BG56C issue reaches full throttle for 15 seconds then quits

[TallCanuckinSC]

First time poster, howdy everyone!

Friend of mine asked me to look at his Stihl BG56C leaf blower. It arrived to me and he said "I can't crank it!", easy diagnosis: it was full of gas inside the cylinder. Drained the cylinder, easily got it running... or so I thought. It starts easily and maintains a low idle without any issues, but when rev'ed up, it will only hold the high RPM for 10-15 seconds then it will either maintain a low idle or quit.

So far I've put a tune up kit in it (spark plug, gaskets, fuel filter, both hoses from/to fuel tank, priming bulb (it was in the kit), air filter).

I took apart the carb and it looks in very good shape, cleaned and reinstalled it.

Removed the spark arrester to test, no difference, revs 10-15 seconds and then quits.

I also checked the bottom of the engine (below the flywheel) to see if it was leaking, didn't notice any oil from the crankshaft seal.

Any thoughts?

Thanks!

TC

 

[Russ2251]

There is an itty bitty fine mesh screen inside carb body. Is that clear of debris?

 

[TallCanuckinSC]

There is an itty bitty fine mesh screen inside carb body. Is that clear of debris?

The carb was very clean (not so much on the outside), did not see a mesh in there. The diaphragm was clean, cleaned and reinstalled.

Do you mean #18 from this exploded view?

If so, I didn't remove anything past #12.

JP

 

[bertsmobile1]

First rule with cube carbs is do not take them apart till you have diagnosed that there is a problem with them
Second rule is never ever reuse the gaskets Once they have crushed and taken a set it is very difficult for them to create a proper seal

You clean # 18 by removing the needle # 2 and blowing backwards from the seat but it is best replaced, they come in all rebuild kits
Try screwing the high speed jet # 19 out 1/6 th turn at a time
If it makes no difference then either the high speed circuit is blocked or the check valve inside the carb is stuck and now days they are not included in the current rebuild kits, but can be ordered from Walbro in packs of 8 or 10

 

[Fish]

Here is the price of a new carb from your Stihl dealer....
4241 120 0608 Carburetor C1M-S204 $34.01