Poor starting - Yamaha 30 2S, 2 Cyl

[HughN]

Hi,

I have an early 90's Yamaha 30 (the same '689' engine they made for Mariner).

It eventually starts if I open the throttle, close the choke and wind it over for about a minute (in ten second burst sso the starter motor doesn't get too hot). After that it runs quite happily and, if stopped, starts with a touch of the starter or pull of the cord.

I've only tried it when its running but pulling off the spark plug boot shows a spark across a gap of about 2 cm.

Any thoughts about why it is reluctant to start but runs happily after that?

Thanks

Hugh

[neil.mccrirrick]

Sounds like not enough fuel I'd see if your pilot jet is blocked I'm assuming it's a carburettor


Sent from my iPad using my finger

[RIB-Teccie]

Is your fuel bulb priming up the carb correctly? It sounds like lack of fuel but not once it's started so I have to think that the carb is not full of fuel when you first try. Failing that it's a fuel pump check and a carb clean.

[HughN]

When I prime it I can hear fuel going into the carb - up to the point that the bulb goes hard (the float has closed off the fuel to the bowl).

Tomorrow I'll try and start it with someone pumping the bulb.

[Peter_C]

Pull twice on the choke. If that doesn't work pull three times on it. Assuming it gives it a shot of fuel of course.

You could also take some starting fluid and give it a quick squirt.

[RIB-Teccie]

If it's the older 30 yam, pulling twice on the choke won't help. It's not a primer like on the Mercury's. Priming fluid will ruin an engine as it washes the oil off the bore and over time causes engine wear and loss of compression. It sounds like your fuel bulb is ok. Here's what I would do.

1) Use new petrol/oil mix (the old might be rancid if it's been sitting). It's unlikely you got bad fuel from the pump, but not impossible.

2) Ensure there is no water in your tank before you refill.

3) Take off the airbox and squirt fuel right down the intake.

4) Use the normal starting procedure.

5) if it fires straight up, clean out the carb. It will certainly be a fuel issue.

I'm trusting you've not adjusted the timing or the needle on the carb!

[Davie]

old fuel or the choke butterfly is out of adjustment

[lukewhiting]

I have the same problem in my Yamaha 115 v4. Starts fine once warmed but is a pig from cold

[RIB-Teccie]

Sounds like they may need a compression test.

[Peter_C]

Compression tests are always good. First rule out major mechanical before messing with anything else.

Originally Posted by RIB-Teccie

Priming fluid will ruin an engine as it washes the oil off the bore and over time causes engine wear and loss of compression.

If you are referring to "starting fluid" it may cause damage over time, but a use once or twice as a diagnostic will not do any harm, unless you over use it. A single shot into each carb is all it takes.


Extra Strength Starting Fluid for the fastest starts
Starts engines quickly and reduces drain on batteries
Compatible with gasoline or diesel engines
Contains upper cylinder lubricant


It is a quick way to see if an engine is getting enough fuel. Then once diagnosed it can be properly repaired.

Does this Yamaha have "Prime Start". Do you have the owner manual? If not I recommend buying one.

Does the motor have one of these levers?



What is the year of the motor?

I used to have a Yamaha 90HP years ago. It was a fantastic engine that only failed me once when the starter bolt fell down. Put the bolt back in and it fired right up. Other than an occasional impeller, lower unit oil change, and spark plugs it never needed a single repair over 100's of hours of use.

[HughN]

Thanks All,

It doesn't have one of those levers.
It is approx 1991.
I have a workshop manual but can't find the flippin' thing!

I'll run another compression test and report back.

I swapped the carb for an identical one yesterday and its response to squeezing the primer bulb was different. I think I have found a leak in the fuel line.

The fuel pilot jet seems OK in that I can blow through it with the necessary other ports blocked.

With the new carb the symptoms were the same. Interestingly, the mixture needle had to travel a long way in either direction to affect the running. If for no other reason than to satisfy myself I might check the timing anyway.

Call me a wimp but investigations had to stop when it started to tip down with rain yesterday.

Thanks for the inputs.

Watch this space.

[RIB-Teccie]

Upper cylinder lubricant is for four stroke engines. Please look at the note towards the bottom of the specs.

If you try to use the fuel that's in the tank, you also are inspecting the quality of the fuel. I squirted some fuel down the carb once and it was that which caused me to discover the operator has filled his tank with diesel and mixed with two stroke.

[Peter_C]

Originally Posted by RIB-Teccie

Upper cylinder lubricant is for four stroke engines. Please look at the note towards the bottom of the specs.

Upper cylinder lubricant is just that, upper cylinder lube which is exactly what 2 stroke Yamaha's fitted with Autolube get, with or without fuel.

I guess I got the good stuff As you can see my can is probably 10+ years old since I use is sparingly.


Propane works great too.

Originally Posted by RIB-Teccie

If you try to use the fuel that's in the tank, you also are inspecting the quality of the fuel. I squirted some fuel down the carb once and it was that which caused me to discover the operator has filled his tank with diesel and mixed with two stroke.Attachment 103075

I have seen diesel put into older gasoline vehicles, and gas put into diesel vehicles, which is all too common. We had one company we serviced where it happened to the same truck twice in one month, even though it was labeled in BIG lettering, DIESEL ONLY in block lettering above the fill cap.

You are 100% correct that bad fuel is often the cause of issues, and unless checked thoroughly can waste a lot of time being diagnosed. The nose is always a good first check.

[RIB-Teccie]

I really can't be bothered to debate this one.

1) pulling choke in and out - bad advice

2) showing the incorrect outboard - bad advice

3) Recommending easy start and not naming a suitable brand (if one exists) - bad advice

4) Upper cylinder lubricant is for the top of a vertical cylinder engine. It (as the name suggests) lubricates the upper part of the cylinder of an upright engine, usually one which is older.

5) The yamaha autolube system is not an upper cylinder lubrication method. It injects just forward of the carb and mixes with the fuel as it hits the reed valves. It is drawn through the intake port as an air oxygen mix and is detonated on the compression stroke. It lubricates the rear of the Pistons and bearings as it comes through the reeds. It has nothing to do with upper cylinder lubricant in the traditional sense. On a Yamaha outboard or any two stroke outboard the majority of the lubricant comes from the rear of the Pistons and cylinders. Any unburnt oil will have some lubricating capabilities but when you remove the head you will find a 4mm (ring) at the top of the cylinder which has missed out on lubrication (to a minor extent) over the life of the engine.

[Peter_C]

Originally Posted by RIB-Teccie

I really can't be bothered to debate this one.

Then lets try to help the guy get his outboard running

Is propane okay to use? I really try to discourage people from dumping raw gas down a carb. I have seen too many fires in my automotive career.

[beerbelly]

4) Upper cylinder lubricant is for the top of a vertical cylinder engine. It (as the name suggests) lubricates the upper part of the cylinder of an upright engine, usually one which is older.

5) The yamaha autolube system is not an upper cylinder lubrication method. It injects just forward of the carb and mixes with the fuel as it hits the reed valves. It is drawn through the intake port as an air oxygen mix and is detonated on the compression stroke. It lubricates the rear of the Pistons and bearings as it comes through the reeds. It has nothing to do with upper cylinder lubricant in the traditional sense. On a Yamaha outboard or any two stroke outboard the majority of the lubricant comes from the rear of the Pistons and cylinders. Any unburnt oil will have some lubricating capabilities but when you remove the head you will find a 4mm (ring) at the top of the cylinder which has missed out on lubrication (to a minor extent) over the life of the engine.[/QUOTE]

he,s right you know the 2 stroke oil does most of its lubricating whilst being compressed in the crankcase before going through transfer ports into the upper cylinder.(I don't remember much from collage )

[RIB-Teccie]

I am assuming the engine has been run on 1:100? On 1:50 there is a chance the rings could be gummed in.

[HughN]

Originally Posted by RIB-Teccie

I am assuming the engine has been run on 1:100? On 1:50 there is a chance the rings could be gummed in.

It's got 1:50 in it at the moment as it has just had the cylinder walls tickled with a hone, new pistons and new rings. No autolube and judging by the crankshaft it never had one.

Cold compression tests (with a cold battery) showed 120 psi on both cylinders. (Nothing has had a chance to bed-in but the fact they are the same is reassuring).

Using a DIY manometer showed the TDC pointer to be on target and the timing mark aligned with that.

The check valve in the primer bulb is a bit suspect so I'll fit a new primer bulb and see what happens...

Flippin' thing.

[RIB-Teccie]

Now we're getting somewhere.

1) why did the engine need a decoke or just stripped down?

2) At a guess, how many hours would be on it when it was stripped?

3) TDC may be fine, but we're the timing stops altered?

4) the yams are usually forgiving even if the rings are gummed in.

5) Try a squirt of fuel down the carb from cold and let me know how it fires.

6) You have good spark so it can only really be a fuel system or timing issue unless you went mad with the honing tool!

[HughN]

Thanks,

1) The thermostat got blocked with a bit of impeller and it slowed to a dignified halt. After cooling it restarted but then slowed to a halt again. The pistons were scuffed and there was a small amount of scoring on the cylinder wall (not enough to catch a fingernail or edge of a credit card)

2) Hours unknown.

3) The timing stops weren't altered. The timing mark on the ignition plate lines up with the timing pointer when at minimum throttle.

4) Let's hope so...

5) Will do.

6) The honing was pretty light and I am confident in the chap who did it: he wears a brown shop-coat with biros and a vernier caliper in the top pocket plus 'Michael Foot' glasses - old skool Engineer (with a capital 'E').

The real killer is that this engine was bought to replace a Mariner version of the same engine that ground to a halt after picking up a carrier bag round the lower unit. That started first time, every time, for the twenty years we'd had it (ex MoD contract).

I'll squirt some fuel into the carb tomorrow and see what happens.

Many thanks

Hugh