I came across this thread by searching for the same answer a lot of others on here are seeking. After reading the entire page, I had to join to point out an observation in regards to rusyj14's comment that "Occasionally, the help doesn't work, mainly because the help seekers can't follow instructions" But, the fact is, the seekers Are following instructions. No disrespect meant, as I see many have resolved their problem with your help. But the others that are still at square one have done as instructed. They have repeatedly stated those instructions back, as to what they had done, but with no fix. And as you also mentioned for them to do, they Are here asking for help, but it seems their posts are going unanswered. From someone who at the age of 10, or younger, got his hands on his first lawn mower with instructions from his Dad to only tear it apart to see what was inside, with a Tecumseh that had sat out in the weather since who knows when, with a crankcase full of rain water, but defied his Dad and got it running to have it mow his grass for the next six or more years, I've been accustomed to getting things running. But having already done what all others on here have suggested before finding this thread, I am leaning towards the flywheel magnets having somehow lost their strength. It is the only part not bought new to replace. I thought I had read somewhere else that someone was able to compare the strength between a good set of magnets and weak ones by use of a fish scale and how much it took to pull away from it, but I couldn't find it again. I'll be completely dumbfounded if a new correct flywheel does not solve my issue either, as I've mentioned, it is the only part I have not yet bought to have everything brand new with regards to the ignition system. If I had a shop nearby that could magnetize it, I would go that route, but it will be cheaper to purchase a new one than to invest in the shipping and shop time to have it done.

well it blew up. As mentioned above, oil was added and it ran fine. I bought a kit to change the oil, filter and plug. I decided to let my son use 1 more time before the maintenace since the grass was so high. Oil was full...I checked. After 10 minutes he came screaming that the side of the motor blew out an oil was everywhere....looked like aprett violent event. Not sure what happened. Perhaps the oil was low at some point or simply not changed for a few years. The funny thing was I thought my toro was going because the engine seamed quiet compared to pop's...I guess it was the other way around.

Im working on a 2014 Toro XT6715-2070 149cc engine where its having issues on warm up. After starting it will run well for about 30 to 40 seconds or so then start to stumble for about 10 seconds, then runs OK for about 20 seconds, then goes back an forth doing this for about two and a half minutes then just starts to run well from then on. After its ran for about 6 minutes it still does not fully open the choke butterfly. The carb is a new OEM carb and I pulled the fuel filter to eliminate any possible issues with fuel restriction. The air filter is also new. Iv had this on other identical mowers and have not yet found a solution. The choke is one of these that mount directly the muffler and is the size of about a fifty cent piece that mounts flat on the muffler. It does not appear to be adjustable in any way. if I hold the choke rod open fully I do not experience this issue. Im sure Ill see this again so if anyone has any information for me that would be most helpful.

OK, you guys were right. I did have two seperate problems. When I went to cut my grass on Thursday, the motor was "hard starting" again. During the initial crank it did stop turning, which I suspect was that "stop on compression" you guys mentioned. It eventually started and I cut my grass and confirmed that my previous gas tank venting problem has been resolved. Later, I checked my valve gaps and they were not too far out but I am not sure what constitutes far out. First, I did Walt's test and confirmed that the intake valve seems to do a small movement after it closes that I believe is the compression release. I checked this before and after I adjusted the valves. When I first checked my intake valve clearance, at first I couldn't seem to even push a 0.005" feeler through the gap. Then when I played with the rocker arm it went though no problem. An 0.008" was very snug. So I took that as out of spec. for the 0.003"-0.005" it should be. Now, even with me playing with the rocker arm a 0.004" will go through but the 0.005" will not. On the exhaust side, when playing with the rocker arm, a 0.006" will snuggly go through but an 0.008" will not (I don't have a 0.007"). So I took that as OK for the 0.005" to 0.007" spec. and never changed it. When I was done the motor started up very well but I had that happen last week when the motor only sat one day, so next week I will be able to test for sure. It seemed to be more hardstarting when it sat for more then 5 days. Since I like to understand these things, I have a few questions that maybe someone could help me with: 1) Since the intake valve seems to control the compression release, how important is the exhaust valve clearance? 2) Does this compression release keep happening when the motor is running or just during start up? Seems that you would like it during start up and hate it during running. 3) If the valve gaps were to wide why would my motor seem to only have hard starting issues during initial start up but when warm it seem to start up just fine? Thanks for your help.