So I bought my first house almost a year ago, included was an old 11hp Roper mower.. Its pretty old and has done a fairly good juob to this point, I am however having a few problems. I hve almost and acre of grass, and when I get about half way through the mow the engine is really struggling, almost stalling out, even on full throttle if I lower the throttle it stalls out.. Any ideas? Also the last time I mowed the lawm I put er away and when I went out to the garage a few days after I noticed the belt that goes around the blades and drive shaft had fallen off. I am assuming that I need a new belt there, but the boggyness of the engine really has me worried she is about to die.. Could the belt be the problem with the engine struggle? ALso anyone know where i can find a manual for working on these things, I don't have a clue how to change the belts even..
Thanks in advance.
CC

First try sharpening the blades and run it on premium gas.

I cut an acre of grass also....
6.5 hp Craftsman mower - 6 hours
16 hp Craftsman lawn tractor - 3 hours
21 hp Craftsman lawn tractor - 1 hour
The 21 hp had two cylinders, thus it never bogs. 6" of grass is no problem at high cutting speed.
The 16 hp will struggle in deep grass, half cutting speed must be used. If there are hills then it really heats up.
OPINION
1)16 hp minimum
2)two cyl is best
3)Craftsman products as the manual and parts can be accessed on the internet.
4)Cast front axle , now you can push Snow!

Thanks for the replies, the blades are razor sharp, I think the guy must have replaced them recently..
West thanks for your reply, wish I had a 16hp mower..

Would a gaskt have anything to do with it? In the garage he left me a belt, and a gasket thingy..

You might want to check the compression. It might be time to go new mower shopping.

This mower looks like it cuts pretty good.

Texas, how would I do that, by removing the plug?

There is a chance that it is the bad belt causing it to bog down like that. If there is a lot of stress on the PTO, it will make the engine run rough.

Just for ish and giggles, I'm currently mowing about 3 acres a week at my parent's new house with a Case Garden Tractor. Its only about 13 years old but the thing is a total piece compared to our 30 something year old Gravely. That thing still runs perfect after a good battery charge. Busted the front axle once and had it welded back together and haven't had a problem with since (about 6-7 years) Best ride-on I've ever used, doesn't seem like they make them like they used to.

not to steal the thread, but my dad inherited a riding mower from his dad, its an old Jacobson which apperantly my grandfather purchased used in the 1970's at which point it was already 10 years old... Nothing like a 40 some odd year old mower that still runs and cuts grass well today. it has a 7 horsepower briggs and straton motor. The electric starter doesnt work anymore, but you can pull cord it Im sure that your mower only needs some minor work.

I bought a house on 1.3 Acres with a sloping back yard. Lots of trees and landscaping means there isn't a lot of striaght cuttings. I got a commercial walk behind. Love it. Takes 1h15m to cut and looks better than every other neighbor's lawn who use lawn & garden tractors.

Anyway, it sounds like the motor is overheating if it cuts fine for a while then loses power. Change the oil, plug, wire. If that doesn't help, you can look into motor work, but honestly, you can replace it with any other used $500 mower that will work better, or a $1000 Sears special. Lawnmoers of all types have very poor resale value which makes working on them pointless.

Thanks alot guys for the responses, I mowed er last night, ran surprisingly well. I think I will get the belt changed and giver another tune job, I changed the oil and plug and filter last fall when I put it away for the winter.
Someone told me the belts are good till they break however I tend to disagree.
The heating up makes sense as she mows great in med to low gear till about half way through, then near the end I have to giver full throttle and ride er in high to finish, I too have a sloped back yard a bit hilly in spots, I find letting it idle with my foot on the break every so often brings er back to life near the end of the mow..

Originally posted by coatsy:

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I changed the oil and plug and filter last fall when I put it away for the winter.
Someone told me the belts are good till they break however I tend to disagree.

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Change the oil in the spring before you use it, not fall after you are done.

Belfts can stretch and wear which could cause increased resistance causing more load, but unlikely. However, belts are cheap and easy to replace.