Need chainsaw carb and starting help

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  #1  
Old 10-08-12, 03:14 PM
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Need chainsaw carb and starting help

Have probably around 20 year old Craftsman chainsaw I wanted to get running again... I took the carb apart and cleaned with carb cleaner. I have also replaced the fuel line as it was totally rotted. I used a plug out of one of my trimmers. After pulling multiple times I did hear a few sputters but that was it. I can't even get that now. It doesn't appear there's gas in the fuel line -- should there be? There's no primer. How does it get sucked into the carb? Anything obvious or easy I should try?

Thanks for any tips.
 
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  #2  
Old 10-08-12, 03:53 PM
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Did you replace the diaphragm and other gaskets? That's where I would start. It should cost about $8 for a Walbro or Zama kit.

The fuel gets to the carb with the primer bulb and then into the motor with the motor with suction. Dribble a few drops of gas in the throat of the carb and see if it will start.
 
  #3  
Old 10-08-12, 04:23 PM
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No I just reused the diaphragm that was in there. There isn't any primer bulb -- that made me wonder how gas gets into the carb in the first place. The tank is lower so not gravity fed. I assume some type of vacuum (?). In any case, the fuel line doesn't appear to have fuel in it.
I did try dumping some gas into where the spark plug goes. It did crank but only for a second or two.
 
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Old 10-08-12, 04:40 PM
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Cranking for a couple of seconds is a good sign. The diaphragm is likely shot. That is what opens the valve to get gas to the carb. The high and low speed needles get the right amount of gas to the motor. Ebay is a good source for kits. Just get all the numbers off the carb and find the kit that fits.
 
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Old 10-08-12, 04:51 PM
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Ok, I'll look for the kit but why isn't fuel in the line? If I pull the fuel line from the carb nipple, shouldn't gas leak out of it? I read somewhere about an impulse line but I don't have that.
 
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Old 10-08-12, 05:14 PM
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I agree the diagram and and kit is needed to start with. In particular the one with the spokes on it. If you replace the fuel lines you also want to make sure you connected them properly. If after kitting the carb, you still have issues, you might try priming the carb with a bit of fuel...sometimes that is enough to pick up fuel from the tank.
Also note and take care of the order the gaskets come off from the carb and replace in the same order.
Both Walbro and Zama have good sites on replacement and kitting their carbs...either search this site or someone will certainly chime in with a link for you.

You don't have to wait for ebay, you should be able to go to a local small engine repair shop, take the saw in and they should have a kit or be able to get you one for 12 bux or less.
 
  #7  
Old 10-08-12, 05:24 PM
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The fuel line was brittle and broken off but I only saw what looks like one line that went from an opening on the top of the fuel tank all the way up to the right side of the carb. I don't see any other lines or nipples. Definitely only the one nipple on the carb. I just pulled the fuel line off again and there isn't any gas in it. How would it crank and run without gas flow?
I understand to purchase the carb kit but can someone explain how the gas flows up from the tank and into the carb nipple (without a primer bulb which mine doesn't have)? I would like to understand just for my curiosity. Thanks again.
 
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Old 10-08-12, 05:41 PM
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I wish I could be of more help, however, I still think you should have more than one fuel line. Also you should have a filter in the tank on the end of a fuel line. You might need to fish it out with a hooked wire and replace that also. Empty the tank and shake the saw, it should rattle. If you only replaced the line to the top of the tank, there may be another pick up line that goes to the filter. Usually I found these to be not cost effective for the customer to work on so, I am no guru....others here have done much more than I have so....I relent to their wisdom.

Basically tho, the diagram is pulsed by the engine and draws fuel to the carb. Sometimes it just needs a good prime if all else is intact.
 
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Old 10-08-12, 05:48 PM
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Yeah, it's just one line (spliced with the butt connector in one part) but it goes from the carb to the gas tank. There's no other place on the carb to attach another line. Oh, I used a fuel filter from an old trimmer I have. It's old but it works fine in the trimmer.
I can't believe that diaphragm somehow creates enough pull to suction gas all the way up from the lower positioned gas tank. Pretty impressive. Anyway, I'm not getting any gas to the carb so that must be it.
What's an impulse hole and what does that do?
 
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Old 10-08-12, 06:01 PM
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To begin with, these two strokes are finiky enough, if you are using old parts even if they were working on other equipment, you are just BEGGING for frustration! Chances are you will now have problems trying to re-install components on the original equipment and making them work.
If you understand the basics of a piston moving up and down, it creates both vacuum and pressure, it move pretty [email protected] fast and with the small amount of volume in the fuel line, well could suck the chrome off a trailer hitch given the right condition

Take a piece of that fuel line, stick one end in some fluid, blow accros the other end and see if fluid is not drawn up into the line
 
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Old 10-08-12, 06:16 PM
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yeah I know about the old parts. it's over 20 years old so just wanted to see if I could get it cranked with just cleaning the carb out. i'll get a new filter if it's going to crank and run. i can't get it cranked so not sure it's worth anymore time and money. the diaphragm looks flexible -- about the same as I remember on the last trimmer carb I cleaned. anyway, no gas flow so something isn't working. maybe I'll give a new diaphragm a chance since the consensus is that's the problem.
 
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Old 10-08-12, 06:44 PM
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I have gotten many an old 2 stroke running in years past with only minor replacing of parts. If it runs a little with gas it is worth fixing IMO.

If the valve that the diaphragm opens, is not open, no gas will flow in the fuel line.

If you can, post a picture of the carb and saw. Also, please post the model of the saw, Sears has a great parts dept.
 
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Old 10-09-12, 03:57 AM
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Here are some pics. I just took the diaphragm apart and the area is dry of any fuel.
 
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Old 10-09-12, 09:47 AM
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On those, it takes a lot of pulls to get fuel coming up the line. I think that saw used to cost something like $60 (something to keep in mind when buying parts and spending time on it). They are better than the new junk poulan is making today though.
 
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Old 10-09-12, 06:21 PM
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IDK why I was thinking it would have a primer bulb. I have seen many chainsaws without a primer bulb.

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The black circle is what the diaphragm moves. The red circle is the needle valve the opens to let gas in.

Maybe try sucking some gas to the carb (try not to get a mouth full. YUCK!) which would be a good idea anyway to make sure the fuel line is open. Or, with it assembled, start it with some starting fluid. Maybe that will be enough to suck some gas to the carb.
 
  #16  
Old 10-09-12, 07:49 PM
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To get fuel to the carb fast, take the line loose, shake the saw. The gas sloshing in the tank will create pressure and cause gas to come out the line. Connect it to the carb and see if you can get it to start.
 
  #17  
Old 10-10-12, 04:11 PM
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Hey!! I got it running. I'm really not sure what I did differently but gas finally did end up in the line and it cranked. I ordered a kit but it seems to be running ok. I guess I'll save it for the future. What's the best method for starting cold and hot? It has a choke lever that slides a cover over the top of the carb. Do I use choke with no throttle cold?
 
  #18  
Old 10-10-12, 04:17 PM
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Choke it, give it full throttle, and pull until you hear it start and shut back off, then take the choke off and start it. Full throttle all the time until it is running. If the saw dies after removing choke, repeat process.
 
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Old 10-15-12, 07:51 AM
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another ques:
the bar on this is small. will it be ok to put on a larger bar? if so what length would be the max i should look at? thanks.
 
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Old 10-15-12, 10:00 AM
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I think those came with up to 14" bars, maybe 16", but they don't really have the power to make a big cut.
 
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Old 10-15-12, 02:56 PM
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I see some bars look like mine with that adjustment slot but say Intenz on them. Will those work with mine?

Also, what is the proper way to adjust the one I have now? I just used a screwdriver to pry it tight and then tightened the bolt on it. Probably too tight like that?

BTW, thanks for the help.
 
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