4 replies [Last post]
312Icarus
312Icarus's picture
 Offline
Joined: 07/15/2016
Posts: 409

Still chasing the mysterious chirp on my recently rebuilt engine. I now have a couple hundred miles on the engine. Here is the deal...Start the engine, and it runs like a kitten, just ticks over. Twist the throttle quickly it revs just fine, no muss, no fuss, no noise.

Pull the bike off the center stand and lean it over a bit to back out of the garage, twist the throttle and it chirps! Very high pitched, clearly coming from the front of the engine, maybe upper 1/2? Returning to the center stand and it keeps chirping. Go for a ride, and ~1500-2000 rpm it chirps, then goes away above (and below) that. You can hold the rpm and it continues to chirp.

I tried removing the field coils from the generator thinking it might be in the genny, but no change. I have lubed the rubbing block on the points, the advance weights, sprayed WD 40 behind the armature where it enters the case.

One more mystery, if I tip the bike on the side stand simulating the angle Ihave to use to pull it out of the garage it won’t chirp (the first time, once it has started chirping it will chirp on the stand) For a while I though it might be the stand squeaking but that is not the case.

I am at my wits end. Listening with a stethoscope you can’t hear it. There is no bearing howl that I can hear, no grinding, no other strange noises. It almost (but not quite) sounds like a air whistle rather than a scrapping. Someone suggested that the vent washer on the end of the cam might be scraping, but against what? ( I have sent the oil off for testing). Here is another question, I know the vent washer holes line up with the holes in the case to vent case pressure. My breather seems to be puffing just fine. The question is, where does the case get air? If it is exhausting through the cam vents, that air must come into the case somewhere? Is there something I’m missing? Does anyone have any idea beyond what I have looked into. I am convinced (hope over logic perhaps!) that the noise is not catastrophic so I will keep riding it, but it still worries me.

Thanks for any and all ideas,

Icarus

Daves79x
Daves79x's picture
 Offline
VBMWMO #9030
Joined: 08/09/2015
Posts: 348
The Crankcase

The crankcase draws it's air - ready for this - through the rear main seal. Hence the chirping that some modern rear main seals produce. I still think that's what you are hearing. The crankcase vent disc on the end of the cam DOES run right up against the corresponding surface in the timing cover - that's the only way it will function properly. It has to seal tightly against the timing cover. A good supply of oil keeps it from galling. I found this out the hard way.

Dave

__________________

Dave

312Icarus
312Icarus's picture
 Offline
Joined: 07/15/2016
Posts: 409
thanks for that Dave. I don’t

thanks for that Dave.

I don’t think in this case your are right about my problem. The noise is coming from the front of the engine not the rear, and as Vech suggested, pulling the dipstick while running should make the noise go away, and it doesn’t. As I said, I have sent the oil out for analysis, if it comes back high AL I will pull the timing cover, something I really don’t want to do.

Icarus

312Icarus
312Icarus's picture
 Offline
Joined: 07/15/2016
Posts: 409
Problem solved!!! It turns

Problem solved!!!

It turns out, that coming off the centre stand was the key. Turned out to be the top engine mount, between the mount and the frame, the one with the rubber bushing. It was too tight, although I think it is worn out. It is a castellated nut, and had no cotter pin, so I ran a piece of safety wire.

It still chirps a bit, but I think with a new one it will be grand.

Moral of the story, keep your head in the game, and when things don’t make sense, keep at it and follow the logical answer(s) and eventually you will find a solution. When nothing else is it, it must be what you are missing!

Icarus

schrader7032
schrader7032's picture
 Online
VBMWMO #7032
San Antonio, TX
Joined: 10/27/2006
Posts: 6788
So not coming from the front

So not coming from the front of the engine! Wink Glad (and hope) that you get more to the bottom of this.

__________________

Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2

Comment viewing options

Select your preferred way to display the comments and click "Save settings" to activate your changes.