Blackhood tweaking

[cdsl810 181]

I literally need to do some tweaking to the hood on my C-125. It rattles, I mean REALLY RATTLES at about 1/3 throttle. That seems to be the resonant frequency of the loose hood. The issue is that the hood is actually 2 separate main pieces joined right below the Horse sticker on the front. The pieces are just tabbed and bent, or crimped, in place. That has all loosened up now and rattttttttttles like crazy. I'm considering using a urethane caulk to adhere both pieces together at the seam. I have two questions... (1) What have others done to fix similar problems with loose, vibrating, rattling sheet metal? (2) Should I be doing something different--other than caulk--like tack welding the tabs, or J.B. Weld on the seam, or something like that? My 310-8 had a similar issue, but I never did fix it before I sold the tractor. It drove me nuts also. The Magnum engine ran very smoothly and then you would find the rattle RPM and it would sound like the whole tractor was about to shake apart.

[WNYPCRepair 1,923]

I would spot weld if you can weld, pop rivets would probably work if not

 

[DennisThornton 4,769]

I have a C-85 so I could take a look and try to better understand what you mean, but for now, can you get some vice grips or clamps in there to help find just where it is rattling?  And where you could best stop it?

Then Brian's idea to weld or pop rivet.  Or maybe some well placed adhesive or recrimping?

[cdsl810 181]

The entire seam where the hood top and hood front are joined is separated and rattling. On my 1980 C-125, the hood is made of two separate pieces very cleverly assembled to look and act as one piece. The seam is tucked up under the lip beneath the horse sticker. While it's rattling, all I have to do is push down on that area and the rattle stops. I can actually lift up on the top edge and wiggle it 1/16" or more, up and down. On the inside of the hood at this location, you can see tabs and crimped areas that mechanically join the top to the front. I think may try a two step fix by tack welding all the tabs and then using a permanently flexible sealant along the entire seam.

Am I the only one that has a rattling hood? This is the 2nd WH I have owned with a rattling hood. The funny thing is that both are single cylinder earthshakers. The 20hp Onan is very well balanced and smooth, and the 22hp Kohler Command Pro is buttery smooth too (looks like a car engine sitting in there with the shaft drive on a slight angle...I jokingly call it a V2)

[bmsgaffer 2,046]

My black hoods have rattled, but it was never the seam in the hood. Mine rattled where the hoot met the hoodstand and at the hinges.

Single cylinders are hard on hood hinges and when you have some degraded rubber isolation mounts that can give you that resonant frequency issue that amplifies the vibration at some mysterious low RPM (usually a very inconvenient one).

[shallowwatersailor 3,213]

My black hoods have rattled, but it was never the seam in the hood. Mine rattled where the hoot met the hoodstand and at the hinges.

Single cylinders are hard on hood hinges and when you have some degraded rubber isolation mounts that can give you that resonant frequency issue that amplifies the vibration at some mysterious low RPM (usually a very inconvenient one).

I agree on the hood and hoodstand.when at low idle. When I bump it up it goes away - or the exhaust note takes over that I can't hear it! I have never had it separate at the hood seam joint. 

[wrightorchid 261]

what are running a 22 Kohler command in?

[cdsl810 181]

what are running a 22 Kohler command in?

That would be my Wheel Horse 522xi. The beastliest beast of all! Except maybe the 523dxi with the diesel. 

[DennisThornton 4,769]

I just looked at my C-85 and basically have little to no advice...  My hood to grille connections are pretty solid, certainly secure with no movement and appear to have been spot brazed from the factory.  I do have some foam tape where the hood meets the dash tower and I do make sure I latch both sides but it doesn't rattle.  Now anything on top will vibrate off in short order!

I'd say if you have a loose connection between the hood and grille to try something simple first like Goop and work your way up to whatever it takes, including brazing it.

[SPINJIM 1,981]

My C-85 hood vibrates at the hinge, where the hood rests on the frame.  Anyone have a source for the rubber bumpers to take the play out of the hinge?
  Jim

[Pullstart 63,201]

what are running a 22 Kohler command in?

That would be my Wheel Horse 522xi. The beastliest beast of all! Except maybe the 523dxi with the diesel. 

I'd like to see that diesel horse some day.

[cdsl810 181]

I used a black polyurethane sealant, the kind that you can use on roof flashing, etc. I put a bead on both sides of the hood to grille joint. The sound and vibrations are completely gone. Cost less than $5. It looks kind of like a weld, and it can be painted after it cures for a week. I will be using this stuff in the future for similar repairs.

[boovuc 1,090]

If you have an old tractor seat laying around, take the seam runner off of it and put it down around the metal contact points under the hood. Works like a champ on Blackhoods. The seam runner or whatever the official name of it is, is the seam that goes around the back and bottom of the upholstery on the seat. It's just a strip of upholstery that goes around the metal on the seat.