Yamaha 28A outboard prob .....

STEVEDUNSTABLE

STEVEDUNSTABLE

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Hi All ...... have been "assisting," (getting in the way and being a pain in the ar*e) spannermonkey of this parish, with his Yamaha 28A circa 1978,ish (s/n 664 s05132 if that helps)....it was running yesterday but then, (while lake pottering) lost power and now wont start... fuel lines clean, (inc fuel) plenty spark, fuel getting to cylinders (not flooded) plenty compression, just no start ....any thoughts, ideas please ??..........nothing illegal !!!!....THANKS ALL ....ps. its a pull start. So you can only try so often before arms drop off !!!!
 
Try priming the cylinder with a teaspoon of petrol.

or the plug has a crack in its insulation causing an intermittent fault. (Most likely)
 
I have a 28a yamaha, worked in the garage at home and the next day failed to start at the ramp.
Had a spark but changed plugs for new ones. Worked straight away. To get a better start try getting someone else to hold the engine while you pull the cord, get a longer and faster pull that way. For your info the plugs I use are NGK B7HS
 
Had a 25A with exactly the same symptoms, Turned out to be the diaphragm in the fuel pump was breaking up (I was told the older diaphragms break down in unleaded fuel) new pump (all of about 20 quid) and a good clean out of the carb because the pump is after the filter and the jets were full of little bits of rubber and she was back to sweetness and light.
 
After stripping fuel system removing bits from the cork sealing washer from the top of the tank cleaning every last part of the fuel system rebuilding and changing the plugs the boat started first pull today . very happy bunny .
 
Be aware that a faulty plug or lead may spark out of the cylinder, but under compression may well bleed current away before peak voltage is attained. Never assume that the ignition system is good under load unless you can see the peak voltages on a scope or the yamaha way is to measure the spark gap. IIRC from my motorcycle techie days, 6 - 8mm spark gap sounds about right.

You can buy a special tool from yamaha to do this or make one out of a bit of wood and a couple of nails.
 
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Plug should be an NGK BRHS10
The 'R' means resisitor, the 10 means a plug gap of 30 thou (I don't do metric!) as opposed to 25 thou as per norm.
So its a 'standard' plug in effect, ie normal seating and standard 'reach' if there is such a thing
Like what yer put in yer Bantam or FS1E Tinny!!
;)
 
Plug should be an NGK BRHS10
The 'R' means resisitor, the 10 means a plug gap of 30 thou (I don't do metric!) as opposed to 25 thou as per norm.
So its a 'standard' plug in effect, ie normal seating and standard 'reach' if there is such a thing
Like what yer put in yer Bantam or FS1E Tinny!!
;)
 
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