Stihl BR400 engine question.

dlathemanNovember 23, 2007

I have a Stihl BR400 backpack blower. Engine has become hard to start. Once started it will run to a high RPM and then quit until the RPM drops, it then starts hitting again and returns to the high RPM and repeats above. I have checked the gas tank cap, fuel filter, gas line, air cleaner and carb, all are in working order. I have replaced the spark plug and the exhaust screen is clean. I am thinking the coil may be breaking down at the higher RPM's. I would love to hear from anyone who has experience with Stihl products.

Thanks.

Thank you for reporting this comment. Undo
gator_rider2(z8 Ga.)

I had a little problem with 4 year old use very little but way was use may been cause coil over heating I run full throttle until gas ran out fill run again four time on hot day coil went out. before went out it would Idle down some and then rpm's to high because missfiring load crankcase with gas. New coil came with washer that insolate heat transfer from block and I add better cooling practice to operation HS 85 mounted on 2x4 to cut tops out 6 acres blackberries.

    Bookmark   November 23, 2007 at 10:49PM
Thank you for reporting this comment. Undo
josephtm(CHN India)

Sounds like the carb is not pumping up enough fuel.
Probable causes: 1. Partially blocked impulse passage.Remove the carb.On the black carb mount there is a small hole.Blow compressed air or use a cleaner to make sure this passage is clean.If it is clean, when a few drops of oil are poured into the hole, and the engine cranked over, the oil should shoot out.
2. Pumping chamber blocked.Remove the bottom cover (held with one screw).There is a tan colored diaphragm.Lift it off the cover.If there is any tarry stuff below, clean it off.
On the carb body, there is a small circular well which has a mesh.
Prise the mesh out gently and clean it.
Apply oil to the carb body and gasket and refit the cover.
3.Metering chamber blockage.Open the top cover with four screws.Refit the carb in on its mount.
Hold the metering lever down and crank the engine over.
If everything else is fine gas should shoot up thru the inlet needle.
Refit the cover.At this stage I need to know the type of carb you have.If the blower is old, it has a 3 screw carb without limiters.If its a fairly new blower there are limiter caps on the adjustment screws and there is not much that you can do other than opening the 'H' and 'L' screws to their stops.
Try starting it now.
Don't go to full throttle at once.Take it to partial throttle first and gradually increase the throttle.
And, do all this without the filter elements.

Joe

    Bookmark   November 26, 2007 at 7:40AM
Sign Up to comment
More Discussions
IS it ME ? OR is this site/Forum Gone in hibernation?
This used to be such an informative and active site!!...
bertman_gw
Troy Bilt Horse Drive Shaft Bearings
I took my horse apart because the front transmission...
gildomilo
Toro 826 Drive Belt Jumps Off Crankshaft Pulley
Hello, I have a nine year old Toro Powermax 826. Late...
ronpr2112
Predator 212cc Engine, Harbor Freight FYI
Hi Folks, Been thinking of getting one of these for...
exmar
Primer not getting Gas?? After Carb Rebuid?
I just rebuilt a couple snow blower Carbs (both Tecumseh...
bertman_gw
© 2015 Houzz Inc. Houzz® The new way to design your home™