B&S 6.5 Quantum not starting well

[Mr_Accord]

I have a 8yr old Craftsman lawnmower with an B&S 6.5HP Quantum Series engine that up until today has been running great this season, one pull and she starts no problem. This mower had its general beginning of the season maintenance done on it at around the first week of may, new air filter, NGK spark plug, AMSOIL ASE SAE30, and it always gets fresh gas that has a splash of seafoam in it to keep the engine clean. I have a large property, it usually take me between 1 to 2 hours to bag the whole lawn. Today after about 1 hr of cutting and bagging I stopped to empty the full bag into the trash can, went back put the bag on and gave her a pull and nothing...wouldn't turn over. After about 10 good pulls the engine finally turned over but it was chugging for a few seconds with slight puffs of white smoke coming out of the muffler before it completely got up and going again. I was able to stop and start the mower 3-4 more times without any trouble before it wouldn't start again and it took another several good pulls to finally get it going. What could be the cause of this? it only seems to happen after the machine has been in use for awhile?

Thanks

 

[spasm3]

Try the old spark plug back in. sometimes i've had them go bad early, if nothing else, take it out and look at it.

 

[Thax]

On my B&S 6.5 hp mower it runs better on a Champion plug for some reason , have tried autolite's , NGK etc just runs better on Champion other than that dont know what to tell you, good luck
.

 

[Warstud]

If your raising the deck to clean the grass out...then you'll have problems re-starting it.

 

[Mr_Accord]

Quote:
Try the old spark plug back in. sometimes i've had them go bad early, if nothing else, take it out and look at it.

Well this is the 5th time I have mowed my lawn and the other 4 times the mower worked fine so I doubt it has something to do with the spark plug or else why would it start at all?

Quote:
On my B&S 6.5 hp mower it runs better on a Champion plug for some reason , have tried autolite's , NGK etc just runs better on Champion

I switched to NGK because the Champions I used since purchasing it new never lasted that long, switched to NGK and I find it runs better and they last 2x as long.

Quote:
If your raising the deck to clean the grass out...then you'll have problems re-starting it.


I never raised the deck at any time

 

[greenaccord02]

Originally Posted By: Mr_Accord
Quote:
Try the old spark plug back in. sometimes i've had them go bad early, if nothing else, take it out and look at it.

Well this is the 5th time I have mowed my lawn and the other 4 times the mower worked fine so I doubt it has something to do with the spark plug or else why would it start at all?


You come here for advice and then argue. You could have spent that time changing the plug.

Clean the old one, check for proper gap, and reinstall.

 

[hounddog]

Put another slug of seafoam or MMO to the fuel. Sounds like trash in the carb. to me.

 

[Mr_Accord]

Originally Posted By: hounddog
Put another slug of seafoam or MMO to the fuel. Sounds like trash in the carb. to me.


yeah in my mind its either some dirt caught in the carb or maybe the charging system is going, because it only seems to act up after it has been run for awhile and the engine is hot. But when I can get it running, the mower runs fine and continues to run perfectly until I stop - start it, so thats why I'm not really leaning towards a faulty plug, but I will take spasm3/Thax/greenaccords advice and start with the plug and then begin looking at the more technical stuff.

Thanks guys

 

[Mr_Accord]

Alright purchased a new champion plug today and it had trouble starting when it was both hot and cold. I noticed my gas line is cracking pretty badly when I was taking my carb off. Could that cause problems?

 

[greenaccord02]

Yes, and thanks for trying the plug. Easy stuff first. It would be good to replace the line and clean the bowl to make sure no line debris has clogged the jet.

 

[hounddog]

Takes a lot to make a plug bad on a lawnmower. Now a cracked fuel line sucking air is a issue.

 

[2Fast4U]

Pull off the float bowl and clean it very good especially the nut that screws the bowl to the carb. That nut has very small holes that must remain free of debris. Spray the bowl, nut and float with carb cleaner. Resemble and start.

 

[97prizm]

I also installed an inline fuel filter for the same type engine. This will help keep the carb clear of dirt in the future.

 

[01rangerxl]

How old is this mower? If it is more than a few years old, replace the fuel line and get new gaskets for the carb (there are three).

Taking the carb off for a good cleaning and gasket replacement is easy. Take out the two screws holding the air filter housing on, unbolt the two bolts holding the carb on the engine, and remove the linkage (there isn't much - one or two parts). Take the bowl off the carb and clean everything really well. Put in a new bowl gasket and new mounting gaskets, put it back together and you're done. New gaskets and a piece of fuel line should be about $6 or so. Carb cleaner is about $4. So, for $10 and 20 minutes you can do a lot for the engine.

 

[Scoot_4_20]

My 1993 B&S 3.8 HP seems to start a lot better after putting non ethanol gas into it.

 

[Scoot_4_20]

Originally Posted By: 97prizm

I also installed an inline fuel filter for the same type engine. This will help keep the carb clear of dirt in the future.



Sounds like a good idea.