Evap to crank case? (Hunting for hesitation)

[mathias]

I'm on a wild goose chase for what might be an air leak on my 1994 K75S - I have hesitation off idle, and it seems to be because the engine is running lean, since pressing the starter right before blipping the throttle helps the hesitation a bit.

Anyway, I see a few mentions here and there of an evap system having been standard on California bikes. If i understand things right, this consists of a hose going from the fuel tank, trough a valve on the hose, which then goes to somewhere on the crank case. The hose would essentially channel excess vapors in the fuel tank into the crank case. Often these hoses have been removed, and the crank case opening has been plugged up.

I don't have the evap hose, but in the off-chance that my bike started out in California, I'm to figure out where that hose would have gone, to make sure it's plugged properly. Can anyone describe where to look, or even better, have a picture of it?
I have a long list of things I've done and places I've checked, so it would be fantastic if it turns out this was the problem.

[Westone]

I recently plugged this very connection on my '88 K75S, as a PO had simply cut the hose running to the connection under the tank and left it dangling open.

The connection is on the top of the block, in the front and centered, under the radiator. In order to access it easily, remove the plastic air intake tube that runs from the right side of the radiator and press fits into the bottom of the air filter box. It will be easier to see then.

I capped it with a 5/32" rubber vacuum cap from the auto parts store.

[mathias]

Aha, found it! It was capped off properly, so unfortunately that didn't end to be the problem. The search goes on...

I wonder if all K75s has that vent connection, but it's only used on the California models?

[Scott_]

Aha, found it! It was capped off properly, so unfortunately that didn't end to be the problem. The search goes on...

I wonder if all K75s has that vent connection, but it's only used on the California models?

I think that vent connection was on all US bikes, then BMW wouldn't have to worry about where the bike ends up after it hits the shores.....

[K75RT Keith]

Since I'm late to this party, I'll ask my regular dumb questions. 
Have you:
Checked for leaks at the rubber intakes on the throttle bodies?
Replaced the crankcase vent hose (Z shaped)?
Replace the Fuel filter lately?
Checked the Filter sock on the bottom of the fuel pump?
Confirmed that the TPS is set properly?
Checked the timing, and valve adjustment?
Confirmed the the air filter isn't clogged or there isn't a bunch of junk in the air box?
Made sure the Mass air is seated functioning & properly set?
Checked compression?

[mathias]

I've done most, but not all of the suggested stuff:

Fresh rubber above and below the throttle bodies.
Old crank case vent hose, but carefully inspected.
Fresh fuel filter and sock.
TPS set.
Freshly checked valves (exhaust needed new shims)
Nothing done with the timing.
Fresh air filter, squeaky clean air box.
Mass air is moving freely, and adjusted as well as possible, considering.
No compression check.

New spark plugs.
Fresh oils and coolant.
Checked for air leaks with both carb cleaner and propane, no change in idle speed.
Checked the resistance of the temp sensor - 2.2k at room temperature. I've seen differing numbers for this, is this normal?

[Westone]

Probably not related and I'm sure you've considered it if it is/was an issue: how much slack is there in the throttle cable? I ask because I had a similar issue this week after adjusting the throttle body valves on my K75, hesitation coming off of idle while the bike was moving. The TB valve adjustment and concurrent idle adjustments left about a 1/4" of slack throttle travel when coming off idle. I took all the slack out of the cable and problem solved.

I don't know exactly what the TPS does, but I have read there are times when the injectors are not feeding fuel to the intake based on its position along with other inputs. The dead space in throttle below idle had a negative effect on the behavior of the engine, and not just when accelerating from idle. In some circumstances when decelerating it would feel like the engine died. Taking the slack out of the cable resolved that in my case. The TPS clicks on and off exactly as the throttle reaches and leaves the end of its travel at idle. I like the way it behaves much better.

[mathias]

No, the throttle cable operates beautifully, settling back against the set idle position very nicely. And the TPS clicks at the right time, just as you start twisting the grips.

In fact, I'm amazed at the precision of these things. Before this, all my wrenching was on a beat up Vespa! On the other hand, the Vespa has no TPS, FPR, fuel pump, AFM, temp sensor...