one and a half cylinders

[B-rad1983]

Hey there i have a 1993 25hp 6l2twin carb and it seems that the top cylinder only gets half the rmp as the bottom one i was wondering if any one had come across this befor im not sure if it is the cdi or what and with a new onenear 500dollars i dont realy want to go and buy one to find the problem is still there

[Inducted]

Always give a complete model # !!!! How do you know the top cylinder is getting half the RPM of the bottom? Is the spark not firing every other time? Just a guess maybe a fuel issue. Top cylinder is performing poorly due to fuel issue not CDI (spark) issue.

[99yam40]

As always check compression, spark,and timing.
If all that is good then look at the fuel / carbs

[bumperfood]

I believe that model has a coil with two leads to the spark plugs. Both plugs fire at the same time. You can check to see if its the coil giving you a problem, by taking the lead from the the top spark plug and replacing it it with the lead from the bottom spark plug and putting the lead from the top spark plug on the bottom spark plug. If your problem is now with the bottom cylinder then your coil might need replacing.