I have a Toro MX4250 that started surging yesterday. I cleaned the air filter, tried Seafoam, checked the fuel filter and added new gas. I looked at the throttle when its surging and can see a mechanical action triggering the throttle. I included a video below showing whats happening.
Either too much air or too little fule.
So eliminate the first by saturating the manifold with WD 40 or similar from a trigger pack ( NOT A SPRAY CAN ) .
If the mower blows white smoke or significantly changes engine speed there is a manifold leak.
Fairly rare but they do come loose, crack etc.
After that is it remove the carb for a proper clean.
Thank you. I am an IT guy and not very mechanically inclined so am getting a bit worried about fixing this myself.
Do I soak the air filter in WD40 or spray it into the manifold? (I assume the manifold is the area around where the air filter fits on)
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Intake manifold: Is the part that the carb bolts to & has runners that bolt to the engine.
You spray around the outside of the intake manifold, where it bolts to the engine, this is where it sucks in when running, so "if" you have a leak it will show out the exhaust as Bert described.
Bert means saturating the areas between the carb and the engine, that is the intake manifold. If there are no changes in engine speed, that is good, but means the engine is running lean and probably a carb issue.
Hello, I took apart the carburetor today and cleaned it using Berryman Carburetor cleaner. I ran a paper clip through the two jets coming up from the fuel bowl and shot the spray through it until it came out the other side. I cleaned the entire carburetor using the cleaner and ran the paper clip through all the holes.
I also sprayed the cleaner around the manifold and saw white smoke. However, i think the spray was landing on the exhaust which was causing the smoke as opposed to the smoke coming from the engine.
The good news was that I was able to get the carburetor back together and the engine started! (I was worried about this . The bad news was that the engine resumed the surging. However, I noticed something today and its that the engine only surges and runs rough when idling without load. Once I engage the blades the engine runs fine.
Looking at the attached diagram I don't think I cleaned the single jet in the bowl (See attached picture)... Could this be causing the surging when idle issue?
Carbs have 2 fuel circuits.
One for low speed running or idle and anther bigger one for high speed running.
In your case the idle circuit has a blockage in it .
So it is back off with the carb for more cleaning.
And a carb is not a Macintosh so please no paper clips. :laughing:
A strand of copper wire or something softer than the brass the parts are made from.
try this site http://outdoorpowerinfo.com/ and look for the cleaning instructions for your carb.
bertsmobile, thank you for all the quick responses! :thumbsup:
I ordered the proper cleaning tools from Amazon and they'll arrive tomorrow. Wow!
My carb has the name Huayi engraved on the top of it. I assume this is the company who makes the carburetor. I'm not having much luck finding information in this unit from the internet including the site you sent. Is there a way to tell which circuit is the highspeed and which one is for idle?
Should be on the parts breakdown.
Main jet is the high & idle jet will be the idle.
Your carb will be copy of one on the page I sent.
It is a Chinese copy.
I'll clean it again tomorrow.. One more question though.
The engine surges when running at full throttle without the blades engaged. It stops surging when I have engage the blades without changing the throttle (still on full). I just wanted to make sure this problem would still be the idle/low speed jet?
The engine is governed.
There are 2 circuits in the carb
They are not independent but overlap.
At WFO 95% of the fuel comes through the main jet & 5% through the idle jet or around those sorts of amounts.
So untill the throttle is open far enough for the main jet to fully overwhelm the idle, a blocked idle will cause surging
flat out without the blades running or the mower moving the throttle butterfly is barely open .
When you put a load on the engine then the throttle opens up wide thus bypassing the idle jet problem.
Get some one to sit in the seat & work the controls while you watch the throttle open & close.
. The bad news was that the engine resumed the surging. However, I noticed something today and its that the engine only surges and runs rough when idling without load. Once I engage the blades the engine runs fine.