cameron Posted September 16, 2005 Share Posted September 16, 2005 So a friend of mine gave me his old go-cart. I dunno why I took it being that im in my 4th year of college and my life is busy busy busy! but I took it and after a mid term yesterday I thought I would tear into it today so here its goes... its an old 5hp briggs and stratton. the guy before me blew the motor so he put a new cam,lifters, piston, rings, but the dam thing still wouldn't run. When u pull to start it, it back fires through the carb, so I though it might be timing so I rip the motor apart and the crack dot and the cam dot are lined up on TDC. also if I cover the carb so the only air getting in is from the crank case it shots a 3 foot flame out the exhaust side and it happens about ever 3-4 pulls so I have spark, timings right the only thing I can think of is that its the carb. I know its a pulsa-jet carb so it needs vacum to pump the gas to the needle jet so my thought is that its the diaphram in the fuel pump or maybe the spring in there, I dont know. any help would be great I searched all over the net and nothing, so I came to my fellow gear heads... Quote Link to comment Share on other sites More sharing options...
jt1 Posted September 16, 2005 Share Posted September 16, 2005 Ignition timing is determined by the flywheel keyed to the crank. Sounds like the crank key may be sheared. This is pretty common when a motor stops quickly. The gap from the coil to the flywheel is also a possibility. It should be 10-12 thou. Loosen the coil, insert a 12 thou brass feeler guage between the coil and flywheel, slide the coil down till it's snug, tighten and remove the guage. If you don't have a guage, 5 or 6 pieces of paper work pretty good. Also check valve clearance, something like 16 intake/18 exhaust. John Quote Link to comment Share on other sites More sharing options...
redruM_0381 Posted September 16, 2005 Share Posted September 16, 2005 Also check valve clearance' date=' something like 16 intake/18 exhaust. [/quote'] Briggs motors dont have adjustable valves, , although you CAN grind the stem if its too tight. If its a bit too loose, dont worry about it, briggs are robust, and I've seen them run fine with over a full MM of lash on the valves.. LOL got a fresh plug in this motor? Quote Link to comment Share on other sites More sharing options...
JMortensen Posted September 16, 2005 Share Posted September 16, 2005 My ex-boss's kid raced go karts. His 5 hp Briggs put out 14 hp, ran 14:1 compression and ran on methanol. Are you sure this one isn't in need of some different fuel? Quote Link to comment Share on other sites More sharing options...
74_5.0L_Z Posted September 16, 2005 Share Posted September 16, 2005 When you put your hand over the carb you are choking the death out of it . As the piston goes down you are creating a heck of a vacuum at the carb and pulling in a bunch of fuel. After 3 or 4 pulls you have enough fuel in the exhaust to combust, and it goes boom. This would also suggest that the ignition is firing on the exhaust stroke, or late in the power stroke after the exhaust valve has begun to open. Quote Link to comment Share on other sites More sharing options...
cameron Posted September 17, 2005 Author Share Posted September 17, 2005 thanks guys, jt1 u hit the hammer on the head with the crank key that was the prob... but on a bad note after i broke in the cam and everything seem fine the rod broke.... hahaha oooooo F%$#ING well. it was fun while it lasted! thanks agian on the fast info...... Quote Link to comment Share on other sites More sharing options...
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