Rideawaysenior 25 #1 Posted May 20, 2009 I need some advice and assistance here. My neighbor has an old Noma rider with a 14hp Vtwin Briggs Vanguard engine that backfires through the carb. It has solid state ignition so no points or condensor. I cleaned the flywheel and both coil packs and have a good spark. We then pulled the valve covers and cycled the engine while warm several times and the valves are moving freely. Can anyone offer any other suggestions? We are going to tear into the carb today and see what is in there but I have my suspicions that is ok. Any help would be great. Jack Share this post Link to post Share on other sites
W9JAB 156 #2 Posted May 20, 2009 :omg: Fuel is the most common problem. As long as the fuel is comming out of the inlet there's no need to worry about the float. Remove the main jet out of the centre if there is a slot in it & clean out with an airline. If not it's fixed so you just spray up the middle as best you can. (use a piece of wire to clean as last resort) Take out and spray any mixture jets if it has them. Hold float & needle secure in carb while spraying to avoid loosing any seat from the inlet. Problem: Engine backfires. Possible causes: 1. Carburetor set too lean. 2. Magneto is not timed correctly. 3. Valves are sticking. Armature Air Gap Adjustments 1. Rotate flywheel until magnets are away from armature. 2. Loosen both armature mounting screws (A) and pull armature away from flywheel. 3. Snug one screw. 4. Insert the proper thickness gauge between armature and flywheel. SEE SECTION 14- ENGINE SPECIFICATIONS. 5. Turn flywheel. Loosen screws and allow the magnets to pull armature against thickness gauge . 6. Tighten screws to listed values :drool: Share this post Link to post Share on other sites
brybrychrismer 17 #3 Posted November 20, 2009 Check the valves could be out of adjustment newer b&s have that problem bryan Share this post Link to post Share on other sites
Indy w h 4 #4 Posted November 20, 2009 If the b & s has been hot there's a good chance the valve seat has come loose in the block. Buddy of mines had the same prob so I tore into it that's what I found wrong. Been runnin eversense Indy Share this post Link to post Share on other sites
TT-(Moderator) 1,127 #5 Posted November 20, 2009 Depending on the year, a Vanguard twin either has diodes in the kill wire harness between the coils or they are contained in the insulated terminal block mounted in the blower housing. If one of the diodes malfunctions, it can allow current to backfeed to the other coil causing it to fire at the wrong time(s). Share this post Link to post Share on other sites
