2 stroke not running right

[Kelpie]

My generally very dependable little Mercury (rebadged Tohatsu) 2.5hp 2 stroke has let me down.
I didn't think it was giving me full power yesterday so I took the carb apart and cleaned it up as best I could. There was some gunk at the bottom of the bowl but other than that it looked good.

Now, however, my preventative maintenance has led to it barely running at all. It will start and chug along very slowly, but as soon as I put any throttle on, it just dies.

Is it possible I've reassembled the carb incorrectly? I was using a spray can of WD40 to clean it, could this have blocked the jet (seems unlikely to me...)?

 

[geem]

My generally very dependable little Mercury (rebadged Tohatsu) 2.5hp 2 stroke has let me down.
I didn't think it was giving me full power yesterday so I took the carb apart and cleaned it up as best I could. There was some gunk at the bottom of the bowl but other than that it looked good.

Now, however, my preventative maintenance has led to it barely running at all. It will start and chug along very slowly, but as soon as I put any throttle on, it just dies.

Is it possible I've reassembled the carb incorrectly? I was using a spray can of WD40 to clean it, could this have blocked the jet (seems unlikely to me...)?

Carb cleaner works best. All the chandlers sell it. Check fuel for water as well. Thst will give similar symptoms

 

[Close hauled]

I had one of those and it was brilliant. Could it be gunk in the tank and fuel line?

 

[TSailors]

The usual suspects: Fuel? Spark plug?

 

[QBhoy]

Odds on to be the float in the carb sticking.

 

[ashtead]

How’s the compression? If you get it running maybe invest in some Aspen fuel from the local lawnmower salesman?

 

[FairweatherDave]

I agree with the others (it sounds very familiar to problems I have had in the past). Dirty fuel, the carb still being clogged - the stuck float valve being first check. Clean and clean again, particularly if you found a little crud in the bowl. New spark plug costs peanuts and just seems to solve things. Dirty old fuel is a pretty close second . Got nothing new to add really except I know the feeling and it sounds like it is flooding once you open up the throttle. I doubt you need to get to more exotic reasons.

 

[richardh10]

Almost certainly still the carb. Remove the jets, there should.d be 2 if its like the 5hp that I have, and give them a good blow. You should be able to see down the hole if you hold it up to the light. Also blow down the barrel that connects them. If you have crud in the fuel you may need to do this a few times. And fit a small inline filter so it makes it less likely to happen again!

 

[Blueboatman]

Don’t forget there may well be a tiny sleeve like fuel filter at the outlet from the fuel tank?

 

[penfold]

Unlikely but possible you've reassembled incorrectly, but those things are very simple with not many parts; more likely you displaced some of the grot from A(the bowl) and moved it to B(probably main jet/passages) where it's more of a problem. Repeat disassembly and blast through all the orifices with carb cleaner, which is horrible for both humans and the environment and thus much more effective at shifting grot. Compressed air is also very helpful at grot removal.

 

[PetiteFleur]

It's the fuel! I've had similar problems, clean the carb and use E5 Premium petrol and it'll work fine. Cured my Honda outboard, Honda lawnmower, 2 stroke strimmer and 2 stroke small generator.

 

[Kelpie]

Thanks for the replies.
I found that when I took the face plate off it would run just fine- so it seems like it wasn't getting enough air.
I had a spare carb which I put on and all good now. But I'll have another look at the dodgy one and maybe try to get some carb cleaner.

 

[Slowboat35]

Mine behaved exactly like this and it turned out to be degradation of the fuel pipes causing debris in the carb due to that foul E10 'petrol' stuff.