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With the infamous early Merc triples (that I run and love) the top cylinders tend to fry pistons on a regular basis: Of the dozen plus to come through my shop, only two had a good top piston. Merc's solution was to put .0785 jets in the top carb (there are only two carbs) and .072s in the lower. (Normal jetting was .074 in both.)
From running hell out of them, I find that the test plugs run about the same with this unbalanced jetting.
Jeff
"We live at the bottom of an ocean of air." - General Marvage Slatington
I'd say its usually exhaust tuning that determines the final mixture in a 2 stroke combustion chamber regardless of what went in via the carb.
Do you think cutting a tuner down would cause a lean condition? My plugs look lean after modding my exhaust on my yamaha 30hp 3 banger.Originally Posted by Powerabout
Yes!
Does any anyone know were I can buy a jet kit for a small Yamaha with Nikki carbs?
I would try Ebay, you guys seem to have all the parts available in the US.
On the note of exhausts and tuning, why do 2 stroke outboards have a simple flared tube exhaust and housing and not develop an expansion chamber similar to that of 2 stroke motorbikes and jetski engines etc. The amount of power gained from a tuned expansion pipe giving reverbing sound waves holding in the mixture is phenomenal. Is the mid section just too narrow or does the exhaust exit have something to do with it also ? Could you not rid of the exhaust housing and tube and then squash in a power pipe that could be water cooled to reduce heat if needed ? I know it would sound great ! Ring ding ding ding. Power band !!
The race never stops
MX bikes make a lot more power for sure! A Kawasaki KX 500 probably makes twice as much power compared to my 496cc Yamaha 30hp.
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