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Craftsman 21' mulcher with bag, b&S engine, needs more power

Posted by davesa (My Page) on
Wed, Apr 21, 10 at 0:41

Basically the mower I have is a craftsman 21 inch with no side shoot and mulching ability and an attachable bag to the back. It would never mulch, people just kept saying my blade wasn't sharped right and I kept getting it re-sharped for mulching, still no joy. Well the grass is tall since it is green so yesterday I mode on highest setting and it was fine and today I mowed same area two settings lower just to get to normal height and mower was acting normal, sounds like low rpm,s no mulching, then it would go real low rpms and no mulching then die. Aftermarket sure everything is clean, it has fresh gas, new plug, clean air filter. new oil. It was acting like it had 2 horsepower then almost no horsepower to stay running when it was bogged down. I noticed the butterfly on carb wasn't open even half way when mower was engaged, and when it bogged it went to like an idle, so I played around with the spring and now under normal ops it runs very good at higher rpm as butterfly is all the way open, and when it bogs down it goes less than half way then returns to all the way open. Question is, is this normal ops. Mower is a craftsman model# 917.388740 and the Brigg's and Stratton 6.5 hp 2BSXS.1901VH and also the number 275260, as it seemed no one online new these as typical Brigg's and Stratton motors, I also found this number online 125K02 or model 12000


Follow-Up Postings:

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RE: Craftsman 21' mulcher with bag, b&S engine, needs more power

Sounds to me as if you are attempting too low a cut at any one time. Try raising the deck by a wheel height adjustment, and then mow it several times, instead of trying to do it all at once. Did you sharpen the blade? And, allow the grass to dry. Wet grass will bog down the mower! Mow more often. This will allow the engine to run at higher RPM's, which should make it mow better. Don't let the grass get so high!


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RE: Craftsman 21' mulcher with bag, b&S engine, needs more power

It was just so high because first time I mowed since spring, and its growing fast. I normally cut it at 3", and mow when it gets around 4". ( I read that is one of the better ways to cut it including only taken off one inch so you are not cutting more than 1/3 of that grass stalk) Also I always try to cut dry grass and constantly keep undercarriage and mower clean. When it was high when I cut it and cut it at highest setting and it was fine, then I cut it from like 5" to 3" and it bogged a lot, and even when lawn is 4" it still bogs and doesn't mulch the best. Can't I just get a more powerful motor that will fit and a better blade?


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RE: Craftsman 21' mulcher with bag, b&S engine, needs more power

You can make such a change, but the mower is not worth the expenditure. I'd suggest a new mower with a 190cc or larger engine and a max cutting height of 4"+. When you have 5" of grass and leave the mower cutting height set on 3", you should expect exactly what happened. When you have to cut tall grass, sometimes you have to discharge the clippings and come back and bag them up later. Then the next time you can mulch if you can cut 1" or less. I think you probably need mowing lessons more than a new mower, but you should maybe take it by the shop to make sure its running right and at the max speed.


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