Confounded. Engine rattles with headlight off... smooth with

[Thunderdome74]

So i have put the carbs in and out umpteen times... but i think i finally have them dialled in. The clutch noise is still there however...until i switch on the headlight ...then it smoothes out.

Do you guys kmow if the alternator draw increasing somehow smooths/damps the engine at all?

Alternator has new bearings etc... so i am trying to figure out what is actually happening in the engine when headlight is switched on

Thanks for the help
Thor

[daves79x]

The extra draw on your alternator is obviously changing the idle a fraction, getting your particular CBX into a sweeter spot. Idle speed has everything to do with how much noise a clutch makes.

Dave

[Thunderdome74]

Hey Dave , thanks for the reply (merry xmas btw:)
Here is the video i made,
https://youtu.be/CCvAIS0J3Ss
It's weird as the clutch rattle dissapears by nearly 95% when i put the headlight on.
Am i right in that there is no reason for the revs to drop other than the additional "load" the headlight draws from the alternator?
If you look at the video, the revs just seem to smooth out. Not complaining mind, i'll take it, i am just not understanding.
If i increase the revs slightly via the throttle (headlight off) the rattle remains there.

Does the draw on the alternator "tighten up the alternator chain" possibbly preventing slop and engine balance?
Just trying to figure out reasons... BTW the bike is not a low milage sample, 70 000km.
Valves shimmed, new rings, gaskets, carbs done (many times)


Thanks again for the advice
Thor

[divan]

Hi Thor. I noticed in your video that the voltmeter is showing about 12v and appears to fluctuate a bit when you flip the switch. It usually takes a while for the "frying saucers" -- aka clutch disks -- to heat up enough to fully engage the alternator. Could be that at least some of the clunk is coming from those disks (as well as the clutch). Works that way on my '79. Headlight draw would cause the alternator to try to meet the demand, and maybe tighten the disks up a smidge, reducing some of the noise. Just a guess. Weak spring on the clutch disks would contribute too. Primary chain is also a known noise-maker at idle. Just saying those clunks can be hard to isolate to just the clutch basket.

[msnitker]

Hi Thor. I noticed in your video that the voltmeter is showing about 12v and appears to fluctuate a bit when you flip the switch. It usually takes a while for the "frying saucers" -- aka clutch disks -- to heat up enough to fully engage the alternator. Could be that at least some of the clunk is coming from those disks (as well as the clutch). Works that way on my '79. Headlight draw would cause the alternator to try to meet the demand, and maybe tighten the disks up a smidge, reducing some of the noise. Just a guess. Weak spring on the clutch disks would contribute too. Primary chain is also a known noise-maker at idle. Just saying those clunks can be hard to isolate to just the clutch basket.

New here, thanks for the thoughts and video Thor--my CBX does the exact same thing! I thought about looking at the frying saucers (LOL), spring, and guess the clutch hub rubbers tired and adding to the noise.

Mine too not low milage--46K miles, but well care for. I dont have any spares (clutch hub, motor,), so when I take it apart, I'm not riding it!

Any thoughts--should I start with the alternator first?

[daves79x]

Your rattling noise at 46K miles is 90% the clutch hub rubbers. The alternator should make no discernable noise under normal operation. If it is constantly chirping or whining, you need to address that, but just a loud rattling noise at idle, which changes pitch when you pull in the clutch, is the old hard clutch hub rubbers.

Dave

[CBX-tras]

My business partner, Kurt at KM Carburetor has the clutch dampers if you want to DIY. Or, I can do it for you.
Additionally, we have sourced a very special fastener for re-assembly than won't interfere with the shield that protects the oil pump chain.

https://www.kmcarburetor.com/products/1 ... d-bolt-kit

J.R.

[msnitker]

My business partner, Kurt at KM Carburetor has the clutch dampers if you want to DIY. Or, I can do it for you.
Additionally, we have sourced a very special fastener for re-assembly than won't interfere with the shield that protects the oil pump chain.

https://www.kmcarburetor.com/products/1 ... d-bolt-kit

J.R.

J.R. excellent, thanks! What an excellent solution with the flat screws--I'll find a used hub (unless you have laying around and ready to roll with KM kit installed). I'll probably replace the friction discs and other items while I'm there, with the new hub.

I'll make a video to post/share.

Which clutch tool do I need for the hub? I've read some different information--44 MM, 54 MM, and the web is replete with different tools--and, we'll all had the experience of buying a tool to find it doesnt fit, and not worth returning LOL

Send any other clutch tips, and thanks again!

[msnitker]

Your rattling noise at 46K miles is 90% the clutch hub rubbers. The alternator should make no discernable noise under normal operation. If it is constantly chirping or whining, you need to address that, but just a loud rattling noise at idle, which changes pitch when you pull in the clutch, is the old hard clutch hub rubbers.

Dave

Dave--thank you--that's exactly it. I just got the bike, and we're still getting to know each other--it's an unsettling noise, for sure, but the other video helped.

I recently got this bike, after wanting (another one) for many years, made room in my shop now. I had a 79 Persius silver sport kitted version, which I sold for probably little when I joined the service in 1990, before selling it, I would ride to concerts on the CBX all over the pacific NW, whether I had a girlfriend on the back didn't matter. Long story shorter, I rode the one I just acquired--with rattle at idle--with my youngest kiddo--what a machine! Wow, I am truly grateful to have a CBX again. One question I am wrestling with--can one have too many CBXs? :)

As I mentioned to JR--I'll look for the proper clutch hub tool (size? I've seen all kinds of suggestions of 44 MM and 54 MM) and if you have any other clutch repair tips while I am in there, (I'll look through the forums), please send along.
https://photos.app.goo.gl/ddmsG6kZtyajszux9

Thanks for the expertise here, Go CBXs! Mikael

[msnitker]

Your rattling noise at 46K miles is 90% the clutch hub rubbers. The alternator should make no discernable noise under normal operation. If it is constantly chirping or whining, you need to address that, but just a loud rattling noise at idle, which changes pitch when you pull in the clutch, is the old hard clutch hub rubbers.

Dave

I put a stethoscope up to the covers--the alternator is quiet as could be, guessing you're spot on here. I'll source a hub, and rubber kit mentioned, otherwise bike runs great.

Still considering the upgraded alternator from Tim's, but one thing at a time. LOL.

[CBX-tras]

My business partner, Kurt at KM Carburetor has the clutch dampers if you want to DIY. Or, I can do it for you.
Additionally, we have sourced a very special fastener for re-assembly than won't interfere with the shield that protects the oil pump chain.

https://www.kmcarburetor.com/products/1 ... d-bolt-kit

J.R.

J.R. excellent, thanks! What an excellent solution with the flat screws--I'll find a used hub (unless you have laying around and ready to roll with KM kit installed). I'll probably replace the friction discs and other items while I'm there, with the new hub.

I'll make a video to post/share.

Which clutch tool do I need for the hub? I've read some different information--44 MM, 54 MM, and the web is replete with different tools--and, we'll all had the experience of buying a tool to find it doesnt fit, and not worth returning LOL

Send any other clutch tips, and thanks again!

Tool - It's special. I machined my own years ago but, they are available online.

Clutch Hubs - No spares on stock as they can run anywhere between $500 and $1500 depending on model and wear.

LMK, J.R.

[msnitker]

JR thanks, I found a hub, and after some wrangling with it finally got the rivets out. Just need to tap it, and reassemble. Great kit from km carbs !!

Will get a tool online and some friction plates.

Thanks much !