View Full Version : Stihl BG55 Blower Problem!!!

05-01-2008, 10:31 PM
I will truly be thankful if you guys could give me some input on this annoying issue that I'm having with my Stihl BG55:

My BG55 cranks up just fine after a couple pulls with the choke on and will run great across the entire rpm range when I initially start using the blower. After the first couple minutes of running, the blower will normally bog down briefly and then I let off the throttle. Once I reapply the throttle, I can normally bring the blower back up to full speed. The blower just seems to do this at random times. Often times I will have the blower under full throttle and then it will bog briefly and then come back up to speed. Occasionally it will do this several times in a row, almost like a random slow surge. At one time, I thought this issue was linked to something in the fuel system because when I would slightly tip the blower one way or another it would start or stop bogging down. When I was running the blower today I found that this was not the case because I set the blower on the concrete while at full throttle and it was still exhibiting this bogging surge behavior. My other thought is that it could be an ignition related problem once the ignition components get heated up.

Here are the things that I've done to fix this issue but have had no luck:

New mid octane fuel properly mixed with oil
New spark plug
New fuel filter
New air filter
Pulled out exhaust spark screen
Checked lines running between tank and carb
Adjusted carb to specs listed in manual (this made the blower run better but I still had the bogging issue)

Do you guys have any other ideas? Maybe a carb rebuild or new ignition coil?

Thanks so much for the help,


05-01-2008, 11:22 PM
I guess check to see if the exhaust port are clear....usually this unit don't clog...

05-02-2008, 12:11 AM
Yeh look in the manual on how to reset the L + H adjustment screws.
Now if you do it wrong it will never run right again lol, but you can do it over until you get it right.
Just be aware those stupid screws the heads wear off after so many times, so better if first try gets it.
Far as I know you turn them all the way to the stop, then 3/4's turn the other way (just not sure which way to the stop).
Also it might be diagrammed on the machine itself, right where the set screws are usually.

Btw the 55 is a really nice blower, I have one thou I bought the flat tip nozzle for it...
Then I just got me the 85, figuring it would be better.
I am not impressed, it's a wee bit better but keep the 55!

05-02-2008, 01:14 AM
Thanks for the quick replies!

Yeah I set the L, H, and Idle Speed screws exactly as directed in the manual and, like I said, my BG55 ran better overall but did not fix my original problem.

To check the exhaust port, do I just pull the two torx screws on the muffler and then pull the muffler off? If I remember correctly, those screws looked lock tited on.

Any other ideas?



05-02-2008, 02:34 AM
It could probably use a fuel pump diaphragm.

05-02-2008, 10:37 AM
So how would I go about changing the fuel pump diaphragm? Is this also part of a standard carb rebuild on these Stihls?

I've been thinking that this could also be a fuel tank vent related issue so could that be a possibility?

Also, is there a pdf version of some sort of Stihl factory service manual that I could reference to take things apart correctly? I'm quite mechanically inclined but I don't really like to just start taking things apart without some sort of instruction.

Thanks so much,


05-02-2008, 02:49 PM
I've been thinking that this could also be a fuel tank vent related issue so could that be a possibility?

Yes, I`d definitively check this first.

I think the BG55 has a ZAMA C1Q carb. Don`t know which variation.
These are hard to rebuild. I suggest you buy a new one. You can then play with the old one and if you can get it fix, have a neat spare part always on hand.

Here`s an IPL for the C1Q, it covers all serials, so your carb won`t have all the components listed here.

Good luck.

05-02-2008, 02:59 PM
Could someone please walk me through the steps of properly diagnosing the tank vent?

Thanks so much,


05-02-2008, 06:58 PM
Could someone please walk me through the steps of properly diagnosing the tank vent?

I believe the blower's vent is built into the fuel tank cap. When running the unit, wait till the same problem presents itself, and loosen the fuel cap. Does this improve anything? Usually when there's a problem with the vent (blockage), the unit will stop altogether, after 10 minutes or so. Underneath the fuel cap is a venting system with a "duck bill" check valve, a sintered filter, and a host of other parts. Before you embark on cleaning that, do the previous.

I thought this issue was linked to something in the fuel system because when I would slightly tip the blower one way or another it would start or stop bogging down.

Yes, this symptom is usually related to the carburetor and a weakening (brittle) diaphragm, or possible air leak.

How old is this unit?

05-04-2008, 08:16 AM
It probably has a separate vent. Its a black round plastic piece that pushes into a rubber grommet in the top of the fuel tank. Did you check the fuel lines real closely? They have a tendency to develop small cracks. They are black rubber. When you get the fuel line out, stretch it a little and look for cracks. The updated lines are green color and seem to be much better then the black ones.

05-04-2008, 07:57 PM
My unit actually does have the green fuel lines rather than the black ones. There are two lines that run from the top of the tank to the carb. One is the fuel pickup and I'm assuming that one is the vent?

Thanks so much,


05-04-2008, 08:06 PM
My unit actually does have the green fuel lines rather than the black ones. There are two lines that run from the top of the tank to the carb. One is the fuel pickup and I'm assuming that one is the vent?

Thanks so much,

Wesone is the pick and one is the return, If you do not have a third line the vent is most likly in the cap. When it starts to surge, remove the fuel cap and listen to hear if it sucks air.

05-20-2008, 12:15 PM
Well, this definitely is not a vent issue because I loosened the fuel cap and the issue did not improve. It's kind of an odd problem because it will bog on the top end most of the time but sometimes it runs just fine. As far as the new carb goes, my Stihl dealer wants $60.32 for the correct Zama C1Q carb. That's pretty hard for me to to justify since I bought the blower used for about $75 and a new one won't be much over $150. I'm pretty mechanically inclined so I think I'll try to pull the blower apart and purchase a gasket/diapragm kit for the carb which will be about $6 and see if that helps me out.



05-20-2008, 10:54 PM
I has the same problem (i tried everything, new plugs, filter, gas nothign fixed it) and I seafomed the engine and then added seafoam to the gas and everything works fine now

05-27-2008, 10:45 AM
Well I'm about at my wits end with this problem. I pulled the Zama carb and installed new pump gasket/diaphragm and new metering gasket/diaphragm but had no luck. It just seems so much like a fuel problem to me since it runs great sometimes but then will randomly start to bog. I also pulled my fuel lines again and checked them by looking and putting a vacuum on them. Maybe it has something to do with the carb metering lever or inlet needle valve? I'll also try the seafoam later today and see how that works. Honestly, I was about to put my BG55 blower out on the curb with my trash this morning!



05-27-2008, 10:51 AM
Put some in the gas to and it will take a couple of days for it tp work

05-27-2008, 01:26 PM
you said you checked the fuel lines may i ask how? you need a pressure pump to do this right. but to be honest it sounds like the primer valve or flange as is called is bad. it the part that goes under the primer bulb (they go bad all the time) but again to know if its bad and so you dontkeep throwing parts at it as you have you need a pump to test that also but i will give ten to one thats what it is.

05-28-2008, 02:08 PM
Okay, I think that I've got my problem straightened out. When I got home from work yesterday, I realized that I had a half full can of Sea Foam that I used on my truck several months ago. I decided to give it a shot so, while running my BG55 with the air filter off at a fast idle, I very slowly poured 1/2 ounce of the Sea Foam through the carb. The engine wanted to die and it made alot of smoke but I noticed that it was running pretty much fine once the smoke cleared. I then proceeded to add about 1/2 ounce of Sea Foam to the gas tank and threw the air filter back on w/cover and then ran my BG55 again. The intermittant bogging problem came back! I swapped the air filter on and off a few times and then came to the realization that the air filter was probably causing the engine to run rich due to lack of air at the upper rpms. I put the filter back on the engine and then adjusted the high speed screw slighty to the lean side and the blower began to run better. I adjusted the screw a bit more and then it started to run perfect at the upper rpms, with no bogging. Everything was fine but the idle still seemed to be off a bit. I have a photo tach so I decided that I would stick a piece of reflective tape on the blower impeller with the cover open and see what I came up with. The idle was reading slightly under 1200 rpm. I flipped through the manual and discovered that idle speed should be somewhere around 1800 rpm so I adjusted the idle screw accordingly. Now my BG55 runs better than it did when I bought it! It was my fault all along and I was blaming it on my beloved BG55... Now that I think about it, I should go ahead and get a new air filter just to see if that works better than the existing one (which should be clean since its almost new). Is there a way to just clean these filters or should I just purchase a new one?

Thanks for the help,


David Thompson
05-28-2008, 08:12 PM
I had one of these come into the shop today and the customer said " it will idle but not rev up good" I looked around and saw the little spark arrestor thing that screws into the muffler only had a pin hole left to breath thru . Cleaned that and it was running perfect again . Then the shop owner wanted me to install a new carb , new plug , new fuel filter and lines and put a new pull rope on it .
So I am in the market for a new job today.
I have all of the certificates listed on the stihl ecadamy web site not just the bronze level 1
So if you know of an honest shop or would be interested in starting one in the atlanta area?

05-30-2008, 02:19 PM
David, way to go, glad to read you stuck to your guns. I'm so sick of rip off dealers, that's why I work for myself, maybe you can't do that right now but... I worked for a big outfit here in Ft. Worth and got the same deal, then they started telling me I couldn't charge this or that customer so much, like the song goes "Take this job and shove it" I now work out of the house with loyal and good folks and there is a lot of trust between us. Took a few years to weed out all the residential junk, now all I do is about half a dozen commercial landscapers and it keeps me hopping, don't need anymore, don't want anymore, ain't getting rich, but damn sure happier.

05-30-2008, 04:45 PM
Yeah, dealers pretty much suck. Can't make an honest buck. Most guys would stick with a dealer if they were sure they wouldn't hoodoo them. I'm jaded now, dealers suck. Tony