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


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

Postby Thunderdome74 » Wed Dec 25, 2019 5:09 am

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

Postby daves79x » Wed Dec 25, 2019 8:12 am

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

Postby Thunderdome74 » Wed Dec 25, 2019 3:25 pm

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

Postby divan » Thu Feb 13, 2020 3:17 pm

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.
Dick Sullivan
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