Stihl BG 86 blower problems
Discussion
Hoping someone can help, I am fairly useless with the spanners but....I bought a used BG 86 blower last month. I then purchased the vacuum kit for it and noticed on the first go (literally 2 minutes) that it was running pretty hot, well very hot compared to my other Stihl machines.
Fast forward a week and the same thing, although this time it conked out after 3-4 minutes use with a small amount of smoke/steam. I then put a tank of fresh fuel in (with Stihl oil), changed the air/fuel filters and the same thing is happening. It gradually dies after a few minutes use. It does start on the first pull and sounds very healthy until it dies.
Is the next step going to be resetting the carb to standard settings? From what little I know, I thought overheating issues were usually to do with it running too lean? I would go back to the seller but it's second hand and they live some distance away (and haven't responded to my text which could be a bad omen!). I am hoping to fix it myself rather then spend a load at the local mower shop!
Any help would be great.
Fast forward a week and the same thing, although this time it conked out after 3-4 minutes use with a small amount of smoke/steam. I then put a tank of fresh fuel in (with Stihl oil), changed the air/fuel filters and the same thing is happening. It gradually dies after a few minutes use. It does start on the first pull and sounds very healthy until it dies.
Is the next step going to be resetting the carb to standard settings? From what little I know, I thought overheating issues were usually to do with it running too lean? I would go back to the seller but it's second hand and they live some distance away (and haven't responded to my text which could be a bad omen!). I am hoping to fix it myself rather then spend a load at the local mower shop!
Any help would be great.
Not familiar with this machine, but you say you have put the vacuum kit on and it has this problem. It it OK as a blower, i.e. without the vacuum kit?
If so is it possible that you have fitted the vacuum kit incorrectly in some way?
Instructions here if you don't have them
http://www.stihlusa.com/WebContent/CMSFileLibrary/...
If so is it possible that you have fitted the vacuum kit incorrectly in some way?
Instructions here if you don't have them
http://www.stihlusa.com/WebContent/CMSFileLibrary/...
Edited by Etretat on Thursday 8th October 18:21
Thanks, the vacuum kit is definitely fitted correctly - I will remove it inc. the shredder blade though to check. Think the next step will be to change the plug and clean the spark arrester screen to see if that helps. Is really frustrating but I don't think anything is too seriously wrong as surely it wouldn't start/run at all?!
Unrelated to your issue, but these blowers have a well documented problem of the flywheel housing screws coming loose and jamming in the flywheel, which if you're unlucky can lock the engine at whatever revs it occurs at and cause catastropic damage. Well worth removing them and retorquing them up with threadlock.
Two stroke engines are very simple. You say it runs very hot which indicates either;
a) The fuel/oil mix is badly wrong and the engine is about to seize. After it has stopped does the engine turn over as normal on the pull start?
b) I take it the cooling fins on the engine are not clogged up?
c) There is an overloading of the engine which can only be the shredder. Have you run it in blower mode to see if it expires in the same way? If it does then my money would be on the fuel pipe.
The petrol that we now have in the EU breaks down the fuel pipe from the inside. It may look OK externally but you can get a restriction inside the pipe when the engine is sucking fuel through it, until the carb is empty and the engine stops. Do get the correct pipe from your mower shop, take the pipe there as there are several sizes which are all pretty similar.
I take it you know to run the carb dry if you aren't going to use the machine for more than a couple of weeks, otherwise the fuel forms a silicone like substance in the carb which is almost impossible to clean out.
Whilst changing the plug and cleaning the spark arrester are good things to do anyway, I doubt that this alone will solve your problem
a) The fuel/oil mix is badly wrong and the engine is about to seize. After it has stopped does the engine turn over as normal on the pull start?
b) I take it the cooling fins on the engine are not clogged up?
c) There is an overloading of the engine which can only be the shredder. Have you run it in blower mode to see if it expires in the same way? If it does then my money would be on the fuel pipe.
The petrol that we now have in the EU breaks down the fuel pipe from the inside. It may look OK externally but you can get a restriction inside the pipe when the engine is sucking fuel through it, until the carb is empty and the engine stops. Do get the correct pipe from your mower shop, take the pipe there as there are several sizes which are all pretty similar.
I take it you know to run the carb dry if you aren't going to use the machine for more than a couple of weeks, otherwise the fuel forms a silicone like substance in the carb which is almost impossible to clean out.
Whilst changing the plug and cleaning the spark arrester are good things to do anyway, I doubt that this alone will solve your problem
Great thanks - fuel is definitely good.
I'll check the cooling fins this weekend - failing that will replace the fuel pipe as well. I will remove the shredder to test though but can't believe/hope it isn't that as it's designed for this model and the only reason I bought the damn thing anyway! Fingers crossed
I'll check the cooling fins this weekend - failing that will replace the fuel pipe as well. I will remove the shredder to test though but can't believe/hope it isn't that as it's designed for this model and the only reason I bought the damn thing anyway! Fingers crossed
Thanks - I took it apart last night, sadly not had the time today to test it properly. I did have it running for a few minutes inc. full power last night and it ran well/wasn't anywhere near as hot. Not a proper test though.
I found the exhaust was fairly loose, quite possibly explaining the heat I could feel on the casing? The plug was also slightly loose. I did have a look at the cylinder/piston - difficult to tell but I think there were signs of very very minor scoring, not sure enough to cause much issue though but I might be wrong. I'll give it a good test tomorrow and keep my fingers crossed. Hoping the exhaust was the issue!
I found the exhaust was fairly loose, quite possibly explaining the heat I could feel on the casing? The plug was also slightly loose. I did have a look at the cylinder/piston - difficult to tell but I think there were signs of very very minor scoring, not sure enough to cause much issue though but I might be wrong. I'll give it a good test tomorrow and keep my fingers crossed. Hoping the exhaust was the issue!
minghis said:
Enlighten me please?
Well pretty much what I said. The workshop manager of my local garden machinery place told me this, looking on the net it happens a lot. Something to do with the Ethylene IIAC. Not a problem on a bigger engine but the carb drillings on small two strokes are very fine and easily blocked. Garden machinery place has a bit of kit that cleans out carbs but won't shift this stuff, only solution new carb apparently.So when I've finished working one of mine that won't be used for a few weeks I stop it, empty the tank back into the can, restart and let it idle until it stops. Only takes a couple of minutes
Fingers crossed no problems so far
Nick_MSM said:
Shall I just reset it to the standard settings and go from there? It was supposed to have had a full service/carb set up, looks anything but so far.
Most two stroke diaphragm carbs have a base setting of 1 to 1.5 turns out on the L & H. Lightly, and I mean lightly, turn them both in (the seats are soft) then turn each on 1 turn out and try and start it. If that doesn't work, open them out another turn.Once you have it started, it should run. Let it run for 30 seconds to warm up and the follow Youtube instructions on "tuning the carb".
If the carb needs tearing down and rebuilding, its not difficult at all. Whatever you do, don't get carb cleaner on the diaphragm and diaphragm gasket, since it will ruin them.
Philemon said:
Nick_MSM said:
Shall I just reset it to the standard settings and go from there? It was supposed to have had a full service/carb set up, looks anything but so far.
Most two stroke diaphragm carbs have a base setting of 1 to 1.5 turns out on the L & H. Lightly, and I mean lightly, turn them both in (the seats are soft) then turn each on 1 turn out and try and start it. If that doesn't work, open them out another turn.Once you have it started, it should run. Let it run for 30 seconds to warm up and the follow Youtube instructions on "tuning the carb".
If the carb needs tearing down and rebuilding, its not difficult at all. Whatever you do, don't get carb cleaner on the diaphragm and diaphragm gasket, since it will ruin them.
1. Set meter to measure hertz.
2. Take a spare probe and cut the probe off leaving the plug and cable.
You don't need a negative probe.
3. Plug the lead into the positive of the meter.
4. Wrap the cable around the HT lead four to five times.
5. Start the engine and observe the average reading in Hz.
6. Simply multiply the reading by 60 to get RPM.
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