89 Force 50 HP Has spark but only bottom cyclinders starts.

[WarrenJ]

My engine starts but only one of the cyclinders is running.

Following checks have been done:
Fuel is going to both cyclinders.
Spark is on both cyclinders.
Dont have a compression gauge, but both cyl seem to have equal compression.

Any ideas why the top cyclinder will not startup?

 

[WarrenJ]

Re: 89 Force 50 HP Has spark but only bottom cyclinders starts.

Update:

I have now done a compression test and have 150 on both cylinders.

I am completely stumped, I have spark, gas, compression but the top cylinder will not start.....any ideas guys...lets hear them :-(

 

[john from md]

Re: 89 Force 50 HP Has spark but only bottom cyclinders starts.

Warren,

Can I why you believe that only one cylinder is working?

You seem to know something about engines so I will keep this short. In a normally asperated engine (carbs), you need fuel, spark at the right time and air to cause ignition. The fuel mixture which will burn is relatively narrow and optimum is about 14parts of fuel to 1 of air.

You say that fuel is going to both cylinders. Have you determined this by spray coming out of the spark plug holes? If so, it still may be an incorrect mixture.

I suggest that, if you know that your carbs are clean and the floats are not stuck, to set the idle mixtures on both to 1 to 11/4 turns out. Try starting then and see what happens.

BTW, was the spark orange or blue when you tested it? Blue is the stronger of the two.

Regards,

John