Talk Morgan Forums Morgan Sports Cars Morgan Three Wheeler & Super 3 Neutral Rattle

If that's the case about the Miata trans rattles in neutral, add to that the uneven crank pulses and the rotational slop in the Centa versus a perfectly balanced smooth and evenly firing straight 4-cylinder motor.

That should make all the backlash in the gears sing like a drunk bird.

All,

I wanted to close the loop on this one for everyone's benefit.

It was a long story (they all are with our favorite toy, it seems), but ultimately, it was the centa coupling rubber barrels in the compensator. Having failed, they were the culprit of the awful rattle under the engine.

Separately, I would point out that, during this process, I learned that some of the cars in the US have experienced problems with the ECU forcing the engine to run too lean. I understand that this is what caused some discoloration in the exhaust for me, but it has also been known to seriously harm the cylinders in some cars (mercifully, mine's were unaffected).

Cheers,

Gabriel

Glad you're back on the road but Centa rubbers failing after 2000 miles - that must be some kind of record!

Is the car driven with a heavy foot and a lot of down shifting? Cents should last a bit longer than 2K

Almost exclusively city/traffic driving...don’t consider myself a heavy foot, but maybe should...?

So lots of stopping and starting. Good to know, since I plan to stay out of the cities.

Krazy Horse here in the UK have developed a replacement for the centa drive using a Rubber drive coupling from a BMW. Lifetime replacement.

Good to know - any details or anyone tried this?

From a BMW motorcycle?

I was looking at possibly a couple ways of eliminating the comp when the original HD ones were crapping out.

The original ones used a driveshaft rear isolation coupler that was supposed to flex just a little axially but not radially. So not really much of a cushion effect from it.

BMW Couplers

But not allowing much for the torque pulses, I was looking at a Lovejoy rubber coupler that mounts about the same way, but allows for, depending on the coupler, 7 to 15 degrees or torsional twist. This would be similar to the HD or the Centa units.

Just a flat mounting plate on the crank and a shaft in the middle for the output to the trans and flywheel. Really doable in my mind. I found one of the LF series that is good for over 6k rpms and about 250 lb/ft torque.

Lovejoy LF Couplers

I ruled out the first type, like the BMW as they would not allow any torsional rotation. JV sent me his old HD comp from his M3W and it had the BMW, Mercedes type isolation coupler as part of the comp package. It has a fiber inner plate that keeps it from twisting up under pressure.

Phil Bleazey's more solid urethane inserts reduce the rotational twisting of the Centa and that's been proven to work, but they still have "some" cush to them, not totally solid in nature.

I'm guessing though that the Krazy Horse one is just a plate for the motor to stand off the coupler with three bolts and then a flange with three bolts as part of a shaft that will then couple to the flywheel stub shaft in the trans adapter plate. Or something similar to that configuration.

Anyone with a little engineering skills could adapt the Lovejoy LF to replace the Centa comp with the same stack height parts. The coupler is just one molded part, not multiple pieces.

But the only thing that's a consideration will be the heat. I believe that's what is driving the Centa rubber rods to fail, just my opinion though.

If anyone has any info on the KH comp, please share.