Low RPM Clatter

My bike runs quietly at idle, and has a nice throaty sound ranging from a cackle to an obligato in different RPM's and throttle changes. But there is a distict clatter at around 1600-2000 RPM's at the front fork, resonating through the bike. It happens at high idle when I first start the bike and raise the air screw until it warms, and it happens on slow accelerations and when stopping and the revs drop off. I would call it a clatter, or a chirping sound and it's associated to the bike vibrations. The vibes on the handlebars noticeably increase until it reaches a threshold one way or the other, and then it mellows out. Additionally, I wouldn't say that the bike is smooth as silk at highway speeds, although it's not bad. It may be that it's still making the racket and I can't hear it for the engine.

I don't have decades of experience with these bikes like many on this forum, so anything I learn is here, or learned the hard way. As a result, for many things, I don't have a strong basis of comparison. Ride quality is one of them. I'm guessing the front isolastic is needing replaced. I will check the clearances, although I would appreciate any insights on this. I would also appreciate any feedback that can describe to me what should be happening ride quality-wise, particularly in the lower RPM range. I suspect every bike is a little different. I know it's supposed to smooth out around 5000 RPM, but I can tell you after 2 hours on the bike, my ass and legs are glad to be off the seat, because there is at least some shaking going on, and it wears on me, getting old, dammit.

I've worried that the clatter was valve noise, so I've lashed, checked, lashed, and rechecked the valve clearances. At idle, I hear nothing but the slight clickety-click I would expect, and I know the valves and head in general are in great shape, wear is minimal. I guess there could be something loose on the front fork, but why else would the fork be vibrating except for a sloppy motor mount? Anyway, thoughts before I go searching?

Normal isolastic motion is that the bike will shake the ground at idle and suddenly smooth out at about 3000 rpm. What you get in between can be odd, with things resonating at certain points along the way.

That said, have you tried touching things (dampening vibrations) with your hands? I had a loose front fender once that made the strangest noises at a certain RPM. And my buddy had a loose primary chain that dragged the bottom of the chaincase during deceleration and made clanking noises.

And you're right about having something to compare against.. after 36 years I know every squeak and rattle.

If your ISOs are OE than they have not been doing you any favors for years, if your forks have not been serviced in over three years or rebuilt in the last 10 they need a good look. If you have an OE head steady the rubber bushes are dead if they haven't been renewed within the last 3-4 years.

If you still need shims for your ISOs, do check, even dead ISOs will respond a bit to proper shimming, just make sure that you place the shims evenly on both sides or your rear wheel will take a noticeable set to the (left) usually. The vernier ISOs are so worth the pain to install; just get it over with and for at least 5 years you will have a nice feeling Norton.

Best wishes on your quest to domesticate your Norton, mine is paper trained...

RS

Slupdawg
Maylar maybe onto something. Grab your headlight when the clatter happening and see if it stops. If it does, then you have missing 061900 O-rings in the headlight brackets ...2 at bottom 1 at the top of each side....... Thats my guess... :idea:
If no change move to something else.
Cheers
CNN

Or maybe you could check the head steady isn't loose.

Like mysterious noises are so strange. Try putting it on your centerstand and with a friend to hold the throttle open at the range that the sound occurs you can use your ears to walk around the front end and listen for location. But like don"t burn your ear or hair off on the exhaust pipe like I saw once in the distant past. Good for a laugh if it's not you.

I. Fork ears oil ring gone rattle.
2. Fractured 750 head steady plate.
3. Tank fouling
4. Coil bracket flapping
5. Side or center stand clanking.
6. ? ....................

oh yeah, a full fettered Commando goes silent by mid 2000's rpms.

2300 R.P.M.'s

Yeah man Toro, you braggart, but Phil of Norton Villlers history says their early test rides went silent at 1800! I don't want to ride my friends that don't go silient till mid 3000's as always temped to stay above that in too dangerous condition to get away with it.

I had a pebble get trapped between skid plate and front iso that was so suddenly rough and cattery I thought I'd thrown a rod!

Commandos will make a man of ya or throw ya back to an infant in a tantrum.

Bleedy Concentrics .

I bet it is your gas tank slapping against the bikes frame.Thats about the RPM range that will do it if the tank rubbers are not right. I now use a section of foam pipe insulation on the frame tube to prevent this from happening.

My 850 had a loud allmost harmonic sound that drove me nuts last year for a while. I just kept checking everything that it could be & getting things tight & isolated. Like you Bruce I use pipe insulating foam I find at work on job sites. It comes in a couple differant diameters & I just cut it in half and tie wire it on. Something I did got rid of that sound. Check your chains too. When I first start my bike and the Mikuni's choke is on I can hear so
me funky noise from the timing side that sounds like the cam chain. It goes away with the choke off & a more smooth idle. Guess I need to man up & check my timing chain. Been to lazy to do it for a while but it's been about 5,000 miles so guess it's time.

Once found a socket left in one of the recessed holes for the small head nuts on a friend's Commando. Rang like a bell.

When I first got my 1800 ES Volvo about 15 years ago I had a guy work on the front end. Turned out he was a total hack, when I got it back it was worse and he left two big pry bars and a very expensive big Snap On ratchet with an extension and deep wall socket all IN the engine bay under the hood! Lucky I looked in as soon as I got home & nothing fell into any moving parts!

That reminds me of when I was 16, I worked at a gas station. A guy came in complaining that he need his front tires balanced because he had a bad shimmy. I broke the first tire down (Tubeless) and found a 2 cell flash light still lit inside the tire. The guy said he the tire plugged 2 weeks before!! Note gas was 29 cents a gal. back then

I have noticed a clatter on my bike while in low rpm that worried me. Put my knees tight on the tank and it stopped. Picked up some rubber insulation for copper pipes and put it on earlier and cranked it up, sounded so much better! Excited to see how she does tomorrow morning, was riding really smooth and quiet today doing 50-70 mpg locally! Had a bunch of Harley guys trying to give me heck today at work, had to remind them I do not have to take my bike to a dealership to service it ( none of them even know how to change their own oil)! :twisted:

Just tell em what new exhaust system costs on your Norton, that'l hurt em more.

I just love how they invest as much in HD leather as they do chrome and hardbags. Lord forgive the dealership that does not carry the latest cupholder, LOL! just took the bike out for a quick shakedown on my tank insulator and it works great! Saw a few old bikes with apes on them at the local bar. Had to get home and get to bed soon. Think either my timing is a bit off or carbs are not dialed in good. Getting what sounds like misfire out the exhaust, may need to check the valves?! Just nice to have her running!

Also check that the primary case or the left exhaust header is not touching the frame. The zorst on this side runs very close to the side stand lug.