Help Please...anyone know 2-HP pilot screw specs?

[ChakaRaka]

I know single thumper 2-horses are not very exotic, but I am just as eager to get back on the water as the rest of you (just poorer). Can anyone spare a moment to help answer my question please?

Does anyone know the factory procedure for setting the pilot screw (air/fuel) mixture on a mid to late 80's 2hp 2 stroke? Don't be daunted by the age, I think they were almost the same until 2000 (with the exception of CDI being an upgrade made sometime in the 90's). I have a very generic shop manual but it covers way too many models so it never gets as specific as it should be.

I was going to just do it by ear/feel but I am fouling plugs at low speeds like no tomorrow and am about to toss the thing overboard. Running this poorly and unreliably it is more trouble than it is worth. I think my fuel and spark plug costs are about neck and neck at this point...

Thanks.

[boats.net]

That setting is not listed in manual but would still need to make final adjustments with engine running.

[ChakaRaka]

Yeah I have a very generic manual and it does not say anything specific in it. I am having a problem with plugs fouling really fast and I have tried setting it by ear, but the motor will run quite happily in any setting. So I wanted a baseline to start with so I could go from there. Seems everything I try is way too rich. When it is fuel starved, when the tank is running out or when you shut the fuel valve off to run out the fuel in the carb, it really picks up. Probably just like it is supposed to be running the whole time if it was mixing properly. There was another guy on this forum asking basically the same thing, but the other half of the conversation was missing for some reason and you could just see the single side of the original poster. I too originally thought that screw was just for setting idle, but from the limited information that I have found, I believe it is mixture. That or my carb has some serious issues.

[boats.net]

It is just the idle or low speed adjustment screw. Sounds you have a problem in carb, may need to be rebuilt.

[ChakaRaka]

Any chance there are different jets available for different elevations? This thing looked perfect when I took the carb apart. I don't want to just throw parts at it taking shots in the dark. It does run rich, but the internals look good. Seeing as I work on nearly nothing with a carb, any suggestions of likely culprits?

Thanks!

[99yam40]

Do you have any history of this motor?

I found out a previous owner of my C40TLRX had drilled out the main jets which caused over rich problems, Took me close to a year to figure it out.
Some people must think they can just add more fuel to try and get more HP,
Something to look at

[ChakaRaka]

I'll look into it, I was wondering if maybe because it came from low-lying Ontario and is now being used in a higher location in BC maybe the Main Jet was incorrect. Maybe I should just order one and compare. I live in a pretty small town, so local parts will be costly. That was why I wanted to narrow the issue down, because I still think that everything in the carb looks okay...with the exception of maybe needing a smaller jet.

[99yam40]

what is the altitude the motor is run at now?
A 2 hp motor does not have much HP to loose and still turn a prop against a load

[ChakaRaka]

I currently live at about 1500 ft but use is a bit lower than where I am now and quite often higher also. If I can get it to run right in the summertime I will be higher yet in the mountain lakes around here. I am not sure what the elevation was where it was sold, nor do I know how sensitive these are to elevational changes. I just know that in some cases other motors have to be rejetted (motorcylces etc). I agree a 2HP does not have much to give up before it becomes useless but it has run stronger and seems to keep getting a little worse...

[99yam40]

If it has run better for you in the past, then I would be cleaning the air and fuel jets and passages very well. Maybe a ultrasonic cleaner will help.

Does it still have good compression and spark?

[ChakaRaka]

I have owned it for about a month, so that timeframe is short. The carb looks immaculate inside, this motor has never seen salt water. There is compression and spark. The only problem is there is too much fuel to air...

[99yam40]

From what you have stated something is changing and you will have to measure what you can to see.

Not sure about a 2HP motor but on larger ones a too rich condition could come from a leaking fuel pump dumping extra fuel into the crankcase

[ChakaRaka]

That is a good call and something that I have come across before on an older 7hp. I was going to change that, but because it settles down when being starved, I am not too sure. I am going to pop the carb off and have another look, then see where to go from there. I am still very curious if Yamaha made different jets for different altitudes though?

[99yam40]

would not hurt to take apart the pump and see what you find

[ChakaRaka]

Took the carb apart again today. I couldn't remember if it had a diaphragm pump or not. It is strictly gravity fed and has no fuel pump. The jet is clean and seems untampered with. I did note the number on it was 96 (but was so tiny and hard to read so might be 98). But I don't think the manual I have references jet number. Anyone know if that sounds correct? The rest of the carb looks perfect so I wonder if I should order a new jet?

Thanks again for the responses.