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canisterectomy tank venting question

psikora

psikora

Member
I finally got around this weekend to a bunch of maintenance and other bike related work on my '94 R1100RS. One job was to follow the IBMWR-posted canister removal procedures. Somewhere near the end I either lost my perspective or didn't find what I was expecting to find. But I can easily summarize my question.

Of the two venting hoses coming from the tank, I'm not touching the fuel overflow one. But I'm not sure what to do with the other one, which appears to be some venting for the tank. Do I plug the end or let it vent into the air?

Thanks,
phil
 
The rim drain line exits down by the footpegs. You should route your tank vent line down there, too.
 
My 94 RS has been happily venting away for over 160K now, with no issues. I did the canisterectomy at the 3k mark and never had a problem.
 
Its simply cosmetic. BMW for their lack of cosmetic thinking in some cases (like those horrid brown colors in the past) will mount a component wherever it seems most convenient. Perhaps the charcoal canister could have been better hidden, like under the tail section of the seat, but that would negate the storage option.

Seems BMW at times still goes by "form follows function" and since the canister is a functional part of the emissions system to make it visible is a no-brainer. Other times, BMW decides a high muffler position on a sport touring bike is ok even if it make the saddlebag pratically useless. That one still gets me.

The looks of the RS is much cleaner without the canister hanging on the RH side. That's all. Well, also, the canister could someday become clogged and then not vent at all, which causes other issues.
 
Its simply cosmetic. BMW for their lack of cosmetic thinking in some cases (like thos

Thanks. Seems like a lot work for a cosmetic improvement.
Is there a way to tell if the canister is clogged?
 
Zaasu said:
Thanks. Seems like a lot work for a cosmetic improvement.
Is there a way to tell if the canister is clogged?
Click to expand...

It can be more serious. IF the canister becomes clogged it can cause a vacuum to form in the gas tank. People have reported that their fuel gauge has crushed/collapsed from this.

What I've heard is that you can feel it when you open the lid to add gas. I have no first-hand experience with this so maybe someone who has can describe it better.
 
Zaasu said:
Thanks. Seems like a lot work for a cosmetic improvement.
Is there a way to tell if the canister is clogged?
Click to expand...

It is hardly a "lot of work" and actually pretty easy. You yank off some hoses, undo a couple of clamp bolts holding the cannister, re-route one rubber vent hose and put two rubber plugs on the bottom of your throttle bodies! DONE.

The charcoal filter canisters are required in California for gas fumes and maybe elsewhere, not sure about that. They introduce a host of vacuum leak possibilities as your bike ages due to all the rubber hose connections and do little if anything to reduce pollution. If any gas splashes back down the line into the canister it is ruined and no longer works. If enough gas gets in there, it plugs up and your gas tank cannot vent and breathe.
 
PULL THE (DARNED) THING!

It's more than just cosmetics.
All of the above is true, plus -
The charcoal can be sucked into the cylinders because of high vacuum, causing quite a bit of damage.
Without the extra hoses and valve, you'll also get better vacuum at idle and just above idle - helping your bike run better. This will also make your idle & low-rpm throttle body sync process more consistent and more accurate.

Enter "charcoal canister" into the Search Forum box at the top right - there's quite a bit of discussion on this already.

I've not heard of anyone ever getting a citation due to the smog mod; California does not smog bikes (yet...). Maybe around Phoenix or Tuscon?
 
156327 said:
It is hardly a "lot of work" and actually pretty easy. You yank off some hoses, undo a couple of clamp bolts holding the cannister, re-route one rubber vent hose and put two rubber plugs on the bottom of your throttle bodies! DONE.
Click to expand...
+1 :thumb I removed the canister and related hoses on my new-to-me '04 RT-P this weekend in less than 5 minutes.

Your dealer has the vacuum stub rubber caps for pennies.

Five steps:

1. Pull the hoses off of the throttle bodies and install the stub caps.

2. Remove the now-useless hoses from the throttle bodies back to the purge solenoid.

3. Remove the hose from the other side of the purge solenoid that runs to the canister.

4. Unbolt/remove the canister (on my RT, and IIRC on the GS, unbolt/remove the canister's front frame clamp and slide the canister off its rear mounting tab).

5. Remove the tank vent hose from the canister and re-route the hose alongside the tank filler bib drain hose near the right swingarm pivot (there are three hoses at the canister: the hose to the purge solenoid which you just removed, the canister's atmospheric vent hose (which is not connected to anything) and the tank vent hose).

Have fun! :D
 
I ran a hose from one TB to the other to help equalize or stabilize them. I've not had much issue at all in syncing them and I've had it this way for the last 60K.
 
bdiver said:
I ran a hose from one TB to the other to help equalize or stabilize them. I've not had much issue at all in syncing them and I've had it this way for the last 60K.
Click to expand...

Interesting idea. Did you ever try running it with just the rubber plugs vs. a crossover hose? I wonder if it would make any difference.
 
156327 said:
Interesting idea. Did you ever try running it with just the rubber plugs vs. a crossover hose? I wonder if it would make any difference.
Click to expand...
The ports are so small compared to the length of the hose that the effect is minimal -- this just doesn't "help" somehow "equalize" the throttle bodies -- they adjust just the same, connected for not.

In the original arrangement, when the purge solenoid is not open the throttle bodies are connected to one another in the manner suggested by bdiver (with a third hose to the not-open surge valve). Having balanced multiple oilheads/hexheads with capped vacuum ports and with canisters present, I can say there is zero difference in balancing with either connected or separate throttle bodies.

I prefer to remove the hoses and cap, primarily because it gets rid of excess hose which can get cut and generate a vacuum leak; it also has the side benefit of removing a bit of clutter around the throttle bodies.
 
mneblett said:
The ports are so small compared to the length of the hose that the effect is minimal -- this just doesn't "help" somehow "equalize" the throttle bodies -- they adjust just the same, connected for not.

In the original arrangement, when the purge solenoid is not open the throttle bodies are connected to one another in the manner suggested by bdiver (with a third hose to the not-open surge valve). Having balanced multiple oilheads/hexheads with capped vacuum ports and with canisters present, I can say there is zero difference in balancing with either connected or separate throttle bodies.

I prefer to remove the hoses and cap, primarily because it gets rid of excess hose which can get cut and generate a vacuum leak; it also has the side benefit of removing a bit of clutter around the throttle bodies.
Click to expand...

This makes sense. When you consider the amount of air honking down the throttle bodies vs the tiny ports it makes sense that connecting them would not have much effect if any.
 
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