briggs 5hp won't idle and other issues

[traxxasislife]

ill start with the specs first: 5hp flathead, shaved eyebrows, billet rod, stronger valve springs, and strait pipe. engine ran fine, then i took it off the bike (doodlebug) and changed the oil, i noticed that i was missing a head bolt (the one inbetween the intake and exhaust ports) so i put another one in. after i put it back in the bike it wont idle, but it runs great in the higher rpm range(3000-4000) until about 7 minutes later it stalls out and won't go anymore. any help would be appreciated. Thanks!

 

[Cyanide]

the coil may be going out bad coils wont idle and die without anything changing on the motor also check fuel, tuning, and spark plug fouling

 

[traxxasislife]

thanks! ill swap the coil with another briggs i have. hopefully that solves the issue, because now it wont start at all:sad:

 

[traxxasislife]

swapped it out and tested it again... no difference:mad2:

 

[jim210]

Is the head gasket blown? What type of gas cap are you using?

 

[traxxasislife]

could possibly be, i havent checked the gasket but there appears to be mysterious oil on some of the cooling fins of the cylinder. and its the metal gas cap with 3 holes in the top

 

[traxxasislife]

bump

 

[minibikin']

Try running it with the gas cap loose. If they are not venting it will not run correctly. Also check the carb to block bolts and be sure they are tightened correctly.

 

[txAggie]

to me, sounds like you might have blown your head gasket. Oil, running at top end but sounding like you have a small air leak, dying and not starting when warm...I'd check that head gasket. Easy thing to check.

After that if it isn't fixed you might use the carb cleaner trick and squirt it around your carb manifold and see if you can find a gasket leak there.

 

[traxxasislife]

thank you, im hoping to order new intake, exhaust, and head gaskets today. however, i may end up just getting a new predator motor. ill try the gas cap thing too. also, regarding the tank to block mount, I'm using an adjustable gas tank/carb from an older briggs 5hp, and the block mount doesnt line up. should i make a bracket for it?

 

[Mikez3202]

I had a similar problem with my 5 hp briggs. It turned out to be the fuel tank gasket that's under the carb. It seemed fine but was allowing the engine to suck air between the carb and tank. But while I was at it i replaced all the gaskets just to be safe. Hope this helps!

 

[txAggie]

I had a similar problem with my 5 hp briggs. It turned out to be the fuel tank gasket that's under the carb. It seemed fine but was allowing the engine to suck air between the carb and tank. But while I was at it i replaced all the gaskets just to be safe. Hope this helps!

Yup, that is an easy one to have go out on you. Using carb cleaner with the engine running, or I've used a propane torch (unlit), will help isolate where the leak is. You will hear the engine surge.