Talk Morgan Forums Morgan Sports Cars Morgan Three Wheeler & Super 3 Diagnosis help

My M3W is just passing 1200 miles. Under heavy acceleration from a dead stop I occasionally get a loud "gun shot" noise coming from the rear. It's a single loud bang and then all is normal. I've pulled covers and inspected the rear and cant find anything. I suspect the belt is slipping however when checking it for tension it seems tight, maybe too tight. I get about 1-1.5 inches for deflection and approximately 45 degrees of twist at the center of the belt span. There is no sign of the belt rubbing or snagging and it appears to track true. The belt alignments on the outside of the pulley.

Your feedback is welcome.

I'm no expert but could this be the belt jumping one tooth?

Mmm this could be the BB.

I suggest that u drain the oil from the BB. Then filter it though a mesh filter ..or a pair of ladies tights.

See if there are any metal filings or chips of BB in the residue .

I suspect that some BB gear mesh can break off/ fail. Causing the Bang which is the slack taking up.

Anyway it's no big deal to do this ....if the oil if clear ...then u know it's all ok internally.
Hope this helps.

see topic below in forum "slamming sound"

How many times has this happened ?
Will it happen every time in a predictable way ?

I very occasionally get a 'bang from the back end' , and to date have put it down to slop in the drive train being suddenly taken up , with no after effects or detectable damage. It usually happens to me when coasting in a low gear , then suddenly accelerating.
I think it sounds louder than one would expect from drive component due to the sound echoing round the body shell and due to the shape being focused on the cockpit area. I have grown to ignore it , after checking everything is screwed down tight.

I have recently seen a Harley belt that had been used in drag racing and suffered catastrophic damage as a result , with some belt slipping taking place. A number of teeth had been partially ripped off the belt , others were obviously in a bad way. So my gut feel is if belt slipping happens often , the belt will visually be in a bad way , which I have never see to date on an M3W.

Don't forget to take the lady out first.

... or not ...

That sounds like the ratcheting sound made by the belt slipping a tooth. With a 1-1/2" deflection it is entirely possible to do this. That is on the looser side. If it happens again, either tighten the belt or don't jump on it so hard. I would tend to keep the belt on the loose side as it is better for the bevel box, bearings and seals as well as the sprocket.

So the choice is: "Doc, it hurts when I do this!" "Then don't do that!"

or

Tighten it up and hope that doesn't cause other problems.

This does seem to be a "feature" of the Centra compensator and the rest of the driveline.

I never had this with the origianl (2013) comensator but after a change to Centra get what feels like backlash somewhere in the system. Having spoken to several owners who had also changed ot the Centra we all have the same thing.

It doesn't happen every time and I can drive for miles without anything then it goes.

I've now stopped worrying about it

The dealer was very confident the noise was the belt slipping. I was instructed to check belt tension from the bottom, not the top. There should be roughly 10mm deflection when pushed fairly hard. When checked from the bottom my belt deflection increased to 1.5-2". I have now tightened the belt to the dealer recommended 10mm deflection and the loud bang/gunshot sound has stopped. I'm now worried the I may have tightened too much. The bevel box was whisper quite before but now makes a very distinct sound during deceleration. It sounds like a generator winding down.