Engine Lawnboy 7229 2 cycle 21 inch lawnmower with F100 engine

[RLB]

Hi everyone,

I had a Lawnboy model 7229 21 inch lawnmower with a 2 cylce F100 engine given to me last summer. I used it about 8 times with no problems. It always started on the third or fourth pull after priming and would run great during the 45 minutes it took to mow my small lawn. Towards the end of last season I started having trouble getting it started. I would prime it like always and then give it a few pulls. It would almost take off on the third pull or so but then die. I could keep priming and pulling but not get it started. Often if I waited until the next day it would take off on the third pull after priming. Of course I didn't take time to address it this winter and now am having the same trouble this year. Early this week the wife got it started while I was at work and mowed for about 35 minutes before it died on her.

Any ideas of what part of the mower I should start looking at? I tried a new spark plug (even though the old one seemed okay - it was easy and cheap) and that did not make any differnce. I am thinking the problem is fuel system related. I have burned all of last years gas through it by now so the gas in the tank is only a couple of weeks old and is mixed properly at 32:1.

I apprecaite any help you can offer me.

RLB

 

[Rivets]

I would check to see if the crankshaft seals are out or leaking. Common problem on older LB's.

 

[Fireman 123]

Hi everyone,

I had a Lawnboy model 7229 21 inch lawnmower with a 2 cylce F100 engine given to me last summer. I used it about 8 times with no problems. It always started on the third or fourth pull after priming and would run great during the 45 minutes it took to mow my small lawn. Towards the end of last season I started having trouble getting it started. I would prime it like always and then give it a few pulls. It would almost take off on the third pull or so but then die. I could keep priming and pulling but not get it started. Often if I waited until the next day it would take off on the third pull after priming. Of course I didn't take time to address it this winter and now am having the same trouble this year. Early this week the wife got it started while I was at work and mowed for about 35 minutes before it died on her.

Any ideas of what part of the mower I should start looking at? I tried a new spark plug (even though the old one seemed okay - it was easy and cheap) and that did not make any differnce. I am thinking the problem is fuel system related. I have burned all of last years gas through it by now so the gas in the tank is only a couple of weeks old and is mixed properly at 32:1.

I apprecaite any help you can offer me.

RLB

A few things I would do are clean the carb, and make sure the float, needle, and seat are working properly. Leaving last years fuel in it could be causing part of the problem. I would take the shroud off, and clean the rust from the magnets on the flywheel, and ensure the gap between it and the coil is set at 0.10. I use a business card. Then I would remove the muffler and check the exhaust ports to make sure they're not clogged with carbon deposits. And I would check the compression. If you don't have a gage, you can turn the blade the opposite direction than it runs until you feel compression. Then quickly throw it in the direction in which the engine runs. If it goes so far and bounces back, it has enough compression to run. It sounds like it runs good after a cold start, then after getting hot, not so good, so it could be any of the above issues. I know it sounds like a lot, but to me it's part of keeping the old lawn boys going. I guess that's why either you love them, or you don't haha. Good luck. I hope I have helped you.

 

[Fireman 123]

Yes I forgot to mention the seals. If the crank is wet underneath the mower after running it the seal is worn. Good point!