I have a lawn boy push mower that will not start. I have changed out the cd pack and cleaned the carburetor inside and outside. I recently had a plug that was too long and I think it hit the piston, however, there does not seem to be any damage to the piston head as observed from the spark plug hole.
Any suggestions would be appreciated.
#2
reynoldston
It needs spark, fuel, compression, and timeing and it will run.
thanks for the reply. I have spark, compression and I think the timing is good without tearing into the engine.
a while back a long shank spark plug was installed and was incorrect since a short shank is required. what this did was hit the top of the piston. I check from the outside spark plug hole and looked for damage on piston and looks good and I can hear compression.
I will open the carburetor and clean out again because looks like the carburetor is not receiving much gas i found out today. I will check again if I installed the fuel jet correctly below the float.
Another thing you could try is pouring a little fuel right into the carburettor and try to start it , see if it run for a little while with the gas you poured directly into carburettor. Then try pouring gas in once and a while to keep it running a little bit, that might help determine carburettor problems . Just a idea good luck.:smile:
#5
reynoldston
The only good way to check compression is with a gauge. You might have a tight valve which would give you compression but not enough to run the engine. You might be able to rent one from a auto zone. I know no one likes starting fluid. I don't know why because I use it all the time and never have a problem with it. The starting fluid of today has a lub. in it so it doesn't hurt your engine. I say spray some starting fluid in the carburetor and see if it runs this will tell you if it is a fuel problem or not. Timing would most likely be a flywheel key which would be off if the engine stopped fast like if you hit something or maybe the plug hitting the piston. Spark get a spark tester from a auto parts store because the spark should be tested with the plug in the engine. A plug may fire out of the engine but not under compression. The spark tester is less then 5 dollars money well spent.
has anyone had trouble removing the under the deck muffler. I have taken the blade and nut, however, the muclhcing flange does not seem to move. is there a clip holding the flange to the cranshaft?
any help appredciaed as always
Dennis
#7
Briana
I moved your thread to the Small Engine & Mower Repair Forum. :smile:
Since you have an underdeck muffler,your mower is likely a two cycle. Do you mix oil with the gas? A lot of those older lawnboy's had a fuel shut off if it has one, take off the fuel line at the carb and turn on the fuel. If you get no flow or little flow the fuel shutoff may need to be rebuilt. Kits are available.
I have checked the carburetor, rebuilt it, poured gas mixture in the carburetor port to the cylilnder, I have spark tested, the piston moves, cleaned the muffler, the timing seems good since the piston does move with the turn of the crankshaft, however, I noticed a small imprint on the top of the piston in the cylinder as viewed from the spark plug port, i think this was caused by a long shank spark plug but there does not seem to be any hole of any kind. The mower still will not crank.
Gas poured directly into the piston will flood it immediately. Usually takes 15 - 30 minutes to dry out. I just pour a little gas on the the air filter and try to start it. If that works, it is a gas/carb problem. The only reliable spark test is to hold the spark plug in one hand place the same hand on the engine and pull the cord. If you jump sparks ok. I'm 65, been using this method since I was 6, never fails. I have developed a stutter in my speech.
I forgot to mention, I have seen and put a lot of long shank plugs in short holes, ruined the plugs never damaged the piston. You can't pull the rope hard enough and an electric starter isn't strong enough to poke a hole in the piston.
I'm of the "acouple of squirts of fresh gas" school of engine starting. If the thing fires, it is typically a fuel delivery issue, as has been stated. The affordable spark tester is a super handy tool, too. Make sure you've got known, fresh gas, mixed with the appropriate 2-cycle oil as (if) needed.
Have you removed and cleaned theain jet? There are several small holes that must be clean. Also have you checked the float to see if it has become too heavy to allow proper operation? What about the float level? Your problem seems to be fuel flow related. Keep your attention on the carb and I feel you will get it going. If all else fails, PM me. I "cut my teeth" on those Lawnboys when I first started repairing mowers
#15
reynoldston
I take it that this is a 2 cycle engine? Just because the flywheel turns does not mean it is in time. I don't know what you have for a engine but a lot of lawnmower engines have a aluminum key and it doesn't take much to be off timing. You have to pull the flywheel to check it. You are checking compression with a gauge and checking spark with the plug in the engine under compression. This is the only true way to check these two things. Is the spark plug wet or dry when you pull it out of the engine. This will tell you if you are getting fuel or not. Compression, spark, fuel, and timing and it will run and not if you are missing one. If this is two cycle make sure your crankcase seals are good.
You really have to check for compression. Just rebuilt a '79 2 stroke, had 20 psi and when removed the piston found only 1 ring. Installed new rings and brought the compression up to 90. Starts right up
I have a Lawn Boy 10686 w/ a Tecumseh 4 cycle engine. It won't start but it feels like a backfire when I'm trying to start it. It gives a single "pop" and yanks the starter rope out of my hand. This only happens when I spray starter fluid in the carburetor inlet. Otherwise it just keeps turning over and doesn't even try to start.
Thank you in advance for your help.
John
