Brand New Briggs & Stratton 3.5 HP Old Stock (2009) Flathead engine wont start, it has Spark, tank full of good fresh gas - I sprayed carb cleaner in it and still not even a hint of starting. don't know what to do??
could be the fly wheel key, but how would have it gotten sheared on a new never run engine? Unless the factory forgot to put one in. The first thing I would try is a new or at least different spark plug. I have seen brand new ones that were defective. Also, does it seem to have proper compression? An engine sitting around a long time could have gotten a sticky valve. If it has spark, (at the right time) compression, and fuel, it has to run. If not, something that looks ok actually isn't .
side-draft carb or pulsa-jet?
Also: have you check the flywheel key to see if it's shifted or sheared?
\Pulse a Jet - No I have not, is it behind the pull starter? the spark is blue. New plug in also. I have a feeling its a stuck valve - how do you go about fixing it? maybe the sheared/no key too. it has NEVER ran. choke on or off does nothing. Thanks for all the help.. I need it..
check sheared key first, replace it if deemed the issue.
Then check carb. Pulsa-jet carb can be taken off (replace 1 diaphram (with spring)) to restore functionality. While you have it off, don't forget to perform a rinse of the tank to rid of debris. Carb hate debris, and these carbs don't have any sort of good debris filtration set up so beware. Get some compressed air (canned compressed air ok) and simply blow clear of all the orifices you have access to (on the carb).
Install it, fill with fresh gas before you try it again.
Lastly: I don't buy that stuck exhaust valve notion. So far, of all the bad (yeah, restore a couple of them that were tossed on the side of the road), and only one of them suffered from a gummy exhaust valve stem (wirebrushed and fine afterwards). That one suffered from severe neglect that I can tell: rancid gasoline, broken(Fallen apart) muffler, no oil change (compression ring a bit word), key sheared,etc. but was still restoratble and now in full service @ pop's place.
If yours was running fine until recently and been properly maintained up and until that point, then I'd keep the "stuck" exhaust valve analysis as the very last one to look for.
If it is brand new and never ran, I would look closely at the primer bulb. Takes a lot of pumping to get a dry fuel system going. As for the carb cleaners, some brands hardly light off unless you have a open flame on them. Use gumout carb cleaner, betting it'll fire off then.
Since the engine is NEW, I doubt if there is much wrong. IF it has decent compression, AND you have changed the plug, AND it has good spark as you say, put about 1/2 teaspoon of gas (fresh) down the carb throat, and it nearly has to at least try to run. Try that and let me know what happens.
Does it have compression? Pull it over very slowly and you should be able to tell when it gets to the compression stroke. If no compression, then a valve is stuck open. If you have compression, it is either flooded (too much gas) or not primed (not enough gas)
Remove the spark plug and dry it off. Then squirt some gas directly down the carburetor and press the primer bulb about 3-5 times. Should start right up.
Since it is kinda older it COULD need new diaphragm gaskets between the carb and the gas tank. Although they usually last just fine on new engines and should be fine. But they could be deteriorated.
Also, what is the spark plug numbers? Briggs experimented with different spark plug part numbers and had lots of spark plug problems around that time, so I would replace the plug with a new one. Champion RJ19LM is less than $2 at Wal-Mart. Gap it at .30.
Found the problem - This motor came from an educational facility - I was told it was overstock - it turns out this motor was used to learn on & they forgot to put the LIFTERS IN - I took the side cover off & wala - no lifters- everything looks new - cam was perfect. Valves go up & down just right with screwdriver - seller is shipping me a brand new motor at his cost & I get to keep this motor. turns out OK as I was able to learn a lot about these B&S engines.. Thanks for all your help.. Happy Thanksgiving to all..your great..