Engine only starts with throttle advanced

[srr5008]

I recently rebuilt my carbs and replaced all my fuel line components. Now the engine will only start with the throttle advanced. As soon as I pull the throttle back to neutral to shift it into gear, it cuts out. Any ideas?

 

[SumDumGuy]

I would re-check the carb (???).

 

[KMixson]

How clean is the gas/oil mix you are using? Is it the same fuel you were using before rebuilding the carburetor? Is your fuel tank clean? Is there any debris in it? It does no good to rebuild the carb and then run the same dirty fuel through it. Fuel can look good and actually be bad. Sometimes it can be very hard to tell if it is good. I would try a different fuel and then if it still gives you problems I would clean the carb again.

 

[kilroywashere1911]

I would re-check the carb (???).

I'm having similar issues, recheck the carb for what?

 

[SumDumGuy]

kilroywashere1911 » 12 Jul 2014, 10:58[/url]"]

I would re-check the carb (???).

I'm having similar issues, recheck the carb for what?

Ensure that it is clean and properly re-assembled.

 

[srr5008]

I just rebuilt the carbs, so I am pretty sure they are clean (but as a last resort, I'll probably wind up taking them apart again). And I've tried several fuel sources, boat gas tank and right from a 5 gallon can, with no luck.

 

[kofkorn]

Sounds like your idle circuit may need cleaning or adjustment. The idle circuit is the hardest one to clean because of the small hole size and there is usually no straight shot to the tiny orifice that provides the fuel. Many times, these holes don't fill with cleaner when you are soaking the carbs. Take a VERY small pin and use it to clean the two or three holes right next to the throttle butterfly plate. Also find out what your factory setting is for the Idle mixture screw and reset it. If you are able to start and run on a high idle, a good cleaning and adjustment should take care of it.

Good luck!

 

[srr5008]

kofkorn, I am trying to figure out where the idle circuits are located. My carbs have what I would call the main jet (that for whatever reason does not show up on any of the carb parts diagrams) that runs through the carb body and runs right through the throat of the carb by the butterfly valves. This jet has 3 holes on each side of it. Is this the idle circuit assembly? Or are the holes located in the carb body?

 

[kofkorn]

This probably isn't your exact carburetor, but it should be close. The idle mixture screw is circled in red and will be on top of the main throat. From what I can see, 1.5 - 2.0 turns from the gently seated position is your starting point.



It may be worth taking this out and spraying a little carb cleaner through it first. Before removing the idle needle screw, write down the current position of the screw by screwing it in and counting the turns of the screw until it gently reaches the stopping point. Then you can unscrew it and remove it completely for cleaning.

Don't attempt to use carb cleaner when the motor is running. It is essentially ether, and will remove the oil from your inner components. Best to use it when the carb is completely separated from the motor. When you are spraying into the idle screw hole, check to see if / where the spray is entering the main throat. This will be where the tiny hole will be to clean. It's usually right next to where the throttle butterfly plate closes against the carb throat.

Again, not the right carburetor, but it gives you an idea:




Good luck!

 

[srr5008]

I've attached my carb diagram:

I have already taken the idle screw out and sprayed carb cleaner in when I had the carbs apart. Strangely enough, both of them were at different settings (about 8 and 9.5 turns out - compared to the 2.5 turns recommended by the repair manual). I will try the idle circuits tonight - Thanks for all the help!

 

[kilroywashere1911]

I tried carb cleaner without results- took it to a boat shop where they did an acid dip(?) Rebuilt them and it solved the issue.

 

[huntinfool]

Sounds like your idle circuit may need cleaning or adjustment. The idle circuit is the hardest one to clean because of the small hole size and there is usually no straight shot to the tiny orifice that provides the fuel. Many times, these holes don't fill with cleaner when you are soaking the carbs. Take a VERY small pin and use it to clean the two or three holes right next to the throttle butterfly plate. Also find out what your factory setting is for the Idle mixture screw and reset it. If you are able to start and run on a high idle, a good cleaning and adjustment should take care of it.

Good luck!

This!

It doesn't take much to plug an idle jet.