FC150V Carburetor

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We've got a 20 year old John Deere push mower with the Kawasaki FC150V engine. Last year it developed the annoying habit of surging at idle. I'm interested in at least opening up the carb and checking everything out. Does anyone know anything about these carburetors, where the jets are, etc?
 
If you see screws on the side of the carburetor with springs on them those of your jets. I think on the four strokes though the jets are inside the carb and you have to take it apart to get to them. Surge at idle would be the low speed jet is clogged or partially cogged. Peronsally when I have a problem with a carb I just take the entire thing apart clean it and put it back together that way I know it's clean and their isn't another jet fixing to get clogged up
 
This carb looks pretty simple, here is a diagram...
http://www.ereplacementparts.com/kawasaki-fc150ves18-stroke-engine-parts-c-30157_30211_30498.html

The main jet is the one just above the bolt for the float bowl. Soak it with a lot of PB Blaster or something similar before trying to remove it. It is notched for a flat screw driver and just unscrews from the body of the carb, but it's probably not going to come out easily. Clean every passage you can get to with a small piece of wire and some carb cleaner. If there's a lot of varnish you may need to remove welch plugs to really access the inside of the carb. Make sure the gaskets are in good shape too, after 20 years they are probably disintegrating.
 
I took out the jets and cleaned them, but they did not look dirty. Nothing in there was varnished. There was a few tiny pieces of grit in the bottom of the float bowl but nothing much.

There doesn't seem to be much of anything to adjust on the carb in the first place. There is a low-speed idle screw but that's about it.

Of course I've never dealt with carbs in the past and this mower has always run perfectly before last summer so I'm a little out of my element.

What else should I be looking for/doing?
 
How do the gaskets look between the carb and engine?

Try holding the throttle at the same position when it starts surging and see what happens. If the engine runs fine when the throttle is held in place, it's a governor problem. If not, it's a fuel/air mix problem.

If the carb is clean and adjusted, the fuel is fresh, and there are no air leaks between the carb and engine, then it pretty much has to be a governor related problem.
 
Originally Posted By: 01rangerxl
How do the gaskets look between the carb and engine?

Try holding the throttle at the same position when it starts surging and see what happens. If the engine runs fine when the throttle is held in place, it's a governor problem. If not, it's a fuel/air mix problem.

If the carb is clean and adjusted, the fuel is fresh, and there are no air leaks between the carb and engine, then it pretty much has to be a governor related problem.


+1.

In addition to that: you have to do your usual due dilligence by doing the following:

(1) check the throttle plate shaft to body clearance, if it's deemed excessive, you need to replace your carb (small carbs tend not to be over'bored to oversize throttle shaft, not too economical).

(2) check to see if there's any nooks and crannies within your carb: e.g. assuming that there's no hidden rubber o-rings, etc. try dunk it into carb dunking solutions and then clean it afterwards.

(3) carb float maybe off a bit. As carb becomes old, float goes out of adjustment. Need to replace the carb float + needle +seat in order to restore that part.

(4) need to do idle adjustment again. Don't assume that the just because it was working fine before that it shouldn't be adjusted now, for it may be off by just that little bit.

(5) always start by a fresh new air filter (esp. paper filter type of engine). If the filter is slightly clogged (but still passes light test), you still gonna throw your idle air mixture ratio off...

6) whenever you take apart a carb, always consider using a fresh new gasket kit/set. Don't recycle old parts for you'll get into more trouble down the road (e.g. mysterious air leaks of all sorts).


Just my thought on carb rebuild subject.

Q.
 
I took out the two jets, cleaned them, and then re-assembled. The trouble is I'm not sure if it's the same or worse than before.

When the blade is engaged and I am cutting the grass, it typically does not surge. Only at idle, blade dis-engaged does the surging happen.

The filter and spark plug are both fairly new (within the past 2 years or so).

I admittedly don't completely understand how to adjust the idle. The manual is ridiculously vague on the subject, and goes something like this:

1. Turn screw A clockwise until you feel the needle lightly contact the seat. Back out the screw 1 turn.

2. Warm the engine at half-throttle, no load.

3. Pull the throttle lever back to the SLOW position.

4. Adjust screw B until the engine runs smoothly.

5. Adjust screw A to get maximum RPM. Back the screw out 1/4 turn.

6. Adjust screw B until the engine runs smoothly.


Frankly those instructions make no sense. Obviously 1-3 are straight forward. Screw B basically moves against the throttle plate, putting it in far will basically just peg the throttle wide open. If I turn it in far enough, the surging stops, basically because it's running at full throttle. If I back it out from there, it starts surging. So pretend I follow Step 4 and adjust the screw basically to full throttle. Then I have no slow idle at all, i.e. no engine speed difference between SLOW and FAST.

The function of screw A is completely foreign to me. It is pointed like a needle at the end and turning it seems to have no impact whatsoever on operation at any time.

Steps 4-6 make no sense to me anyway, even if screw A did something in the first place.
 
What steps can I take to confirm correct governor operation? From my reading the only adjustment is the position of the governor shaft on the arm. I reset that according to instructions - fast throttle position, arm fully counter-clockwise and shaft fully counter-clockwise.

If I hold the throttle in place, engine runs correctly.
 
In addition to all the great advice above, are you positive you're using fresh fuel?

I've seen these issues caused simply by fuel that's been sitting around a bit too long.

Even though all the passages appear clean, they may not be. Carbs can be finicky buggers. I'd try a new carb as a last resort.

Joel
 
That's a good point to make, but this is fresh 89 octane.

Carb is definitely last resort. I'd be surprised that something is worn out but anything is possible. The carb for this lists for something like $160 so I'm trying to avoid anything that major.
 
Ouch! I forgot about the cost of a replacement FC series carb. We had a discussion about that some time ago in regards to a Kawi V-twin carb. That's nuts.

I'm wondering if parts costs will come down though, now that you can buy an ~$1800 riding mower with a Kawi V-twin on it. They're really pushing their way into the residential realm these days.

Joel
 
I just finished taking the carb apart again and cleaned everything a second time. Everything looks like new in there in terms of cleanliness. The float is plastic and in looking at, I don't think there's anything funny going on with it.

I can get the surge to disappear by holding the governor throttle plate, at which point even if I let go it will hold the speed.

I'm kind of at a loss here.
 
This engine uses an internal governor and the gear is made of plastic. It's possible some teeth are missing or damaged. The bad news is the sump has to come off to check/repair it. The good news is the part is $5, plus the cost of a crank seal and sump cover seal. I'd probably fiddle with the carb some more before tearing into the engine though.
 
Is there a better way for me to fiddle with the carb than what I'm doing now? That consists of variously turning the only 2 screws I see and hoping for the best.
 
Replace all the gaskets. You can use generic gasket sheet from the parts store. You can also try soaking the carb, then blowing out all of the passages with compressed air. The parts cleaning can kits they sell at parts stores can eat plastic parts though, so you will need to disassemble the carb as much as possible. At that point the only way you will get a cleaner carb is to buy a new one. Honestly though, since you have already cleaned it twice with no change, and the engine runs fine when you hold the governor, I'm not sure the carb is your problem.

Usually on something that has been used consistently, the carb won't be that gunked up. On a 20 year old engine I wouldn't be surprised if the governor gear has some sort of wear or damage though.
 
I've got that same engine on my Snapper. I had trouble with idle quality for a while. The ethanol in the gas was the culprit. I switched to 100LL, Avgas and my problems went away.

My version of that carb has a jet on the outside, located on the LH top. Make sure it's not clogged with dirt, if you have it.

The instructions you posted make some sense. They want you to adjust the idle speed (screw B) and idle mixture. With the eventual goal being the idle mixture 1/4 turn "richer" than the mixture that gives the highest idle speed.

As the mixture that gives the fastest idle speed will be a bit lean for good throttle response and cold engine running will be difficult.
 
Thanks for all of the help so far.

I understand the basic structure of the instructions for setting idle, but I don't notice any difference in turning screw A ever, and the only way it will run smoothly by adjusting screw B is with it all the way in, which basically just holds the governor.

It may be time for a trip to a repair place.
 
It does sound like your idle jet is clogged. Might want to take it apart and ensure all of the idle passageways are clear.

If the idle system is clogged, it will act exactly like you describe. Carbs are one of those things that take "thinking" to get right. And time to ensure absolute perfection when it comes to clear passages.
 
one more note: one of the best tools to have RE: servicing carb rebuild is compressed air. You shall use it to blow dry the fuel bowl, blow clear of any nooks and crannies and clear any possible small debris left behind inside certain passages, or clear very minor clogs.

W/o compressed air: you cannot do much(really).

Fortunately: those B&S carbs I serviced these days (mostly the 6xx series, with a side-draft carb made in China) are so cheep that a replacement typically costs between 28~38USD each. So I'm not crying over the cost of a new carb if it's deemed faulty (and surely not gonna expect much out of such cheep carb either).

Q.
 
Originally Posted By: Cujet
It does sound like your idle jet is clogged. Might want to take it apart and ensure all of the idle passageways are clear.

If the idle system is clogged, it will act exactly like you describe. Carbs are one of those things that take "thinking" to get right. And time to ensure absolute perfection when it comes to clear passages.


Interesting thoughts. I brought the mower in this morning to have the "experts" fix it. We'll see what they say, although I admittedly don't have much faith in small engine repair outfits.
 
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