The International CBX Owners Association

Hi everyone, took my 79 Z out friday afternoon for its first ride of the year. Eveything was going fine until the bike started making a horrible grinding noise at low revs. It isnt all the time and seems to happen more when pulling away from junctions over taking cars etc. On a 40 mile run it happened about 5 times. The noise seems to be coming from the top end, but is hard to tell when riding ! Started it up this morning ran it for 10 mins not a peep. When it makes the noise it lasts for about 5 seconds and does not affect performance. Any ideas? When it happens it is loud.

Could it be coming from the left side? Maybe the alternator?
The plates can make a grinding noise when a bearing start to go south. It can also make a racket when the brushes need replacing or the spring gets sacked.

Hi Steve,just been out for a gentle ride of about 15 miles. It made the noise again about 3 or 4 times, i was trying to find out where it was coming from with no luck. If it was something serious in the motor woudnt it make the noise all the time? Sods law it has only done it once when pulled over with no helmet on. Because it only lasts for 5 seconds or so coudnt tell where its coming from. The bike starts first time and appears to be charging ok.

Merv could it be the rev counter bearing ? The alternator clutch "chatter" is normally on acceleration from stop or idle.. ?

Hi Larry nice to speak to you again ! Disconected the tacho cable still doing it. It is so infrequent i cant tell where the noise is coming from. I was doing about 70 75 braked and changed down to turn right and as soon as i opened the throttle again there it was

Merv, the chatter/chirping/grinding noise from the alternator plates and/or bearing usually only happen under low rev load or at idle like Larry said.
Have you had any charging problems?
I ALWAYS go for the simple fixes first. I am sure the braintrust here will have more places to look.

Merv, Check the alternator cover for excessive heat around the center bearing area, pull the alternator off & have a look at the clutch plates. If there is evidence of "galling"( looks like serrated radial marks) that may be the problem...
As discused over the phone, these intermittent probs are the hardest to find....
Keep us updated, as Steve said, look for the silly easy things first & get them out of the equation.. Then, drop the sump plate & look for fragments..copper/ zinc, aluminium, steel or rubber, as the noise is intermittent & power isn't compromised, it kind of leads away from catastrophic problems...

Thanks to everyone that has taken the time to reply. Going to take the alt. off monday, no problems charging as far as i can see. The volt meter stays on 12 volts for about 5 mins after starting then goes up to 14 dont know if this is normal. Cant take the alt off today as wifey has plans for me !!

Enjoy your day with the Family Merv...

When you remove the alternator, spin it by hand. If there is ANY roughness or resistance, replace the bearings and seal. It's a simple job, just be careful not to break the brush holder.

Thanks Rick will be having a look monday morning, will let you know.

Hi its fixed !! Guys you were right it was the alternator. Just as Larry said there was serrated radial marks on both plates. I swapped them for ones off my restoration bike and now it runs fine. Can i get the serrated plates machined or are they still available from honda? Thanks guys, Larry gonna buy you a drink or two at the rally.

Its been a few years but I got new ones from my Honda dealer.

merv 1 wrote:Hi its fixed !! Guys you were right it was the alternator. Just as Larry said there was serrated radial marks on both plates. I swapped them for ones off my restoration bike and now it runs fine. Can i get the serrated plates machined or are they still available from honda? Thanks guys, Larry gonna buy you a drink or two at the rally.

Glad I could help Merv but it was a system of elimination by a group/ team effort.....

I'm sure they are available Merv, try Honda or David Silver or Louis. If a problem getting them give me a call....
I'm not too sure about machining as there are oil slinger slots, if you did you would have to take up the spring tension with washers, I'm sure someone will advise further....

A friend said he could turn mine on his lathe. The tool could not cut it. It was too hard. I bought a new set from Honda.