JD B Shakes At Mid to High Throttle

Hey all, this is my first JD 2cyl and nobody else in my family has ever worked with these before and frankly tells me they're a waste of time (red power...). I have a 51 B and I finally got it running and mostly driving, however if I go above low throttle the machine shakes bad enough that if you have a wrench on the operator station, it will vibrate it right off.

Now I can't imagine these old 2cyl tractors would have sold as well as they did if they vibrated so bad so with that I'm trying to narrow down what could be causing it.

I have seen on this forum that various clutch components can cause vibration, so I replaced all the discs in the clutch including the drive disc making sure the 2 Vs are pointing at each other. Unfortunately that hasn't made any difference at all so I'm looking for suggestions as to what to do.

Any suggestions are welcome!
 
I have seen that when EITHER the Flywheel or clutch are on the incorrect crank spline causing out of
balance. The clutch is more often the cause as its been removed instead of the flywheel and usually the v
marks you speak of can be used to insure the correct clutch to spline location. One other way to insure
balance is that the offset heavy weight on the clutch is 180 opposite from the heavy side of the flywheel.
BOTH are out of balance but when the two out of balances are 180 opposite (on correct splines) it balances
out. Dig around for John Deere or You Tube Two Cylinder clutch and flywheel balance problems.

John T
 
You say the clutch V marks are lined up. So then it must be the flywheel. That model has a set screw in
one spline that goes into the deep groove on the flywheel. I have seen them put on wrong before as they
lined it up with one of the 2 slots where the flywheel is split so it can draw up on the shaft.
 
(quoted from post at 13:48:53 03/06/23) You say the clutch V marks are lined up. So then it must be the flywheel. That model has a set screw in
one spline that goes into the deep groove on the flywheel. I have seen them put on wrong before as they
lined it up with one of the 2 slots where the flywheel is split so it can draw up on the shaft.

I haven't had the flywheel off yet so that could very well be the issue. are there marks on the flywheel and crankshaft of the flywheel side as well? Does the flywheel need to track perfectly straight as it rotates, or is a slight "wobble" acceptable. Very slight, just need to know if it has to be 100% perfect.
 
Those usually do not have marks but as I explained earlier had the set screw and tall spline. The
flywheel casting will move around some as it is not true. But the ring gear should run pretty much true
as that area is machined.
 
I don't know, I've always heard that if you left one running after you got it stuck, it'd vibrate itself deeper in
the mud.
 
A neighbor replaced clutch facings and put on the counterweight wrong. He had an A and at any engine speed it vibrated so bad the steering sheel brused his hand when he tried to grab it. It was just a blur. It
scared him so ad he had the JD dealer come and get it to fix it. Since speed is somewhat a factor, I think the problem is on the flywheel side where centrifugal and other forces would increase greatly with speed. Two
things come to mind. One is that the ring gear is so worn in the two places the engine stops at on the compression stroke for 1 and 2 that it's throwing things out of balance. I personally doubt that, as with that
much wear the ring gear would probably break. The other usual suspect is a flywheel cracked at the hub. That happens when the flywheel is just a bit loose on the splines and the clamp bolts are tightend just a
bit.There isn't enuf spring in the flywheel to tighten up against the very slightly worn splines. Don't ask me how I know . . .

It could be a miss-matched rod, a broken piston skirt, a fan blade missing or dozens of other things. The other posts give A-1 advice on checking things from scratch. Also, try to lift the flywheel to be sure the left
main is not perished. Good luck. The B is a nice machine to use, but a frustrating yard ornament!!!!
 
I agree with others about the cause being either the flywheel or the clutch driver being installed incorrectly. If you're not sure about timing marks, a simple effective way to confirm correct timing is to roll the flywheel side piston to top dead center. You can remove the spark plugs and use a bent piece of wire to feel the top of the piston. The counterweight on the flywheel should be at 3 oclock, or directly opposite of the crank throw. The clutch counterweight should be 180* from the flywheel counterweight.
Hope this helps.
 
(quoted from post at 08:38:12 03/08/23) I agree with others about the cause being either the flywheel or the clutch driver being installed incorrectly. If you're not sure about timing marks, a simple effective way to confirm correct timing is to roll the flywheel side piston to top dead center. You can remove the spark plugs and use a bent piece of wire to feel the top of the piston. The counterweight on the flywheel should be at 3 oclock, or directly opposite of the crank throw. The clutch counterweight should be 180* from the flywheel counterweight.
Hope this helps.

GOOD information, Mike, for those not familiar with how that is set up!
 

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