4 hp Tohatsu won't idle.

[oregonducker]

MFS4A2D 2005
Starts easy and runs fine at high idle and up but won't idle down and stay there.

I've had it several years and the carb always hates sitting around not being used whether I drain it or not it wants to be cleaned. Anyway, a week ago I went to run it at home and it wouldn't idle so I pulled the carb, took it apart, soaked it/cleaned it the way I always do and put it back on but got the same problem. So I took it off and made extra sure it was clean. I could see carb cleaner spray coming out of all the little holes and through all the passages. I'm pretty sure it's clean. Still wouldn't idle. I then ordered new gaskets for the insulater/spacer thinking one of them was letting air by. Just put those on today and it still won't idle.

How many turns should the pilot screw be at to start with?
I have the throttle stop screw set to where it just comes off high idle which, if I'm right, is where the pilot screw takes over. I've adjusted that from 1/2 turn out to over three turns out but it does the same thing no matter where the pilot screw is and now I don't remember where it's supposed to be to start with.

Is there supposed to be an o-ring on either the pilot screw or the pilot jet? Someone referenced one on an older post but I don't see any listed in the parts.

 

[MattFL]

It sounds like something is still dirty. Blow cleaner and compressed air through every tiny itty bitty hole. Use a hot ultrasonic cleaner if you have one. For the future, using ethanol free gas significantly reduces issues after storage, and draining all gas from the carburetor is even better. Use the drain plug, it gets more out than just letting it run until it stops.

 

[km1125]

So you have drilled out the cap and did remove the idle needle valve when cleaning? The needle valve would be between 1.5 to 2.5 turns out usually.

When the carb is apart (and the needle valve removed), try pushing air into the OUTLET side of the carb when the throttle is closed. That would push air backwards through the idle port (tiny hole closest to the outlet side of carb). There is also an air bleed that needs to work so that any fuel will flow through the idle and low-speed circuits. I think that starts inside the choke end of the carb, but I'd have to look at one of those carbs again to confirm. If that's blocked air won't be flow to the idle and low speed circuits to atomize any fuel in those circuits so you won't get enough to run. I think I have a flow diagram of the carb that might better explain, but I'll have to poke around to find it.

And... not sure what you use the motor for... but have you thought about "upgrading" to a 6HP carb? Might be worth the cost if you could actually use the extra oomph.

 

[km1125]

Here is a diagram of what I was talking about...

 

[oregonducker]

I got the motor used and the needle cap wasn’t on it. I didn’t even know it ever had one until I saw it on the parts diagram a couple years ago. Thanks for the help. I’ll take it apart again soon.

 

[pvanv]

I have seen those up to 6 turns out. Set by machine at the factory. Of course, the proper way to remove one is to close it (gently) and count the turns. When reassembling, set to same number of turns.

 

[oregonducker]

Well six turns it is. Or almost. Running great now. Glad I saw that post before I took it apart again.