View Full Version : Sportster Intake Manifold
05-28-2010, 12:51 PM
Hi guys, building an old Sportster and have a problem with the intake manifold. When I place it against the Heads there is a small space and it does not sit 100% correctly on the heads. If I make it sit flush on the heads as it should it sits slightly farther back leaving a small space in the front. The space isn't too big but enough to cause a problem. Not to mention I can't even get the O Rings on without falling off. How can I create a better seal? I saw on JP that they have a Manifold Adapter Kit PN: 4000200, not sure if this would help me. I'm using all stock components. I wish that the intake manifold would actually fit inside the port on the heads, that sounds like it would have been a much better fit, but maybe there is a reason they designed them this way. Any help is appreciated.
05-28-2010, 02:38 PM
Sounds like you need to know the secret of installing "O" rings. There will always be a gap. The "O" ring will seal this gap. Roll the "O" ring onto the manifold flange. Hold the manifold in position and roll the "O" ring into the gap between the manifold and head. Install the clamps. Adjust manifold for correct position and tighten the clamps. :D
05-29-2010, 12:08 AM
remember stroker plates? now those played heck with manifold fit,drive ya crazy till u figured ya needed an s n s one.in the bad ol days we would set the o-rings and wrap the joint with pvc electical tape,held the manifold in place,don't know if it was wise,but they didn't leak.
05-29-2010, 02:15 PM
I really do appreciate the help guys, it helps to have forums like this where I can pick your brains. I guess it was just a poor design. I was telling my father I thought it would have been better if the intake manifold was slightly smaller in diameter to the intake ports on the heads this way it could actually fit inside the ports on the heads just slightly for a perfect fit, makes sense to me. I guess everything was crude on these motorcycles back then. I'm trying to get this bike ready for the Rhinebeck meet but I don't think its going to happen. Having my generator rebuilt and still waiting on some chrome to get back, not to mention its fighting me every step of assembly. Thanks again guys.
06-02-2010, 07:22 PM
1) You need to "install" the intake when you put the heads and cylinders on. They can rotate quite a bit. Loosen the cylinder base bolts and wiggle them around till you have the best possible fitment for a seal. It still will not be perfect(See Chris's o-ring post above) but without this step, it will leak air, you will run lean, bike will run like crap. This is in the service manual.
2) Get the air craft style clamps if you not worried about correctness. These are the ones that wrap all the way around and have one long bolt secured in one side.
3) Use a carb support bracket, or air cleaner support bracket, else it will leak.
4) Forget about the adapter seal kit, Teflon tape, or any other BS. Do 1,2 and 3 above and all is good.
To install, it sucks. Push the o-rings on the heads or manifold, wrap the clamps around, curse when the o-ring goes flying, try again. Be careful of carb and other stuff clearing the bolt of the clamps. After installing, feel around the seal for any major gaps.
06-02-2010, 07:39 PM
Joestuff has it right. There is also a surprising amount of wiggle in the heads. You can loosen the head bolts and the base cylinder nuts, make the best mate you can (you should be able to get it pretty close to flush) then carefully tighten the nuts and bolts.
You have to be real patient clamping the manifold on, making sure the O rings aren't twisted. After you get it on and the bike running, use WD40 or some such substance to check for manifold leaks. No matter how careful you were or how good the mate looked, it often takes more than one try to get a good seal. If your bike is running hot at first start-up, a manifold leak is most often the culprit.
The carb support is a must. I haven't seen it in a while, but back in the 70s we used to put Mikunis on all our choppers. They were held on by a piece of flexible rubber hose, and their was no easy way to support them. Even though they're a light carb, they still fell off. More than once, I've seen a carb bouncing on the pavement at the end of the throttle cable while guys were going down the freeway.
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