QuestionQUESTION: So I've posted on two other sites with no answers. Either people don't know or they are on vacation. I'm hoping to get an answer here. I am only able to start my Lawnboy L21ZSM once or twice a day. I smell gas shortly after the unsuccessful tries leading me to think it's flooded. I tried pulling the plug,(which is mildly wet and brand new) and pulling the cord to clear out any gas, but that doesn't help. It starts whenever it wants and only once or twice a day with many hours between starts. My shoulder hurts. The fuel is 32:1 and fresh. I've cleaned the carb and everything in there looked clean anyways and fully functional. Pulling the cord slowly verifies good compression as the pistons cycle, but I have not officially tested for compression and wouldn't even know what values are within normal range anyways. I measured the plug gap (on the brand new plug) and it was smaller than the recommended .035. I adjusted it, but still no increase in the starts per day. Once it starts it's fine. Please help me narrow this painful problem down!!
Regards,
Steve
ANSWER: You need to pull the muffler apart and clean the engines exhaust port. While you are there look at the lower crank seal. You probably will have to look between the mower deck and the engine where the belt rides on the deck. If the seal is out press it back in with a screw driver. That will last about 1 mowing. Then you will have to replace the seal.
Clean the exhaust ports!!!
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QUESTION: OK I forgot to mention that I had already cleaned the exhaust ports and they weren't that bad either. I did, however, notice a pool of black sludge by the belts and sure enough the bottom seal was resting on the pulley, just like you said. I pulled the engine off and split it apart and replacing the seals is not a problem. My question now, is is the crankcase half under the piston with the rod bearings, etc supposed to filled with oil and it all leaked out because of the seal? Also, why would the bottom seal prevent the mower from starting; less compression? Also, there is a lot of carbon soot buildup on top of the piston and at the top of the cylinder where the spark plug is. Should I clean these surfaces thoroughly and with what? Finally I was thinking of replacing the piston rings, even though they are freely moving and loose, but how do i put the piston back into the cylinder? The rings get in the way and I can't seem to figure out how to get my fingers/tool in there to compress them to fit the whole thing into the cylinder. Many thanks again!!
Regards,
Steve
ANSWER: Wow! At this point most people just use the Lawnboy as a boat anchor. But you are refreshingly competent so I will give you the complete story.
The oil in the bottom of the crankcase shouldn't be there. You have 2 problems. You have unburnt fuel because of the seal, and a carb that's probably leaking a bit.
Now some 2-stroke engine theory.
When the piston goes down the volume of the cylinder has to be filled with something to take it's place. When the piston goes up the crankcase has to fill up.
When the piston goes up the crankcase is filled with a fuel air mix. That's why the carb is on the bottom of the engine. As the piston goes up, air is pulled through the carb into the crankcase. It's kinda like when the doctor fills a syringe for a shot. As he pulls the plunger (piston) out, it fills the syringe(crankcase) with medicine. In a 2-stroke engine the medicine is a fuel air mix. That's stroke 1.
Now the piston has reached top dead center and starts to head down. In a properly working engine the reed valve (that's those 2 metal things right behind the carb) close and as the piston comes down it forces the fuel air mix through the ports in your engine. The ports are those passages you see at the sides of the cylinder. The air is forced into the top of the piston and is compressed and then the spark ignites this fuel air mix. The explosion forces the piston back down staring the process all over.
Your seal is out so instead of the fuel/air mix going up to the top of the piston it blows out the bottom of your engine.
If you got it apart you might as well clean it. My personal favorite cleaner would be HOT soapy water. It works great. You can keep from having these deposits reoccur by buying a premium synthetic oil. You can't buy this anywhere but a dealer. With modern fuels i don't think Lawnboy oil is worth a damn. Premium oil. I recommend Opti. Any dealer should have it.
What the hell. Hit it with some new rings. You don't need a compressor to install these rings. The bottom of the jug is tapered so you can just squeeze them in. It will be easy.
What ever you do, don't take the rod apart. It will have about 40 loose needle bearings. It will suck to reassemble.
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QUESTION: I finally get to follow up on my Lawnboy troubles. I did everything listed above. Successfully changed the rings and lower seal. The lower seal was completely broken in two. Put everything back together and still no start. What's the likelihood of two things breaking at the same time? What would that second thing be? You mentioned the carb leaking as a possibility, but what do you do to fix that? The main float needle seat? I am not getting any gunk leaking out the bottom of the lawnmower anymore so I think my oil seal fix was good. I used an anaerobic gasket maker sealer (Locktite 518) when I put the crankcase back together. I gapped the CD module to 0.01. Could it be the CD module? Of the three rib sectiosn on the module, which of those do you gap to 0.01? If I do two of the three, the third is not at 0.01 but greater. Should the ends be gapped with the middle one almost touching (less than 0.01)? I'm about to post this as a "will not start" on craigslist, but I still have some patience and after spending 25$ on some new parts, I would like to get it working and sell it for more. Thanks for everything and hanging in there with me!!
Regards,
Steve
ANSWER: All posts on the coil need to be set the same.
Here's what you need to do.
Step 1. Move the flywheel magnet away from the coil. Loosen the bolts and pull the coil as far away from the flywheel as you can and retightent the bolts.
Step 2. Rotate the flywheel so the magnet lines up with the coil.
Step 3. Insert 2 business cards between the flywheel and the coil.
Step 3. Loosen the bolts on the coil and let the coil "suck up" against the business cards and magnet and retighten the bolts.
When you pull the plug out is the plug wet or dry and do you have spark? If you have spark and the plug is wet you need to reclean the carb. You probably got the needle contaminated with crap when reassembling. If you have spark and the plug is dry you either jacked up the seal (I mess up 3 out of 10 and I have done 100). Or your crankcase is leaking. I have found that the only thing that works on this case is Lawnboy case sealer. You can buy this from your dealer for about 4.00 for a one time use tube.
Rember when I first told you this would be a boat anchor to most people? Do you have a boat?
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QUESTION: OK, I'll try the business card trick, but what do you mean about "jacked up the seal"? I didn't extend the sealer around the oil seals, just up to them. Should I have covered them as well? I'm feeling better compression than before however, so I think I sealed it right. As for the spark plug, it was dry when I took it out. So another carb lookaround? The trouble with the carb is that there is almost nothing in there to adjust. No boat. Might have a decorative anchor in the backyard.
Regards,
Steve
AnswerNow we have the answer. You needed to seal around the seal. When I say "jacked up" the seal, I mean that you damged the actual center of the seal. The part with the spring around it. The dry plug means that the suction when the piston goes up it is sucking air from somewhere besides through the carb. IE.. Seals, case half, etc. The engine still has good compression because it is compressing air, it just doesn't care where the air comes from.
