So, what have I blown?????

[Poly]

Originally Posted by beerbelly

with autolube jet sizes adding oil to the fuel tank will reduce the amount of petrol in the mix the air volume is fixed with the throttle opening the jets can only flow so much fluid so by adding oil you will lubricate more but be running a weaker air fuel mixture which we all know isn't good burns pistons ect, surely a better idea would be to increase the amount of oil the oil pump sends into the inlet . or am I overthinking this I grew up on 2 stroke mopeds and kh 250,s and had a few seizures in my kack handed tuning attempts

Beerbelly - you are beyond my area of expertise, but I do know that the break in procedure is to run the first tank on premix. I'm not sure if the dosing rate is variable on the engine? Or perhaps premix is just more reliable at getting everywhere it needs to quickly?

[papajoe]

As far as I'm aware you can't change the pump dose. I have a feeling that the original issue with the block needing reboring was a blocked check valve from the oil pump to the fuel filter. Another thing replaced. I can't see how an increase in oil (to a certain amount) will effect the electrics to the plug.

[A1an]

Originally Posted by papajoe

As far as I'm aware you can't change the pump dose. I have a feeling that the original issue with the block needing reboring was a blocked check valve from the oil pump to the fuel filter. Another thing replaced. I can't see how an increase in oil (to a certain amount) will effect the electrics to the plug.

It won't.

[9D280]

Originally Posted by beerbelly

and run it on just petrol cos your weakening the afr putting oil in

Aye, it'll smoke like a Marlboro' red addict & not pull the skin off the proverbial rice pud, but I also ran in a premix 2- stroke on 25:1 for 60 odd litres after a total rebore rebuild and apart from cleaning the plugs (which kind of happened on it's own when I swapped to a 50:1 tank) it worked fine on the same plugs etc for the rest of the season.

Originally Posted by Poly

He's just rebuilt it. Normal run in procedure is 50:1 plus the autolube for the first tank.

Yep. Seagull mix is what you need for the first few hours! (along with a gas mask!)



No spark is likely going to be one of three things:
- dead coil
- dead trigger
- Short somewhere.

Now, I assume both plugs don't spark? I don't know your engine but I would be initially looking at anything wired in the stop circuit - could be overheat switch, stop button (some Yams had one on the side of the case) or possibly a low oil switch In the oil reservoir.

Remember the key switch also shorts the deadman circuit when in the "off" position.

I'm assuming you have separate HT coils on this engine? - If one of them (or the trigger circuits under the flywheel) had failed I would have thought only 1 plug would be "spark free". On a 2 cyl engine one down is usually enough to stop it. A 3 cyl it will run like a dog - just - if one cyl goes down. (don't ask me how I know! )

Check all your kill circuit switches - plenty of Yam wiring diagrams out there...

[matata]

I did a total rebuild of my force 120 10 yrs ago from re pistons up. As part of the diagnosis and testing I needed a digital voltmeter that measured ,from memory, not the peak voltage but the root mean square voltage and that gave a true reading of the coil or stator output. I have one of those meters and happy to lend it to you for diagnosis. I'f your electricity knowledge is not great you may need someone to hold your hand while you work things out. Give me a shout if I can help. Nik

[thestig1973]

Originally Posted by matata

I did a total rebuild of my force 120 10 yrs ago from re pistons up. As part of the diagnosis and testing I needed a digital voltmeter that measured ,from memory, not the peak voltage but the root mean square voltage and that gave a true reading of the coil or stator output. I have one of those meters and happy to lend it to you for diagnosis. I'f your electricity knowledge is not great you may need someone to hold your hand while you work things out. Give me a shout if I can help. Nik

Nik

That is a very kind offer and any assistance you could offer would be very much appreciated, and obviously I would make sure your efforts are rewarded via pound notes/beer tokens

[thestig1973]

Originally Posted by matata

I did a total rebuild of my force 120 10 yrs ago from re pistons up. As part of the diagnosis and testing I needed a digital voltmeter that measured ,from memory, not the peak voltage but the root mean square voltage and that gave a true reading of the coil or stator output. I have one of those meters and happy to lend it to you for diagnosis. I'f your electricity knowledge is not great you may need someone to hold your hand while you work things out. Give me a shout if I can help. Nik

Nik

That is a very kind offer and any assistance you could offer would be very much appreciated, and obviously I would make sure your efforts are rewarded via pound notes/beer tokens

I have good mechanical knowledge and very basic electrical from many years ago when I was an apprentice car mechanic...... However the only knowledge I have of 2 strokes is rebuilding motorbike engines, but never had major electrical issues

[papajoe]

Well, the search goes on, I managed to get another coil and still no spark, whats next down the line! starting to drive me crazy!!!!

[matata]

Go to a site called marine doctor. He's a guy in canada and from there he helped me diagnose and rebuild the engine. Trawl his site, watch his videos, be methodical and understand what your doing. You may need to download a manual. Keep me posted Nik

[papajoe]

No luck on the marine doc site so I've got hold of a new cdi pack, with new stator exciter coming. I've got hold of some used coil but I'm confused. Reading the manual about testing ignition coils, the primary coil is giving a continuity reading in specification but when I check the secondary coil (ht lead to black wire) I don't get any reading. Either my existing and replacements are dud or am I doing something wrong?

[papajoe]

Turns out it was the cdi, cheers for the input

[Last Tango]

I know it's a long shot, but I've seen corrosion in the wires themselves cause internal breaks in the harness. Probably going over stuff you've already covered but double check the internal ground connections around the engine. Pay particular attention to anything that's mounted on rubber/plastic stand-offs because it will rely on wired grounds and I've had issues with these before.

[spartacus]

Originally Posted by Last Tango

I know it's a long shot, but I've seen corrosion in the wires themselves cause internal breaks in the harness. Probably going over stuff you've already covered but double check the internal ground connections around the engine. Pay particular attention to anything that's mounted on rubber/plastic stand-offs because it will rely on wired grounds and I've had issues with these before.

The OP traced the fault to the CDI, but good post before starting to strip an engine down. Outboard manufacturers should be forced to use tinned woring as a matter of course. Any multimeter set to continuity (audible signal) should be the first port of call.