Top end noise?

[ccambern]

Finally got the bike up and running and spent the last couple of days getting the carb right. It was dead rich and missing from idle to 85% open. I screwed around with different pilot jets and finally ended up drilling some emulsion holes in the needle jet to get it to run right.

At any rate, now that I have decent idle and throttle response, I've noticed that the top end makes a fair amount of racket. I'm getting ready to verify that it's still getting oil (it was a few days ago), and I'm planning to double-check valve lash. I guess the question is... should I be able to hear the valves, or should I be looking for something broken? Having never heard one of these run I don't really have a reference point, but it does have more top end noise than the other stuff I've worked over the years...

Thanks,
Clark

[DewCatTea-Bob]

" Finally got the bike up and running and spent the last couple of days getting the carb right. "

____ What carb are you using?


" I've noticed that the top end makes a fair amount of racket.
I'm getting ready to verify that it's still getting oil (it was a few days ago), "

____ Had you changed the oil any time since those "few days ago" ? _ If so, did you then make sure that the oil filter-tube reinstalled cleanly -(properly & without any slight issue)?


" and I'm planning to double-check valve lash. "

____ What did you have your settings at ? _ (Should be: .008"-Ex. & .006"-In.)


" should I be looking for something broken? "

____ I doubt that anything is actually broken in the top-end.


" but it does have more top end noise than the other stuff I've worked over the years... "

____ Is the top-end noise consistent, or intermittent? _ Are you familiar with the noise of piston-slap/knock?
__ Another excess top-end noise is due to a loose tower-shaft... So when you go to look for oil to be expelled from the center-hole of the camshaft, then while at slow idle, also look to see if the bevel-gear (of the tower-shaft) shows any sign of any side-play -(slight back & forth) movement, (as it also spins [slowly]).


Dukaddy-DUKEs,
-Bob

[ccambern]

Bob,

Thanks for the input. Responses below...

____ What carb are you using?

It's a VM30 (round slide) Mikuni. I guessed at the jetting based on some numbers from a Honda XL250, but the carb had a 2-cycle style needle jet and a needle that was too small, which caused poor atomization and flooding at mid-throttle. I couldn't get the right needle or needle jet locally, so I hacked at it a bit to approximate the 4-cycle jet. Still needs some tweaking, but It's actually working pretty well now.

____ Had you changed the oil any time since those "few days ago" ? _ If so, did you then make sure that the oil filter-tube reinstalled cleanly -(properly & without any slight issue)?

This is a fresh build and the engine has only been run for maybe 20min total, so this first oil its seen. That's why I'm unsure- I don't really have a reference point for a healthy Duc engine sound. I was very careful when I installed the filter and I'm sure it's seated properly.

____ What did you have your settings at ? _ (Should be: .008"-Ex. & .006"-In.)

Yep. Ex was a couple thou tight, so I ground down the shim a bit to get it in range. Intake was fine. I also looked at the top of the piston through the spark plug hole and there are no signs of contact with the valves (head was also clayed during assembly).

____ Is the top-end noise consistent, or intermittent? _ Are you familiar with the noise of piston-slap/knock?
__ Another excess top-end noise is due to a loose tower-shaft... So when you go to look for oil to be expelled from the center-hole of the camshaft, then while at idle, also look to see if the bevel-gear (of the tower-shaft) shows any sign of any side-play -(slight back & forth) movement, (as it slowly also spins).

Noise is consistent. This sounds more like valves than piston slap. I didn't have an air filter on, so it could just be that I'm hearing the intake out of the carb. Thanks for the tip on the bevel shaft. I did confirm oiling and I looked at the bevel gears while turning by hand, but I'll check while running.

What exactly loosens up? Bearings are all brand new.

Thanks,
Clark

[DewCatTea-Bob]

" It's a VM30 (round slide) Mikuni. "

____ How did you get that to mount to the cyl.head? _ Got any pix?
What happen with the original Del.carb?


" I was very careful when I installed the filter and I'm sure it's seated properly. "

____ I only asked about that because you had stated: "I'm getting ready to verify that it's still getting oil (it was a few days ago)",
and so that raised the possibility that it may have been (very slightly) possible that something had then since gotten drawn into your oil-pump.


" Ex was a couple thou tight, so I ground down the shim a bit to get it in range. "

____ Only two-thousandths tight, is not a concern to the point that it NEEDS to be reset ! _ I'd never suggest grinding-down any (virgin) shim-cap just for fixing that slight amount off-setting. _ Only if the exhaust-clearance was found to be tighter than .005" would I then bother look for any means to loosen it up.


" I looked at the bevel gears while turning by hand, but I'll check while running.
What exactly loosens up? "

____ Something that can add to the top-end noises is when,, near idle, the valve-springs can force the camshaft to spin the tower-shaft bevel-gears at a faster rotation-rate than the crankshaft is doing, so that causes a back & forth pressure on the top-end of the tower-shaft, and if that bevel-shaft is not held tight, that would then cause an additional clanking-sound in the top-end !
__ What leads to that occurrence to happening, is when the bushing, which holds the upper tower-shaft's ball-bearing, becomes an untight fit into the cyl.head's casting hole -(intended for that bushing to fit snugly into), and therefore allowing the back & forth whacking of the tower-shaft/ball-bearing/bushing-assembly against it's fit in the cyl.head.
This issue is not a common one but, Ducati did offer several over-sizes of those bushings, for addressing this matter.
__ Everyone who thinks that their DUKE's top-end has a clanky-sound (in addition to the valve-train tappet-noise), should check for this possible issue, while the engine is SLOWLY running.


Ducati DUKEs,
-Bob

[ccambern]

____ How did you get that to mount to the cyl.head? _ Got any pix?
What happen with the original Del.carb?

Motor came with a ratty Amal. I have no idea where the original carb went. I fabbed a manifold and connected the Mik with a piece of radiator hose. I'll post some pics in the next couple of days and jetting info when it's fully sorted. The VM Miks are fairly common and cheap on ebay, but they're usually set up for 2-strokes, so need all the jets and needle changed to work.

____ Only two-thousandths tight, is not a concern to the point that it NEEDS to be reset ! _ I'd never suggest grinding-down any (virgin) shim-cap just for fixing that slight amount off-setting. _ Only if the exhaust-clearance was found to be tighter than .005" would I then bother look for any means to loosen it up.

It was actually at .004 before grinding.


____ Something that can add to the top-end noises is when,, near idle, the valve-springs can force the camshaft to spin the tower-shaft bevel-gears at a faster rotation-rate than the crankshaft is doing, so that causes a back & forth pressure on the top-end of the tower-shaft, and if that bevel-shaft is not held tight, that would then cause an additional clanking-sound in the top-end !
__ What leads to that occurrence to happening, is when the bushing, which holds the upper tower-shaft's ball-bearing, becomes an untight fit into the cyl.head's casting hole -(intended for that bushing to fit snugly into), and therefore allowing the back & forth whacking of the tower-shaft/ball-bearing/bushing-assembly against it's fit in the cyl.head.
This issue is not a common one but, Ducati did offer several over-sizes of those bushings, for addressing this matter.
__ Everyone who thinks that their DUKE's top-end has a clanky-sound (in addition to the valve-train tappet-noise), should check for this possible issue, while the engine is SLOWLY running.

Hmm... pretty sure the bearing was a snug fit when installed, but I'll check it out.

[ccambern]

Resolved...
Noticed the top end was clattering more and more so I decided to tear into head. Turns out the cam gear nut was loose. Sorta surprised it didn't shear the key, but now I have it tightened down the engine sounds a TON better.

[frankfast]

That shouldn't happen if the proper washer was used. It keys into the keyway at the end of the cam and the outer diameter is bent over the flat side of the nut.

[Bevel bob]

Once the motor has run its worth having a look at the top bevel to see what the mesh and clearance is, Mine looked ok (its not easy to feel any clearance when the rockers are installed),so i used a small screwdriver under the top tower bevel to see if it would lift ,I was most surprised when it did!!. I found worn bearings, I also had similar problems with the bottom bevels where the shim under the housing was too thin and allowed the whole assembly to rise and fall, not easy to spot as the assembly is a tight fit in the case when cold.Its all sorted now and the bike would give a 350 goldstar a tight race, its still noisy though.

[ccambern]

Frankfast,

The proper washer was used, but the nut still worked free, apparently bending back the tab. The bottom line is that I just didn't get enough torque on the nut, but I wanted to post this in case someone else encountered the same.

[frankfast]

There was a post recently on how to tighten that nut and get the proper torque. You really have to lean on it without damaging gears, cams, rockers etc. It's not easy without the proper holding tool.