HELP!!!! poulan bicentenial will not run

[Jim C]

My brother gave me a poulan bicentenial chainsaw. Its a small chainsaw from the 70's. It had a 10" bar, but I changed it to a 12". The compression is 150 PSI, it has spark, I'm guilty of using starter fluid to see if it wil fire, and it does. The problem is it will not stay running and I do not want to use starting fluid to start it. I have two carbs and have tried both with the same results. I'd really like to get this saw running and starting easy so I can trim some branches without using my bigger saws. Anyone with any info/experience on this older poulan that can help? Please no cracks suggesting I throwing it away. I've spent to much time to get this far and now pride just wants me to make it run!!!! Thanks in advance, Jim

 

[Lakeside53]

It sounds like fuel is not getting to the carb, or, the impulse is not operating the fuel pump side. If you want to prove this, connect an external fuel tank ( like a weedeater or even another saw) and hang it three feet above your problem saw so gravity feed pressure is working for you. This will eliminate all variables except the carb itself.

 

[retoocs555]

It sounds like fuel is not getting to the carb, or, the impulse is not operating the fuel pump side. If you want to prove this, connect an external fuel tank ( like a weedeater or even another saw) and hang it three feet above your problem saw so gravity feed pressure is working for you. This will eliminate all variables except the carb itself.

If that doesn't work. I've had a lot of small poulans run like that when they have a bad bearing.

 

[Fish]

just follow the fuel line to the tank, then rebuild the carb.....
after 30 years, the fuel lines turn to poop.

 

[Jim C]

Thanks for the input. The fuel line is brand new. I pulled the line off the carb, blew into the line, then watched gas pour out the line. I think the tank, filter and line are OK. I have two carbs and tried each one. same results: engine starts with starter fluid, but will not stay running.

 

[TimberPig]

It sounds like you have a good fuel line, good top end of the engine, 2 carbs that are both in need of rebuilds, and if rebuilding the carbs doesn't work, you aren't getting any impulse to operate the fuel pump, possibly due to the bearing issues mentioned earlier. Try tearing down a carb, cleaning it, and throwing in a rebuild kit.

 

[Jim C]

There is a carb, brand new on ebay w/ no bidders yet, for the same cost as a rebuild kit. Do I need three carbs? Please explain this bearing issue and how it affects fuel pumping. I've had the flywheel and clutch off and did not notice any play at either crank end. If fact the hole unit seems to have a low amount of hours on it.

 

[Lakeside53]

There is a carb, brand new on ebay w/ no bidders yet, for the same cost as a rebuild kit. Do I need three carbs? Please explain this bearing issue and how it affects fuel pumping. I've had the flywheel and clutch off and did not notice any play at either crank end. If fact the hole unit seems to have a low amount of hours on it.

No, you only need one... First just try adding fuel under gravity pressure, or, open your carb wash out the old junk, soak it overnight in naptha or even just gas, reassemble in the morning and it might just work.

The bearing - if the bearing goes REALLY bad, the crank seal will be compromised. If the crank seal is shot, you won't have any impulse pressure to activate the fuel pump. A pressure test will tell you thing pretty quickly. Often with a bad seal you can get the saw running at high RPM, but it won't idle or even close it it..

 

[Jim C]

I'll try taking the carb apart and cleaning 1st. When I did get it started on starting fluid it did seem to run only at high rpm. How and what do I need to do a pressure test? I have compression tester. Do I just get the cylinder up to max PSI and wait to see if it leaks?

 

[Lakeside53]

I'll try taking the carb apart and cleaning 1st. When I did get it started on starting fluid it did seem to run only at high rpm. How and what do I need to do a pressure test? I have compression tester. Do I just get the cylinder up to max PSI and wait to see if it leaks?

no...... pressure testing is done at very low pressures (like 9 psi) is to test the integrity of the crankcase and other seals... Do a search on the site - there have been many explanations on pressure testing, some by me. If you can't find them, I'll dig around after dinner (the wife is calling...)...

 

[Jim C]

lakeside

I found the ATV website that talks about pressure testing the engine from intake port to exhaust port at about 6 psi for 6 minutes. I need to make plates for both ports, install a fitting to to pump in 6 psi, and install a fitting for low pressure guage. I will work on the carb 1st then try a pressure test if it still does not run.

thanks Jim

 

[Lakeside53]

lakeside

I found the ATV website that talks about pressure testing the engine from intake port to exhaust port at about 6 psi for 6 minutes. I need to make plates for both ports, install a fitting to to pump in 6 psi, and install a fitting for low pressure guage. I will work on the carb 1st then try a pressure test if it still does not run.

thanks Jim

Go to www.giftsofwood.com, download a Stihl 026 service manual, and look at the pressure and VACUUM testing on a chainsaw (in the engine section). It's similar to the ATV, but different enough that you'd want to look. Seals That pas a pressure test can fail under vacuum. Not likely the problem in your case though.

 

[Stumper]

New fuel line is nice...but does it have a new fuel filter? Most old small Poulans have at least one of 2 problems-clogged fuel filter,or carb in need of cleaning and rebuilding. Half the time a new filter and a carb cleaning works-the other half of the time the carb needs an actual rebuild.

 

[Jim C]

Thanks everyone for all your advice. I finally bought the carb rebuild kit and installed it. Seems the diaphram was ripped. The rebuild kit had the wrong float needle so I used the old one which was in excellent shape. Put the carb on the saw, pulled the pull start a few times, and it wouldn't start. Gave it a shot of starter fluid (I know I shouldn't) and it fired up. Got it warmed up, set the single carb screw @ 1 turn, set the idle, and now I have a running light weight saw for a total of about $30. One more thing: the original air filter was no good. It looks like a window screen withsomething sprayed onto it. When I bought the rebuild kit the parts guy sold me a foam air cleaner to a lawm mower. I cut out a piece of foam to the correct shape and installed it. Should I spray any oil on it like whats used on motorcycle filters or run it dry?

 

[Wood Butcher]

I'd oil the foam. also, use an old oil-squirter can with mixed gas in it to get the saw running next time. Sometimes you can squirt it enough to get them running they will run on their own and clean the old varnish out of the carb.

I said sometimes, most of the time you still have to do all the work but it is like casino games, you lose your a$$ but they let you win just enough to keep you coming back.