Troubleshooting 1989 Yamaha 50DETO 2 Stroke, Idle/Low rpm rough running

[YAM50DETO]

Yes the sync of all 3 carbs together was with the throttle plates completely closed not just at the idle position.
The Yamaha instructions and some good videos online show the process well so I'm happy with that.
Thanks

[YAM50DETO]

After sorting out an air leak on the main fuel tank pickup connector I recently replaced all the fuel lines from the carbs including the fuel connector on the engine. Tested last week and seemed to run fine from idle through to WOT over about 65NM and about 4 hours. I would close this as fixed but need some further testing just to confirm.

Also on the return journey I had an engine issue I hadn't had since the first time I tested the engine about 2 years ago and after about 45minutes a workaround to get me home. I'm not sure if it a separate issue or related but when cruising along the engine slowed down and refused to go above an indicated 1600rpm (4-5Kts). Like I say in the last 2 years and maybe 1,000NM this is only the second time this has happened so I would like to know if the symtoms mean anything to anyone?

• If you try and edge the the throttle any more than the indicated 1600rpm it will bog down and die unless you bring the throttle back
• I checked the autolube oil tank and that was nearly full
• There were no error lights on the engine, engine switched off and on again
• Checked all three spark plugs they looked to be burning normal
• If you pump the throttle quickly it won't bog down and away you go again the engine running fine at high rpm

Thanks

[99yam40]

I am guessing you meant to say pumping the throttle and not the primer bulb, is that correct?
because pumping to me means operating it multiple times.
I see no reason pumping the throttle would change anything.
Now pumping the primer bulb pushing more fuel into the carb bowls might make a difference if the bowls were not staying full

only thing I can think of would be to check to see what the timing was doing when this problem shows up.
if the timing is not advancing as it should, that could affect the power

[YAM50DETO]

Thanks.

Yes I meant pumping the throttle, opening and closing the throttle quickly a few times and the engine then goes past 1600rpm. If it dropped below 1600rpm repeat and rinse. Actually re-reading my thread and I did see this issue one other time prior to an ultrasonic carb clean, etc.

I will take my timinig light on the boat so if and when it happens again I can check the timing. Also I haven't cleaned the carbs since replacing all the fuel lines in the engine so that won't hurt to do either.

[zenoahphobic]

I have a feeling wear in the linkages or even butterflies is it. Therefore can be timing or a sudden influx of air.
Slowly advance your throttle (engine off) and observe and test the play with your fingers at various points to see that the butterflies and the advance is progressing smoothly. Then test your ignition timing whilst the engine is running for sudden advance or a sudden retardation, it need not be much at low throttle input.
To confirm one can alter the timing to see improvement, sometimes advancing ignition slightly above what is specified (in old two strokes) can solve stalling issues.

[YAM50DETO]

Thanks haven't had a chance to check the timing yet.

Not sure if this is related or a separate issue but I fitted a fish finder last week and when taking it out it was shuting off when I went above about 10kts, not sure what rpm as the tacho rarely works. Also when I start the engine the fishfinder reboots. As it shows supply voltage I noticed above idle it is putting out over 16v before the fish finder shuts off, at idle it is putting out around 13v.

I have tested an aftermarket regulator rectifier (6J8-81960-00) and I am getting the same issue of overcharging and no tacho. The battery is 70ah, a few years old, but holds charge and starts the engine fine. Also the battery maintenance window is light green so appears to be healthy.

[YAM50DETO]

IMG-9763.jpgIMG-9761.jpg

[YAM50DETO]

Ok I found out why the, in the online parts diagram, the reg/rectifier looked different! Mine is actually under "alternage 10" and listed as a rectifier assembly 6G1-81970-61 so would appear to be unregulated and not overcharging.

[99yam40]

that does now explain why the aftermarket RR did not regulate