# Husqvarna 372 Help



## tomatick (May 5, 2011)

I have a 372 that will only start if choked. Will barely run at medium to full throttle. Will not idle or run slow. Replaced fuel line, fuel filter, air filter, coil, spark plug, re-built carb, cleaned carb, atempted for days to adjust carb, Started high and low one out. Does not seem to effect saw. Did pressure and vaccum tested on the case. Saw is tight No air leaks.

Suggestions just can not get the saw to run. Do not think I have any air leaks. Have spark and fuel. What about purchasing a new carb? If so what kind, heard husky recalled Walbro carb. I got to get this saw running. Anyone please help!!


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## paulr44 (Oct 14, 2008)

First, we need to know what the compression is like - should be 150 or better given the size of saw.

Unlikely on saws, but could be plugged up exhaust screen or port.
Could be bent/sheared flywheel key, also unlikely on saws.
Could be throttle plate isn't opening fully.
Could be restricted fuel line/filter (delivery to carb.).

Haven't heard anything about a walbro or husky recall on saws. I reviewed the bulletins on the 372XP/EPA, nothing about a carburetor problem.

These saws do have a rev-limiter built into the coil, it could be that it's faulty. I've had Stihl 4-mix motors have trouble revving up intermittently or not at all and it ends up being the coil.


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## tomatick (May 5, 2011)

*Further information*

Paul,

Thanks for the help, determined to figure this out.

I think Carb is bad or something as I replaced everything else. That said do not know. I will have to get a pressure gauge to check compression. Would saw run with low compression just not have power or will saw not run with low compression? When pulling starting cord feels like compression but understand not an exact way to measure compression. I will get a gauge

Exhaust is not plugged

Fly wheel key good. Timing looks OK

Replaced coil already

Throttle plate is opening all the way. What about clogged jet or port in carb?

Tested fuel line, with pressure test, removed fuel filter, same issue. Again seem to be intermittent

I had saw running of the weekend, but would die after 1-2 minutes of cutting. Would bog when accelerating finally get up to speed cut for a minute and then die. Again adjust carb, I ran low jet adjustment all the way in and seem to have no effect on saw while running then put back. Would start but will not run, then will not start unless choked. Then would not run, gave up got another saw as wood needed cut.

Help please


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## paulr44 (Oct 14, 2008)

I know you said you did CC pressure test, but what you're describing actually sounds like a vacuum leak. In specific, won't go near idle, and needs choke to re-start.

QUOTE: "_Tested fuel line, with pressure test, removed fuel filter, same issue. Again seem to be intermittent_"

What do you mean, intermittent? Does it run great SOMETIMES?

YES, get a compression gauge! Vital for 2-stroke diagnosis. MAKE SURE if the one you buy has an extension hose, that is has a schrader valve in the end of it. If it doesn't the hose becomes an extension of the combustion chamber and gives you a false lower reading.


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## tomatick (May 5, 2011)

Yes did a crank case pressure test. Saw is tight.

No saw does not run great ever. 

Got pressure gauge, check cylinder pressure got 70 PSI. Is this low? Pressure gauge does have extension hose.

What is the lowest cylinder pressure a 2 cycle engine will run


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## paulr44 (Oct 14, 2008)

A 372 is 70cc, I'd expect to see at least 150 PSI compression. If it has a decompression valve, ensure the valve is closing. Sometimes these valves leak a bit, also leading to false compression readings.


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## Sir Thomas (Dec 7, 2013)

tomatick said:


> Paul,
> 
> Thanks for the help, determined to figure this out.
> 
> ...


Remove the cover to the crankcase and check the gasket. If there is any leakage then there is not enough vacum to make the diaphrams work properly. Also make sure the carburetor mount gasket is good and lined up properly. If it is blocked, you have the same problem.


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## Spit (Nov 3, 2006)

70 psi is very low for any 2 cycle. I have always thought over 90 is a bare minimum. If you have always had good proper gas mix, I would not suspect a worn cylinder but you should check and see if there is any scoring on the cylinder walls. Can you see if a piston ring is stuck? the rings need to be able to expand into the walls of the cylinder. If they get gummed up and stuck in the piston groove you will not get proper compression. Not sure on this saw how the crankcase and cylinder are connected. Some 2 cycles have them connected with screws and a gasket make sure it's tight if applicable


Spit


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## usmcgrunt (Sep 16, 2007)

Hello tomatick, here is a link to the 372 service manual. Select file W0001001.pdf to view and save. I hope this helps.

http://www.mymowerparts.com/pdf/Husqvarna-Service-Repair-Manuals/


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## paulr44 (Oct 14, 2008)

This is kind of difficult, you are there with the saw, we're here in digitaland.
I'm going to go back to indicating we need to know compression, and your report of 70 is so low, I doubt it would run at all.

That being said, please do this:
Inspect the intake side skirt of the piston by looking through the carburetor with the butterflies open, or with the carburetor removed.
There should be horizontal machine marks (lathe grooves) in the piston skirt. If it's dull and/or scratched up badly, then there's internal wear/damage.

That'd be my take on this - worn piston skirt/cylinder wall or damage thereof.


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## tomatick (May 5, 2011)

OK, Getting back to saw. Removed head cylinder was slightly scored on the exhaust side.

Going to get new head and cylinder and carb. Should I get after market and the big bore 52mm? Was planning to leave the bottom end of the saw alone. Is this a good idea? Crank, bearings, and seal seem to be good.

any advice?


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## Sir Thomas (Dec 7, 2013)

tomatick said:


> OK, Getting back to saw. Removed head cylinder was slightly scored on the exhaust side.
> 
> Going to get new head and cylinder and carb. Should I get after market and the big bore 52mm? Was planning to leave the bottom end of the saw alone. Is this a good idea? Crank, bearings, and seal seem to be good.
> 
> any advice?


Depends. Determine what is the market value on the saw. Then price the parts you mentioned. Estimate the mileage left on the rest of the parts and how far down the road you'll be replacing other parts. If you just want to rebuild it like I would just to hear it run and know I fixed it yeah. If you need and saw and it's more than 50% of the price of a new one, no.
Curious to know what caused the score. Do you use Ethanol free gasoline? Ethanol can cause heavy carbon buildup in the 2 cycle engine and a chunk proably broke off and scored the cylindar when it got trapped between the exhaust port and the piston. Is there heavy carbon buildup around the head of the cylindar and around the exhaust port? You may need to clean the muffler if that's the case. Did you notice where in relationship to the piston and the gap with the pin. Perhaps the ring slipped.


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## paulr44 (Oct 14, 2008)

IN ALIGNMENT WITH SIR THOMAS - *IT IS IMPORTANT to determine WHY a 2-stroke failed else it may fail again if only replacing the failed components.*

Translation - as with any engine or transmission failure, what you see failed may only be the symptom, not the disease. Crankcase vacuum leak, bad carburetor, collapsed fuel line and other things not working right can cause a 2-stroke catastrophic failure.

You said you did a CC pressure test, other than a fuel restriction or improper mixture (which could be as simple as water in the fuel or too much alky), replacing the cylinder w/piston and carb. you should be safe.

HOWEVER - I've been doing this for 40 years, and will ADD:
Had a Stihl 088 with some scoring, replaced the cyl/piston assy., test ran, tweaked the carb., SEEMED FINE. A week later came back scored. BAD CARB WHEN HOT was the problem. That's one we absorbed, couldn't rightfully charge the customer other than for the new carb.

2-strokes are NOTHING like 4-strokes for failure analysis nor sympom vs. disease. Keep that in mind. As per THOMAS, it'd be good if you can get a bearing on why it failed, so as to keep it from recurring.

OH, AND ALWAYS replace the DEKO valve - if it leaks it can cause a lean mixture condition. Not so much an issue on older 2-strokes running richer than today's engines, but on newer saws I replace them now as part of a service. Maybe not cheap at about $25 - $35, but much cheaper than a major failure! If it's got limter caps on the carb., I say treat it as a routing maint. item.

Paul


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## tomatick (May 5, 2011)

Ok,

Trying to figure out why the saw piston was scored. Looks like some buildup on the exhaust port. Perhaps a little peice got wedged between piston and cylinder. Scoring is not so bad but might as well fix. I think saw got hot as well from lean. I blame carb. As saw is tight on the low end. 

I plan on new carb as well. Any suggestions? Original or after market. 

What is DEKO valve - assume decompression valve. Why would this need replaced?

To you question Paul why are there limit caps on the carb? Dont understand why these are needed

The gas I use has eythanol but I use in 4-5 other saws with not issues. Also use in weed eater, pole saw, snow blower.

I do not understand in relationship to the piston and the gap with the pin. What pin? The saw has two rings. The gaps are off set.


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## paulr44 (Oct 14, 2008)

tomatick said:


> Ok,
> 
> Trying to figure out why the saw piston was scored. Looks like some buildup on the exhaust port. Perhaps a little peice got wedged between piston and cylinder. Scoring is not so bad but might as well fix. I think saw got hot as well from lean. I blame carb. As saw is tight on the low end.
> 
> ...


*Does this help?*

P.S. DO USE Plus or High-Test fuel ONLY in all your 2-strokes!!! Most OEMs require it as these engines are high compression.


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## Sir Thomas (Dec 7, 2013)

tomatick said:


> Ok,
> 
> Trying to figure out why the saw piston was scored. Looks like some buildup on the exhaust port. Perhaps a little peice got wedged between piston and cylinder. Scoring is not so bad but might as well fix. I think saw got hot as well from lean. I blame carb. As saw is tight on the low end.
> 
> ...



Take my word for it. Ethano damages 2 cycle engines. You don't aways see it until the engine fails. Doesn't happen right away. 
Concerning the rings. I had one with two rings and had a time getting them in. I've worked on several, most with just one ring, and I could see the pins. I took the piston with two ring to my bench and was preparing to clean the landing because I thought maybe carbon buildup was preventing the ring from seating. That's when I noticed the pins. They are small and deep set but they are there. Get a magnifier and look all the way around. When I found them, I marked where they were with a marker. Remember they are offset so the gaps do not line up.
The limiter caps are mandated by the EPA to control emission. It sets the limit to how far you can adjust the mixing screws without putting out harmful exhaust. 
I'm not sure about the Deko Valve since I've not worked on a machine with one but I'm assuming that it prevents over-compression to make it easier to start but that's a guess.
It's best to stay with the same type or style of carb as the original. I put a carb from another unit onto one I was working on to see if the unit was working correctly. It was running wide open even with the throttle down. It worked fine on the other unit so carbs and machines are tailored for each other. If you have worked on several different carbs you'll notice that different series have different pump sizes.


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