Things I learned this week

[heimannm]

I have been messing around with small engines for 55+ years and have been pretty serious about working on chainsaws 14 or 15 years. So, when a saw comes in with a problem I usually start looking at the more complicated solutions. If there is a fuel delivery problem I normally attack the carburetor after have a quick look and the fuel line and impulse line when they have one. My tree service friend dropped off an MS880 that would act like it was running out of fuel at WOT, idle was fine. So naturally I looked at the fuel and impulse lines (both had been recently replaced, and decided I needed to pull the carburetor for a complete inspection. Everything looked good so all I could think of was raising the metering lever a bit. Carburetor still held pressure so I gave it a go with no significant improvement. Finally I replaced the fuel filter (even though the fuel filter and fuel line were part of a complete rebuild within the past year) and the problems was instantly resolved.

I also had a Husqvarna blower vac that would not run correctly, no amount of carburetor adjustments would help, I could see that the spark plug wire insulation had been burned/abraded through contact with the cylinder fin so I assumed the wire inside had been broken as well. Thought I'd change the wire like I do on the old McCulloch saw by unscrewing the wire and installing a new one and only succeeded in breaking the wire off. I bought a new after market ignition assuming that would solve the problem but the engine ran exactly the same way. Finally I removed the spark plug and discovered a small bit of carbon accumulation on the electrodes that nearly shorted the gap. A simple cleaning of the spark plug and it good as new. This is the third problem I've encountered in the past month or so where the problem was nothing more than a bad spark plug.

Finally, I had a John Deere/Echo saw (Q500F) that sounded like an ignition problem with a lot of missing and would not rev. First step was to disconnect the kill switch and nothing changed. I then pulled the flywheel, inspected the plug wire and connection, and cleaned the points. The condenser tested good so back together with no improvement. Next I pulled the carburetor for cleaning and inspection, the metering diaphragm was pretty stiff so I put in new gaskets and diaphragms after a good cleaning and still no change. Finally I pulled the flywheel again and replaced the condenser with an NOS one I had on hand...problem solved.

I hope in the future I will remember to try the simple things first, spark plugs and fuel filters are easy to replace and don't cost much. If a saw runs like it has an ignition problem, change the spark plug and focus on ignition. If a saw has a fuel delivery problem, don't assume the fuel filter is O.K. just because it isn't obviously plugged up.

Hopefully that will allow me to use my time more effectively.

Mark

 

[Chevboy0167]

Same here. Got burnt on a small minibike for a friend at work this mid summer. 80cc China special.

He said he put a new plug in it.. still no start/run. He orders a coil kit, entire new carb, kill switch and a few other things. He is not very handy let's say so wants me to look at it. Ok... no problem.

Get it to my shop, pull recoil, feels like weak compression but continued. Fuel tank cap was missing so he installed a CORK stopper.... no joke! Pull cork out and see fragments in the tank...ok, carb plugged cuz there is no inline filter... thanks China!
Pulled tank and carb to clean out. Tank has crud, flushed out, but carb was spotless. It was working perfectly. Re-assemble everything. Fuel getting to carb but still no start/fire.

Pulled plug wire off, installed new "test" plug in and layed it on the head. Pulled over and we got damn good spark!
WTF??? Put wire back on plug that was "new" already in head. Then shot some fuel into throat of carb... still no fire!!

Now I'm baffled... until I remembered he said he put a new plug in himself. Bad plug maybe??? Pulled his plug out of head to discover NO GAP at all. Ground and center electrode physically touching! DOH!!!!

He thought they always come pre-gapped and payed no mind to it out of the box. Now, this is an NGK plug. Maybe the boxed fell to earth and shut the gap... I don't know. I re-gapped his plug, installed and it fired right up and ran smooth as could be. GTBFKM....

But I wasted about an hr or more by not checking the simple things first. Good lesson that day even though I knew better to check.......

And I did find a fuel tank cap that worked so got that sorted... for now????

 

[GoBigRed]

This weekend I forced myself to replace the check valve under the Welch plug on an SDC carb on a 10-10 that was giving me trouble. Actually, it turns out the issue wasn’t the saw but the carb that was getting passed around to saws that needed work and I used the good one for something else.

I think this has been a problem for several of the “bad” carbs I’ve had trouble with but yesterday I took it slow and figured it out. Even made a check valve from some carb gasket material and a 223 casing

never stop learning. Old Macs depend on it

 

[Patrick1903]

Finally I replaced the fuel filter (even though the fuel filter and fuel line were part of a complete rebuild within the past year) and the problems was instantly resolved.

I have been tinkering for a few years and enjoy the projects and challenges. A friend brought a Stihl blower over that would start but soon die. You could coerce it with choke to keep running. Fuel pickup/filter appeared ok. Spark plug replaced (to eliminate possibilities), gas smelled ok. Plug appeared somewhat wet. Thinking carb blockage or stiff diaphragm. Pulled and cleaned carb, replaced diaphragms (after waiting 3 days for kit). Same results. Decided to look closer at fuel. Drained into glass jar. Some water and debris. Tank needed flushing for sure. Put fresh fuel in. No different still. Finally convinced myself it was a starvation issue, let me pull the pickup/filter off the fuel line. Fired right up, no hesitation, revved to full power. That was it. Filter blocked. Can’t trust a visual inspection of the filter (at least I don’t know if I should be able to or not, I’m not a pro.). Now his carb is extra clean and he shouldn’t have to worry about diaphragms for awhile. New filter and he’s got his blower back. Probably 30 mins of troubleshooting turned into several hours of time (I’m not fast!). Thanks for sharing your lessons learned.

 

[Patrick1903]

Now I'm baffled... until I remembered he said he put a new plug in himself. Bad plug maybe??? Pulled his plug out of head to discover NO GAP at all. Ground and center electrode physically touching! DOH!!!!

He thought they always come pre-gapped and payed no mind to it out of the box. Now, this is an NGK plug. Maybe the boxed fell to earth and shut the gap... I don't know. I re-gapped his plug, installed and it fired right up and ran smooth as could be. GTBFKM....

I hear people say they come pre-gapped, how could that be? Doesn’t it depend on the application? Or it’s a generic .025 gap (or something similar) that is the “pre-gap?” I’m often closing it on new plugs for the 0.020 needed on Stihl stuff recently. Does it not matter enough to most people that you can run it at whatever gap it arrives in the mail (as long as its not grounded out!)?

 

[Huskybill]

The PO can be a problem if he worked on it first. Bought a suzuki 50 dirtbike once. Didn’t run. Good compression. The PO swapped the lighting coil with the ignition coil. Swapped them back ran perfect.

 

[chainbrake]

I have been messing around with small engines for 55+ years and have been pretty serious about working on chainsaws 14 or 15 years. So, when a saw comes in with a problem I usually start looking at the more complicated solutions. If there is a fuel delivery problem I normally attack the carburetor after have a quick look and the fuel line and impulse line when they have one. My tree service friend dropped off an MS880 that would act like it was running out of fuel at WOT, idle was fine. So naturally I looked at the fuel and impulse lines (both had been recently replaced, and decided I needed to pull the carburetor for a complete inspection. Everything looked good so all I could think of was raising the metering lever a bit. Carburetor still held pressure so I gave it a go with no significant improvement. Finally I replaced the fuel filter (even though the fuel filter and fuel line were part of a complete rebuild within the past year) and the problems was instantly resolved.

I also had a Husqvarna blower vac that would not run correctly, no amount of carburetor adjustments would help, I could see that the spark plug wire insulation had been burned/abraded through contact with the cylinder fin so I assumed the wire inside had been broken as well. Thought I'd change the wire like I do on the old McCulloch saw by unscrewing the wire and installing a new one and only succeeded in breaking the wire off. I bought a new after market ignition assuming that would solve the problem but the engine ran exactly the same way. Finally I removed the spark plug and discovered a small bit of carbon accumulation on the electrodes that nearly shorted the gap. A simple cleaning of the spark plug and it good as new. This is the third problem I've encountered in the past month or so where the problem was nothing more than a bad spark plug.

Finally, I had a John Deere/Echo saw (Q500F) that sounded like an ignition problem with a lot of missing and would not rev. First step was to disconnect the kill switch and nothing changed. I then pulled the flywheel, inspected the plug wire and connection, and cleaned the points. The condenser tested good so back together with no improvement. Next I pulled the carburetor for cleaning and inspection, the metering diaphragm was pretty stiff so I put in new gaskets and diaphragms after a good cleaning and still no change. Finally I pulled the flywheel again and replaced the condenser with an NOS one I had on hand...problem solved.

I hope in the future I will remember to try the simple things first, spark plugs and fuel filters are easy to replace and don't cost much. If a saw runs like it has an ignition problem, change the spark plug and focus on ignition. If a saw has a fuel delivery problem, don't assume the fuel filter is O.K. just because it isn't obviously plugged up.

Hopefully that will allow me to use my time more effectively.

Mark

One of my saws was bogging down with uneven/low power earlier this year. I had changed the filter a few months back so I thought it was the carburetor. The local shop had some saws like mine laying around for parts and could switch out the carb if need be. I left it with them. A dirty fuel filter was the culprit. They had changed the filter first before jumping into the carburetor - just like anyone with a lick of experience should! They are a busy shop with a half hour (minimum) for labor (which is only fair because they have a building and front-end to maintain). I lost 1/2 day of work in the bush and had to pay for someone to do something simple because I had made an assumption. The worst part was the embarrassment.

 

[Patrick1903]

The worst part was the embarrassment.

My neighbor told me about a problem he had with his blower. It wouldn't run. He checked the fuel level - looked good. Pulled it 100 more times. Eventually took it to the shop. No fuel! He somehow saw a tiny bit of fuel in there, but didn't have his glasses on and assummed fuel level seemed ok. I appreciated that he told me the story (instead of being too embarresed to say anything) and that he was able to laugh about it. Live and learn!

 

[KASH]

This story could be called Being Cheap or Not Checking The Basics.
Very good friend from childhood had a mint 1975 340 SkiDoo Olympic 400 miles on it he stopped to visit one day in the summer and he told me about the machines problem.He said it did not happen all the time but every once in a while after a long run it would stall and not start but after a half hour or so it would run fine.I told him it was probably a coil.Years went by and one day he called and gave me the machine still only 4oo miles.
I went all through it cleaned points checked coil etc It had a Tillitsion HR with a separate fuel pump I installed a primer and a Mikuni from a 78 Oly.Good gas line hose is hard to find around here I used the best I could buy changed all lines except the impulse line as it looked new.I put about 20 miles on her ran great all short trips a couple miles at a time.One afternoon decided to see what she would due breaking trail went down the unplowed logging road with about two feet of powder ran flawless for about five miles then instant stop Bingo coil right pulled plug and lots of spark pulled nut on bottom of carb bone dry no gas WTF I slid my hand along the impulse hose to make sure it had not fallen off the engine and what did I feel a split in the hose.The hose was just the right length that when It got really hot under the hood the line would swell and open the crack.Sitting there waiting for the crack to close allowed me to swear to my self to quit being a cheap skate and to check the simple things also.
Kash

 

[lostone]

I would have to say the one that kicked my butt the worst was one of the first saws I worked on, a Stihl 046 that I owned. The saw would start up and run fine then die after about a minute then it would have to sit for about 10 minutes before it would restart. So I checked the spark to see if coil was cutting out and it was fine, next I rebuilt the carb and that didn't fix it. Next I replaced the fuel filter and line still no go then I replaced the impulse line still no go. I didn't own a pressure/vacuum pump at the time however after going through all of this finally it dawned on me, hey try loosening the fuel cap and restarting it, WE HAVE A WINNER, replaced the fuel tank vent and it ran great. So I learned firing the parts cannon at something isn't finding the problem and a pressure/vac pump is a wonderful diagnostic tool to have.

 

[Patrick1903]

firing the parts cannon

Never heard that one before…hope you don’t mind if I borrow that.

 

[lostone]

Never heard that one before…hope you don’t mind if I borrow that.

I heard it from Erik O, South main auto, on YouTube.

 

[pioneerguy600]

This story could be called Being Cheap or Not Checking The Basics.
Very good friend from childhood had a mint 1975 340 SkiDoo Olympic 400 miles on it he stopped to visit one day in the summer and he told me about the machines problem.He said it did not happen all the time but every once in a while after a long run it would stall and not start but after a half hour or so it would run fine.I told him it was probably a coil.Years went by and one day he called and gave me the machine still only 4oo miles.
I went all through it cleaned points checked coil etc It had a Tillitsion HR with a separate fuel pump I installed a primer and a Mikuni from a 78 Oly.Good gas line hose is hard to find around here I used the best I could buy changed all lines except the impulse line as it looked new.I put about 20 miles on her ran great all short trips a couple miles at a time.One afternoon decided to see what she would due breaking trail went down the unplowed logging road with about two feet of powder ran flawless for about five miles then instant stop Bingo coil right pulled plug and lots of spark pulled nut on bottom of carb bone dry no gas WTF I slid my hand along the impulse hose to make sure it had not fallen off the engine and what did I feel a split in the hose.The hose was just the right length that when It got really hot under the hood the line would swell and open the crack.Sitting there waiting for the crack to close allowed me to swear to my self to quit being a cheap skate and to check the simple things also.
Kash

I found out no matter how diligent one can be about equipment its better to actually check the operation of the unit before taking it somewhere remote. This happened only once , to me. I had a cancellation one day at work, being very early morning and me wanting to get back to our backwood fishing camp I wanted to make the most of that day off. I hastily threw a lunch and day pack together, fueled and oiled saw I often took into the backwoods, put the canoe on the truck and headed out, 15 mile drive then take the canoe another 8 miles, several portages and get to the camp mid morning. Make a coffee and a snack. Grab the saw and lets get down to business of cutting up some dead dry black spruce. Just one pull on the recoil and , WTH, the saw had no compression. Couple more pulls and no compression, pulled the AF cover off and no dang sparkplug, WTH, where did that go? Now am stumped, saw won`t run without a plug, I am about 30 miles from getting one, sat down and thought for a moment. Then remembered the spare outboard we stored hidden back in the woods behind where we keep the trolling boat. Canoed over and fetched it back to the camp, used the sparkplug from it, not quite the right one but it fired up and I got my wood cut up, AF cover didn`t fit but the saw cut anyway. Just doesn`t pay to rush off on a trip even if pressed for time, got me twice so far but now since I check every piece of gear before leaving home. Oh, have needed to use vice grip for a fishing reel handle once, deep into the woods, 4 hour walk in or out and had an 10 hp Johnson twin someone borrowed one sparkplug out of but the outboard did start but just wouldn`t rev/speed up, did get me across the lake though, had spares at the camp.

 

[Patrick1903]

Johnson twin someone borrowed one sparkplug out of but the outboard did start but just wouldn`t rev/speed up, did get me across the lake though, had spares at the camp.

Wonder why the plug was missing from the boat?!
How do you canoe/portage 8 miles (after everything else) and get there mid morning? I would be trying to get there before dark!

 

[pioneerguy600]

Wonder why the plug was missing from the boat?!
How do you canoe/portage 8 miles (after everything else) and get there mid morning? I would be trying to get there before dark!

I can do 8 miles in 4 hours, left home at 4 in the morning, I was in shape then and participated in canoe races that spanned clear across our Province from the Bay of Fundy to the city of Dartmouth, paddle fast and could run with a canoe on my shoulders, cover long distances in a day. My brothers worked out of the same shop/garage as I did, they were known to rob parts from everything sitting still. Have found about any part imaginable missing from all machines at one time or another. Of course they were supposed to replace anything they borrowed/robbed but more than once they, forgot, hence I learned after a few failures to check everything before leaving for remote areas. Missing starters, carbs, batteries ,alternators, rectifiers, solenoids or empty fuel tanks all came my way but most were caught before leaving the yard.

 

[9050lx]

I found out no matter how diligent one can be about equipment its better to actually check the operation of the unit before taking it somewhere remote. This happened only once , to me. I had a cancellation one day at work, being very early morning and me wanting to get back to our backwood fishing camp I wanted to make the most of that day off. I hastily threw a lunch and day pack together, fueled and oiled saw I often took into the backwoods, put the canoe on the truck and headed out, 15 mile drive then take the canoe another 8 miles, several portages and get to the camp mid morning. Make a coffee and a snack. Grab the saw and lets get down to business of cutting up some dead dry black spruce. Just one pull on the recoil and , WTH, the saw had no compression. Couple more pulls and no compression, pulled the AF cover off and no dang sparkplug, WTH, where did that go? Now am stumped, saw won`t run without a plug, I am about 30 miles from getting one, sat down and thought for a moment. Then remembered the spare outboard we stored hidden back in the woods behind where we keep the trolling boat. Canoed over and fetched it back to the camp, used the sparkplug from it, not quite the right one but it fired up and I got my wood cut up, AF cover didn`t fit but the saw cut anyway. Just doesn`t pay to rush off on a trip even if pressed for time, got me twice so far but now since I check every piece of gear before leaving home. Oh, have needed to use vice grip for a fishing reel handle once, deep into the woods, 4 hour walk in or out and had an 10 hp Johnson twin someone borrowed one sparkplug out of but the outboard did start but just wouldn`t rev/speed up, did get me across the lake though, had spares at the camp.

Good to have two of everything, except of course,wives.

 

[chainbrake]

My neighbor told me about a problem he had with his blower. It wouldn't run. He checked the fuel level - looked good. Pulled it 100 more times. Eventually took it to the shop. No fuel! He somehow saw a tiny bit of fuel in there, but didn't have his glasses on and assummed fuel level seemed ok. I appreciated that he told me the story (instead of being too embarresed to say anything) and that he was able to laugh about it. Live and learn!

I'm over the embarrassment, now... that's why I'm sharing.

 

[Wood Doctor]

OP said, "I hope in the future I will remember to try the simple things first, spark plugs and fuel filters are easy to replace and don't cost much."
------------------------------
I just did a similar thing with a Stihl MS290. When starting, it would fire and die, fire and die. I replaced the fuel filter and also noticed someone had forced a small nail into the tank vent nipple that blocked it completely. I removed that nail while I was at it. The saw starts now and runs perfectly.

 

[a. palmer jr.]

I have 3 or 4 saws over here that I can't quite figure out what's wrong. I've checked everything I can think of and yet nothing. One example: McCulloch 3200 (I think that's the number), 150 compression, good spark, new fuel. Put a small amount of fuel in the sparkplug hole and it won't hit even once. I haven't checked yet but the only thing I can come up with is a sheared key on the flywheel allowing spark but at the wrong time. If that's not it then I don't know what to check next...

 

[lostone]

I have 3 or 4 saws over here that I can't quite figure out what's wrong. I've checked everything I can think of and yet nothing. One example: McCulloch 3200 (I think that's the number), 150 compression, good spark, new fuel. Put a small amount of fuel in the sparkplug hole and it won't hit even once. I haven't checked yet but the only thing I can come up with is a sheared key on the flywheel allowing spark but at the wrong time. If that's not it then I don't know what to check next...

With what you described, I agree with what you believe it is and that is where I would start looking first also.