14-year-old weedwacker engine having problems

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Deathfire138

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Okay, so I found this old Model 1940 John Deere homelite weedwacker engine that's been sitting in my garage for 5-10 years... I saw it and figured I might as well put it to good use. I tried priming it, but to no surprise the bulb and lines were rotted out so I replaced them along with the filter plus I washed out the gas tank, put new two-cycle gas in it and it started on choke for a good 40 seconds and died. So then I put it on half-choke and it died out as soon as I started it and that's how it was ever since. So I took off the muffler, noticed it was carboned up. I then burned the muffler and tapped the carbon out, it ran a lot better but still wouldn't go into half-choke for long. It would run on choke for a long time, but as soon as you put it on half choke it would gain what sounded like at least 2-3,000 rpms and then die. I'm thinking the fuel-air mixture is too lean? Any ideas?

P.S. I also had taken apart the carburetor and it looked very clean, so I'm sure that's not the problem...
 
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Since it will run on choke you may only need to run some fuel system cleaner thru it. So try some Seafoam, Techron or Chemtool thru it and see if that helps...if not you'll have to soak the carb. and blow it out with compressed air.
 
Originally Posted By: Warstud
Since it will run on choke you may only need to run some fuel system cleaner thru it. So try some Seafoam, Techron or Chemtool thru it and see if that helps...if not you'll have to soak the carb. and blow it out with compressed air.


I'll try that later today or sometime this week, thanks.


Originally Posted By: flatlandtacoma
It is running too lean. Maybe an air leak on the carb from dried out gaskets? .


How could I check for a leak?
 
I'm assuming that it's a diaphragm carb. If it is, being that the engine runs on full choke only I'd guess that the pumping diaphragm might be weak, dried out and no longer pliable or it may have a small hole in it. A machine that sat unused for all those years likely needs a carb kit.

If you have an air leak, it will more than likely be between the carb and the engine. Check the carb mount bolts/nuts to ensure they snug. One way to test for an air intake leak is to get the engine running and very carefully spray ether (Quikstart) around the joining surface between carb and engine. If the engine rpms rise while spraying, there's a leak. Be careful not to get any spray into the carburetor intake. That will cause the engine to speed up and give you a false reading.

The age of the machine would lead me to think that it might have a Walbro or a Tillotson carb. If so, a kit should be readily available if you can determine the model of carb it is. I'm sure that if you research enough, you'll find what you need.

Good luck and let us know how things turn out.
 
Originally Posted By: boraticus

I'm assuming that it's a diaphragm carb. If it is, being that the engine runs on full choke only I'd guess that the pumping diaphragm might be weak, dried out and no longer pliable or it may have a small hole in it. A machine that sat unused for all those years likely needs a carb kit.

If you have an air leak, it will more than likely be between the carb and the engine. Check the carb mount bolts/nuts to ensure they snug. One way to test for an air intake leak is to get the engine running and very carefully spray ether (Quikstart) around the joining surface between carb and engine. If the engine rpms rise while spraying, there's a leak. Be careful not to get any spray into the carburetor intake. That will cause the engine to speed up and give you a false reading.

The age of the machine would lead me to think that it might have a Walbro or a Tillotson carb. If so, a kit should be readily available if you can determine the model of carb it is. I'm sure that if you research enough, you'll find what you need.

Good luck and let us know how things turn out.



Thanks for your input! I'm almost 100% sure the carburetor diaphragm is fine. When I took the carb apart I checked it and it moved freely and easily and looked intact. I'll check for a leak soon and it is a Wilbro carburetor. Thanks and I will let you know how it turns out.
 
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Ok, so I got it running on choke and sprayed some pyroil starter fluid around the carburetor and careful not to spray any in or around the air filter and I noticed no rev changes at all... I noticed one peculiar thing that I noticed a while ago as well... The air intake will periodically spit out a bit of gas during engine use and even if I pull the pull started slowly it will spit out gas... Not a lot, but little spits of gas. When I replaced the air filter I noticed the old one was the color of two-cycle gas and one corner of it seemed to be shriveled up and soaked in gas... Any reason why this might be happening?
 
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Are you sure a carb kit is necessary? I was trying to avoid having to buy one of those... The carb seemed fine. I checked some things like the diaphragm, the little rod and the float and what-not... everything checked out okay...
 
No. I'm not sure. I don't have the carb available to inspect it and it seems the electrics are working well.

If the carb is getting fuel and the engine isn't running correctly with the carb set in it's normal running position, what else could it possibly be?

These are pretty simple machines and if something goes wrong with the fuel system and a diaphragm carb is involved, it's either blocked orifices, passages or galleries, or defective parts within the carb. You've cleaned the carb. So.......
 
The only thing that could be possibly wrong with the carb that you've listed would be a defective part... But I checked a lot of them and they seemed fine. The passages and whatnot seemed clean... How much is a carb kit and where would I obtain one?
 
Find out what kind of carb it is, do an internet search for carb kit for that carb and you should find it. Should be less than $10.00. If you look around on ebay, you might find a complete, new carb for around $20.00.

I understand where you're coming from concerning spending money on an old machine but, it would appear you may not have much of a choice. But for ten bucks, it's probably worth it.
 
Ditto. I found a Walbro carb kit for $12 shipped, as well as a brand new carb(in the box) for $18 shipped for my 15 yr old trimmer. PO'd I wasted time fussing with it when it took 10 minutes to throw a new carb on it and adjust 2 mix needles. Ebay is my friend. Just google the carb number.
 
A couple years ago my 20 year old Stihl trimmer started acting up. Pulled carb to get the make and model, went to a Stihl dealer, laid down my $8 for a kit. I'd bet that a Stihl dealer would have a kit for your carb. There are only a couple of manufacturers of carbs and the kits are will cover several models. You'll likely get more parts than you'll need so lay everything out as you take it apart
 
Sorry for gravedigging.

I found and ordered a carburetor kit and only installed the pumping diaphragm. It worked! It started up and I put it to full throttle on half-choke for 30 seconds for warm-up then switched it over to no-choke and it worked great, just needs some tuning. I have only one problem, it has massive 'fuel stand off' or gasoline coming out of the air intake of the carburetor. I'm not sure if it has any affect on performance because whenever I let it idle on no-choke and then pulled the throttle it cut out, not sure if it's lean or rich I'll have to check, also when a lot came out it wouldn't start up again, so I let it cool down. In a bit I'll try to turn it over again. Any ideas, could it be another part gone wrong with the carburetor, I have the parts I only bothered to change that diaphragm.
 
The needle valve is leaking fuel. You should have one in the kit. Just change it out with the new and also use the new spring and retainer.

While you have it apart, it might be worthwhile to replace all the fuel lines.
 
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Originally Posted By: boraticus

I'm assuming that it's a diaphragm carb. If it is, being that the engine runs on full choke only I'd guess that the pumping diaphragm might be weak, dried out and no longer pliable or it may have a small hole in it. A machine that sat unused for all those years likely needs a carb kit.

If you have an air leak, it will more than likely be between the carb and the engine. Check the carb mount bolts/nuts to ensure they snug. One way to test for an air intake leak is to get the engine running and very carefully spray ether (Quikstart) around the joining surface between carb and engine. If the engine rpms rise while spraying, there's a leak. Be careful not to get any spray into the carburetor intake. That will cause the engine to speed up and give you a false reading.

The age of the machine would lead me to think that it might have a Walbro or a Tillotson carb. If so, a kit should be readily available if you can determine the model of carb it is. I'm sure that if you research enough, you'll find what you need.

Good luck and let us know how things turn out.



x2. Right on the money.
 
The main nozzle check valve has failed. It's a fixed jet carb. Sorry man it's junk. You can try to suck/blow through the main valve by holding fuel line up to the hole, and drip some seafoam on it, and it might free up, put your unit is running on the idle circuit supply.
 
Originally Posted By: boraticus

I'm assuming that it's a diaphragm carb. If it is, being that the engine runs on full choke only I'd guess that the pumping diaphragm might be weak, dried out and no longer pliable or it may have a small hole in it. A machine that sat unused for all those years likely needs a carb kit.

If you have an air leak, it will more than likely be between the carb and the engine. Check the carb mount bolts/nuts to ensure they snug. One way to test for an air intake leak is to get the engine running and very carefully spray ether (Quikstart) around the joining surface between carb and engine. If the engine rpms rise while spraying, there's a leak. Be careful not to get any spray into the carburetor intake. That will cause the engine to speed up and give you a false reading.

The age of the machine would lead me to think that it might have a Walbro or a Tillotson carb. If so, a kit should be readily available if you can determine the model of carb it is. I'm sure that if you research enough, you'll find what you need.

Good luck and let us know how things turn out.
No doubt borticus is right, replace fuel line and filter while at it
 
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