Tapered bearings.....How do they fit?
 

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I just picked up a Sportster Wide Glide front end identicle to this. I'm trying to mount it on my 2003 Sportster frame. What all do I need? I'm guessing the tapered bearings fit in a steering cup?

The cups should be in the frame. So long as they are okay and the bearings on the yoke assembly are okay and the sizes of each match then it should just go together.

This is based on me changing the yokes on a Sportster trike I assembled for the raked ones that Frankenstein supply.

In my opinion...

All new inner and outer races should be installed.

The steering cup as you call it is the outer race for the bearing. Bearings, whether ball or roller, wear into the races slightly till they get a perfect fit, kind of like rings in a motor seating in the cylinders. No two different bearings and races are going to exactly fit. On a wheel bearing, that's a potential bearing failure, on a steering head bearing that doesn't even turn a full circle, you might get away with it, and even if it does wear badly, you'll feel it and should get some warning a problem is developing. Would I risk that? Hell no, considering the work to replace those bearings when the bike is all together, I'd replace them now - that's the full set, bearings and both races - so they'll never be a problem. If you do replace the outer races, don't pound them in with a hammer, if you don't have a proper tool for it, get a long enough length of threaded rod and using spacers or sockets, squeeze them in that way so they go in straight with no damage. Use a good quality grease, not the buck 99 stuff, and coat everything inside the frame and the steering stem with grease to keep them from rusting. Packing the steering full of grease isn't a bad idea, but some thin viscosity synthetics can seep out the bottom.

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I was thinking the bearings need to seat INSIDE the neck tube also. There is no way a bearing is going in that tube. I had the frame built by Paughco. I measured the inside diameter of the neck with my caliper and the top & bottom is 1.30". Does it sound like Paughco didnt use the right size tube?

You need the taper races that go in the frame.. If the frame is the wrong size you may need both tapered races and bearings to fit. Or send the frame back.

I know this is 8 months old but with this frame you need external race cops to put the races into. The race cups get pressed into the frame and the races go into them.