. Once the engine is running, it is supplying voltage to the two wires, which heats up the primestarter and once the element warms, the plunger drops back into it's passage and closes off the fuel passage and air passage.

The fuel passage works runs down through the carb body, out the bottom and into the bowl. There is a small brass "pin" with 4 holes in it. This is where the fuel runs through to the primestarter. Now then...in the bowl itself there is about a 3/8" dia "hole" where the primestart pin sits. This is the fuel source. It is fed through a hole that is drilled from one end of the bowl and this passage also feeds the accelerator pump. That passage is capped on the end by a brass ball in the bowl. The passage, if it gets gelled, gummed, or really dirty, occasionally it can't be cleaned. This is when typically the bowl gets replaced.


What I found is that if you drill the brass plug out you can reach in there with a jet cleaner. WAY down inside the passage is a tiny brass jet which is the primestart jet. It gets plugged easily because it is tiny. It's pressed into the bowl so it can't be removed. However, it can be cleaned with a jet cleaner. I use a piece of electrical wire and strip it back to expose the strands. The softer copper wire won't increase the jet size as steel wire will (or tip cleaners tools). Once the passage and jet is cleaned, then you have to cap the end of the passageway. I drilled and tapped for a 10-24 screw and installed it with a soft aluminum washer to prevent leaking. So far so good.

just thought I'd pass that info along.......might help someone who's fighting with an accel pump or primestart problem.

BTW it was 24 deg this morning and the little primestart 25 fired right up with not much more than a couple revolutions of the starter.