OutdoorKing Repair Forum Forums Repairs and Maintenance Questions On Hand Held Blowers/Vacuums Petrol Blowers & Vac's Stihl BG85 carb settings

Hi, I am currently looking at my step fathers BG85 handheld blower.

My question is regarding the carb setting which are written on the aircleaner housing from the manufacturer. The L screw has a 1 turn setting and H has 3/4 stamped into the plastic. Are these setting a guideline upon reassembly of the carb? I pulled the carby down for a clean and find the machine runs best at 2 turns of the L screw once warm.

Secondly he gave me this blower to sort for him after it simply didnt want to run after an extended period of sitting.

I pulled the carb apart and cleaned and inspected the gaskets, did a compression test,inspected the fuel lines to the carb, checked the plug, gapped the coil and tested for spark all to no avail. Scratched my head and thought to try the muffler for carbon build up and found a hornet nest right up into the muffler not protruding out out of the tip at all. Removed it and have a nice running blower. What a pain in the rump.

Hi Aldo, if you post the make and model of carburetor we can look for the overhaul manual for that model and perhaps see what the "first try" mixture settings are supposed to be.

As a rule of thumb, if the best setting is substantially different from what it is supposed to be, you may need to look for some other problem affecting it.
1. Is that 2 turn setting of the L screw before or after you removed the hornet nest from the muffler?
2. Does it require a lot of choke for quite a while after cold start?

What I am getting at here, is that there was probably a minor fault somewhere when you found you needed that 2 turn setting. It might have been the hornet's nest, or a very slight air leak from one of the carburetor insulator gaskets, or the metering lever height might not be precisely right. I won't suggest you might have missed a small piece of crud in some inaccessible area of the carburetor behind a welch plug. No doubt there are other possibilities as well.

Once again on the money Grumpy. I was happy with the clean I gave the carb and thought I would go over things again.

I noticed the two 10mm carb nuts were a bit loose. I reckon it was due to the two bolts having a bit of play, along their length in the insulator housing. This time when doing them up I made sure they were fully extended out before tensioning up the nuts. The blower ran quite well and was easy to cold start. I will try again in the morning and see how it starts before I am happy to return it.

I had something similar myself a couple of weeks ago, Aldo. My bent-shaft trimmer needed choke for about 15 minutes after cold start, with the carburetor settings optimised. One of the carburetor insulator gaskets looked pretty crummy, though not cracked or with pieces missing, just had some surface ripples. I squeezed it between a couple of flat plates. Tried 1 ton and it wasn't flat enough. Tried 2 tons and it looked flat. I didn't want to go further because gasket material just flows like butter when you put it under a press. The snipper now starts easily and runs well. It still needs choke for a hot restart, but only until it fires, then it runs very nicely unchoked. It still won't idle slowly enough to disengage the clutch, so the gasket is probably still leaking very slightly, but it has become a pleasant machine to use, which is quite a change.

Carburetor insulator gasket air leaks are a common source of trouble on engines that have flanged and bolted, gasketed intake pipes that have been dismantled at some time. Briggs had a better idea, on their small side valve vertical crankshaft engines, with the O ring seals they use, but of course that means no insulator, so less power from the engine.

If your final test on that blower isn't satisfactory, please bring us up to date. If I don't hear from you I'll take that as good news and close this thread.