Two engine questions

[geol]

1. Why the breather in the valve cover? I looked through the factory service manual for the GS1000 and couildn't find an explanation. With carbs and exhaust attached to the head, it doesn't seem like there is cause for ventilation.
2. How does the crankcase vent?
3. What are the small black rubber plugs between the cylinder for? Are they really necessary?

These questions relate to the GS1000 but probably other models as well.

[bwringer]

The answer to #1 is #2, and the answer to #2 is #1. There's a great big cam chain tunnel in the middle that allows crankcase vapors to reach the head and valve cover. 850 and larger shafties have a small vent fitting for the secondary gear space -- this is that widget about the diameter of a AA battery with a small tube coming out of it that runs to the bottom of the starter cavity and vents out the Mystery Hole.

As to #3, they are not at all necessary and most people just pick 'em out and toss 'em. The original purpose was supposedly to quell high frequency vibrations for noise testing. There us no humanly detectable difference in sound with or without these dampers, but supposedly there was some government test equipment aeons ago that was sensitive to high-frequency ringing, so motorcycle makers started stuffing rubber blocks in between the fins on air-cooled engine. There have been all sorts of crack-brained theories about these, and if you're very lucky you might see a few pop up here.

[fastbysuzuki]

1 & 2 The crankcase breaths via the cam chain tunnel into the valve/cam cover a certain pressure is built up with heat generation/movement and some blow back passing the piston rings (not much hopefully), the crankcase is sealed via the Pistons & rings therefore cannot vent via the carbs & exhaust
3 The rubbers in the head fins are to soak up vibration and to strengthen the fins to stop damage.

[JTGS850GL]

As to #3, they are not at all necessary and most people just pick 'em out and toss 'em. The original purpose was supposedly to quell high frequency vibrations for noise testing. There us no humanly detectable difference in sound with or without these dampers. There have been all sorts of crack-brained theories about these, and if you're very lucky you might see a few pop up here.

How's this for a crack-brained response... Suzuki was primarily a two stroke engine manufacturer before the GS series bikes. A two stroke engine tends to "ring" with large cooling fins and lots of vibration. Most common solution was to insert rubber dampeners to suppress the high frequency ringing. Suzuki just continued the practice when they developed their first 4-stroke counterpart. Later years the rubber inserts were eliminated from production.

[storm 64]

The rubber helps absorbs HEAT?? I've heard that one before... I have new ones on my motorcycles, well just because... Actually when I wanted new rubbers for the 1100e I order four of them. When I picked them up, I received four 5inch long cut to fit strips. Way more than I needed. Rubber Chicklets for everyone. ☺

[JTGS850GL]

The rubber absorbing heat would sure be a crackpot answer.

[geol]

I didn't think my way through the crankcase venting and I am sure that is a great response given by all of you. As far as the rubber things, engine ringing? Government engine ringing sniffers? Engines ringing louder than an exhaust? Well, maybe! thanks

[Brendan W]

Being a little picky but it's not simply a vent. Technically it's a recirculation system, back to the airbox.

[dorkburger]

Well, true. .... until the dreaded pods are installed.

[Brendan W]

In that case it just ends up in someone else's airbox.