yamaha 1977 15hp hard to pull start

[RuanGallant]

hi guys

i have a old yammie 15hp outboard, it was running fine until i left for a month and didnt use it.When i came back i cleaned the carb up sprayed carb cleaner into air intake and she ran.i then switched her off when i tried to start it teh next day it was almost impossible to pull the rope, however if you remove a sparkplug it turns freely.

PLEASE HELP??????

[TownsendsFJR1300]

Did you run the engine with pre-mix fuel and on muffs?

Carb cleaner has no lubrication properties and spraying into the intake isn't the best thing to do.

Your situation is odd but try putting a couple teaspoons of 2 stroke oil into the cylinder (spark plug OUT) and spin it over quickly. Once all that oil is blown out the spark plug hole, try starting again. (with water to the engine and pre-mix)

If you need starting fluid to start it, the carb is NOT clean or the choke doesn't work..

Please post back what you find..

[RuanGallant]

i always use water and pre mix fuel with a 50-1 ratio, i dont know what to do here. i have tried putting some 2 stroke oil in the cylinders and although it makes it a bit easier to pull i still cannot get it turning fast enough to fire up.

[ausnoelm]

Why did you spray carb cleaner into it? probably the first step is to remove the cover and see if it turns OK by hand, just to make sure the starter isn't jammed somehow, then next step might be panic......worrying about what the carb cleaner did!

[TownsendsFJR1300]

Very odd...

Again, if you need carb cleaner to start the engine (before this issue), the carb ISN'T CLEAN and should be re-cleaned or the choke addressed... That will help with starting at least..


Throwing this out there for S&G's....

The one thing that comes to mind is if your now (why now I dunno), getting water into the top end causing a hydraulic lock/hard to pull. **It is a very old engine and possible the head gasket just failed over time**

Can you spin the engine over (ignition OFF-PLUG wire disconnected) with the plug out, (to to make sure it's clear).

Then, ignition still off, NO WATER, spark plug in try pulling it over and see if there's a difference...


**(what I'm thinking is if some water is getting in the cylinder-maybe a bad head gasket-water gets pumped into the cylinder causing the hydraulic lock)

Please post back with the results...

[RuanGallant]

i did not have to spray the cleaner into the carb to start it but i thought it a good idea to clean all the little pipes and everything( which in retrospect might not have been such a great idea) . i have removed the head gasket and it is not in great shape but i cannot see anywhere where is is broken or where the water could get into the cylinder.i have taken the plugs out and she spins like a dream,then i took her out of the water and tried pulling but still the same problem which means it cannot be water there...am i right or completely wrong?

[99yam40]

Someone that is familiar with these small motors will have to answer this,
do they have a compression release to help during starting?

if not you need to find out what is getting into the cylinders that is not compressing.
Air compresses, liquids do not

[TownsendsFJR1300]

i did not have to spray the cleaner into the carb to start it but i thought it a good idea to clean all the little pipes and everything( which in retrospect might not have been such a great idea) . i have removed the head gasket and it is not in great shape but i cannot see anywhere where is is broken or where the water could get into the cylinder.i have taken the plugs out and she spins like a dream,then i took her out of the water and tried pulling but still the same problem which means it cannot be water there...am i right or completely wrong?

DID YOU TRY AND SPIN THE ENGINE OVER W/O WATER and the ignition turned off and spark plug installed. This is important and needs to be answered..

We can't help if you ignore the help/suggestions and jump ahead of us...

Now, back tracking, WAS the spark plug super clean?

When the head was off, did you see any corrosion in the head where water could leak thru? (inspection?)

**Now, if the engine is re-assembled, IMO, do a leak down test at TDC with the crankshaft locked up and check to see if it holds compression.

IF there's a water jacket, head, etc crack leak, the leak down test will fail and you should hear where the airs going to (IE and where water is coming in)..

[Jason2tpa]

It is rather strange that when a spark plug is removed he can turn the flywheel. I'm not familiar with these older engines. But it sounds like when plugs are installed and flywheel turned, the cylinders become pressurized. Shouldn't the exhaust outlet prevent pressure from building?

[ausnoelm]

You have heard of "compression" I guess?

[Jason2tpa]

Lol indeed i have. A pressurized cylinder is the result of compression. But in this case, i was asking if it were possible the cylinders had become pressurized without compression. I don't know how or if it's possible...i was just throwing it out bc im not familiar with this engine.

Again, it seems strange that when a plug is removed the pistons will move, but not move when plugs are in.

[TownsendsFJR1300]

It is odd.

And Jason, the design of the two stroke (with reeds) are the same as your engine. I don't think his is a piston / port design (no parts fisch available at least here). A stuck carb float could flood the crankcase but would most likely leak to the exterior. * P/P design is used on most small 2 stroke engines(weed eaters, chain saws, etc with NO reed valves).

I do wish the OP would answer the questions I posted.

Can't help without any feed back. The hard to pull issue has to be water intrusion causing an internal hydralic lock. Just a little with the piston at the top (all the cylinder ports are closed), WILL lock it up, period... And there's NOT much extra room atop the piston for any liquids.

I suppose it's possible (not sure how unless the carb flooded the engine below the piston and eventually was pushed into the combustion chamber) fuel could cause the lock, but with this design, not nearly as likely..

With no response lately from the OP, perhaps he found the leak/issue and isn't updating for some reason..

[boscoe99]

* P/P design is used on most small 2 stroke engines(weed eaters, chain saws, etc with NO reed valves).

Explain please?

[TownsendsFJR1300]

Explain please?

There are No reed valves in these engines. The carb is on the side of the cylinder and the piston skirt act's as the valve opening and closing at the correct time sucking in fuel into the crankcase.

Once in the crankcase, fuel/air is forced into the combustion chamber like any other 2 stroke..

This is my favorite/current weed-eater pictured below:

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You can see there are NO reeds. The carb bolts direct to the cylinder. (there is a plastic manifold inbetween for heat). If you have a 2 stroke weedeater, most chainsaw's, etc, you can pull the carb and SEE the piston/rings DIRECTLY.

Reeds are much more efficient and of course open with any vacuum. PP is set UNLESS you modify the cylinder raising/opening the ports..

Back in the 70's, Kawasaki and some other machines, used a "Plate/disc" on the side of the engine. The carb was INSIDE the case(NOT crankcase). When the disc spun with the crankshaft, it opened and closed (like the piston port engine, allowing fuel/air to be sucked in. This bike I'm referring to was called a "Big Horn" 350cc single 2 stroke. I actually had to swap the main cases out on this bike (my friends dads bike) as he threw the drive chain thru the cases. I was about 16 at the time...

[ausnoelm]

There is no need for reeds on a single cylinder two stroke with the carb on a manifold on the side of the cylinder.