Choke problem

I have a 2004 115 h.p. Yamaha 2 stroke w/manual choke. It has been nearly impossible to get it started when cold i.e. first start up in the morning. After it finally gets started it will start right up after that all day. It was always a little hard to start but now it takes about 15 min. of playing around with it to finally get it to start. I took the cover off the carbs and the butterflies seem to be working as they should. When I put my hand over the bottom carb and completely cover the carb it fires right up. I'm at a loss as to what could be causing it to act this way. I don't use Ethanol and last year I had a new fuel pump installed and the jets adjusted. Any thoughts on what the problem could be? A local Yamaha expert said there was a few years where Yamaha had bad chokes. Anyone know about this?

Llrowley1253 said:

I have a 2004 115 h.p. Yamaha 2 stroke w/manual choke. It has been nearly impossible to get it started when cold i.e. first start up in the morning. After it finally gets started it will start right up after that all day. It was always a little hard to start but now it takes about 15 min. of playing around with it to finally get it to start. I took the cover off the carbs and the butterflies seem to be working as they should. When I put my hand over the bottom carb and completely cover the carb it fires right up. I'm at a loss as to what could be causing it to act this way. I don't use Ethanol and last year I had a new fuel pump installed and the jets adjusted. Any thoughts on what the problem could be? A local Yamaha expert said there was a few years where Yamaha had bad chokes. Anyone know about this?

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Do you hear a click when you push in the key? If not, your automatic choke is not working. Do you still have problems starting if you use the manual choke? If it is hard starting with the manual choke, you might want to check the compression on each cylinder.

solinsky said:

Do you hear a click when you push in the key? If not, your automatic choke is not working. Do you still have problems starting if you use the manual choke? If it is hard starting with the manual choke, you might want to check the compression on each cylinder.

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It has a manual choke.

Covering the lower carb with your hand I think was the clue. By covering the carb you are creating a richer fuel to air mixture. You are running to lean on that carb. Why ?. First I would check the gasket under the carb and all other possible lines & gaskets that could be sucking air. A carburetor has a float system which is basely a bowl with fuel in it that is used for starting. Think of a toilet and how it works. If the float is adjusted wrong ( sticking up ) there could be less fuel in the bowl.Which could cause a lean mixture on starting. Assuming it only starts when you cover one carb as you said I would removed it and have it rebuilt and replace it with a new gasket. You said you checked the butterflies on each carb. Check again and make sure the lower one is as closed as the other. Here again if it's open to much you are sucking to much air and leaning it out. Good Luck

There is a cold start technique that works for every carb'd Yamaha 2 stroke that I have tried. You need to check that your choke butterflies are properly connected to the manual choke and operating when you pull the choke out. If that is all good, try the following -
1) Pump the primer bulb hard
2) Pull out the choke
3) Put the fast idle lever up to around 1/3rd throttle (if you have the controls with a separate fast idle lever this is about 1" past the point where it gets hard to move - the initial easy movement doesn't do anything)
4) Wind the engine over to start
5) If it doesn't start after 2 or 3 seconds of winding, try pumping the fuel bulb again and then wind over again

A 2004 115TXRC/TLRC has both a manual choke and an electric choke. Actually, the mechanical choke is driven by an electromechanical device when the key is pushed in.

Pull the manual lever and see if the choke plates close on both carburetors. Then, push the key switch in with the key in the on position and see if the choke plates close. They should in both cases. Putting your hand over the carburetor inlets is doing the same thing that the choke plates should be doing. Yours might need to be adjusted.

I disagree with opening the throttle somewhat during a cold start event. When a motor is cold there is not enough fuel for the amount of air that is flowing through the carburetor. The choke plate closing causes additional fuel to be provided. Opening the throttle during cold start is allowing more air in at the very same time that there is already too much air.

We will have to agree to disagree on the open throttle Boscoe. I run a charter fleet that has had many of these engines and whilst I understand what you are saying, it isn't true in practice. Don't forget that opening the throttle with the choke closed will change the airflows (and hence fuel delivery) over both the main and idle jets. It is not just a case of 'extra air'.

If a motor with a choke plate has to have the throttle advanced to facilitate a cold start then something is not correct with the motor.

Yes, in your case advancing the throttle apparently works. I can't disagree with what you say works for you.

I am saying that advancing the throttle is trying to compensate for something else that is amiss.

Just like if a hot motor is flooded then opening the throttle will allow more air to flow through which will facilitate clearing out the extra fuel. When the air/fuel mix gets right then the motor will start. The throttle is being opened to compensate for a problem within the motor.

All I can say is that 12 years of running over a dozen of these engines, plus helping dozens of others, this is what works very time. I know the theory, I've rebuilt carbs, rebuilt engines, checked chokes, cleaned jets, comes back to the same procedure each time for the fastest cold start. I had a classic case recently where a guy beside me at the ramp had virtually flattened his battery trying to cold start his SWS2 150. He was packing it up and getting ready to drive home in disgust. I went over, asked if I could show him something, went through the procedure described, and the engine fired up on the 2nd or 3rd wind on an almost flat battery. The guy was dumbfounded and said that his engine never started that easily even with a fully charged battery. If you own one of these engines, try it yourself next time it is hard to start when cold.

As I said, I agree with you that a motor with a problem can be finessed to make it work. But, the core problem is not being fixed. A temporary solution is being used each time to get the motor started.

A fellow with a crappy leaking carburetor or a leaking fuel injectors might have a flooding issue each time the motor is turned off. It can be very hard to start again when hot. There is a way to start a flooded engine. One can use that procedure each time or one can fix the problem that is causing the override procedure to be needed in the first place.

A guy will ****ty brakes might have to pump them before each stop to get them to work properly. Or, he can repair his brakes and not have to do anything with each stop.

Maybe the OP will want to use your procedure. Maybe the OP will want to fix the motor so that your procedure is not needed. His call.

Here is what I am talking about. Using a half assed solution to override a problem and not actually fix a problem.

A guy has a problem with a 27 year old Yamaha because the spark plug caps come loose from the spark plugs. Instead of fixing the problem (replacing the caps) he solved it by using a band aid approach.

Hey, it works. Can't argue with success I suppose. He could have used glue and it would have also worked.

I must admit that I have never understood why, in a motor with 4 carbueretors ( 2 of 2 each), would at least 1 or 2 be working enough to start the motor if there was a problem with the others. Must we assume that a problem be experienced by all at the same time? In this post, Llrowley choked the bottom 2 carbs and the motor started.