vibration issues on the 1115

[bobansen]

Those of you in the know may laugh as you read this but I dont know how to explain the problem.
My engine has a vibration that is cyclitic, that is it goes up and down. Its not ignition related, more of a rotation issue.
What happens is the engine will vibrate from nothing to severe and back again, following the same axis as the engine ie from cyclinder head to starter motor. no vibes from side to side
think of some one turning the volume up and down over and over again, the volume =vibration
No matter what the revs are fast or slow it is present right through the range, revs fast= vibs fast ect
What I have tried.
All bolts tight and bed secure and square.
running engine alone with genny belts off.
Counter weight timing gear, one tooth advance/ one tooth retard/ and correct setting.
From what I can see of the c/w bearings, they look and rotate without a gritty feel to them.
Question is: where do I look next?


Bobbie

[playdiesel]

Boy ? I dont know what to tell you on that one?  Pretty sure there is no room inside for the counterweights to be moving in and out of time without a big train wreck but you might want to pull the side cover and make sure you dont have an issue like the shaft moving inside the timing gears. I would also remove the rear cover and bar the weights back and forth while watching the shaft/gear relationship. If something like that is going on it isn't going to be long before the big trainwreck happens. Also could be the load side crank bearing going out, have you tried baring the flywheel up and down? ANy change in gear noise when all this is going on? I have two 1115s, one is very smooth and the other is a vibrator but they dont change minute to minute.

[Ronmar]

Is the governor hunting any?  You should be able to tell this by watching the governor spring arm.  If the engine was alternatly accelerating and decelerating, could cause some vibration, particularly if there is any room for the engine to move, say really sloppy vibration isolators...  I also would reccomend pulling the timing case for a through inspection of that side...

[bobansen]

Good news.. Taking your advice I started to remove the flywheel. To do this requires that first I remove the belt pulley and low and behold what do I find? the answer to the problem. I fitted a cush drive pulley in the hope of having a softer snatch when a load comes on line. Inside the pulley combination is a spider of three chunks of rubber. Simular to that in a Lovejoy . One of the rubber segments had been chomped to peices so the effect was the pulley drove on the two remaining and shook on the third. Refiited the standard drive pulley and found peace in our time. No vibes, just a nice chugga-chugga-chugga.
Thanks for all your input, its a very nice feeling to know one is not alone whenever problems crop up.
Bobbie (smilin again)