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chain saw not firing

Posted by shakushinnen (My Page) on
Mon, May 5, 14 at 13:21

Hi,
I bought a used Mastercraft chain saw (2.3 cu.in..... 38cc) model 54-5663-4 last year and decided to fire it up this spring. It didn't even fire. I changed the plug, and it saw that it was sparking, but no fuel to plug. The line to the carburetor was fine, no gas appeared to be going to it; so I decided to pull it see what's what. At this point I should tell you that I really don't know much about engines, but what I saw made me scratch my head. There was a plate over the bottom of the carburetor (Walbro) and the carburetor appeared to lead directly to the crank shaft. Am I missing something? Shouldn't the carburetor be open, and lead into the cyclinder?
Thanks,
..... john


Follow-Up Postings:

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RE: chain saw not firing

The carburetor goes to the crankcase because it's a 2 cycle engine.

I'd guess that the choke is on also.


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RE: chain saw not firing

Thanks Jake,
So, should there be plate over the bottom of the carburetor, between the carburetor and the crankcase?
...... john


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RE: chain saw not firing

That plate is probably the reed valve---which acts like the intake valve---opens when the piston stroke is creating a vacuum.

The reason the saw is not starting is most likely inside the carburetor---varnish from evaporated gas has plugged the feed ports.

I repaired chain saw for professional tree crews for 20+ years---seldom was able to reliably rebuild a carb. Buy a new one, will be cheaper/better in the long run.


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RE: chain saw not firing

Agree with handymac,

When I would rebuild them the rubber diaphragm in them was regularly trashed from varnish, as were several other parts (float valve on lawn mower engines).

Just a tip, before you store it for the winter, empty the gas out of it and then run it until it's out of fuel. It will prevent some of the varnish from building up.

One of the best inventions for those small engines was the priming bulbs.

BTW handymac, I was the Go To Guy for rebuilding Mopar thermo quad carburetors at one time... about as useful a skill as typewriter repair now.


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RE: chain saw not firing

Hi Guys,
Thanks for the help. I have no idea where I'm going to get a carburetor for this beast. It's a Canadian Tire product, not likely made by them, so I'm told. I live near Toronto. Any thoughts.
Thanks again,
...... john


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RE: chain saw not firing

is it a Poulan 2300-CVA?
Google it and see if it matches your machine.


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RE: chain saw not firing

jakethewonderdog

You have my sympathies---I did a pile of Quadra-Jets back in the day. Tried a couple of thermo-quads---ugh!!!!


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RE: chain saw not firing

Hi,
Sorry, I wrote a reply last week, but for some reason it didn't get posted.
"Is it a Poulan 2300 CVA?" It could be, I can't really tell. I took it apart, looked at the carburetor. All the membranes seem supple and clean. Then I tried it again, same result ..... no firing. I don't think the carb is getting any gas. How is the gas delivered to the carburetor?
....... john


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RE: chain saw not firing

Fuel delivery pressure is produced as the piston moves down, pressurizing the crankcase and the pressure is directed through the port into the carb to the underside of the diaphragm that pushes the fuel into the carb to be directed into the carb venturi and into the engine.

The problem is most likely in those small passageways drilled in the carb body. When leaded gasoline evaporated, a substance called varnish was left. That substance would clog those passageways. The newer unleaded fuel leaves a similar substance---and gasohol(10% alcohol gas) causes even more plugging.

As I said, I repaired and maintained a fleet of over 300 chain saws(Homelite/Husky/Tanaka) for 20+ years. I was a factory certified repairman for Husqvarna(had to be to be able to stock repair parts) and worked on several different brands.

I had repair and test equipment to rebuild carbs according to factory specifications. I was only successful about 50% of the time. In fact, the last 10 or so years, we just replaced defective carbs rather than try rebuilding---was more cost effective.


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RE: chain saw not firing

Thanks mac. I appreciate your insights. I have no idea where I can get a replacement carburetor, but would like to take a crack at cleaning it up. What if I remove the seals and soak it in a strong solvent containing methanol, toluene and methyl ethyl ketone (MEK)? Do you think that might do it?
.... john


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RE: chain saw not firing

You can try---be sure to use compressed air to blow out all the drilled passageways.

I had a carb cleaner machine---solution and agitator(speeds cleaning time) and used it often.

You can find the numbers on the carb and ask a saw repair shop or Google them, there are a lot of identical carbs on different make saws.

Good Luck!!


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RE: chain saw not firing

Is this it?

Here is a link that might be useful: Poulan 2300-CVA Parts Blowup


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RE: chain saw not firing

Hi Mac,
Thanks for the suggestions I'll try the blow out first.
Hi Saltidawg,
Thanks for the carburetor blowup reference.
..... john


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RE: chain saw not firing

Alright. I took the carburetor apart, blew and cleaned it as well as I could. Unfortunately, I separated the two gaskets (one on either side of the unit) into their component parts, a soft membrane and a stiffer frame, and forgot which goes outside and which goes inside. So, the question is ....... thin membrane inside or outside?
Thanks,
..... john


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RE: chain saw not firing

john,

The arrangement is shown in the D panel Parts Blowup linked to three posts up, is it not?

Here is a link that might be useful: Carb Drawing - Maybe

This post was edited by saltidawg on Thu, May 15, 14 at 12:18


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RE: chain saw not firing

Hi Salti,
Yes, I looked at the link, but was not sure weather the thin one was inside or outside. I thought it might be a standard configuration, i.e. 'thin out' or 'thin in', kind of a rule of thumb. I'll try it both ways, and see which one works.
Thanks,
.... john


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RE: chain saw not firing

Hi Salti,
I had another look at the link, and can now see which way the layers go.
....... john


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RE: chain saw not firing

Three more things.
There is now gasoline in the fuel line.
1. I notice that there is no air filter. (I assume it's a piece of foam?)
I doubt that this would prevent the saw from firing?
2. I am using regular gas, in order to see if it works, before I go to
the trouble of mixing it will oil. This shouldn't prevent it from firing?
3. Could the on/off switch be faulty? I see it leading into the housing, but haven't looked at it. (I'm getting a spark at the plug.)
Thanks,
....... john


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RE: chain saw not firing

Remove the muffler and check the cylinder/piston for scoring. Both should have a mirror finish---any score lines means the jug/piston are trash---no fixing them. The cost to replace will be as much as a new saw.

The only lubrication for a 2 cycle engine is the oil added to the gas. Even just trying to start with plain gas can damage parts.


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RE: chain saw not firing

there may be lot of ideas to deal with this issue but in my opinion handymac did his best


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