Small Engines (Lawn Mowers, etc.)/Stihl BR 400 Blower


Hi Paul,
I have an old Stihl BR 400 that's giving some trouble.
I replaced the tank because it was leaking, and the carb along with gaskets and a fuel line.

It's very hard to start, and when it does, it barely runs and dies.

I also put in a new spark plug and tried running with and without the air filter.

Any tips would be helpful.


Hi Chris

Have you checked  ex port  and muffler for clogging / restriction?

what is compression pressure like  ? visuall on piston / rings / bore  
should be no signs of of scoring, blueing,  blowby etc  

is the spark  under compression pressure good  , should jump a 6 mil gap minimum

you have a new carb and tank  along with fuel line  - they should be ok

check timming key in flywheel

then try this  -  spray some 2 stroke into the plug hole and try run , if runs on that assume
compression / spark ok ,  next spray 2 stroke into throat of carb - if runs on this thens stops then you have a fuel  or at least a carby problem.

but if it does not fire when sprayed into carb throat , more likly you are dealing with a  crankcase  air leak.

you will need to remove carby, muffler , flyheel and starter assy  , block off  ex port and carb manifold  with rubber and steel plate(s) - make  spark plug adapter to fit in place of spark plug to pressurise  c/case through plug hole , with piston @ bdc   pressurize to 7-8 psi
check for air leaks at   barrell / case gasket, manifold boot , impulse hose , c/case seals
spray around those areas with soapy water  you will see bubbles  if a leak is present

if so  air leak comnfirmed -

air leaks tend to show  up as  , hard to start, no start  inconsistant idle , stalling, low power,  frequent adjustment of mixture screws , excessive revs

sounds more like a air leak to me  - check manifold boot and impulse hose carfully for splits / holes

take look  , let me know what you find

hope this helps  

cheers paul  

Small Engines (Lawn Mowers, etc.)

All Answers

Answers by Expert:

Ask Experts




Briggs and Stratton MST qualified Tech - Certified Kohler Expert Tech 12 years experience in repair of Small Engines -Briggs,singles, twins Kohler, Honda , Kawasaki ----Husqvarna chainsaws and trimmers -shindiawa -chainsaws & trimmers etc Walker Mowers - Kubota Ride ons - Husqvarna ride on and outdoor power equipment, -Mtd Ride Ons, Push mowers etc


Briggs and stratton MST qualified Tech - Certified Kohler Expert tech 12 years experience in repair of small engines Husqvarna chainsaws and trimmers -shindiawa -chainsaws & trimmers etc WALKER zero turn mowers Kubota Ride on mowers Husqvarna ride on and outdoor power equipment Mtd Ride Ons, Push mowers etc some experience in 2 and 4 wheeler repair - Honda, Suzuki , Yamaha

Qualification - Briggs and stratton Master Service Tech 2005 onwards Qualification - Kohler Certified Tech Qualification - Mito NZQA National Certificate Outdoor Power Equipment Basic automotive trade skills & year 2 & 3 of Motorcycle engineering

©2017 All rights reserved.

[an error occurred while processing this directive]