Stihl BR600 runs only on full choke

[Steve56]

Hi everyone i am new to this forum.
Blower is 3 years old. Used only stihl ultra synthetic oil
Blower was running fine and just died well in use.
Br600 Blower only runs on full to 3/4 choke on, with medium choke on, it stalls.
Here is a list of things i tried.
- put in new fuel lines
- fuel filters with fresh gas
- replaced fuel pump bulb
- put in brand new carburator
- valve adjustment done.
- new spark plug
- swapped coil from another working BR600
- swapped air filter
- cleaned spark arrestor
I am not sure what i should try next. I was thinking that it is something to do with chiped or cracked valve.
I do not have a service manual for this Blower
Anyone have any suggestions.

 

[Conquistador3]

What oil mixture have you been running? Too high an oil content will cause carbon buildup on the valves, resulting in the valves struggling to close, meaning poor compression... you get it.

 

[Steve56]

I use 50 to 1 mixture

 

[Conquistador3]

OK, so stupid question time... before pretty much tearing it apart have you checked the tank vent? Yes, 99% of the time is fine but given the time and effort it's worth doing.

 

[Steve56]

Ok i poped out fuel vent on both of my br600's and swapped them. I have the same result. It's sure looking like a tear down.

 

[Conquistador3]

I re-read your previous posts and saw you run Stihl oil which is... really no guarantee, regardless of what the dealer tells you.
Hence I wouldn't truly run out carbon buildup on the exhaust valve, especially if the blower is high hours.
Another two possible causes are fuel lines not bent in the right fashion (even if new) and worn camshaft pins.

PS: If you need a shop manual go into the Chainsaw section, then the "Stockies" subsection and post your request in the "Beg for Manuals" thread.

And thank you for reminding me why I don't like 4-Mix and C4 engines and I stick to proper two and four stroke engines.

 

[Steve56]

Thanks for the advice. I do have lots of hours on it i am guessing at 3 or 400.

 

[Steve56]

Just wanted to say that the problem was carbon buildup between sparkplug hole and exhaust value. I took it apart and cleaned it out, reassembled it now run perfectly.
Thanks for the push to take it apart. First time for me.

 

[chipper1]

Just wanted to say that the problem was carbon buildup between sparkplug hole and exhaust value. I took it apart and cleaned it out, reassembled it now run perfectly.
Thanks for the push to take it apart. First time for me.

Welcome to AS Steve.
Glad you got it up and running.
Thanks for returning and posting the fix, many come and ask about a problem get lots of help, then never return to let anyone know what they found out worked or even what didn't work.
Brett

 

[Conquistador3]

Just wanted to say that the problem was carbon buildup between sparkplug hole and exhaust value. I took it apart and cleaned it out, reassembled it now run perfectly.
Thanks for the push to take it apart. First time for me.

Hey I got one right, huzzah!

If you want to reduce carbon buildup, use a JASO-FC or -FD rated premix oil.

 

[Steve56]

I think i will look in to getting AMSOIL SABER® Professional Synthetic 2-Stroke Oil and give that a try. I don't know about the 100:1 ratio they suggest though. Would you suggest sticking to 50:1 mixture.

 

[Conquistador3]

Without descending into yet another oil thread, leave the brand alone and just buy a JASO rated oil. There are plenty of cheap JASO-FC oils around and -FD aren’t much more expensive. Amsoil looks like a whole lot of marketing: if they had access to some revolutionary technology, BP, Nippon Oil, Exxon or somebody else would have bought them out already.