Tohatsu 4hp 4-Stroke Cutting Out at Idle – Seeking Advice

[onemanorthree]

I’ve got a Tohatsu 4hp 4-stroke that’s been giving me a bit of trouble. It runs fine at higher revs, but when I bring it down to idle or put it in gear at low RPM, it has a tendency to conk out, even if it’s warmed up. I don't know what my idle RPM are, as it's not got a count. There are no warning lights.


Engine starts first pull. I've changed the spark plug and oil. The fuel is a mix of this year and last, not sure if that can be an issue, esp as it runs well at higher revs.
This happens when I use the external tank and the internal, so not an air leak in the external hose.

Before I go pulling the carb completely, I was wondering if anyone else has had this issue and can recommend a fix? Could it be something like the idle mixture setting, a vacuum leak, or a sticky float?

Appreciate any tips or ideas. Thanks in advance!


Cheers,

 

[Seastoke]

It will be gunged up shit in the carb, when you used it last did you turn off the fuel and let the engine stall.

 

[onemanorthree]

"when you used it last did you turn off the fuel and let the engine stall." - No, I didnt think I had to?

Here is a pic of the carb, I dont think it looks too bad? Float is moving fine.

I took the idle jet out and the plug for the mail jet and soaked them in carb cleaner, the sprayed the main jet with it.
Should I use those carb cleaning rods on the mail jet?

 

[Seastoke]

That yellow crap is from fuel , have you had jets out , I am no expert but I guess they are blocked

 

[Fantasie 19]

If the idle jet is clear and the carb clean you could just ootch the idle speed up a bit by turning the grub screw that controls it?

 

[wonkywinch]

The seal on the float chamber lid looks wrinkly. Is it possible you fixed an idle jet problem but now air is leaking in, weakening the mixture?

 

[Seastoke]

The seal on the float chamber lid looks wrinkly. Is it possible you fixed an idle jet problem but now air is leaking in, weakening the mixture?

If that carb is clean , I hope he does not run a car wash.

 

[wonkywinch]

"when you used it last did you turn off the fuel and let the engine stall." - No, I didnt think I had to?

Standard "laying up" practise for all small engines, lawn mowers, strimmers, chain saws etc. Especially important for two strokes and 4 stroke with E fuels in them.

 

[Boathook]

Sounds like the idle jet is partially blocked. Take it out and look through a magnifying glass. Even a slight 'lump' in the round jet hole will cause problems.

 

[onemanorthree]

If the idle jet is clear and the carb clean you could just ootch the idle speed up a bit by turning the grub screw that controls it?

This is waht I ended up doing, after fully cleaning the carbs, and it's no iddling perfectly.

But yes, on reflection, the carb was dirty. Replaced all fule, put in new fule filter too, so hopefully no more issues.