carb problem??

[ProbeGT]

I have a force 120 on a Sportjet mercury unit.

I did a decarb yesterday on it and noticed something strange.

I removed the air intake box, held the engine to 1800RPM then sprayed deep creep trough the top carb. nothing happened. sprayed deep creep trough bottom carb, engine struggles.

Is something wrong with my top carb??

I also did a compression test (hot) and it has given me 145 135-137 145 145.

engine seems to run fine and has plenty of power and reach maximum RPM effortless.

 

[john from md]

Re: carb problem??

Your top carb may be running lean. When every you spray Deep Creep or WD40 etc, you should get a noticeable decrease in rpm. If not, there is either a problem with your mixture or you have a dead cylinder. Since your performance is good, I would speculate that the cylinder is running lean.

John

 

[Eshaw150]

Re: carb problem??

Your top carb may be running lean. When every you spray Deep Creep or WD40 etc, you should get a noticeable decrease in rpm. If not, there is either a problem with your mixture or you have a dead cylinder. Since your performance is good, I would speculate that the cylinder is running lean.

John

he hit it right on the money

 

[ProbeGT]

Re: carb problem??

ok, but 1 carb feeds 2 cylinders.

and plugs were all the same color on all 4 cylinders. Correct me if i'm wrong, but leaner cylinder would give a whiter plug wouldn't it ?

Should I rebuilt and clean my carbs to make sure everything's alright? Also i don't have a fuel filter between the pump and carbs, I think i should install one.

 

[john from md]

Re: carb problem??

It is interesting that your plugs are all burning correctly, yet there is no effect when spraying in the top carb. Their is no getting around the fact that the plug will not be the normal tan or grey color if it is burning lean. Yet, dumping all that fluid in the intake should have an effect.

I'm afraid I am stumped on this one.

John

 

[Eshaw150]

Re: carb problem??

I agree on whats stated above. I am also stumped. Something should have happened to the way it runs if the plugs are firing corectly.

This is an odd one!!!