We have an Ariens snowblower with a Tecumseh engine, and this unit has had an uneven idle since it was brand new. However, it starts on the first pull, even in the winter, and it settles down and works well when it is loaded. The manufacturers of small engines have been trying to reduce emissions since the 1970's, and they are all going to carburetors that run on the lean side, compared to equipment built before. Given that this engine is 17 HP, it likely has two cylinders, and there is a possibility that one of the cylinders runs a bit more lean than the other. This would result in an uneven idle. Cleaning the carburetor should help, but you might never succeed in getting it to idle as smooth as a fuel-injected car.

It is very hard to imagine the cap coming off the valve while the engine is running and not having an extreme affect on the engine running if it would run at all. I am not sure but what the thickness of that valve cap would be such that it would exceed the depth of the indention in the rocker arm, which holds the push rod in place, letting the push rod fall out and rocker arm dislocate. I would come nearing thinking that it was dislodged when someone was working on the valves and left out when the valve was adjusted. Also, a dislodged valve cap is not going to cause the engine to "makes an awful clanging noise from the engine." It would be noisy of course. Sure, put the cap back on, adjust the valves and see what happens. (Don't try to "pop" it back in place) To answer your question, it is held in place by the close fit of the parts, not enough room for it to come out. Walt Conner

well i DID replace the air filter and also decide to try and let her run a spell without it on altogether to see if I could further diagnose the problem. Seems to be kicking the fuel back from the intake. With the air filter off, I can see fuel spitting back a bit which would explain why it is running a bit rich. looks like I'll have to tear it down and replace the valve and maybe re-seat it. I'll check the rings on the piston while I'm in there and hopefully the cylinder looks ok. I really wanted to avoid tearing it up, but the rest of the machine is pretty rugged and in decent shape, seems a shame to junk it.

sorry just can't help myself, but won't resort to yelling in online terms. with all of you resident experts, and i have lifted flywheels on electric start motors many time yes i am away the charging stator is under there but and this is a big BUT? do they only now sue a coil and no points condenser be it mechanical or electronic to cause the spark needed????? refer to basic diagram in link i provided early on. at this time we can't test or determine if coil is damaged then as was pointed out that some one put 12 volts into it then that was withdrawn, because i can't see that anyone could do that. sorry to say also i am not making anything confusing i have tried to talk in simple terms, that's all i can do, and you all seem to have judged though over the years when a mower mechanic i would have lifted flywheels off of at least 1000 b&s not counting kirby lawson/techumseh, victa, villiers 2 & 4 strokes and some other models of engines foreign to australia. now the B&S motor may be a US engine from wisconsin but sadly the US does not own it, it is used world wide, did a great job in WW2 for many small stationary engine applications, still runs my push mower after about 20 years. in all that time we replaced very few coils they are a good strong coil so few in fact i could not even come up with a figure, yes i have lifted flywheels on B&S motors to replace point/condenser set up and when the plunger bush (was weakest link in briggs's wore because owner did not change oil enough, we reamed out the original bush an popped in a brass bush. later on when briggs bought out their great electronic points/condenser system commonly called electronic spark ignition we then would seal off worn plunger bushes and fit this new device absolutely great invention to the degree i fitted one to my own machine. so is there anyone here with the experience to tell me where the spark creator is? or is it contained somehow in the coil that looks like briggs coils have always looked. all i want to do is get this mower a spark for the plug. now if the electronic points/condenser is not under the flywheel and is not visible to my eye where is it. just in case some help comes tia len