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search --workshop manual for Walbro carburetors
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search --workshop manual for Zama Carburetors
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the high speed needle is set first ( one closest to the air filter) to obtain smooth high rpm running then the idle needle ( next to the engine ) is adjusted as you slowly slow down the rpm
final idle speed is achieved by adjusting the throttle screw and should be just slow enough that the centrifugal clutch is not engaged
sounds like a fuel flow problem.Pull the fuel line off at the carb and see if fuel flows well when you turn the gas on.If the fuel is flowing to the carb,you will have to remove the float bowl off the bottom of the carb and check for fuel flow through the needle and seat which the float controls in the carb.If fuel flows well through the needle and seat and the float words well without binding, next is to clean the main jet which may be plugged.Ethanol in the fuel these days can cause problems in these areas.ALWAYS shut off the fuel in all small engines and let the carb run dry when storing small engines for any length of time.
check that you have the governor control rod on the butterfly lever of the carby connected correctly
it appears that the lever is at full throttle when you connected it and so the governor cannot pull it back to correct speed
if correct the throttle will be at full speed when stopped but will move with the go lever to slow when you manually push the gov lever
Like a lot of stationary engines a generator engine is governed, or at least should be governed.
That is to say, when the engine is started it should be running at a predetermined speed which is not an idle speed but the speed the engine works most efficiently and that typically would be in the region of perhaps 1800 to 2500 rpm. In the case of an alternating current (ac) generator the speed will be determined by the alternator and the requirement of the frequency of the ac output to be around 50 to 60 cycles per second.
It is the function of the governer to maintain that preset speed within fairly close limits so when an appliance is connected to the generator and switched on the load increases and if it were not for the governer the engine would slow down which would be unacceptable. The governer therefore opens the throttle and restores the speed to the preset value. When the extra load is removed the engine will speed up momentarily and then restabilise at the right speed.
The governer is somethimes an engine driven set of bob-weights hidden inside the crankcase and sometimes nothing more complicated than a flap moving against a spring in the blast of cooling air from the fan. In all cases the governer is connected to the carburettor, typically by an adjustable link that includes a spring.
From your description it would seem the governer of your generator engine is jammed, broken, seriously maladjusted or simply no longer connected.
Clogged idle circuits in your carbs. Clean jets and passages.
You can try suck dirt out, therefore: Screw the idle mixture screw out ( almost totally ), give full throttle ( 1 second ) and then hold your hand against the carb air intake.
This will give maximum suction and can suck the dirt trough tje circuits.
Also, first drain the carb(s) to be shure there is no water in it...
Most likely the carb is dirty and needs a good cleaning. You can start with the spray cleaner, but it is best to use a good quality fuel system or fuel injector cleaner that you can get at your favorite auto parts store. I use Lucas products, but there are several good ones out there. Mix it into your master can where you get your gas in from the pump. You can use it in all your equipment to keep the fuel system clean. That includes everything from your mower, weed eater, leaf blower, generator, ATV, chain saw, motorcycles or anything that runs on gas.
The reason the engine oscillates like is because the dirty carb doesn't allow the fuel to flow so it leans out and the engine speed slows so the governor gives it gas to speed it up again then when it come up releases the throttle then the engine slows again and because the carb is dirty the cycle continues. If the fuel injector/system cleaner doesn't get the job done the carb may need to come off for a manual cleaning.
There are usually return springs but it could just be that your car coast a long time when in high gear before it starts to slow down. My Jeep is the same way, if I'm running at 55 I can coast for a few miles before I slow down very much.
I'm not quite sure about this answer but it occurs to me that it could be the governor. It sits at the back end of the armature and as the speed control is slid to faster speeds the governor moves away from its rest position pressing against the control plate. If the governor's pivots were to be binding, even slightly, it would explain the symptoms you are describing. A service manual can be found at:
While attending college I worked at a tool rental center and learned a great deal about matching generators to customer requirements and troubleshooting customer owned units. There are simple tests that you can perform, however, first some info on what to expect from a generator. Most generators are overrated and under powered. You should only expect to get about 60 - 75% of rating. Example, a commercial honda 5000w generator has an 11hp motor that can only produce about 9.5 hp at 3600 rpm. If a customer needed 5000w of power, we would rent them an 8000w generator because as the generator is loaded to max the voltage will drop. You generator will probably only provide steady voltage ex. 115v at 60 cycles to about 3500w then voltage will begin to drop. New generators have automatic voltage regulator that varies the power to the armature increasing/decreasing the power of the magnet. These voltage regulators suffer a high failure rate and are expensive. If your generator is not giving you 3500 watt at 115v 60 cycles your engine may have a few problems and your power generator end may need tweaking. (I would not expect to achieve 5500w at 115v with briggs 10hp) .
The governor is about 2 inches in diameter and turns off the cam gear inside the engine. It is flyball type with two or three small arms that react to rpm. The faster the engine turns, more force is applied to the governor arm to reduce engine speed. Easy to test, with engine running use finger pressure against the arm to increase speed and you should feel a greater resistance as the engine speed increases. Another simple test, remove air filter to expose butterfly inside the carb. Move the governor arm and check that the butterfly opens fully. If it does not open fully linkage and governor is not set correctly. Next, start engine and load generator up to max and check that butterfly opens to full as the load increases. When the butterfly opens all the way under load the engine is at max. Add up the wattage of all the tools/appliances you used to load the engine to get an idea of max load . Lets assume that the shop adjusted the governor properly, if the governor was not working the engine would over rev. and damage would occur. As you were told the governor spring controls speed and can be adjusted somewhat by bending tab or adjustment screw. But a review of your generator manual or that series of briggs engine will show that there are several governor springs available and different placement holes on the governor arm to attach the spring that will change the power curve. Pulling on the spring can only do so much, however changing the spring to different gauge /turns/material or differnet location on the governor arm will cause the engine to perform differently. These springs are sold thru briggs dealers by part number for your engine. This would be considered tweaking to get a different power curve.
Now for the generator. Some generators have a capacitor incorporated in the windings. This capacitor must measure within 95% of rating. Remove from circuit for testing. Finally look very carefully at the commutator rings for any evidence of brush bounce. If the brushes do not perfectly seat you will lose power. If your generator is brushless you can only hope that the diodes are within spec. because it is too difficult to test them. They also must be removed to test. Finally if your generator has an automatic voltage regulator the only test would be to replace with a known good part. At the rental center we stocked spare parts so that we could quickly find fault. There is soo much to learn and the life too short. I hope this helps good luck, please email your questions.
I've never been a big fan of the 180 OH family of engines in these things, but here goes. 1 - If the engine will stay running while it surges, close the choke a little at a time and see if it settles down. If it does, there is something amiss in the carb. The carbs on these engines are very picky about tiny bits of dirt. The good news is that they are fairly simple to take apart and clean, the bad news is that lots of the parts are plastic and break easily. At least they aren't too expensive.
2 - I've seen 2 ways to adjust the governed speed on these engines; a spring that connects to the governor arm at one end and a tab bent up from the sheet metal that mounts on top of the engine at the other - bend the tab so the spring is tighter to speed the engine up, and (b) a jam nut and screw mechanism that presses against a lever that pulls on a spring that connects to the governor arm - screw the screw in tighter to raise the engine speed. Note that in either case the mechanism adjusts the tension in a spring that pulls against the governor arm, this is helpful in finding out where to make the adjustment. Here in the US we want our 2 pole generators like this to run at 3750 rpm at no load so that we get very close to 3600 rpm at load. If you're using a DMM to measure the output of the generator in Hz, you want 61.5 at no load.
If nothing you can do with the choke makes the surge go away, you might have a misadjusted governor. The Tecumseh service manual has a great procedure for making this adjustment, essentially what you do is loosen the retaining nut on the governor arm, twist the governor shaft to its minimum speed position, then hold the throttle assembly at the idle stop and tighten the governor arm jam nut. Always keep a finger near the kill switch when running the engine the first time after this procedure, it's easy to mess up and have a runaway engine.