Lawn Mower Will Not Start - You Will Never Guess Why

hey guys welcome back so today i got something a little bit different this is a craftsman push mower and powered by a briggs and stratton quantum engine uh this one was listed only at 25 dollars and in the listing didn't say much other than it doesn't run anyway it looks to be in pretty good shape pretty clean i did pull it over it has compression so most likely we're dealing with a dirty carb so i do want to give it a squirt of starting fluid and make sure that the engine itself sounds good but before i do that i'm going to check the oil in the blade real quick and then we'll proceed from there so let me get you set up a little better and get going on this thing that oil looks good it's nice and clean and filled perfectly yeah not too bad the blade is straight and i mean the deck needs to be cleaned we'll worry about that later i'm just going to double check the torque on that bolt don't know exactly on this model but usually 30 foot pounds will do it i'd say more than half the mowers i pick up the blades are either damaged loose or the wrong blade all together in this case everything looks good so i'm gonna get the spark plug plugged back in just pull it over a few times like this see if we get any signs of life so so yeah we didn't get too much but it was sputtering a little bit so we know we have spark the compression felt pretty good timing i guess is a tbd so i'm gonna get the cover off the air box we'll give it a squirt of starting fluid and make sure we have a good engine it's not really doing much on starting fluid so i'd say we have something else going on besides the carb most likely timing or possibly a top end issue so i'm going to get the covers off the top here we'll take a look at the flywheel key and see how the timing looks [Music] yeah this is not at all what i was expecting to see that is the key and that is the key way on the crank so they line up as far as i can tell the timing's good at least on the outside the only thing that would make sense is if the cam somehow jumped time and the valves aren't opening and closing at the right time so i'm going to give this one a little bit of thought before tearing this engine apart but i think it's going to have to come apart all right it's actually the next day i wanted to sleep on it so i re-secured this cup torqued it down i also pulled the fuel tank off and hooked up this line for the leak down tester so i started rotating the engine with my thumb on the end here until i got to the compression and what i thought was compression is actually suction so that kind of backs up my theory that the valve timing is off also when i do hook up some air not to do a leak down test but just to figure out when the valves are opening and closing discovered something right now the exhaust valve is open now the intake is open so the transition is happening right about there and that's not right the transition should actually be happening right about there so wear a good i'd say 20 degrees off and that's all it takes to keep this thing from running so the cam shaft's an issue i took a look at the part online the gear and the lobes are plastic and they're pressed onto a metal rod so something something moved and now the timing's off so i've already drained the oil i'm just going to tip this up on its side we'll get the blade and blade adapter off we'll get the engine removed and we'll open it up and take a look [Applause] [Music] so [Applause] [Music] hmm yeah something moved there is a tab right here hopefully that shows up this lobe right here is supposed to be kind of between that tab and this cross member here and it's not it's moved for sure and if you look here at the compression release right here it's bent and it's actually hitting these cross members here it's supposed to be kind of more in between so that compression release can can move but where it is right now it doesn't move so even if the timing was on the valve timing that is the compression release would not be working correctly so yeah we need a new one of these okay the parts are on their way wasn't too bad i found a used cam for about ten dollars i also got the oil seal and the sump gasket so all in i had to spend another 25 bucks to get this thing hopefully in running condition anyway just using this time to clean up the gasket material this one's getting pretty close but i do still need to get some more off and then once it's mostly off i'll just use like a fiber disc to get the rest of it off anyway for this i do use a razor blade and i recommend caution this is aluminum you can scratch it and gouge it pretty easily so just take your time this is a slow process okay the new used gear is here it's the one on the left and as you can see this lobe right here roughly lines up with that tab completely different from the old one which is way over here so this should be good i've already cleaned it up looked it over and i think this one will be good to go it's hard to see but that tooth right there has the timing mark on it so i got a new oil seal just going to drive the old one out and we'll install the new and i should have shown you before taking it out when you put the new one in you don't want to drive it all the way to the bottom you want to match to where it was in this case it was about maybe 3 16 of an inch down from the top it's just about it you you all right ready to give this thing a try you know the carb is an unknown to me so there could be issues there and even if the carb was fine you know we did have the engine upside down and some of that oil could have gotten out of the breather and into the carb which will cause issues as well but let's try starting it hopefully it starts because this grass is definitely overdue [Music] [Music] this thing runs great now that the timing's on i mean it it probably would have started the first pull but the grass was so long that i couldn't get a good pull because the grass was hitting the blade anyway second pole started right up had no problems cutting this lawn and tried starting and stopping it a few times no issues looks like we do have a bit of fuel though coming out the top so i'll have to take a look at that maybe that cap is missing a gasket but all things considered you know i picked this up because i thought it would be an easy fix it's springtime and an easy sell and yeah this one threw me for a loop i'm not sure if i would have identified the issue a year or two ago this one was an odd one but you know a lot of engines now have plastic cams in it so if it's not starting you got spark you got compression and you have timing at least on the flywheel you know it could be the cam so double check the valve timing that could be your issue anyway i hope this video helps someone thanks for watching okay a little bit of bonus footage here i was curious which plastic part rotated on this shaft so i made a mark right there on the shaft which aligns with this lobe and i did the same where this timing mark is i made a mark right there on the shaft so i'm going to put this in the vise just turn it and see which piece is actually rotating and the mark still lines up with this lobe if we look at the gear itself there is the timing mark but the mark is not on the shaft you got to rotate it to right about there to find that mark so now we know it's the gear itself that broke loose on this camshaft anyway thought that could be helpful i don't know if it's always the gear that breaks loose but now we know

Channel: James Condon

Views: 1,179,019

Rating: 4.8417077 out of 5

Keywords: Briggs & Stratton, Briggs and Stratton, Camshaft, Craftsman, Fix, Flywheel, Keyway Lawn Mower, Mower, Plastic Camshaft, Plastic Cam, Quantum Engine, Quantum, Shear Key, Small Engine, Timing, Troubleshooting, Valve Timing, Valve, Will Not Run, Will Not Start, 126M02-6863-F1, 126M02, 691449, 492830, 498275, 498817

Id: oY6YZZ72jJw

Length: 26min 21sec (1581 seconds)

Published: Thu Jun 03 2021