Last year my Stihl bg86 leaf blower started playing up. Sometimes the engine would not turn over as if jammed. I would fiddle turning the engine backwards and it would then work, although it wasn’t running all that well. Then the final straw was, I tried to start it and there was no resistance at all on the pull cord and as I pulled, petrol squirted in a jet from the exhaust. It was like the carb was directly connected to the exhaust, with no piston there at all. I assumed all was lost and bought a new Stihl bg86. The old one was thrown under a large tree adjacent to my workshop at the top of the garden out of sight.
Fast forward about eight months. I picked the old machine up and pulled the starter and found normal resistance. I put some petrol in and it started. I gave it to the chap who works for me doing the strimming in the church yards, so he could use it. But now, we have found that it will start but only run for about a minute. It behaves the same with both a new, or the old, spark plug.
So could it be as simple as needing a new carb. The Stihl carbs are known for needing replacing after a certain usage. I replaced the carb on my HS 56 c-e this last winter and all was well, but that was more obviously the carb at fault.
I have thought about it and perhaps it felt jammed sometimes due to hydraulic-ing, with too much petrol seeping into the engine. Has anyone else come across this before? If it’s only down to a new carb then it is well worth the outlay, but replacing parts to fault diagnose is a tricky and expensive job. Any ideas?
Views: 5585
Replies
There's 4 screws under the flywheel that hold the crankcases together................ there was a problem a while back with them not being tight enough so one would work loose and jam the engine up...... turning the machine at a certain angle would sometimes be sufficient to shift the loose screw sufficiently so the engine could be used again. Does sound like you have a carb problem as well................. you can pick up "pattern" carbs on ebay for a tenner from China...... I've found them pretty good. If it only runs for a minute, try taking the fuel cap off when it stops........ if the problem goes away, the tank breather is probably not working as it should.
Sounds like the same problem I had ......I changed the carb and the problem has gone away.
I have no idea why.
I got the new carb off eBay from China for a 10er with all the filters and gaskets....not sure long it will last but it's been working for 6 months without a problem
Many thanks Jason and Graham.
The genuine Stihl carb for the HS 56 was £48 with gaskets, which is fine when it’s the correct fix, but the leaf blower problems seemed a bit more complicated.
I had thought about a cheap Chinese carb but was unsure, but now you say they are good, I will give it a go. For a tenner it’s well worth a try.
Thanks John,
My assistant has stripped it down and can’t make it run for more than a minute. He is actually a very good mechanic, having rebuilt many tractors and land rovers to concourse standard, so he knows what he’s doing, but still no joy. My HS 56 was still under warranty [almost three years old] when it started playing up and the dealer cleaned the carb, but ultimately to no avail and I later fitted a new genuine carb and problem solved. The excellent parts man at the dealer’s told me that Stihl carbs do fail after a certain usage due to 2 stroke gradual erosion.
So I have just ordered a carb kit from eBay, from one of the many people selling them, picked by a combination of selecting the one with the highest feedback crossed with the highest number of sales, as you do. For some reason at checkout there was some discount applied so the kit has cost me £7.69 including postage. So well worth a try. The kit includes the following –
New High Quality Aftermarket Carburettor Fits for Stihl SH56 SH56C SH86 SH86C BG86 Blower
Replace Zama C1M-S261B Carburettor
Replace Part number: 4241 120 0616
Please Note: This is High Quality Aftermarket Parts and Tested for Maximum Performance.
colour: as shown
Material: metal
Package Contents:
1 * Carburettor
2 * Gaskets
2 * Primer Bulb
1 * Fuel Filter
1 * Fuel Line
1 * Spark Plug
It’s hard to believe how inexpensive these Chinese made items can be and the quality seems to be very good. Those of us old enough to remember the 1970’s can recall that a ‘made in china’ stamp meant very, very cheap and nasty plastic items of very low quality. I think that idea still casts a long shadow, but unfairly to a very large extent. Anyway, I will see when it arrives.