OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Engines Questions On Briggs & Stratton Engines Quantum 45 XE

HI All. i am looking for some answers or help with a quantum 4.5, it had been sitting for around 4yrs , i have taken the carby off and found it dry an a build up of like calcium white powdery scale in the carby almost electrolysis like (if you own a boat) ok so i have run a wire through Evey hole , removed seat and replaced it , removed the air/fuel screw and cleaned ,same with the tank. it starts easy but struggles to get off the idle, tried the air/fuel while running but no good , but if i cover half the carby intake it runs normal , indicating a possible air leak so that was checked and tested and ruled out, i have checked (visually) the valves but not the seating? any help on this would be gold

Mark

Mark this is Mark here.
If you manually operate the governor while it is running, does it run OK.
Just thinking it might be something to do with governor spring pressure.

HI Mark, well i will try to explain it wants to go, but seems to get too much fuel which is strange as it will run well when the carby is half choked , its doin my head in .

Governor spring all seems correct , and when operating it by hand too ??

Mark,
If you are restricting air intake to make it run better, you are forcing it to run richer, that would mean that it is currently running lean.

Mark, you dont happen to have the luxury of another carby to try? This would prove that it is the carby at fault.

You could also read the thread called CARBY BUGS. "Grumpy" talks about possible causes.

Mark, let's try to get the symptoms clear.

1. You said Quantum 45. That means it is a gravity fuel feed engine with the governor inside the crankcase?

2. Does it start easily?

3. Does it idle properly after warm-up?

4. When it is idling after warm-up, what happens when you advance the speed control? Does it hesitate, spit, stall, or what?

Grumpy, Yes it is gravity fed, it starts easy usually 1 to 2 slow pulls with the choke on (choke comes on when speed control is at max) it idles very nice and smooth.
if i advance the speed control too fast it will stall after trying to speed up , if i do this very slowly it will get slightly faster but then die, only if i cover the carb half will it act like a normal mower, i have at one stage noticed it was spitting fuel out of the carby while running , much like it was getting too much fuel and forcing some back out ?? or could this be a valve problem? thanks for you help guys, look forward to getting this sorted , and Mark ,no i don't have another carb to try but i am looking around to do just that .

Mark, when you advance the speed control this opens the throttle. If all is well the mixture is momentarily enriched by the carburetor when you do this, but various faults can cause this not to happen and the mixture can become lean when the throttle opens. A very mild case of lean mixture causes "hesitation": the engine speeds up, but it does not do it immediately. A moderate case of lean mixture causes a "lean spit": mixture in the intake pipe is ignited and fuel is sprayed back up the pipe with a kind of pop. If the air cleaner is not fitted, burning fuel may be ejected from the air intake. A severe case of lean mixture causes the engine to stop firing when the throttle opens, so the engine stops.

Your symptoms as described indicate lean mixture. There are some standard steps to take to find the cause.

1. Does the engine respond properly to the speed control if you partly close the choke?

2. If you remove the carburetor float bowl, put a cup underneath the carburetor, and turn on the fuel, does fuel run out of the carburetor full stream into the cup?

HMMMM Grumpy i think you are on to something, yes if the choke is on it runs well as you said it makes the mixture richer , and i will do the cup trick after the footy today Thanks , Also can you tell me how to get back into the manual section? i paid $15 a couple of weeks ago ,downloaded a SB 45 manual but are unable to get back into it to get other manuals ,what am i doing wrong?
thanks for the help

Grumpy, i removed the bowl and petrol flowed out nicely , Lifted float up and stopped no problems, i was told to soak the carby in boiling water with some dishwashing detergent in it for a while , that's where i am at .

Mark, as far as I am aware, boiling water with detergent in it will have little if any effect on the petrol gum that is the key ingredient in most carburetor fouling. There are two ways to clean a carburetor. One is a combination of metal probes and compressed air (you apply the probe, then blow out the gunk, then apply the probe again, to each drilled passage in the carburetor). The other method is a spray can of carburetor cleaner. The carburetor cleaner is faster and more effective, but the stuff is unfriendly to polymers so it may shorten the life of plastic or pseudo-rubber parts of the carburetor. It must be blown out with compressed air, to minimise the amount left in there to do harm. Of course if you reassemble the carburetor, attach it, and run the engine right away, the petrol will tend to wash away the strong solvents from the cleaner.

Since you have a clear supply of fuel to the float bowl, the remaining issues are the main jet, the drilled passages, and the mixture screw. The usual way to attend to them is to consult a schematic of the carburetor then blow the cleaner through each passage. It is seldom necessary to remove the permanent plugs (usually Welch plugs) that block off the ends of some of the drillings.

Once you have a clean carburetor, the next step is to examine the gaskets and flat surfaces, to ensure there will be no leakage. Then assemble the carburetor correctly. Finally, install it correctly so that the gaskets do not leak air into the intake passage.

It seems relatively unlikely that anything not covered by the above would be causing the fairly severely lean mixture situation you have. Leaking intake gaskets are less likely than a blocked jet or drilling, because your carburetor works better at idle than at high speed. Simple air leaks to the intake passage normally cause more deterioration in idle quality than high speed running. (This is because the leakage increases with intake passage vacuum, which is high at idle and almost non-existent at full throttle.)

If you have a problem accessing the same manuals section you have entered successfully before, you have an obscure technical problem and will need to send a Private Message to Bruce, the site owner and administrator. If you are trying to access the engine manuals, after subscribing to the mower frame manuals, you have to pay a separate subscription for each and that will be your problem.

Thanks Grumpy i will go through all the above AGAIN LOL and give it one more go , check and double check , will drop a line about how i got on and thanks for your help it gold .
Mark

Hi All, success with the carby thanks for all that helped it was a team effort , consider this thread closed

Thanks Mark, I'll close the thread. If anyone needs to post to it, just PM a moderator.