Fuel evap system question

[activpop]

My Coppa has developed a miss at even throttle or sometimes a miss at slow accelerating from a stop. Never under more spirited acceleration. I suspect a possible intake air leak from the evap system which is still on the bike. You can see the cracks in tubing terminating at the throttle bodies, but that is only a few inches of tubing. Who knows what is going on under the tank. I will remove the tank this off-season to remove all of that apparatus. To determine if it is truly an air leak, can I just pull the two lines at the TB and plug the inlets to see if that is truly the cause? Will I have any problems leaving those two lines dangling there? I can plug them too. That cannister in front of the rear wheel needs to go. Will I devalue the bike any by not having it perfectly stock?

[docc]

Fine to cap the intake taps and see if it changes your issue. I finally sourced silicone caps that hold up much better to the heat cycling and fuel exposure.

With the tank off, you can "T" the tank vent and overflow together to route an exit behind the rear of the sump. I loosely zip-tie mine to the fitting for the oil evap return line. At some point, my funky, old tub-of-a-Sport started leaving a puddle on the lift, so I added a spooge catcher.

I've never seen anyone devalue a V11 that was without the evap mess. When I pulled mine off the early Sport with dual canisters in the underseat tool tray, I found there was twenty (20!) feet of 1/2" US fuel line and the mess weighed five pounds. Of course, I saved it in the cabinet full of Sport stuff.

 

[Lucky Phil]

4 hours ago, activpop said:

My Coppa has developed a miss at even throttle or sometimes a miss at slow accelerating from a stop. Never under more spirited acceleration. I suspect a possible intake air leak from the evap system which is still on the bike. You can see the cracks in tubing terminating at the throttle bodies, but that is only a few inches of tubing. Who knows what is going on under the tank. I will remove the tank this off-season to remove all of that apparatus. To determine if it is truly an air leak, can I just pull the two lines at the TB and plug the inlets to see if that is truly the cause? Will I have any problems leaving those two lines dangling there? I can plug them too. That cannister in front of the rear wheel needs to go. Will I devalue the bike any by not having it perfectly stock?

No get rid of it all.

Phil

[activpop]

1 hour ago, Lucky Phil said:

No get rid of it all.

Phil

That's the plan!

[docc]

I had a minor vacuum leak at one of the taps that gave me a fit before finding it. Similar fits when the rubber caps had cracked and loosened on the taps.

For a time, I used shortened bolts to block the vacuum access, but one time the threads pulled out and I went back to the taps with silicone caps.

[Lucky Phil]

2 hours ago, docc said:

I had a minor vacuum leak at one of the taps that gave me a fit before finding it. Similar fits when the rubber caps had cracked and loosened on the taps.

For a time, I used shortened bolts to block the vacuum access, but one time the threads pulled out and I went back to the taps with silicone caps.

I decided  remove the things altogether and just use a blanking screw and store the adaptors with my sync tool. One less point of failure.

Phil 

[audiomick]

On 7/13/2025 at 7:34 PM, activpop said:

... a possible intake air leak..

A way to check that which I have often seen mentioned is to spray brake cleaner around the site of the suspected leak with the bike at idle. If the idle speed goes up briefly after spraying, you've probably got a leak.

[activpop]

Found the problem. There was a leak somewhere in the evap system.  I pulled the tubes off of the throttle body taps and then plugged the taps. Runs like it should.  Need to pull the tank to rid myself of all that crap. When I do that I know I'll get into replacing other stuff too. One thing leads to another...

[docc]

28 minutes ago, activpop said:

Found the problem. There was a leak somewhere in the evap system.  I pulled the tubes off of the throttle body taps and then plugged the taps. Runs like it should.  Need to pull the tank to rid myself of all that crap. When I do that I know I'll get into replacing other stuff too. One thing leads to another...