Hi all,

My little beetle with a 1200 has developed some sort of whistle, and the pitch is proportional to the amount of throttle I give it.

The whistle is there regardless of revs or road speed. I took the air filter off and it is still there.

Seems to be coming from the carby. Any idea what it could be? Should I be concerned?

Thank you
Alex

It's probably the generator bearings.

Or could be the fan rubbing on the fanhousing, but that's more of a scraping noise.



Smiley

An air leak between the carby and manifold will do that too.

One of the bolts on dads weber keeps coming loose and doing the same, when it sounds like a bunch of birds in the aircleaner when he revs it we know it's come loose again

My money is on an air leak either at manifold to head or manifold to carb.

I think it is just whistling because ......................... it doesn't know the words. lol lol lol

it could be the fan on the housing, im preety certain mine does the same, it sounds good and i like it.

thanks for your responses
would you expect carby -> manifold to increase in pitch with revs?

The pitch of the whistle is only changed by the amount of (part) throttle I give.

I will have a look this weekend

If it varies noticable between part throttle and full throttle, then yup - air leak between the carb and the manifold.

One good way to prove it is to get a can of carb cleaner or similar, and while the engine is running spray around where the gasket is... if the engine revs change (pick up) then you've found your leak.

Good luck !!!

Air leak at carb is usually dependant on vacuum. I'm thinking maybe fan?? They can whistle when some junk gets caught in the blades. Just stick your hand in the fan and check every blade is clear......with the engine off of course .

Good advice Matt

I had the same problem with a car I was working on, it ended up being the gasket between the carb and manifold, the air flowing past made the gasket vibrate which made the noise. The manifold had been gouged by the po and that created the gap between carb and manifold. Also created tuning issues with it running lean etc

stick a 17mm socket on a drill
take the belts off put it in and slowly rev the drill it make sure u got the right rotation
once full throttle remove the drill and listen

if u don't have some sort of drive converter find a say 2" long m12 with 17mm hex head
and lock it in with the nut so that u have the thread side pointing out the back of socket

Please explain....what are you trying to do Mr Sheppard, drive the engine with a drill to hear the noise? Doesn't make sense to me, the engine would need all the plugs out to achieve that, then there's no vacuum to make the inlet noise.....

Does he mean using the drill to drive the fan while getting the engine up to speed, then take the drill out so the fan stops and all you hear is engine ???

The engine doesn't need to be running long to rule out the fan/gen/alt... maybe 30 seconds all up... and I doubt an engine would cook itself in just that short time...

not driving the engine by the drill
but take the belt off and just drive generator (and fan) with a drill to see if it was the fan making noise
with engine off

dw... it's a stupid idea anyway

I would be looking for a air leak in the manifold some where maybe under carby maybe at ends of manifold. Take belt off run the engine for a short time to eliminate the belt.
I had an annoying whistle noise in my engine too at valla turned out the inlet manifold on the left hand carby had cracked in it( broken on the mounting lug) some aluminium welding fixed it up. As suggested grab some carby cleaner and spray it near the carby gasket and throttle shaft.
Good luck with it

I once had negative presssure in the case when i over vented the case to the intake system and it whistled lots as it sucked air into the case through a leak in the oil cap (could have been a be a poor seal anywhere though)

Newt