Odd metallic noise from a Maxim 550

When I started up the bike to come home after work, I noticed that right around 4k rpm, it begins making a noise which I can best describe as two metal plates spinning lightly against each other. From idle to high 3k everything is as normal.

The noise follows engine RPM exclusively. Speed and gear have no impact. The higher the RPM, the 'faster' the noise is. The volume isn't terribly loud, but it is very noticeable.

The only thing I can think of that has fallen out of the 'norm' is this has been the first colder night we've had in a while, but the noise continued the entire time home, about an 8 mile ride.

First thing I did when I got home was check the oil, and I believe its fine, hard to tell through that sight glass. I'll check again tomorrow after things have 'settled.'

Otherwise, I've no idea what would cause this kind of noise other than perhaps the clutch, but it has been a very sudden onset, and I've not touched the clutch cable.

 

I'll betcha $5 it's got nothing to do with the motor itself.

Tach. Or tach cable, but most likely the instrument itself. Between my two Secas I've gone thru three of 'em so far. Disconnect the cable from the back of the tach and let it drop an inch or so, (it won't fall out) and go for a ride.

They can be serviced: http://xjbikes.com/Forums/viewtopic/t=15303.html

 

Interesting, never thought the gauges could make such a loud noise. My Tach has been slow to respond and acting rather fidgety lately, so perhaps you are right. I will give it a try on the way to work today.

Thanks for the reply!

 

The first time one died on me it was screeching so loud that people we passed MOWING THEIR LAWNS could hear it and would look up to see what was screaming. My son was with me and we got a good laugh out of it.

 

Does this noise also happen when you rev the engine while parked? or only while moving?

you gotta find the area where the noise is happening and then you'll know what to fix.

From the sound of it the gauges or the cables (speed/rpm cables) going to the gauges are likely the problem.

I had the speed gauge/cable making a horrible loud noise, I stuffed balljoint grease at the end of the speed cable and where it screws into the cluster. Haven't heard that horrible noise ever since (5 months ago).

 

Took off and lubed both the cables while I was at it, and went off to work. Still made the noise.

I listened carefully, and the best I can guess is that the noise is coming from the upper engine.

After a bit of thought, the best way I can put it is if you were listening to a brake lathe from a distance. It's not terrible loud, it's a bit softer than the engine noise. The only way I'm picking it up is because of its high pitch.
I'm thinking its possibly related to the camshafts? Perhaps a bit of debris fell off the valve cover when I checked the clearances, and got itself lodged in between a journal and bearing?

 

That or maybe a chunk of cam chain guide is gone and it's rubbing on the metal backing.

I'd pull the valve cover off and have a look for starters.

How many miles on this bike?

 

15300 miles. I'll see if I can get a good audio clip from my digital camera tomorrow.

 

Pulled the cover, nothing obviously wrong, spun the cams around and didn't see any scoring. Guides didn't look worn.

I tried making a few videos, but I couldn't pick up the noise well on my old camera's terrible microphone. You can just barely hear it in the video, I held the RPM around 4k.

http://www.youtube.com/watch?v=cCzJi5pI7ZY

 

OK, I'm guessing now, based on my intimate relationship with the 550.

Check the inside of the valve cover; it shouldn't be able to rub anywhere but it's still worth a look.

Pull the tach drive gear and housing, let's make sure it's not seizing up or something.

Alternator brush or holder? I know it's further back but sounds fool you. Might want to pull the alternator cover and have a look; it's getting to be at least "checking" mileage now.

Pull the ignition pickup cover ("points" cover, LH side says YICS on it) and make sure nothing's come adrift in there and started rubbing.

If none of the above, might want to pull the clutch cover and have a look.

If you STILL don't find anything, then the valve cover should come back off and the cam caps (the real ones, not the "dummies" that only hold the bolts) get removed one at a time and checked to be sure you don't have a cam journal packing up. Be sure they go back on in the exact location and orientation as they came off, and torque to the proper spec.

I'm beginning to run out of ideas...

 

I wish I had a stethoscope or something to help isolate the noise. I already checked the journals, but I didn't check the underside of the valve cover for rub marks, now that I think about it.

I'll give the alternator a look over, although I'm not looking forward to taking that cover off, all the screws on the ignition cover stripped on me something fierce, and I'm sure the rest on the bike will follow suit. Replaced the ignition cover screws with hex heads, maybe I'll do it on the rest for the sake of it.

With the tach drive, is it lubricated by engine oil, or is it an isolated system?

 

tach drive lubed by engine oil; everything you ever needed to know about that little bugger is here: http://xjbikes.com/Forums/viewtopic/t=19538.html

You can use a long screwdriver as a stethoscope: Jam the end of the handle in your ear and touch the business end around on the motor.

 

Everything checked out fine.

I took it on a decent ride yesterday, about an hour and 40 miles. Cruised around on county roads. I noticed that at one of the stops, near the middle of my trip, I didn't hear the noise anymore.

When I got home and took my helmet off, I listened closely around the engine, and could no longer hear it.

Later today I'll take another cruise, and see if the noise is present at start up, and try to and figure out when/if it disappears again, etc. I am wondering if its temperate related, and the stop-go traffic to work and back isn't warming the engine up enough; although you'd assume after just a minute or so the whole thing would be warmer than, say, summer ambient.

Lastly, in wonderful irony, my tach started screeching when I was pulling away from a stop sign.

 

It's the little things that make owning a 27-year old bike interesting.