Tohatsu MFS3.5A S 2008 Carb Setting?

[xixp]

Hi ,

Ive just bought this used engine and the previous owner told me had to replace the carb before putting it for sale becuase it had been left 4 years without being used. (He gave me the original carb and its gummwd).
Engine starts fine but it does not idle smoothly. I was wondering about the pilot adjuster factory setting to try to check its adjustment before attempting to mess with the carb. Thanks!

 

[pvanv]

If you drill out the EPA plug, you can access the pilot screw. But considering that the reason you are having issues is undoubtedly a too-lean condition from the prior owner not running the carb dry at the end of every use... making such an adjustment might work for a while... masking the restriction in the passages, but if you ever run long and hard enough to clear them, the carb will then be too rich. Better to clean it properly first, and then go from there.

The pilot screw is set by instrument at the factory, and was correct when the carb was manufactured. There is no "X-turns-out" specification for it. If you now compensate for some gunk, it may come back to bite you later on.

 

[xixp]

Today i took the carb apart and its in pristine condition so the seller was true when he told me he had a new carb installed before putting the engine up for sale.
The carb does not have the plug in the pilot adjuster but i tried turning it to both sides before taking the reference of how it was but i did not achieve much.
The engine wanders from aost sttoping to high rpm.(its the failure inreferred as not idling well) It doesnt keep any constant idling speed whatsoever. (An air leak may be??)
I cleaned the tank and put fresh fuel, checked the fuel supply hose and it is not clogged.

Any other idea besides the carb or i should just buy another new carb? (Cheaper that taking it to a shop i guess)...thanks!

 

[pvanv]

Odds are the low-speed passaged are narrowed by gas crud. Happens all the time when gas is allowed to sit in there for a week or two. Then, to compensate, the idle speed is turned up to the point where the throttle plate is right near idle, but on the verge of transitioning to power. That causes the inconsistent speeds.

Yes, you could buy a new carb, but I would try soaking this one in real carb dip first. There is even a chance that the original carb might be resurrected.

 

[xixp]

Thanks Paul! I took the carb apart and sprayed it with carb cleaner despite of looking clean . (I did not have carb cleaner to dip the carb ). The surge is much less notorious now; remaining issue is that the low speed setting Is off.(obviously previous owner mess with it to make up for the dirt inside the carb).
I tried to play with it and the idle screw and i cant get the engine idle below 2500 rpms (i attached a tach to it) . Below 2500 it starts losing rpms until it dies.
I put it in a big bin in order to engage the prop and while it idles at 3000 rpms ,once fwd is engaged it goes down to around 1600 rpms which is aceptable i think.
Not sure why the big gap between engaging the prop versus idling in neutral. May be the carb is still dirty or the low speed pilot needs better adjustement? (I just unscrewed two turns from closed as to have an starting point, in my experience with two strokes these adjusters should not be unscrewed more than 2 turns because at that point a bigger jet is needed, may be 4 strokes behave differently?).
Good thing is that it revs up nicely with the prop engaged...

 

[pvanv]

Carb is still fouled; you are idling on the power circuit. Do a 4-hour soak in real carb dip, followed by a liberal flush out with generic carb spray, and it should improve.