Cannisterectomy on R1150RT - How?
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I respectfully disagree -- precisely for the reasons you list -- plus if the canister clogs, it can plug the tank vent and cause the tank to collapse and the engine to stall. I've removed the canister on just about every BMW I've owned.alanrd said:
Before describing how on the R1150RT, you need to understand the system.
When fuel vapor pressure builds in the fuel tank, it is relieved by passing through a hose to the canister, where the fuel fumes are absorbed on the activated charcoal in the canister. The now fuel-free air continues out of the canister through another hose to vent to atmosphere. The fuel fumes are removed from the charcoal either by the air returning to the tank, or by the bike's engine computer. When the engine running conditions are "right," the computer opens a solenoid valve to permit air to be sucked through the canister (where it picks up the fumes) and then out a third canister hose to the two throttle bodies. The engine's intake vacuum provides the suction to pull the air through so the purged fuel fumes enter the cylinders to be burned.
The canister vent path is also the path for getting air INTO the fuel tank as the fuel is used up -- from the atmosphere, through the canister, and back up the fuel tank vent line into the tank. If the tank vent line is blocked (for example, by dissolved charcoal from a soaked/ruined canister), no air can get to the tank. As the fuel pump extracts fuel to feed the motor, a vacuum builds in the tank. At some point the fuel pump can no longer overcome the vacuum and cannot keep the fuel rail to the injectors pressurized -- at which point the engine stumbles and eventually stalls. The short term fix is to open the fuel filler to relieve the vacuum to drive a few more miles at a time. The vacuum can also get high enough to cause the plastic fuel tank to collapse inwards -- on the K12LT's this would dent the fuel level tube and prevent it from going below 1/4 tank.
To remove the canister on an R1150RT, you need to re-route the tank vent hose to the bottom of the bike, and block off the hose(s) leading to the throttle bodies. My preference for blocking the intake hoses is to buy two rubber caps which fit the hose stubs on the bottom of the throttle bodies (dealer has them -- been used on flying brick K-bikes for decades).
Remove the hoses from the canister (but don't pull them off the bike yet). Remove the bolt/clamp holding the canister to the bike and slide it off.
Take the fuel tank vent hose and route it down along the subframe toward the same place the atmospheric vent hose ends. If the tank hose is not long enough, splice it together with the atmospheric vent hose and cut off the excess.
For the throttle body purge path, remove the hose from the canister to the solenoid valve(on the left side of the bike, near the top left of the fuse box).
From here, you can either remove the solenoid valve, or leave it in place and (i) cap it off (and leave the hoses to the thottle bodies in place) or (ii) remove the hose from the other side of the solenoid valve. My preference is to remove both hoses and then leave the valve in place so that I don't have to figure out some way to weather-proof the two-wire electrical connector which would otherwise be left dangling if the valve was removed.
If you choose to remove the hoses from both sides of the solenoid valve (I do, mostly because I like to get rid of clutter and unnecssary hose which can dry out and cause vacuum leaks), remove the hoses between the solenoid valve and the throttle bodies and install the rubber caps over the throttle body vacuum ports.
That's it.
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Good question.pbarney said:
I recommend it because I've seen *many* reports of disabled and/or damaged bikes (as well as first-hand incidents) from canister and/or vent hose clogging due to dissolved charcoal slurry. This was a *particular* problem with the K12LTs (in fact, there was a rash of them when the bike was new because BMW brilliantly routed the canister atmospheric vent hose to a point directly above the rear tire -- where it could suck in all the rain water it wanted during the fume purges!). This is also not time-, distance- or wear-dependent -- you can over fill the tank on the first refueling. The issue is whether fuel or water has accumulated in the canister, whether at 100 miles or 100K miles.
Is the design a guaranteed failure waiting to happen? Absolutely not. But, it is a not-insignificant potential problem that could immobilize my bike on a trip, and I prefer to eliminate unnecessary failure risks.
Some would argue that removing the canister unnecessarily increases unburned hydrocarbon emissions. My response is primariliy two-fold: (i) relative to the other hydrocarbon sources in the world, you could not begin to find the tiny amounts associated with removing a canister to be in any way statistically significant; and (ii) the amount of hydrocarbons released as a result of having to dispose of a ruined canister which has been filled with fuel would appear to far exceed the amount of fuel captured over the life of the bike if the canister were retained. Thus, I see the net environmental impact is at best a wash -- even if the amounts involved were actually significant in the first place.
FWIW, I used to work in the environmental field, and I am very pro-*meaningful* controls on waste streams and other sources of pollution, That said, the engineer in me has no patience for expending scarce resources on mandates which have little to no real-world environmental benefit.
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