Ifixoldjunk 778 #1 Posted May 11, 2022 So I’ve finally got my 71 stihl 020 AVP to the point it will cut. Or so I thought. It will run flawlessly for 5 or so minutes, and then it will randomly decide it no longer wants to idle. I can keep it running if I keep working the throttle but it will die the minute I let off it. And then after that, It will not start for anything. I think it’s a coil, but seeing how hard it is to find anything for this saw I want to be completely certain that’s what I need before I devote the time to it. 1 Share this post Link to post Share on other sites
Snoopy11 5,714 #2 Posted May 11, 2022 5 minutes ago, Ifixoldjunk said: It will run flawlessly for 5 or so minutes, and then it will randomly decide it no longer wants to idle. I can keep it running if I keep working the throttle but it will die the minute I let off it. And then after that, It will not start for anything. Sounds like low speed jet clogged or bad fuel filter... fuel line could have a crack in it... sounds like something with fuel to me... usually is when you have issues like that. Don 2 Share this post Link to post Share on other sites
Snoopy11 5,714 #3 Posted May 11, 2022 Also, it is important to note that this issue can occur between 2 extremes, lean or rich. Once you verify fueling is proper... you may be able to play with low speed adjustment screw to get it to run. One suggestion I would have is pull the muffler out, and check to see if the piston has fuel all over it... if so... you are too rich. If it is dry as a bone... it isn't getting the fuel/oil that it wants. When you have the muffler off, you can also check the cylinder for scarring... particularly if it has been running lean for any amount of time. If it is running rich, that is better than lean for our little 2 strokers... Don 1 Share this post Link to post Share on other sites
Snoopy11 5,714 #4 Posted May 11, 2022 16 minutes ago, Ifixoldjunk said: I think it’s a coil Ordinarily, when we see coils go in these 2 stroke engines, it does have a hard time starting, (if it starts at all), but you loose BOOKOOS of power at the top end, balking, stuttering, looping,... crap like that. Couldn't hurt to take a look at the spark plug, clean it up a little if need be. You can test your coil, using the redneck method... pull out the spark plug, attack it back to the end of the wire, lay the metal threads against something metal on the machine, and give it a crank. You should see good spark. (for this method, you need about 3 hands...) Don 1 Share this post Link to post Share on other sites
Ifixoldjunk 778 #5 Posted May 11, 2022 6 minutes ago, Snoopy11 said: Also, it is important to note that this issue can occur between 2 extremes, lean or rich. Once you verify fueling is proper... you may be able to play with low speed adjustment screw to get it to run. One suggestion I would have is pull the muffler out, and check to see if the piston has fuel all over it... if so... you are too rich. If it is dry as a bone... it isn't getting the fuel/oil that it wants. When you have the muffler off, you can also check the cylinder for scarring... particularly if it has been running lean for any amount of time. If it is running rich, that is better than lean for our little 2 strokers... Don Yeah that was my first thought. I tuned the carb and that seemed to help a little. Let my dad take a look at it and he said it was adjusted right. I’ll have to check the fuel lines then. Since I know the saws whole life story since my friend bought it new I can guarantee they’ve never been touched before 1 Share this post Link to post Share on other sites
Snoopy11 5,714 #6 Posted May 11, 2022 1 minute ago, Ifixoldjunk said: I tuned the carb and that seemed to help a little Yeah, usually if you have some sort of fuel problem (fuel line sucking air for instance, or fuel filter clogged) those adjustments will help a little. Doesn't solve the problem though... Even if the lines haven't been touched, age, and general vibrations/heat from the machine can crack brittle lines... etc. If it hasn't ever had the fuel filter changed on it... that could be the whole problem. If you have a long pair of needle nose, you should be able to grab the fuel line inside the tank, and take a peek. Don Share this post Link to post Share on other sites
8ntruck 7,018 #7 Posted May 11, 2022 My saw was just the opposite. It would idle, but died when the throttle was opened. Turned out to be a cracked fuel line. 1 Share this post Link to post Share on other sites
wallfish 17,014 #8 Posted May 11, 2022 A 2 stroke needs the crank case sealed for best performance. Worn crank seals and such will cause it to run inconsistently and cause random things like it will idle fine on the bench and once you go out to cut with it, it won't. Constantly needing to adjust the carb is another indication of leaking case seals. The inconsistent case pressure from leaking seals causes the carb diaphragm to pump fuel inconsistently or not very well and that's the random changes. Yes, they will start and run with leaky seals but will definitely perform better with a sealed case. Good rings will give good power performance. Guessing I have about 75 or so 2 stroke powered tools in my collection ( O&R and Homelite ) 65-70 of them start and run. 65-70 of them didn't when they were bought. Before I found a stash of NOS parts that included some crank seals, I would swell the original seals with brake fluid. Just a couple/few drops directly on them with the seals still in place on the engine would swell them enough to seal or at minimum, seal better. Let it sit overnight before running the engine. I don't know what material was used for the seals in that saw but brake fluid will swell Buna-N or nitrile rubber seals The small O&R engines have an exhaust set up which I could use to leak down test the cases by using a blown up balloon on the exhaust collector and cover the carb hole. The speed the balloon emptied indicated how well the case is sealed. Some you could hear and feel the air rushing out of the crank seals before treatment. The difference after the brake fluid was noticeable. If you can find new seals and rings and replace them, that's obviously the best solution and it will run like new as long as the cylinder isn't all scored up. There's no quick easy fixes for worn rings or worn cylinder walls. If you can't find those replacement parts then it's no harm no foul to try the brake fluid seal swell hack. You'll probably need to adjust the carb after too. Carb cleaner swells rubber too but the brake fluid seemed to work better. 1 2 Share this post Link to post Share on other sites
Beap52 815 #9 Posted May 12, 2022 Lots of great advice. I also check and clean the screen on the exhaust as it can become plugged up and cause running problems. 3 Share this post Link to post Share on other sites
Lee1977 6,670 #10 Posted May 17, 2022 On 5/11/2022 at 9:56 PM, Beap52 said: Lots of great advice. I also check and clean the screen on the exhaust as it can become plugged up and cause running problems. It's better if you take the spark arrestor out and throw it away. Too big of leak in the crank case and a 2 cycle won't run at all. I hauled my go kart 30 some mile to run with some boys in an abandon inducturas park. Fired it went about 10 ft. ran over a stick and blew the crank case seal where it was bolted together and my day was done. Took it home painted the crack where it was bolted together with Indian Head Shellac let it dry never had any more trouble with it. Share this post Link to post Share on other sites
roadapples 6,983 #11 Posted May 17, 2022 (edited) Wrong number Edited May 17, 2022 by roadapples Share this post Link to post Share on other sites
