97 Force 120 dies at idle with cover off

[ksoltis]

Hello all,

Since last summer Ive been having issues and seem to be getting them dialed in. I have replaced the plugs, cleaned the carbs, done a link and sync, properly adjusted idle, rebuilt fuel pump, installed new inline fuel filter, and replaced broken reeds. Now while idling with the cover off it runs for about 2 to 3 minutes, then sputters and dies. I tried adjusting the mixture screws, they're right about a full turn out, idle, throttle cable, etc, a few times with the same results. Just before packing it in for the night I decided to put the engine cover back on and start it up just to see what happens. It idled great and didn't die. I've heard of things getting better with the cover off but not with it on. Anyone have any ideas?

 

[jerryjerry05]

If it runs for 2-3min then dies??
I'd look at the fuel system.
Check the fuel pump and then the inline connectors.
​The fuel we burn, most has Ethanol and it destroys some older hoses and plastic.
​The connectors have rubber in them and it can go bad and leak.

 

[foodfisher]

Could it be, with the cover off there's lots of air flow through the carbs drawing more fuel through the carbs causing flooding/? Do the rpm's increase before dying?

 

[ksoltis]

I thought increased air flow could be part of it. It sputters and then dies so there's no increase in rpms. I looked over the fuel lines and didn't see any noticeable leaking but that is on my list of things to replace so may as well do it sooner rather than later so I'll give it a try.

 

[jerryjerry05]

Foodfisher, I think your way off on that one??

 

[foodfisher]

Yeh, I was just throwing something against the wall. How about with the cover on there's less air to match less fuel due to bad fuel lines. Ksoltis, Will it do more than just idle?

 

[ksoltis]

It throttles up in neutral and I gave it as much throttle in gear as I dared with the prop spinning out of the water but it responded fine.

 

[foodfisher]

Curiouser and curiouser, are there any hoses or wires hanging loose that installing the cover rearranges?

 

[Jiggz]

No Title

Try increasing the fuel air mixture screw setting about another 1/8 of a turn and see if that'll make a difference. In fact, experiment with it and see if it'll idle good with cover off up to 1 1/2 turn out on the fuel mixture screw. If it does, then you know where the problem is. Double check the tip of the fuel mixture screw make sure it is not damaged.

If it'll not idle good from the above experiment, there is a good chance the idle or low speed jet on the carbs or one of the carbs is probably clogged. Here's a simple diagram of a carb showing the low speed and high speed jets.

 

[ksoltis]

Now that the rain finally stopped and I could get out and take a closer look I noted quite a few things. There is a small amount of fuel leaking from the fuel pump that was rebuilt last summer, and the carbs have fuel all over them. The bottom of the bowl on the outside has fuel on it and I pulled the screw in front of the idle jet, I believe, and there was fuel that came out of there while off. Not sure if that's normal carbs aren't really my strong suit. There's also some fuel on the top of the carbs and every time I go to start it I have to hold the enrichment valve to the point where fuel is overflowing out the carbs. Seems like I have more going on than I originally thought. Thanks all for your help so far.

 

[jerryjerry05]

The enrichment circuit: I believe it only works if you repeatedly push the key in.
The old style choke would stay choking when the key was held in.
​The new gives a shot of fuel each time the key is pushed in.(I think)

​Now if the enricher's diaphragm is bad it can feed fuel all the time.
​Try pinching off the line?

These carbs are real simple, easy to clean.

 

[Jiggz]

Sounds like you are flooding the carbs heavily. Try isolating the enrichment fuel for now and see if that'll improve things.

 

[ksoltis]

Might be a dumb question, but how would I go about isolating the enrichment fuel?

 

[Jiggz]

The actual name is really fuel primer valve or primer valve. It's usually located on the top carb and has two small fuel connections. One of the hoses goes to the carb while the other is connected to the carb's bowl. By pinching the hose coming off the carb's bowl you can isolate the primer valve.

 

[ksoltis]

Ah ok. I know where the valve is I wasn't sure if I just had to pinch it off (I tend to overcomplocate things) I'll give that a try first and see what happens

 

[ksoltis]

I cleaned out both carbs, got a good amount of junk out of the top one, and adjusted the floats. I put it all back together and pumped the primer. Once the fuel filter started to fill up fuel started shooting out of the overflow on the bottom carb every time I pumped the primer. Both the top and bottom bowls had fuel in them. What did i screw up?

 

[Jiggz]

No Title

It has something to do with the proper level of the float. Usually, the float level can be adjusted by a tiny tab where the needle seats. If you have the entire carb dismounted, the float setting can be done easily by inverting the carb (with bowl off) and the float should only drop down to a level point with the body of the carb and closing the needle or inlet. You can test if it is close by attaching a short fuel hose to the fuel connection and blow slightly into it and would not be able to.

If the carb is not entirely dismounted, you can still do the same test by lifting the float manually with one hand at a level position and then try blowing into the fuel hose and should not be able to, indicating the fuel inlet is closing properly. If not, then make adjustment by squeezing or prying open the tiny tab (needle nose pliers are perfect for this) where the needle seats.

There are a couple of reasons why fuel will overflow to the overflow port. Improper float level setting, stuck float, stuck needle valve and debris at the inlet port.
Here's a pic of what the float and needle valve looks like. You might have to save and print it out to see it clearly. NOW YOU NEED TO BE AWARE THAT YOU ARE ONLY TO SQUEEZE THE PRIMER BULB UNTIL IT IS FIRM. If you continue to squeeze it after it is firmed, then there is the possibility of fuel overflow. The final test is when the motor is running, there should be no fuel overflow from the overflow port, unless it is tilted upwards.

 

[jerryjerry05]

You have the metal floats? or the plastic?
Pics?
​The metal can leak and won't work right?

 

[ksoltis]

I have the plastic ones. I adjusted them before I put them back on and I think I adjusted it too high so I'll give it another shot.

 

[ksoltis]

Update:
I pulled the carbs apart again, took another look at the floats and they seemed ok. Then I noticed the needle wasnt dropping down when I turned them rightside up, wiped them both down with some WD40 and they moved freely. I put everything back together and all the fuel stayed inside the carbs! Started her up with much less effort than before, just one click of the enrichment valve and it idled endlessly with the cover off and on. Seems all thats left now is a water test. Thanks for all your help.