Hey guys, for background on the situation, I'm running a universal K&N filter which replaced the stock airbox. I jetted the carb as follows

Baron Jet Kit...(170 main, 37.5 pilot, Baron's needle, slot 4, stock PMS, 2.5 turns out)

I'm now getting a new popping on deceleration which never happened before. The only thing I've done since is remove the filter that sat at the bottom of the pushrod tubes connected to the "exhaust" hose from the carb. This filter would get covered in crud and then leak onto the exhaust pipes causing a horrible smell.

I've since extended that hose and routed it underneath the frame so the waste can instead spill out to the ground. I'm wondering if this open hose is now somehow allowing air back into the system causing a lean condition and thus the popping.

Thoughts? Should I place a small filter in the hose even though it's going to the ground?

All feedback welcomed.

Is the AIS still connected?

Popping on decel means lean condition
Did I check float fuel level idles speed 950? No air leaks new air filter?

AIS is removed.

I guess what I'm trying to ask is, would the removal of the filter from the end of that hose cause a lean condition or allow air to enter the system?

Outside of that, I can troubleshoot the lean condition independently. I just wanted to know since it only just started happening and I had rerouted that hose about a week ago so was trying to understand if there was a correlation there.

Thank you!

NickJFerro wrote:
AIS is removed.

I guess what I'm trying to ask is, would the removal of the filter from the end of that hose cause a lean condition or allow air to enter the system?

Outside of that, I can troubleshoot the lean condition independently. I just wanted to know since it only just started happening and I had rerouted that hose about a week ago so was trying to understand if there was a correlation there.

Thank you!

My SWAG is that they are not related. Especially since you did the hose about a week ago and didn't have a problem until you changed the filter.

Check and make sure you're getting a good seal around the filter/carb interface.

Make sure whatever is sealing the vacuum port on the top of the manifold where the AIS vacuum line used to connect, is in good shape, and not leaking. Check the torque on the exhaust flange nuts. Is it possible one of the exhaust gaskets is letting air past? Make sure the coasting enricher isn't cracked.

SKWEARpeg wrote:
Make sure whatever is sealing the vacuum port on the top of the manifold where the AIS vacuum line used to connect, is in good shape, and not leaking. Check the torque on the exhaust flange nuts. Is it possible one of the exhaust gaskets is letting air past? Make sure the coasting enricher isn't cracked.

Per your post in a different thread, I came upon this thread here.

http://roadstarclinic.com/content/view/46/104/

I believe that this is the same hose I'm talking about, since it seems to dump oil and does enter the carb from between the cylinders and likely the top of the head. In that other thread you mentioned how you should always put a filter on this line.

I'm running a K&N Universal but that mod was done about a year ago and did not have the popping noise. The popping noise only came about shortly after I ran this oil dumping hose to the bottom of the bike, since it was gunking up the filter it was previously attached to and getting oil on the rear exhaust pipe. Would having this line filterless cause the popping? I've made no other changes recently so it feels like a good place to check.

NickJFerro wrote:
.......The only thing I've done since is remove the filter that sat at the bottom of the pushrod tubes connected to the "exhaust" hose from the carb. This filter would get covered in crud and then leak onto the exhaust pipes causing a horrible smell. .

Your description is confusing, but make sure the hose you speak of is attached to the rear cylinder head vent and is not coming from the carb intake filter. The carb intake port should be plugged so it doesn't suck air.

Make sure the hose clamp holding the filter to the intake is snug and not super tight. I had a leak there on my old XS 650 which causes a lean condition. Make sure the hose from the rear cylinder is not blocked or restricted. If it is routed from the rear cylinder below the frame, it will not cause a lean condition. Mine is routed that way and does not pop.

Good to know, I will double check where that hose is coming from, and also check the snugness of the hose clamp.

Regarding the section of the carb that is supposed to be blocked off, does anyone have a picture of that?