Help Req!

[robanfield]

I am having problems with my 50HP Yamaha carb model 4 stroke. I have had carbs cleaned but still not right. I am buying a Morgan carb tune to help get problems resolved but feel there might be more than balance req.
Is there anybody on here who lives within striking distance of the Wirral who could help me. I will obviously pay them. The engine has had very very low hours. Engine will only start with prime start lever full open and runs rough, I can rev it manually from engine head by hand but cuts out when I let revs die.
Plug 1 is clean other 3 sooted which you can wipe off. Motor is in a tank.
Any help advice would be appreciated.
Thanks, Rob.

[neil.mccrirrick]

Sounds like the air mixture is out there will be air screws to adjust the air id screw them all the way in and then a turn and a half out and see where that gets you. It will run black on tick over tho, getting an even colour across all plugs is what I need first then you can tune

[phantom 19]

Good luck with that, the 50hp four stroke carbed model was not yamahas finest hour. The later ones were better but the earlier ones were a nightmare of linkages, thermo rams and auto chokes etc. They need balancing absolutely correctly to stand a chance of running nicely, and when using a vacuum gauge as you need to, you do not balance the carbs to equal intake vacuums, rather the vacuum either increases or decreases slightly with each carb starting from no1 (I can't remember figures offhand).

When I was a yamaha engineer I remember being very pleased when the early one we used to deal with spat a rod out the side in a rare yamaha mechanical failure meaning I would never have to set up an early one again!

[robanfield]

Thankyou, I have the settings and will have carbtune next week. The problem is worse since I had carbs cleaned ultrasonically. Hopefully I might be able to move forward and then ask for more help.