doogie_ac61358 0 Posted June 21, 2007 Ok guys, heres a good one for anyone who wants to jump in. On a briggs and stratton 11 hp vertical shaft engine, is the starter a positive ground or a negative ground. The problem is that it is spinning backwards and pulling a vacuum through the exhaust. I have it on a negative ground system. Won't put in here what brand of tractor so as not to offend the more sensative members here, just know that I am working on it for a friend. If it is a negative ground starter what could make it spin backwards? Share this post Link to post Share on other sites
sandyhillbill 12 Posted June 21, 2007 can you determine if the battery is hooked up so the system is negative or positive ground- if it is hooked up with the neg. battery post to frame of tractor then it should be neg.ground. Share this post Link to post Share on other sites
BLT 715 Posted June 21, 2007 I have not known any gear starter installed on Briggs engines that wasn't neagative ground. Share this post Link to post Share on other sites
RalphABlack 0 Posted June 21, 2007 I thought all Briggs engines were neagative ground. Share this post Link to post Share on other sites
Al 6 Posted June 21, 2007 Hi, Have you had it apart? If so, I will bet the brushes are installed wrong and the ground and the "hot" brushes need to change spots. Al Eden Share this post Link to post Share on other sites
doogie_ac61358 0 Posted June 21, 2007 Hey guys, I haven't had it apart yet but that may be the case. I have determined that the tractor itself is negative ground. But I haven't determined if the tractor the engine came off of is or not yet. The bendix is working correctly though and if you look at the top of the engine it spins clockwise. I haven't dealt with these kind of engines much. Any other ideas? Share this post Link to post Share on other sites
PatRarick 1 Posted June 21, 2007 The starter drive will not kick in if the starter is running backwards. The gear kicks in by centrifigal force on a spiral. Running backwards forces the gear down on the spiral, rather than up into the flywheel. Since the starter drive is kicking in and the engine is spinning clockwise when facing the flywheel, there's no problem there. If you're pulling a vacuum through the exhaust with the correct engine rotation, there are several possibilities. The exhaust valve clearance is set too close. A piece of carbon or other foreign matter is stuck to the exhaust valve or seat, preventing it from sealing. The exhaust valve keeper has come off, preventing the valve from closing. The exhaust valve is stuck open either by carbon buildup on the stem, or the valve stem is bent. The valve is burned or the valve head is warped. The exhaust valve seat has popped out. Share this post Link to post Share on other sites
doogie_ac61358 0 Posted June 24, 2007 Definitely interesting to note. I will check the exhaust valve very soon, but will that also force air backwards through the carb? Share this post Link to post Share on other sites
doogie_ac61358 0 Posted June 28, 2007 Had the head off tonight, looks like there was carbon on the seat. I had no compression before but have compression now. Will be taking the inspection plate off tomorrow and checking the clearance. Does anyone know the clearance and tolerances between the stem and the lifter? Thanks to everyone who threw their two cents in here. I am hoping the get the valve out tomorrow if it won't start now. Will see if it's bent or gummed up or not. Share this post Link to post Share on other sites