Dr Chipper 18hp Briggs Stratton engine laboring...
obviously i'm a newbie here. i have followed these forums over the last couple of months as I have searched for a chipper to clean up around the new house we bought. the house is on half acre - half acre of nothing but woods and trees grown in with about 50+ giant honeysuckle bushes/trees all around the house. the place has been neglected and i plan on cleaning it all up - all the brush, trim trees, plant some grass, etc. there are about 10 fallen trees to be cut up etc. so when i started cleaning up i realized i really need a chipper to do this on my own time when it comes to all the branches. i am in the city and breaking them up and putting in trash bins to be picked up once a week wasnt gonna cut it. wasnt really planning on spending more than $500 or so for a used chipper, but after looking through all reviews on this site i really wanted a mackissic 12pt. since i was in a hurry and couldnt even find a used one under 1200-1300 or so and even those were far away and to be freighted to me, i gave up on that thought. finally i found a dr chipper 18hp towable model which new is ~$3600 for $800 - about 10 years old but hardly used according to the widow selling her late husband's barn possessions. and from what i understand mackissic builds chippers for the dr chipper brand. she did say the guy working for her did something with carburetor to fix it - either replaced it or something since the thing hasn't been used. but now it works fine. so i bring it up here, check oil, fill gas, check blades - very sharp still, check air filter (original and very clean - supporting what she said about lack of use). i then start it up and have a nice afternoon of chipping. the only issue is it would backfire every time I would stop the engine. 2 days later i have another pile to be chipped - so i bring it out, check oil, start up and after a bit the engine is laboring. it is revving itself up rhythmically every 2 seconds or so. but it is working and chipping fine so I just go on with the work. it is sitll backfiring every time i shut engine off. it was in back of my mind and i thought - maybe it was having trouble getting fuel, so i get a new in-line fuel filter, drain old fuel and fill up fresh with stabilizer, check oil and add a little and start up today just for troubleshooting purposes. the thing is laboring again, revving itself rhythmically except it is getting a little worse and now it is revving every half second to a second or so. i look around and see the carburetor is pulling on a rod as it revs. now i think it is definitely something with carb or fuel / gas mixture and hopefully a minor adjustment? i like this thing, seems like a rugged machine and hoping to get years of service with good maintenance but first i want to get it running good. i still have piles of branches waiting for me but i am afraid to keep chipping with engine sounding like this - i am worried that i will ruin it. any help or ideas would be appreciated. the engine is a briggs and stratton 18hp twin cylinder vanguard, model 422437 type 1899 E1.
as you can tell i am not handy with small engines but take on an attitude of - i can learn just about anything. thanks in advance for your advice. below is a gallery of pics of the piece that gets pulled by carb with every rev.
my upcoming purchase is a riding lawnmower to tow this thing around the house since pulling and pushing couple of hundred pounds with only my wife to help occasionally is no fun - our property is all on a slope to boot.
Here is a link that might be useful: pics of piece moving when engine revs