bg86 HELP STIHL BG86 won’t pull over with spark in

[B-rad]

Hello so I have a STIHL blower bg56/86 not sure, so I tried to pull it over and got one rotation out of it then the pull cord snapped I’ve had it in bits and the crank and everything looks good I’ve got the exhaust off and the carb off and it still won’t pull over but with out the spark plug in it pulls over fine no odd noises or anything I’m stumped as the cylinder looks clean, it feels like it has way too much compression and just snappes cords I’m stumped please help

[doobin]

Are you sure it's the right size spark plug?

[B-rad]

Yes I tried two, one off my other blower

[bmp01]

Have you had a look at the thread "MS211C weird problem", different machine obviously but same problem....

[spuddog0507]

Wrong spark plug seen it many times, how can it be free with out plug in and then one revolution when plug refitted ?? Had a saw given me a few years ago and was told it was seized up, took plug out and turned over fine, fitted correct plug fired it up stuck it on flebay £345, thank you very much,

[Dan Maynard]

Wrong spark plug seen it many times, how can it be free with out plug in and then one revolution when plug refitted ?? Had a saw given me a few years ago and was told it was seized up, took plug out and turned over fine, fitted correct plug fired it up stuck it on flebay £345, thank you very much,

I can't imagine someone thinking it needs a new plug, then when they put the new one in it sticks, panic and give the saw away. Take the plug back out? Hold the two plugs next to each other and see one is longer?

Maybe though with that little knowledge about maintenance better they don't have a saw at all.

Owt queer as folk.

[B-rad]

I’ve had a look at a couple threads and it all appears to be too much oil which isn’t the case here as I have stripped it and cleaned it and it’s not to wrong spark as it was run with that spark plug and I tried with a different spark off my other blower same model and it still won’t pull over, and too be extra sure I didn’t screw the plug in all the way just enough to cover the hole like half a turn so it’s not even fully in the cylinder and it still feels like it has way too much compression  thank you for the replies but I did have a read about and Carry out some tests before posting here, I also took the cylinder off and used degreaser, wd40 and carb cleaner and wiped with a cloth to get any carbon build up out 

[spudulike]

Probably a fluid lock....fuel mix in the bottom of the crankcase. Pull the plug, turn the unit upside down, pull it over hard a few times and see if the engine kicks out fluid. 

If nothing comes out, it may be just old oil on the bore  making the compression super high.

If it isn't this, it may be one of the bolts holding the cowel on catching the back of the flywheel which is common to Stihl blowers but the plug being in or out shouldn't matter.

Unlikely to be the plug as it is a CMR6H and they are pretty long anyway and am not sure you can get a longer type!

 

[lurkalot]

Common problem on these machines.  While it sits around, the gassing and changes in temp pushes the fuel slowly out of the tank via the pulse hole and fills the crankcase.  

 

Check the pump diaphragm, that's usually the cause of the flood on these, not the needle.  It'll probably have a line of tiny holes down one side, if you hold it up to the light.

Edited October 2, 2020 by lurkalot
typo

[B-rad]

Right it’s currently upside down with the spark plug out and I am going to leave it like that for a day or so and let it drain any oil out, I’ll then give it a few hard pulls out spark back in try pull it over, if the problem still persists I will take the flywheel off to cover all bases but it turns freely with no issue without the spark so I don’t think it’s this, then I’ll disassemble it yet again and get the crank casing off and have a better look in case any oil is stuck in there, I also did notice there is not a gasket on the bottom of the cylinder? I wouldn’t think this would be a issue though surely if anything it would make the compression lower ?