Model B Vibration

[mr.precision]

Slowly sorting out the ills on my recent purchase - a 1950 Model B.
This tractor has shown a significant amount of vibration at high idle since I got it. I checked the timing of the clutch driver and flywheel... everything right on. The vibration is enough that the steering shaft dances around and the wheels shake.
I thought it might be low compression on one cylinder. The clutch side cylinder doesn't seem to have as much compression when the petcock in opened, as compared to the flywheel side cylinder. Yesterday I brush hogged 2 acres and got the machine good and hot. A compression test showed 95 psi on both cylinders.
Tractor starts easy, doesn't smoke, and has good power. Oil pressure sits right at the H mark when cold, and between M and H when hot. Only leak it has is at the base of the block.
Any ideas?

 

[thdrduck]

I would check that the flywheel and clutch drive are tight. If they are or where ever loose it could tear up the splines on the crank. On my older B there looks like only one way to put the clutch drive on but I have heard that they are balanced and should only go on one way or she could shake. You can also check for end play on the crank tho I don't know if excessive play can cause vibration. A place to start anyway. Hopefully one of the experts will pipe in and we can all learn something.

 

[rick deere]

I really don't think things are right on or it wouldn't shake, I think your looking at the wrong marks. the V marks should be right on and someone else could have made there own markings you might have to ck the weight counters on clutch disk and flywheel.

 

[Mike M]

Sure sounds like either the flywheel or clutch driver is installed wrong.
Flywheel on those is to have a deep slot that a pin screwed into a crank spline locates it correctly.
Clutch is just V marks. Many I had with that problem the clutch driver was off because people are more often in there "monkeying" around.

 

[mr.precision]

Thanks for the quick responses.
The flywheel is at the 3 o'clock position with the flywheel side piston at TDC.
The clutch driver "V" marks line up and the counter weight is at the 3 o'clock position also. To me, this verifies the flywheel is in the right position.
All are on as tight as I can get them. When I removed the clutch driver, the splines look perfect and it took quite a bit of torque to put the thing back on.
What about the low pressure through the petcock on the clutch side cylinder? I thought it was odd that there is a BIG difference between the 2 cylinders.
The tractor will run on one cylinder also, although the clutch side sounds different than the flywheel side.

 

[Vern H]

Mr.P
As usual, lots of good advice on here. I think I would check to see if the flywheel is on the crank correctly. I just did a quick check on my 35A. When no. 1 is at tdc and the mag trips the fly wheel weight is at 3: o,clock, right under the timing mark. If you have to move the flywheel, then the driver must change too. Let us know what you find. Good luck, VH

 

[Anonymous-0]

never heard about 3 oclock, v marks line up there could be your problem flywheel not lined up with v marks

 

[Mark-Ia]

The counterweight on the clutch driver should be opposite the counterweight on the flywheel. The flywheel and clutch driver should not booth be at the 3:00 o'clock position.

 

[teddy52food]

Flywheel is good, driver is not.

 

[mr.precision]

With the flywheel at 3 o'clock facing the flywheel, the clutch driver is at 3 o'clock facing the clutch. That puts them 180 degrees opposed, which is correct according to what I've been able to find.
I'll pull the flywheel cover back off. Are there punch marks or alignment arrows on the flywheel side? I just don't see how if the flywheel and clutch driver are perfectly opposed, that one of them could be incorrect.
Could rod or main bearings cause this?
Thanks
Mike

 

[teddy52food.]

Being you are getting different volume out of the petcock, I am thinking you have 2 different pistons in there . one cast iron & one aluminum. Their weight cancel each other as they move opposite, but if one is heaver , it will vibrate. Pull the plugs & see what you can see if any difference when you turn it over.

 

[Lee B]

No punch marks or Vs on the flywheel rim from the factory, the only V I know of is on the crank at one spline and even then not consistently. Quit using 3 O'clock in your descriptions and others will begin to understand you've done it right and have the counter weights opposed as they should be. No for rod or main bearings causing the vibration. It's just not a perfect way to balance them since there are no piston/rod counterweights on the crank throws, they put it all to either side and could have easily got the mass a tad off just enough to do this. I sometimes think aluminum pistons would either help or hurt this by a noticeable amount, but don't recall reading much about the subject in here or anywhere else.

 

[gtx1967jewison]

1) the flywheel side WILL have more volume out the petcock.
This is due to the throttle plate is nearly closed when running
unless it's under full load, & due to the firing order, #2 gets
starved for air. 2) a proper compression test needs to be done
with the throttle wide open.

 

[thdrduck]

Uh? I'm betting on the two different pistons. I can see that happening really easy...need one piston, found one, fits, stick it in, runs... kinda. Maybe the same guy that worked on my tractor did some work on yours. :lol:

 

[FWB in SK]

Could there be some thing wrong with the fan or fan shaft bearings.

 

[mr.precision]

There's no vibration I can feel in the fan shaft area.

Today I rechecked everything. The clutch driver is aligned with the "V" marks present. I am not reading the other print on the clutch driver as a "V". The flywheel is correctly installed. Both flywheel and clutch driver are exactly 180 degrees opposed. The magneto trips with the punch mark on the flywheel lined up with the "V" on the cover, with the #1 piston at exactly TDC. The flywheel end play is right at .008".

The previous owner said he put a new set of rings in the motor a couple of years ago, and had the head rebuilt. He did not say he replaced a piston, but I am intrigued by the comments made in this posting about dissimilar pistons.
Any idea how I can check this without pulling the motor apart?
Thanks to all for you input - much appreciated.
Mike

 

[41b owner]

This may or may not be important to you and your problem. I have a 41 B that was popping back through carb. Someone else has been in the engine (appeared to be overhauled). I found that the cam gear was mismatched to the crank gear by two teeth (marks are on inside of gears), thereby allowing the #1 exhaust valve to open early. The exhaust impulse did not match the mark on trans case. The engine also has a vibration. I don't know if the gear mismatch is causing the vibration, but I am in the process now of matching up the gears. Will be several days before finishing.