Need a new intake for my ElectraGlide project. Want a Ness Big Sucker.

They don't make those for bottom breathers.

My thinking is I can use a top-breather version, and then find some bushings of correct ID and OD to go in the ears which will allow it to bolt right up.

Any reason that wouldn't work? Anyone know where I could get those bushings, or am I going to need some lathe time to make them?

 

I think that should work fine. I just make all my bushings myself on my lathe, so no idea where you would buy them. Send me the dimensions and I'll make you a pair.

 

That's awesome! I'll get it mocked up to make sure there aren't any other issues, then get the measurements over to you.

Thanks, man.

 

Omaha, I am planning on installing a Big Sucker on my 1990 FXR. I asked the same question on the Forum when I first joined a few months back and the answers I received (Dr. Hess) seemed to think that by installing the bushings I could get it to work. The only other thing that you will have to do is to plug up the passages cast into the backing plate that direct the oil into the carb., but that should be pretty easy. Let me know how it works out for you since I will be making the same mod. to my bike.

 

If I had to GUESS, I would GUESS that the oil passage directs blowby oil/gas to the outside of the actual air filter, not the inside (carb side) of it, so plugging them up wouldn't be necessary.

 

Omaha when I had the Big Sucker I used bolts and spacers / bushings that I picked up at the local Ace and ground the spacers down to the proper length. I believe that bolts are 5/16.

 

On the Big Sucker backing plate, the ears on the backing plate that bolt to the head have oil passages cast or machined into them that direct the oil blowing out of the heads to the radioused mouth of the backing plate where it attaches to the carb. The inflowing air then pulls the oil mist into the carburetor. But you may be right, the bushings will probably block off most the air going into these passages, so blocking off the passages might be a moot point.

 

Dr Hess: Got it mocked up. No surprises.

Here's what I came up with:

- Even with the carb well seated into the intake manifold, the backplate on the Big Sucker sits away from the heads. I measured the gap at 0.172". If you're feeling ambitious, you could build that into the bushings, turning them into a tophat shape. Otherwise, I'll just fill that space with washers.

- The stock bolts going from the plastic backplate to the heads are 5/16". I measured the corresponding openings in the backplate and got 0.42", so the MoCo built a ton of slop into that. I assume that is there to allow for variations in the distance between the heads. On the bushings, I think it makes sense to keep that clearance, so I think the ID should be the same 0.42". That's plenty generous on clearance, so if your closest bit is a tad smaller, that's fine, but I'd want to keep the ID at 0.40" at the smallest.

- With all the clearance between the bolt and the bushing, I think we want the fit between the bushing and the backplate to be close to snug. We don't need an actual interference fit. Just not a lot of slop. I measured the diameter of those holes at 0.515" +-, so I figure knocking a few thou off of that should work. Those holes don't look machined, so I'm not sure how round they are. That fit may end up needing some massage. I figure I'll deal with that when I get there.

- The actual thickness of the ears is exactly 1.5", so I figure knock a few thou off of that to make sure the bolts end up tightening against the backplate and not the bushing. The inside hole on the backplate is stepped at the front and the back, meaning the ID of that hole is larger than the measured dimension for most of it's length, and only narrows down to 0.518" for the last 1/8" or so at either end. All that adds up to the bushing needing to be close to the full length of the ear in order for it to catch that narrower "ring" on the outside end.

Thanks again! And call me if any of this makes no sense!






Looking at it, I'm not sure I see any reason to plug the holes. They run up into the ear, and there are O-rings at either end, so it's going to be sealed up.

 

The heads for my 91 bottom breather don't have the oil passages. That's why I used the 5/16 bolts with the bushings to make the Big Sucker backing plate work.

 

I may be confused or misunderstanding, but... Why do you have to worry about blocking passages that don't have anything blowing through them???