Annoying noise / chirping at high rpm under load

[ilves1985]

Hi folks,


I have a problematic and annoying noise on my -98 standard (Euro Version), 75 000 km (50k miles) (possibly 175 000 km but doesn’t look like that). It's like chirping, like a chain pulled out from a metal bucket quickly, high pitched metallic clatter. It's continuous but only heard above approximately 2500 - 3000 RPM and gets louder under heavier load. Neutral or clutch pulled while driving (high rpm) sound quiets down but doesn’t disappear. Cold or warm engine no difference. Heard on all gears.

I bought the bike last November and the noise has been there all the time. It was quiet but noticeable with standard exhaust but way louder now with my 6-into-6 Cobras. I use ear plugs and at 4000 RPM I can barely hear the engine any more, just the chirp. Low RPM all quiet. And it runs good. 

Buzz bar, exhaust header nuts, carb sync, belts and tensioners, spark plugs, all checked and/or replaced. No loose parts I can see. Desmog done. Final drive and U-joint serviced OK. Valve clearance checked. Alternator checked and its rear bearing replaced. Water pump checked. Injector cleaner used for the last two tanks. Compression OK (~170 psi) in all cylinders. Noise still there. I use 98 octane (Euro) gas, highest octane available here in Finland, 5% ethanol. Carb jets now 38/105, idle screws 1 3/4 open (definitely not running too lean any more, spark plugs are even a bit darker than I'd hope).

I thought about the oil pump chain but since the chirping noise is so much louder with Cobra exhaust I think it comes from the cylinders? So started thinking about engine knock. Idle timing is OK (checked with timing lamp) but the noise is not there at idle. Changed ignition coils, no difference. Engine coolant temp sensor? But it shouldn't affect timing advance above 3000 RPM?

I’m running out of ideas. Could it be engine knock or do you guys have any other thoughts? Piston slap? Crankshaft bearings? And how to verify and fix this? Are there any other things I could still check before taking her to a repair shop for engine removal and complete disassembly? Oh, carb rebuild is not yet done, that's planned for next winter project.

BTW I noticed that using a stethoscope is difficult while driving and when I'm not driving I cannot hear the noise...

Thanks for any ideas, hope I can fix this because driving is not too enjoyable at the moment.   

[Hook#3287]

You state "Heard on all gears " so that would rule out drivetrain.

Maybe clutch pack?

Pulling the back case cover off is relatively easy.

A little more work to pull the clutch pack.

I'd look there before yanking the motor.

[3W-lonerider]

if your bike has the trans covers. remove the one on the left in front of the alternator and see if your noise doesn't go away. on mine it was so noisy when under a load that i was ready to sell the bike. what i found was that the bracket that holds the alternator cover. its a thin bracket. when the trans cover was bolted on it wasn't completely going against that bracket. so that bracket would vibrate between the alternator and trans cover. what i done to fix it was the hole in the front of that trans cover. i took a file and made it alittle bigger. that allowed the trans cover to go forward enough to actually go up against that bracket.

[ilves1985]

Thanks for these ideas, I dont' have transmission covers and I've been testing without alternator cover as well. So that's not the issue.

Clutch, perhaps (grease to clutch slave sylinder pushrod?) but since I hear the noise also when pulling the clutch level I doubt that. And also because the exhaust affects the noise so much I suspect something inside teh engine.

Forgot to mention, oil is Motul 10W40 and Honda OEM filter.   

[Bagger John - #3785]

"Louder with Cobra exhaust" - pretty much rules out engine internals.

Look at the PAIR valves and emissions plumbing, if your bike hasn't been de-smogged yet.

[Jims99]

I would check buzz bolt again. I would think it’s a vibration or exhaust gasket.

[Icelander]

I developed a squeak but it wasn't as consistent as you're talking about. Turns out the Ultimate seat pin that goes into the pocket on the fender is metal (versus the plastic of the original) and had worn through the paint in the fender pocket.

This may (probably) not be the problem for you but I chased that cursed squeak around for a month until it had progressed to the point where initially sitting on the seat caused the squeak. Might be time to go through the bike with a flashlight and look for weird signs of wear. Maybe check the shock bushings, basically just look in places that you wouldn't think would make that noise.

I hope you find it! I'd hate for you to have to pay someone to ferret out the problem for you.

Good luck!

Kendall

[ilves1985]

As John mentioned, I am also puzzled why the noise is louder with Cobra exhaust than with standard exhaust. And that's why I thought about engine knock. Again the noise is not there below 2500 RPM.

Desmog is done and every time I have changed the exhaust I have had new exhaust gaskets and tightened enough so those are pretty much ruled out.

Has anyone had engine / spark knock in Valks?  How does that sound? AFAIK most likely reasons for that are too low octane fuel (I use highest available), carbon buildup in cylinder (possible) or false (too early) ignition timing. Yesterday I realized that Euro models have a TPS (Throttle Position Sensor) that adjusts ICM timing, I tested that according to workshop manual and it seems to be good. ECT sensor hasn't been tested yet. 

Thanks for the support so far, I try to record the noise but since I have to do that while driving so it's a bit tricky.

[Jims99]

You don’t need high octane in these motors. Unless you have had work done. They aren’t a high compression engine, higher octane isn’t necessary.

[Bagger John - #3785]

You don’t need high octane in these motors. Unless you have had work done. They aren’t a high compression engine, higher octane isn’t necessary.

Correct.

Lowest octane that won't knock under load, given your atmospheric conditions. I've never had to use anything besides 87 in any of mine, even 2-up and with luggage in bags and trunk.

[Jess from VA]

One of my interstates came with the 4 degree trigger wheel.  It would knock a little when lugging ;ow PRMs, but not keeping RPMs up.  I got rid of the wheel back to OE.

Now I only run 87 non corn polluted gas, unless I have no choice. No knocks.