OutdoorKing Repair Forum Forums Repairs and Maintenance Questions On Hand Held Blowers/Vacuums Petrol Blowers & Vac's Sthil BG55 Blower Konking out

Hi Guys,
Before I pull it apart and forget how it goes back together I thought it might be a good idea to get advice. I just got this blower and put fresh fuel in it and a new primer bulb and I can get it to start. It runs and sort of idles but when I try to rev it dies. I figure it must be some sort of fuel problem (brain surgeon) but not sure if I need to pull the carby off and clean it, or replace it or if it might be as simple as a fuel filter or hose. My question is has anyone had this problem before and is there a simple fix that can save me from damaging this thing with my 10 thumbs?

Thanks,
Graham

Poor throttle response from idle is usually lean mixture in the transition between the idle system and the main system, or a deteriorated spark plug. If a new spark plug does not cure the problem, incorrect adjustment of the mixture screws is the most likely cause. Restricted flow (due to obstructed fuel filters or poor pump performance) is more likely to cause lack of full throttle performance than poor acceleration.

I suggest you replace the spark plug, and if still not happy, try richening both mixture screws one eighth of a turn (that is, turn anticlockwise). If that brightens it up, play around with the mixture screws a bit. Run it full throttle after warm up and lean the high speed mixture (H) slightly back toward where it was in the first place, listening to the exhaust. When you get it to where it sings the sweetest 2 stroke song, recheck the throttle response. You may or may not have to go slightly richer than the sweetest running, to get the right throttle response. Then, when it is really singing, lean off the idle mixture (L) slightly for highest idle speed, and recheck the throttle response once again. You will end up having to set one or both screws slightly richer than best performance, to get good throttle response.

Hi Grumpy,

Thanks heaps for the reply, some great info there. I have had another go and I noticed when priming the primer bulb does not fill completely no matter how many pumps. Should the primer bulb be full after several pumps and should it remain full?

Thanks mate.

It sounds as if there may be some restriction or air leakage on the suction side of the primer, and it would be worthwhile making a couple of simple checks.

First, try loosening the fuel tank cap and see if either the primer behaviour or the throttle response improves. If it does, you have a tank venting problem, which is not unusual and can be fixed.

Second, check the condition of the filter built into the fuel pickup on the end of the suction pipe inside the fuel tank, making sure it is clean, and check whether there is a split in the suction pipe. I have read that the BG55 blowers are prone to having trouble with aging of that internal fuel pipe - it may crack and suck air, especially if it is an early production blower with black fuel hose (later production seems to have green fuel hose). You may need to block one end of the hose and blow in the other, to see if it leaks.

Thanks Grumpy,

I think you are right with the suction. I tried running it with the fuel cap loose and it seemed to run better. I still cant get the primer bulb to fill though. I have changed the plug and tried adjusting the carby (could only find 1 adjustment ie LD idle speed)and I have cleaned and inspected the fuel filter although I will replace it when I get one. There is some sort of valve or vent thing on the top of the tank that has a barbed spiggett thingy that I assume some sort of overflow line or similar would go on???.

I will pull it apart on the weekend and double check the fuel/vent lines and see if there are cracks etc and let you know how it went.

Thanks mate,
Graham

If you look at the fuel tank cap, you may or may not find it has a disk on the tank side that can be removed, and there is either a flap valve or (more commonly, on blowers) a flattened rubber-like tube that acts as a one way valve. These valves are prone to getting stuck in the closed position due to fuel drying up in the valve, leaving oil behind. The oil then oxidises when the machine is not run for long periods, so the valve gets stuck closed. However, your particular blower does not seem to require a vent in the tank cap because it has other venting arrangements shown in the parts list.

Here is the illustrated parts list for your blower:
http://www.worldoftrainz.com/Downlo...BG85%20-%204140%20-%20Parts%20Manual.pdf

If you page through all of the fuel tank output fitting illustrations, you will see that the fitting is always Item 5, and it always has two barbs. One is connected to the fuel suction line and intake filter. The other looks as if it is just an air vent into the tank, terminating just below the outside of the tank. Note that blowers, unlike chainsaws and brushcutters, tend to always be used with the fuel tank the right way up, so fuel spillage from an open air vent is not all that likely. Hence it is possible that no pipe is supposed to be connected to the second barb. It would be futile to connect fuel suction line for the primer to that second barb since it would only provide air, not fuel. On the other hand it might be a feasible place to connect a vent line from the primer, so it could return any combination of air and surplus fuel to the tank.

You will see that there is always a "tank vent" (Item 3) as well as the fuel output fitting. On Pages 41 and 43 the vent does not seem to have pipe barbs on its external apertures while on Pages 45, 47 and 49 the vent has a single-barb. All of these are BG55 blowers, but seem to be different production variants.

With the available information, I currently do not understand the tank venting and fuel priming systems on that blower. I suggest, though, that you check for air leakage into the fuel tank output fitting (which is all in one piece with the suction pipe inside the tank, and the two barbs on the outside). Then check for damage to the fuel line running from the suction pipe's barb to the carburetor. If both of those are intact, the next most likely problem is that the primer's intake valve is stuck open. Note though that if the output fitting is black rather than green, it is an early one that is reportedly rather prone to cracking and sucking air. There seems to be a thriving industry selling replacements even for the later green ones.


Here is the owner manual:
http://www.getbookee.com/get_book.p...SCA1NSwgU0ggODUgLSBUb29sIFJlbnRhbCAuLi4=