Stihl BR420 non starting issues

[TysonH]

I picked up a BR420 the other day used in non running condition for cheap. The guy told me the dealer had looked at it "fixed" it and it started not running again with the previous owner. I looked at it today and it has a new coil, air filter, fuel filter and spark plug (all OEM parts btw). The cylinder and piston look to be in great condition but I have not done a compression test although that feels fine by just pulling it. I trouble shot the kill switch and the coil it has plenty of good spark and its not the switch but its flooding the daylights out of the cylinder, so I am thinking maybe a carb issue.

Should I rebuild the carb ? or could this be a fuel line problem? Im not sure what the symptoms would be if this was an impulse line ?
Any help is appreciated.

 

[lone wolf]

I picked up a BR420 the other day used in non running condition for cheap. The guy told me the dealer had looked at it "fixed" it and it started not running again with the previous owner. I looked at it today and it has a new coil, air filter, fuel filter and spark plug (all OEM parts btw). The cylinder and piston look to be in great condition but I have not done a compression test although that feels fine by just pulling it. I trouble shot the kill switch and the coil it has plenty of good spark and its not the switch but its flooding the daylights out of the cylinder, so I am thinking maybe a carb issue.

Should I rebuild the carb ? or could this be a fuel line problem? Im not sure what the symptoms would be if this was an impulse line ?
Any help is appreciated.

Sounds like the carb. Check the inlet needle for debri stuck or not sealing . Or just replace the carb it may be around 40.00 or so.

 

[GlynnC]

Will it start with a shot of starting fluid? This is an easy way to determine if it's electrical or fuel problem!!

 

[backhoelover]

the br 420 are bad about shearing flywheel keys. i fix dozen of these with this problem

 

[backhoelover]

they will also flood there self out with only 2 pulls on choke they all are like this. was like that new from dealer

 

[backhoelover]

if it is the flywheel key you have to be careful putting them in. i have had the come to me from the dealer and the so called gold tech pushed it in too far. go slow pushing it in and keep trying the flywheel. once you get it to where the flywheel will bottom out make sure you use a piston lock or you will have to start all over again cause you can easily shear the key again

 

[lone wolf]

if it is the flywheel key you have to be careful putting them in. i have had the come to me from the dealer and the so called gold tech pushed it in too far. go slow pushing it in and keep trying the flywheel. once you get it to where the flywheel will bottom out make sure you use a piston lock or you will have to start all over again cause you can easily shear the key again

Good post. " so called gold tech" I like that

 

[TysonH]

Update:

I well I got it to run now, I took the carb apart and blew out everything that I could. I think the needle valve was a tad lazy in its movement, put it back together. Its still putting a lot of extra fuel but the thing that got it to fire was I rechecked the plug gap

and someone set it far too wide so I had even better spark cranking it grounded to the jug. Its blowing a lot of white smoke out of the exhaust which Im guessing is extra fuel ? I think I may still pick up a new carb tomorrow for piece of mind.

 

[backhoelover]

glad you got it going

 

[BroncoRN]

Pop the limiter caps off the carb and adjust the L side. I think L side should be 1 turn out and H should be around 2 1/4 turns out. Trim the tabs off the caps and put them back in to keep the adjustment screws/jets from moving while in use.

 

[BroncoRN]

My BR420 takes 2-3 pulls while choked and then 2-3 pulls without choke to start. I've never had a flooding issue with it.

 

[lone wolf]

Update:

I well I got it to run now, I took the carb apart and blew out everything that I could. I think the needle valve was a tad lazy in its movement, put it back together. Its still putting a lot of extra fuel but the thing that got it to fire was I rechecked the plug gap

and someone set it far too wide so I had even better spark cranking it grounded to the jug. Its blowing a lot of white smoke out of the exhaust which Im guessing is extra fuel ? I think I may still pick up a new carb tomorrow for piece of mind.

Or check and adjust the needle lever flush. Too high lets in more fuel. Could also be the needle is not seating and sealing.

 

[TysonH]

Pop the limiter caps off the carb and adjust the L side. I think L side should be 1 turn out and H should be around 2 1/4 turns out. Trim the tabs off the caps and put them back in to keep the adjustment screws/jets from moving while in use.

It seems to be running decent at this point, I will pull and tab off the limiters in the future.

Or check and adjust the needle lever flush. Too high lets in more fuel. Could also be the needle is not seating and sealing.

I think that is what is the trouble in the carb, if it does that again a new carb will be the order its a great running machine and I prefer it greatly to the 4 Mix stuff