Squeak from carbs at near idle

[tmkaos]

Hi all,

I have been  noticing a squeaking noise whenever I quickly shut and open the throttle, usually with gear changes just as the throttle position either leaves or approaches idle, or as I gently accelerate away from lights etc. It has been gradually getting worse over the last 3 months.
I assumed it was a throttle cable or a dry linkage, so yesterday I pulled the tank off, and CRC'd everything, took all the slack out of the throttle cables and generally had a look-see..
Static testing with the motor off, no more squeaking. Fire her up, squeak still there. Running the motor with the tank off I seem to have traced the squeak to coming from inside a carb, as you look at the motor from a riding position the left-most one.

Now I'm most curious, so I do a bit more testing, and the squeak occurs whenever there is a change in airflow through the carb just over idle. I notice it around town as I'm lazy shifting at low RPMs, so the motor drops to idle or very near it between gears. It squeaks when I throttle back up as I engage the clutch and match RPMs to speed. It can also happen when I throttle down at low RPMs if I'm crawling in a car park or my driveway etc. At higher RPMs and more load, it doesn't happen as the motor doesn't get back to anywhere near idle, and I'm probably not making it all the way shut on the throttle before the next gear is engaged and I'm back on the kookaloo.

Now what is inside that carb that would squeak? I've never been inside the carbs but I imagine the only major moving part big enough to cause a squeak audible over a running motor is the slide? Would it be as simple as getting some CRC in there or is it a pull the carbs down job?

What do you guys reckon?

Cheers for the input, btw...

James

[racerman_27410]

maybe the diaphram inside the carb has a small tear in it?


KOokaloo!

[tmkaos]

A tear in the diaphram would make that noise? It really does sound like a purely mechanical squeak, 2 dry parts rubbing against one another but it could be a 'air whistling through a hole' noise. I woyul've thought a diaphram issue wuld be apparent at all revs though? I can't tell any performance issues with the noise, she still pulls like demon.

[racerman_27410]

honestly i dont know if a torn diaphram would make a sqeaking noise or not.... just throwing it out there.

have you tried lubing the linkages?


KOokaloo!

[fj11.5]

wouldnt be a noisy speedo or cable would it, mine only made the squeeeking noise when slowing down to idle around town

[tmkaos]

No definately not the speedo cable or drive - you can make the bike do it by loading up the motor against the clutch with the brakes.  On the way into work today it dropped a cylinder for half the trip, so I think that I will need to pull the carbs and clean them out, and actually find out what's inside them. It's slightly annoying because we only have a work car - my wife's, I use the bike as my transport, so once those carbs are off I'm screwed for however long it takes for me to clean and replace any poked components. It's deepest darkest winter here at the moment so the mountain bike ride into work won't be much fun.  I'll stop bitching now.

We don't have the ethanol gas here (NZ) which seems to play havoc with the carbs for you American folks so hopefully it won't be too bad in there but I did notice a few spots of rust in the filter (it's one of those clear ones) when i pulled the tank off, so maybe my '92 tank has succumbed to the dreaded rust gremlin.. Bugger..

Happy riding,


James

[fj11.5]

the carbs   are pretty easy to work on, getting them out is probably the hardest part, that and the screws are made of cheese  , , no dodgy ethanol fuel here yet, but plenty of frost, , did you feel the quake over there mate, heard it was a good one, 

[tmkaos]

Yeah i've just been looking at randy's carb kits..  I just spent this season's maintainence budget on braided lines so bugger it this'l have to be done on the cheap. I'll get them off first and then figure out what I need. I have pod filters so at least I don't have to worry about the airbox. I took it out twice - the first time I said - I'm never doing that again, and the second time was to fit the pod filters 

I didn't feel the quake to be honest but i'm in Auckland, so a bit futher north of where it was centered, but plenty of talk on Facebook with my friends around the country who felt it.
We had a close friend die in the Christchurch earthquake last year, so we don't need any more of those, thank you very much..