Lawnboy starts lean and dies


Old 08-16-00, 07:45 AM
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I have 2 Lawnboy lawn mowers. One is 20 yr old, the other maybe 10 to 15 yr old. Both of them have the same symptom. When I start the mower, I have to push the primer button 3 or 5 times during the first minute of running, otherwise the engine dies. The 10 yr old mower is from a garage sale and I have only started it twice and performed no work on it.

Here's the odd part of the story. The 20 yr old mower has a new carburator kit and new governor assembly. I did the work myself with the help of the service repair manual. I have concluded that it needs a new carb, not just a kit. The mower runs fine after the first minute of priming and is used to mow the lawn. I have already spent an unreasonable amount of money on mower with the carb kit. But more than that, I want get it running so I will have the learning experience of having fixed it.

I realize that Lawnboys are not Briggs & Stratton, but hope that my symptoms are fairly common on most mowers.

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Old 08-16-00, 08:39 PM
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It's possible the choke isn't closing all the way. Check this. Be sure there is full fuel flow from the tank to the carb.

Richen the fuel mixture some with the adjustment screw/screws. Don't remember off hand if there is one for low speed and one for high speed. If there is, try opening them 1/4 turn.

Also possible the compression is too low for cold running. Which may be why the engine runs fine after it warms up.

Old 08-17-00, 07:19 AM
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Thats for the reply.

The lawnboy model I have does not have any adjustment screws in the carb. Now I wished it did. Actually, the Lawnboy has this really flimsy metal tab that you bend in order to set the governor. In my opinion, it is impossible to set, that is why I bought a new governor assembly, but now Im wondering if it needs adjustment too. I don't like the design at all.

Your idea about low compression is intriguing. You now have me thinking buying a compression tester. I only need 1 excuse to spend money on tools and now I have it!
Do you know a web site that sells compression testers for lawnmowers?

I have always wanted to renew an old engine and have many of the simple tools but have never rebuilt one. In the past, many questions have stopped me. One comes to mind just now. Perhaps you could help. The question is, how do you determine which to do; lap the valves with compound, or regrind the seats with a special valve tool?

Old 08-17-00, 10:42 AM
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On the compression tester,I have always used the same one that I use on my cars.It is an old cheap one I got as a kid.Any parts store will have one.
The governor will seem almost impossible to set if to many things are out of whack.The lack of compression and correct carb settings that were mentioned earlier could be the cause of this.
When doing valves lapping is done regardless of whether you use new valves or old ones.The seats are are replaced as needed or cut and lapped.Prepare to dig deep for a quality valve restore kit...$300.00...and this is for a small engine.You would also need a valve guide kit at around $175.00.To get you going,you could really get by with lapping old valves and seats and doing valve guides as needed.The engine will run fine for some time but will need valve work again before long.Still it's a good way to get your feet wet.If you want the details on any rebuild tactics let us know.Ifyou are considering a build on the Lawnboy,take some advice and don't.They don't build very well.Over sized parts and the machine work cost as much as a short block.
Old 08-17-00, 01:11 PM
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Thanks for the advice. I will reconsider the rebuild of the lawnboy. Based on what I have paid for LawnBoy parts already, I tend to agree they are costly. So I will put that idea on the back burner. I like the suggestion to do smaller rebuild jobs like lapping valves to get my feet wet.

Also, it did not occur to me, to use an automotive compresssion tester for small engines, especially since I already have one. Dah!


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