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craftsman chipper extreme vibration


kkalcor's Avatar
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Join Date: Oct 2006
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10-10-06, 10:10 AM   #1  
craftsman chipper extreme vibration

A friend gave me his old 8hp Craftsman chipper!!! I used it for a big job, and he told me the vibration was "normal." Finally the feed chute literally vibrated off--the main mounting (pivot) bolt tore right through the sheet metal at the bottom and the whole chute dropped to the ground. I disassembled the clamshell and found one of the flinger sets on the impeller completely corroded in place. A little heat and some banging and it came free. I thought the vibration problem was solved but no luck. It vibrates just as much now as before, if not more. Any thoughts? Any help would be greatly appreciated!

 
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repair_guy's Avatar
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10-10-06, 04:09 PM   #2  
Check and see if any of the teeth are broken ,or the shafts that hold the teeth maybe bent.This can cause it to be out-of-balance.Or maybe the bearings themselfs are warn.Ether will cause the vibration that you describe.

 
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10-11-06, 02:57 AM   #3  
Post back with the units' as well as engines' ID numbers please.

 
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10-11-06, 06:58 AM   #4  
I agree with the above post in that it's out of balance. Does it have missing cutters? Missing bolts? Broken off pieces? Worn bearings? Less likely, but a bent rim on a sheave making the belt go bumpity bump? You have gotta look at all rotating parts to see what is not semetrical.

 
kkalcor's Avatar
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10-11-06, 10:13 AM   #5  
craftsman chipper extreme vibration followup

Very much appreciate the responses received. The unit is a Craftsman 8 HP, 3 Cutting Stage, Mulching and Bagging Chipper-Shredder, model no. 247.795861. The engine model no. is 190432-6117-01.

The impeller is keyed (according to the parts diagram) on the end of the motor's crankshaft--no belts. A 3/8" bolt holds it in place. The impeller looks to be fabricated from about 3/16 inch sheet steel. The main rotating plate is, of course, round, and about 13" in diameter. Welded to the front of it are some shaped pieces that hold the 4 flail assemblies (of 3 flails each) on the outer circumference at 3, 6, 9 and 12 o'clock. I can email a picture if desired. The shredder blade is In the center, just a piece of flat bar not quite 9" long by about 2" wide. The chipper blades are mounted near two cutouts in the backing plate for feeding material from the other side.

I have tried to remove the impeller assembly first using a three-jaw puller and later a 7/16 bolt, both bearing against the end of the crankshaft. Even with lots of penetrating oil and heat from an oxy/acet torch it wouldn't move. Couldn't find any set screws or other mechanical fasteners that would prevent it from coming off, physically or on the parts diagram. My hope was that I could get it off for inspection, and maybe take it to a machine shop to have it dynamically balanced. I assume the one cylinder Briggs & Stratton engine has a weighted flywheel of some kind, so that is another possible source of trouble, although it seems unlikely.

One other fact of interest... The last time I started it I noticed a bolt missing in the vicinity of the carburetor. A puff of black smoke came out of the hole as I pulled the starter cord and the engine turned over. The bolt holds is part of the mounting for the tube that the air cleaner sits on, and it's threaded into the intake of the carburetor. I think this open hole was allowing more air to get to the engine and the engine was racing as a result. Without a tach I have no idea how fast, but it was too fast. I found another bolt and put it in, which helped reduce the speed a bit, but now I wonder if some of the other carburetor adjustments may have vibrated to excessive speed positions. It still seems to be running too fast. Maybe the vibration caused carburetor adjustments to move, which caused the engine to race, which increased the vibration even more, moving the carburetor adjustments even more, etc. So beyond solving any basic imbalance, I also need to make sure the carburetor is adjusted correctly. There is a governor assembly (a gear on the end of the camshaft and associated linkage to the throttle) but I don't understand how or when it regulates the fuel. It may also be deficient in some way.

More than you asked for I'm sure, but once again your thought would be very much appreciated! I'm headed out of town for a week so responses from me will be delayed a bit.

Thanks again-

Kevin

 
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05-03-08, 06:48 AM   #6  
8hp Briggs confusing

While you are on the subject...I also have an 8hp Briggs (horizontal) on a White chipper. It vibrates as well, but nothing has fallen off yet, It starts easily, but will only stay running if I keep opening and closing the choke every 15-20 seconds or so. I'm thinking that the governor might be set wrong and maybe the carbsettings too. Any help is welcome.

 
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05-03-08, 06:59 AM   #7  
I have the same chipper/shredder, the main problem with vibration is too light of a main flywheel(the round metal plate) that the chipper teeth are mounted onto. mine has vibrated stress cracks in most of the shredder housing parts. finally pulled the starter off of the motor trying to start it. all of the sheet metal is too light guage for what size motor and rating it is. work had a cub cadet chipper that was a 10 horse and we used the heck out of it, never had a stress crack because it had a heavier flywheel and heavier sheet metal on the shredder chute.,
also your flywheel is on a taper shaft and is likely just frozen to it. use a top quality puller and when you have it tight. tap on the top of the puller to loose the flywheel. don't hit to hard as that could damage your engine bearings.
Murphy was an optimist

 
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