OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Walk Behind Lawn Mower Frames Four Stroke Lawn Mower Frames B&S 3.5Hp issues

hey all.

Ive been working on 3 B&S 3.5HP engines for a while now and i just cant seem to fix them. they wont start cold, then they will, they will start cold then wont start warm, then they will start warm. theyl over rev, one just wont turn off. is all this just to do with the carby diaphram or something more?

thanks

For the one that wont turn off check out the throttle cable adjustment, if it doesnt short the black wire going up to the coil it will not cut the ignition. Also check the wire is in ne peice.

After a full system clean out for the ones that wont start cold the diaphragm could be to blame.

Overrevving? check that the govenor setup is working correctly, is the spring too tight or loose? is the whole unit sliding back and forward smoothly etc,

I have a rover baron that continually overevs, since I had to shorten the spring to make it even run with a sprint carby, one day I will sort this issue out, until then it buzzes along the lawn and does a great job at 4500+ rpm, regular oil changes on this motor are a must as the revving puts a lot of carbon in the oil.

Also I have found especially with ones sitting for a few years (IE: the ones I got from melbourne) The carby will not suck fuel properly, tipping a small amount of fuel down the carby and smothering the airfilter hole (With the screw that holds the air filter in is a must) with an old shirt folded over a few times and trying to start it, as it begins to stall, uncover the carby a little, it when uncovered it goes to die smother it again and keep going, this seems to eventually get it pumping fuel.