Mower runs for 5min then dies

[Scum_Frog]

6.5 hp B&S mower, self propelled - starts okay...runs for 5min then dies, after that, it is hard to start and if it does, it will run for 30-60 seconds and dies.

Any ideas on what to check. Air fiilter looks okay.

 

[GreeCguy]

any water in the gas tank? fuel lines clean and clear? How new is your spark plug?

 

[demarpaint]

+1 I'd also drop the carburetor bowl and clean things up, then make sure the float is not sticking and is set properly.

 

[Eddie]

A heat problem. Could be an ignition coil. Check the spark after it dies. Ed

 

[99Saturn]

Originally Posted By: demarpaint
Originally Posted By: GreeCguy
any water in the gas tank? fuel lines clean and clear? How new is your spark plug?


+1 I'd also drop the carburetor bowl and clean things up, then make sure the float is not sticking and is set properly.


+1 on the carb bowl. I had the same problem last year, that did the trick.

 

[oldhp]

Leave the gas cap alittle loose and see what happens. Sounds like it isn't venting. Ethanol eats the inside of the caps up.

 

[Sawdusted]

Originally Posted By: Eddie
A heat problem. Could be an ignition coil. Check the spark after it dies. Ed


I second this. Heat related problems are usually the coil.

 

[toneydoc]

I am with oldhp on this issue. Leave gas cap off or loose and try. Vent issue if it works ok

 

[JTK]

'nother vote for the gas cap not venting.

 

[Propflux01]

Gotta primer bulb? if so, replace.

 

[Quest]

Check the auto-choke puller, on the exhaust port side to see if it pulls the carb's choke flap wide open (when hot).

Also: when you try to re-start when hot, does the intake/exhaust side (muffler side) pops? if so, your valve + valve seat may need to be looked into due to improper valvelash issues. This would call for a head rebuild gasket kit in order to service the valve(clearance,etc.)

Lastly: it's never a bad idea to check the carb bowl for debris (drain and reinstall), spark plug coil (check for sparks when hot), etc.

 

[Scum_Frog]

Great feedback guys.....I'll give them a go!

 

[Propflux01]

So what fixed it?

 

[Warstud]

Your carb might need cleaning. Try adding some Seafoam or Techron to the gas to see if it helps. If not take the bolt/jet off the carb that holds the bowl on and run a wire thru the little holes in it. Also clean the bowl.

 

[earthworm]

Originally Posted By: Propflux01
So what fixed it?

[censored] good question..
When this happens, I think its best to check compression.I know that with poor compression ...less than 50 psi, hard starting is the rule of the day.
pull the plug
dry....no fuel
wet...no juice
I suspect no juice
Try again with another plug, a test plug
I have one of these "less than 50 psi" engines , ether helps....but the engine is weak...I'll check valve lash.

And, I am to understand that ethanol (regular automotive gasoline) is damaging to small engine carbs.....

 

[Spazdog]

totally different engine, but exact same problem with my Homelite curved shaft trimmer. Runs for a few minutes pretty well (as well as a Chinese Homelite will run anyway) then it dies. It's a pain to restart and then will only run for a minute or so at a time

Been through the carburetor thoroughly. The fact that it runs well for five minutes leads me to believe that it may be in the coil. I'll scavenge the coil off the 15 year old worn out McCulloch and see if I can make it fit.

 

[Ross]

Same symptoms that my honda mower did last summer. Checked for spark and there was none. Replaced coil and all is well now.

 

[Kestas]

I had a similar problem where the carburator float valve seat came loose. That one was a bugger to diagnose. A dab of glue took care of the problem.