# Lawn Mower won't Start



## hpmaxim (Jun 26, 2010)

Hello,

I have a simple Craftsman pushmower (built by Husqvarna I think), powered by a 6.5 hp Briggs engine. Earlier this year, I decided to remove the carburetor and clean (using an ultrasonic cleaner). I've had great luck doing this in the past. The mower ran well but not perfect prior to cleaning. When I put the carb back on, I found that the mower would no longer start without the aid of starting fluid. If I put starting fluid down the throat of the carb it would start easily, and it runs great. 

The most obvious possibilities are a bad primer or if there is a separate pathway for the air from the primer that its clogged. I believe there is a separate pathway, but as far as I can tell, its not clogged (I've run a wire down it, and tried cleaning it multiple times -- and it seems unlikely it would suddenly get worse as a result of cleaning anyway). But it seems equally unlikely the primer bulb which is in a completely different assembly would suddenly fail when I cleaned the carb. The primer bulb feels completely normal. I tried removing the assembly and pumping the primer bulb to see if I could feel any air come out... I *MAY* have felt something, but it wasn't much. Is this normal or should it be real obvious?


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## geogrubb (Jul 28, 2006)

If you post the model, type, code etc from the engine it would help, depending on the primer type the gasket between the primer circuit and the carb could be damaged, as it pushes air through to the bowl in some cases it must be replaced if removed and in some cases you must use two gaskets. Have a good one. Geo


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## hpmaxim (Jun 26, 2010)

Geo,

I can't find any B&S numbers, only the original Craftsman numbers, which are probably not real helpful.

Here's a link to someone selling a similar lawn mower. The mower looks identical except my rear wheels are different (same as front unlike this one):http://dallas.backpage.com/ToolsForSale/130-65-hp-craftsman-lawn-mower/10393768

I believe its a 498170 carburetor, or at least it look an awful lot like it.










I presume you are talking about the flat grey gasket in the picture that goes between the air cleaner assembly (with the primer bulb in it) and the carb. I believe the air is supposed to be pushed through a little track in the air cleaner assembly that is sealed by the gasket, until it reaches that little hole directly below the left hole in the flange.


My gasket is in pretty sad shape. It has gotten progressively worse each time I've removed the assembly, but it seems to bolt back up in the correct position although I have no way of knowing for sure.

So I guess the obvious questions are: Is the gasket available without buying a new carb (and if so where), and how much air should be pushed through the track when I pump the primer bulb. Like I said, when I remove the assembly and pump the bulb I barely feel anything coming through, but I have no way of knowing if thats normal.


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## geogrubb (Jul 28, 2006)

Any small engine shop should have that gasket because it is so bad to create havoc, I would suggest getting 2 as it seems a lot of the aftermarket are made of a thinner product, just make sure the holes line up. Have a good one. Geo


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## hpmaxim (Jun 26, 2010)

I got an original Briggs gasket and put it in, didn't make a hill of beans worth of difference. I primed 5 times or so, and got absolutely nothing. Any other ideas? I assume it has to be either the primer or the carb (the pathway through the hole under the flange bolt hole).

With the air cleaner/primer assembly off the carb, if I put my hand over the outlet of the primer air track, should I feel a noticeable gust of air when I prime it?


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## 30yearTech (Sep 14, 2006)

Check the seal around the float bowl. I have had brand new carburetors with the gasket fall inside a portion of the bowl eliminating the seal. If the bowl has an air leak anywhere around the seal, the primer will not work.


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## hpmaxim (Jun 26, 2010)

I'm sure that seal isn't in great shape, but I think its in okay shape, and I'm pretty sure its properly positioned. To be honest, I don't know how I'd check the seal without simply replacing it. I fully disassembled and stripped down the carb a couple times since it stopped working -- and since there is fuel in the tank now, I'd really rather not pull the bowl off. Can you tell me how much air the primer is supposed to be pushing through? Would it be unnoticeable if I put my hand over the assembly, barely noticeable, noticeable, or very noticeable?


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## 440s-4ever (Feb 23, 2010)

Those primers will drive you to drinkin! Not a robust design but kinda clever. 

good luck


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## hpmaxim (Jun 26, 2010)

From looking at the pictures I've seen on the net, the primer seems to be nothing more than a rubber bulb and a plastic clip. Doesn't seem like there's much that could go wrong with it...


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## geogrubb (Jul 28, 2006)

hpmaxim said:


> From looking at the pictures I've seen on the net, the primer seems to be nothing more than a rubber bulb and a plastic clip. Doesn't seem like there's much that could go wrong with it...


You are correct that there isn't much can go wrong with the parts you refer to, however the air that the primer pushes has to travel along a somewhat exposed track from the primer bulb through the air filter housing into the carb primer circuit, into the carb bowl creating enough pressure at the destination to force fuel from the bowl up the nozzle and into the carb venturi to be sucked into the engine. If the outer gasket leaks the air never gets to the carb, if the bowl gasket leaks the air leaks out of the bowl without creating any pressure to move the fuel. When it works, it works, when it doesn't, well you see the results. I think whoever designed the setup was a very sadistic person. Have a good one. Geo


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## jsouth (Jan 31, 2008)

I had the same problem with the same carb. in the picture.I doubled the gasket,still did not prime up.So I change the plastic cover,and put the two gaskets on again,and this time the mower runs great.The other plastic cover was warp so that 2 gaskets would not work. Hope this helps.Part # for the air cleaner gasket is 795629.I have use so many of these gaskets,I go to the auto parts store,and buy gasket material,and have by wife make these.

Jerry


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## hpmaxim (Jun 26, 2010)

I talked to a local repair guy. He said the amount of air going through the primer should be barely noticeable and suggested I should be able to see fluid coming when I prime it. I don't. He said the only likely thing to go wrong with the primer was the clip that holds the bulb could unseat. It didn't appear to be unseated, but I pushed it in anyway, and it made no difference. I tried a 2nd gasket between the cleaner and the carb, but that didn't help either. He also said, that if the gasket between the top and bottom of the carb was bad it could be causing the problem but it would also be leaking fuel, which it's not.

The one thing that I neglected to mention is that to get it to run right, I had to monkey with the governor slightly. The repair guy thought this meant I was probably running a bit lean -- so perhaps my jet is still a bit clogged. Next time I run it out of gas, I'll take the jet out and try cleaning it... for a third time or fourth time.


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## 440s-4ever (Feb 23, 2010)

Does your engine have a plastic intake tube/manifold, and is it cracked? The tube between the carburetor and the engine. Are the bolts tight and the gasket in place? 

One sign of a bad vacuum leak is hard starting because the carb barely gets a vacuum signal. Starting fluid vaporizes easier than gas and is shot with high pressure, so it's going to put "fuel" past the leak point where the engine can pull it in. Once the engine starts it makes enough vacuum/air movement to atomize gas inside the carb. 

Another symptom of vacuum leak is lean mixture. 

Just thinkin out loud. good luck


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## hpmaxim (Jun 26, 2010)

The repair guy I talked to mentioned the same thing. I'm not positive, but I think the carb outlet bolts onto a metal part, not plastic. It seemed like it was in good condition. The gasket (o-ring) was there and in good shape.

In terms of the hard starting. The repair guy claimed that when I pushed the primer I should see one or two drops of fuel come out of the tube sticking out of the throat of the carb. I looked down there with a flashlight and pumped the primer repeatedly and saw absolutely nothing. So I think its failing to prime.

If there is a vacuum leak in the manifold or between the carb and the engine would that cause the primer to not function (as opposed to it just running so lean that it won't start)? When I pull the starter cord, it doesn't even feel like its trying. When I do use starting fluid it always starts on the first pull, and once warmed up it will often re-start on the first pull without the primer.


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## 440s-4ever (Feb 23, 2010)

If you have a plastic intake tube......The carb bolts to a metal bracket, and the plastic intake tube sticks thru that bracket and is what the O ring seals on. There's about 3 inches of plastic tube behind the bracket. 

Regardless of the actual malfunction, you're getting good hot starts because there's fuel remaining in the cylinder and just behind the valve. Pre-primed so to speak. 

good luck


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## hpmaxim (Jun 26, 2010)

jsouth, I removed the air cleaner assembly again this morning, and it is definitely damaged. Is it damaged badly enough to cause a problem? I don't know. Basically one of the flange bolts (the one opposite to where the primer air goes through) seems to be threading into the actual assembly, and the assembly is slightly cracked and deformed near that bolt hole. It doesn't look severe enough to cause problems, but might be worth a try to replace it. It looks like I may have threaded in the bolt too hard at one point.

geo, in terms of the bowl gasket, the guy said if it is leaking air in, I'd be leaking fuel out too, do you think that is untrue? If I recall the gasket seemed a little "loose" when I put it on, but it wasn't tightened down at that time of course.

Is there a good place to get either a new bowl gasket or a new air cleaner assembly type part?


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## 30yearTech (Sep 14, 2006)

There is very little air pushed by the primer, so it would be barely noticeable. If the mounting portion where it attaches to the carburetor is warped or deformed, then you can have an issue. Do not over tighten good and snug should be tight enough. Since the fuel level never reaches the the bowl gasket, you won't see any fuel leak out if the seal is bad, unless you tip the mower. If the bowl gasket has swelled and fit loosely on the carburetor body, this is a good indication that there may not be a good seal. You can pinch the fuel line closed with a pair of locking pliers to prevent fuel from flowing out if you need to remove the carburetor again for service.

If the engine runs good once started, then the intake tube is fine, warm engines generally do not need any priming to restart.

Best Of Luck....


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## hpmaxim (Jun 26, 2010)

I removed the bowl, and found the gasket was pretty well stuck to the top. I replaced the gasket anyway and found it made no difference whatsoever. So this leaves warped air cleaner housing and/or cracked plastic tube that the carb goes into? Any other possibilities?


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## 30yearTech (Sep 14, 2006)

If it's just the primer that's not working then it's not the plastic intake tube. The problem is the air filter base not sealing good against the carburetor body, or the port leading from the face of the carburetor to the bowl area could be plugged.


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## hpmaxim (Jun 26, 2010)

The engine hunts a bit at idle. I moved the governor spring to the other post and moved it around a bit, and it still hunts a little for the first 10 or 15 seconds of operation and then settles down. The hunting isn't horrible, it still runs okay and doesn't stall or nearly stall and then way overshoot. So I'm guessing, the mixture is just a hair off, thats what would make me think it could be the plastic tube.

I'm pretty confident the passage in the carb is clear, and pretty confident the base is slightly warped (probably from overtightening one of the screws), but it doesn't look warped enough to cause a problem and the warping is on the opposite side of the air track in the base. I guess I could pull off the bowl again and see if I can run a wire through the passage and then pull the carb and check the intake tube.


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## hpmaxim (Jun 26, 2010)

Okay, I pulled off the carb. The grey plastic intake tube looked like it was in good condition. I tried to stick a wire (.035" flux-core welding wire, .03" solid wire, and 22 gauge wire with and without insulation) through the primer air intake hole in the carb. I got it about 2" through and then it seemed to stop. I looked on the inside of the carb for where it comes out in the bowl and couldn't find anything. As far as I could see there was the jet, the hole in the same cavity as the jet (no idea what that is), the port where the float needle goes into. There was also a hole that seemed to go up at a diagonal and go no where, and what might have been on the edge of what looks like a freezeplug, but I can't tell the hole went anywhere either.

So where does the primer air intake tube (in the carb) come out? Is this normal? Should I assume I need a new air cleaner base at this point?

Thanks!


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## phillipmc (Jan 27, 2008)

I say replace the air filter housing where the primer is and buy an extra gasket that goes between the filter housing and carb. First try with 1 gasket if it works then great problem solved and the price of the extra gasket isn't that much at all. If it doesn't work put the other gasket on there with it and try again. Remember DO NOT over tighten this plastic air cleaner housing. or it will warp too.


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## hpmaxim (Jun 26, 2010)

Hi Phillip,

I already tried replacing the gaskets (and tried two)... No luck... I think my air filter housing is warped (from over-tightening), and I just ordered one off Fleabay... I'll try that, hopefully it fixes the problem.


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## hpmaxim (Jun 26, 2010)

Got the nused air cleaner assembly and tried it without success. I also tried pumping the primer a few times with the air cleaner housing next to my cheek. I could feel a nice squirt of air. So at this point, I'm thinking the problem is not the air cleaner assembly. I guess that leaves carburetor? Its just hard for me to imagine its the carb. I mean when I finished cleaningit, it was pretty darn **** and span.... 

BTW, there was what looked like a tiny ball bearing on the side of the carburetor which I think fell out while I was cleaning it. I still have it. I can't figure out where exactly it went or what it was for or if its in anyway relevant to my problem.


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## 30yearTech (Sep 14, 2006)

Those little steel balls are used to plug holes that are used to drill jets in the casting of the carburetor. If one fell out, it could be venting the pressure created by the primer and allowing the air to escape without forcing any fuel up the nozzle.


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## hpmaxim (Jun 26, 2010)

So dumb question... How do you re-insert the ball so it blocks air flow and stays in there?


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## 440s-4ever (Feb 23, 2010)

The steel balls are just pressed into the soft metal housing with an interference fit. Give it a gentle tap with a hammer/punch to seat it, then consider a dab of epoxy on the outside for assurance. 

The hole has already been deformed once and will never hold the check ball as tight as it was from the factory. You need a tight seal not only for holding the ball, but to generate a seal. Don't drive too deep and block the passage it's supposed to seal!

good luck


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## hpmaxim (Jun 26, 2010)

JB Weld it is...


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## hpmaxim (Jun 26, 2010)

Well, I stuck the ball in the wrong hole and couldn't get it out. But after one screw up after another, I think I got stuff resolved. I shoved a tiny wadded up piece of paper into both remaining holes and epoxied over the whole area. Epoxy hasn't dried yet, but I tried pushing on the primer and fuel went into the carb.


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## 440s-4ever (Feb 23, 2010)

I hope everything works out. 

Was the wrong hole a blind hole? For what it's worth, I did the same thing with an automotive carb once, not tracing down an extra check ball after rebuild.......needless to say ever since that headache my motto on carb rebuilds is "no extra parts"  Sounds like the no-extra-parts-club just got another member!

Good luck with it all


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## hpmaxim (Jun 26, 2010)

There were basically two extra holes (one on either side of the one with the ball went into). One of them definitely had some form of a freeze plug in it, the other not so sure. It went into the one with the freeze plug and just stuck there.

I left out the part when I filled the whole thing with JB Weld and it stopped working (completely stopped working, starting fluid would get it to start, but then it quickly sputtered out). At that point when I was hitting the primer fuel seemed to come out everywhere but IN the car (around the bowl and the fuel line to the carb). So I dug all the epoxy out of the holes. Pulled the bowl out, reseated the gasket, reinstalled the bowl moved the clamp on the fuel line, and put a piece of tape over the hole. Then it started working. So I decided if I shove a little wadded up paper towel in the hole it should keep the epoxy out and yet still seal the area. If the paper degrades I don't think it'll make a difference since the epoxy is bonded to the metal not the paper.

Anyway, epoxy is probably still not fully cured but I pumped the primer 4 times, didn't see any fuel going anywhere its not supposed to, and it started right up on the first pull.

Early on I also tried blocking the hole with my finger and pumping the primer and noticed some fuel going into the carb. With all the problems I had, after realizing it was the carb, I was seriously thinking of giving up and just buying a new carb.


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## hpmaxim (Jun 26, 2010)

Just as a followup, I finally got around to mowing the lawn today. 3 primers, and the mower started easily on the first pull. So it appears the problem is fixed. Thanks for all the help guys!


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