Engine Noise

[SebringMike]

All,
Another engine noise question; I know I'm asking a question to which it's difficult to come up with an answer without hearing the bike, but here goes...

I've completely rebuilt the engine from the bottom to the top. This past weekend, we were able to get the bike running. While running, my father and I noted a loud noise from the top end of the engine. We thought it was possible that the piston was hitting the cylinder head or valves, or something a more catastrophic.

This weekend we pulled the head and cylinder off, and have found no evidence of any interference. Piston, cylinder, rod and cylinder head are pristine.

We reassembled the bike and started it again.

Same sound. Using a screwdriver as a stethoscope, we are unable to pin-point the location of the noise. It appears to come from the top end, particularly the exhaust valve side of the valve train.

Valves are set at 0.0025" (0.05-0.07mm) per the manual.

I've tried to search Youtube for videos of engines running, but don't seem to find anything that's clear enough to identify the same noise.

This is our first Ducati. We have restored Japanese and British bikes, and ride fairly modern bikes as our daily rides. It's not a noise we are used to hearing on any of our other bikes.

So my question for you all is... is it possible that the noise we are hearing is normal for a 50 year old Ducati? Are they particularly noisy in the top end?

Thanks in advance,
Mike

[Bevel bob]

Slightly loose valve guide going up and down with the valve? Check bevel gear play also end float of cam. Ex valve sticking in guide when hot,free's off by the time you get to check?

[Jordan]

Bevel Ducatis are fairly noisy compared to other bikes' engines.
I've heard it's possible for the top bevel bearing to become loose in its hole, making undue noise.

[Nick]

Did you install the aluminum base gasket/spacer beneath the barrel? I believe it's about 1mm thick. The 350 Sebring uses this but the 250 does not.

You might try kicking (or hand turning the engine) with the spark plug and valve covers removed.

If you're using a different piston than the one that came out of it, maybe check piston/head clearance using some clay. Put four small blobs of clay on at points equi-distant on the piston and a bit of oil on the head to prevent the clay from sticking to the head.

Rocker arm hitting compression release?

My Sebring runs rather quietly, but then I neither own nor ride modern bikes so whatever noises it makes sound normal to me.

[Bevel bob]

There can be play in the cam drive that is only found if you use a screwdriver to lever the gears .

[SebringMike]

Thanks all for your guidance...

Bevel bob... valve guides are in good shape, and there appears to be no movement in them. We've removed the valve covers and kicked the bike over many times, with no apparent movement. The noise is evident from cold to all the way to "too-hot-to-touch", so it does not appear to be temperature dependent. There appears to be no rotational movement in the bevel gears (backlash?), nor does there appear to be any end float.

Nick... my Sebring is very early. It originally had the "paper" gasket (no aluminium gasket), and no decompressor valve. The piston is new, and we've checked the squish. We disassembled the top end of the bike after the first time we started it and heard the noise, and there are no signs of any collisions.We have a "thick" paper gasket in place now. We've kicked it over lots with the spark plug and all covers (bevel and valve) removed, and see nothing moving.

Here's what I have uncovered. I searched youtube for bevel singles, and found one that sounds identical to mine. Check the video at

https://www.youtube.com/watch?v=EjW_NM24sQ8

There are two distinct sounds; the exhaust and a higher pitched metallic "tap".
The metallic tap is what I hear on my bike, and is the noise I'm concerned about.
So hopefully you hear the sound on the "tapping", and can confirm that this is normal, or is caused by....

Thanks,
Mike

[Nick]

Well, doesn't sound bad to me. Alloy heads on old bikes can make a fair bit of racket, especially compared with iron head models of the same make and vintage (Tri, BSA, etc.). Just the valves slamming home on their seats will make a fair bit of noise, and that big head acts like a resonator.

You may remember that back in the day some manufacturers had bits of rubber pushed in between the cylinder head fins and cylinder fins to dampen noise and to quell fin ringing. You cannot compare the quietness of a period BMW airhead with the Duc. The BMW's cylinders are iron, while the Duc is all alloy, and the Duc has much more finning on its head and cyls than an airhead of the same period. Then there's all that German engineering.....

Maybe find some Duc singles in your area and listen to them.

Too, if you can't find anything wrong in there, maybe it's because there's nothing wrong.

Personally, I find that all old bikes run much better when one wears ear plugs.

Beautiful workmanship — the bike looks great!

[halfpast]

My '68 250 Monza widecase sounds pretty much identical to the above video, for what it's worth...

[Bevel bob]

Does not sound bad, a bit rattly,but I would not worry, check the tappets again and turn the motor a bit around tdc. they do take a long time to warm up. 40 monograde oil?.

[SebringMike]

Nick, halfpast and Bevel Bob,
Thanks again for the words of wisdom. I think I'm finally comfortable with the noise my Sebring makes.
Just one minor point of clarification... the bike in the video is not mine... it just makes the same sounds as mine.
This is mine... in the final stages of restoration. Just have to finish the wiring, and I'm waiting for the painted body parts.

IMG_1620.JPG

Thanks again,
Mike