Mine idled very rough until I plugged the BIG hose on the passenger side, going to the air filter housing. The small hose should stay hooked up to wherever it goes. Also, check the other big hose on the other side of the housing, it runs down to the manifold. It is likely cracked (you can't see it until you pull it off) and this will cause a rough idle as well. Both of these things were wrong with mine when I first got it.
Good luck!

 

Alternatively you can just leave the small one open, it doesn't have to stay hooked to the rat's nest (if you still have one).

 

Just plugged my big hose, it eliminate the backfire I would get after runnig WOT and backing off quickly. I like it much better without it.

 

It's worth a try. As a temporary test, just put some duct tape over the hole like ASEmaster did. Just make sure the tape is good and secure 'cause you don't want it to get sucked into the carb.

 

I plugged the big hose from the coasting valve and it killed that annoying duck in a tornado sound and smoothed out the engine bucking while coasting in gear. I tried both having the small vacuum line open and hooked up to the yellow solenoid and I'm still unsure as to which set-up I should go with. All I know is that plugging the small vacuum line causes the engine to run rough at idle. What does this vacuum line do for the engine specifically? Should I connect it to the solenoid or leave it open? If open, what should I use for a filter - I want to eventually eliminate the rat's nest and have a smooth air box (one with no hoses) to take full advantage of the ram air.

 

damn. every estimate i've got is $35 for the part, and they all say they'll slap it on for free while the carb is being rebuilt. even hayes. i think $100 is too much to pay.

lean = all the fuel/air being burned in the motor
rich = some of the fuel/air being burned in the cat

combustion in the cats = hot exhaust

simple solution: remove cats and embrace backfire

 

I wouldn't do that, I'd plug it right at the shutter valve.

I don't believe you need a filter for that, I don't think it goes anywhere.

 

It must go somewhere because it's drawing a vacuum that when plugged, causes the engine to stumble. It's the small hose that connects the coasting valve to the yellow solenoid. I don't think that it would be a good idea to allow dirt to enter a line that's drawing a vacuum into the engine.

 

Sorry, I think I misunderstood you. I meant the small nipple on the shutter valve itself, not the actual line from the rat's nest. Obviously you can't just leave that open, it's a vacuum leak.

But still, you don't put a filter on a vacuum line! Again, it would be a vacuum leak and it will cause problems. I would take the hose off the solenoid and cap it there. That's what I'd do, but I dunno, I ditched the whole shebang when I had a Nikki. Either way, you have to cap that line, you can't leave it open.

 

Okay, so here's what I'll do and PLEASE correct me if I'm wrong...

I will remove the small hose that runs from the yellow solenoid to the shutter valve and cap off the solenoid. Next, I will remove the large hose from the shutter valve and cap off the shutter valve hole and plug the end of the large hose. This should do it, right?

 

Until I figure out where that vacuum is actually being drawn from, I'm only going to plug the large hose and leave the small hose connected to the yellow solenoid.

 

Good move Bass forget the rest.

 

Hey, whatever works, I'm just speaking from my past experience and what worked for me. I junked the whole rat's nest, plugged the big inlet on the shutter valve and left the small one open. I also plugged all the air inlets on the bottom of the air filter housing. For me, with my carb setup like this, my car ran perfectly. No backfires, no roughness, no nothing.

 

Is There a shutter valve on a 13B?

 

Are you running through a carb. or fuel injection? I assume that you are having backfiring problems.