3 degree cups on an Evo...

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Prof
Founder, Choppers Australia
Posts: 6018
Joined: Sat Oct 22, 2005 3:54 pm
Location: Willunga, South Australia
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3 degree cups on an Evo...

Post by Prof » Mon Dec 28, 2020 11:21 pm

Shaun dropped by a couple of weekends ago to get a set of 3 degree raked cups installed on his Evo. HD Big Twin headstem bearings were fitted into removable bearing cups until 1988. After that the steering head is in one piece with the races fitted directly into the steering head.

This means that on Big Twins up to '88 we can remove the stock bearing cups and replace them with the 3 degree raked cups and reinstall the front end with no modification. Later models require the outer races to be removed and 3 degree bearing cups pressed in their place. This necessitates a longer head stem to accommodate the replacement bearings which are now an extra 1½" apart.

Shaun's softail is post '88. and I have a set of cups with the longer head stem so it is all go go go. Shaun pulls the front end off. The top triple tree with handlebars and controls are kept together and laid back over the tank on a blanket. You can clearly see the one piece steering head in this pic...
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New set of 3 degree cups and longer replacement head stem. Because the new bearing cups will sit against the bottom of the steering head, the fork stops will no longer line up so a fork stop is built into the lower bearing cup. To prevent it from turning, it has a hole for a roll pin to lock it into the stearing head...
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Stock head stem is pressed and welded into the bottom triple tree...
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We grind off 3mm which will remove sufficient weld to allow us to press it out with my 30 ton press. If doing this at home you will need to remove extra metal and then knock it out with a sledge hammer, being very careful not to bend the triple tree. Best that you take it to a local engineering shop. Only takes a couple of minutes to press it out so shouldn't cost much. Take the new head stem with you so they can press that in...
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Old head stem pressed out. You can see there is still a couple of mm of weld that had to be broken...
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Shaun using a die grinder to clean out some dags so we can press in the new head stem...
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Sitting on the press ready to be pushed into place...
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Outer races need to be removed from the steering head so we can install the new bearing cups. A round of weld with the mig shrinks the race enough for it to usually drop out or come out easily with a couple of screw drivers as levers...
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Our top race would not play cricket as I got a tiny bit of weld onto the steering head. A G clamp is used to create a leverage point above the cup...
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All this time, the new bearing cups and races have been sitting in the freezer to shrink them slightly and make them easier to install... usually an hour is sufficient. These bearing cups also come without the outer races installed, so we install the cups first, allow them to warm up a little and then install the outer races.

So firstly, cups are now lined up (dots on the new cups) and pulled into place with a tool made from 7/8 threaded rod with a couple of machined bushes to accurately hold the new cups. A hole is drilled through the bottom race into the steering head and a roll pin installed.

Outer races are now taken from the freezer and istalled. You will often need to use a light brass hammer to line the races up as they have a tendency to tilt...
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The new head stem is 12mm longer than we need...
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A spacer is machined up...
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Front legs are slid into place and full lock (minus a little pinky width clearance from the tank) is measured up...
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Some scrap 6mm x 25mm bar is now marked and cut and welded into each side to engage with out new fork stop. I missed a couple of pics here. This pic of testing a piece after shaping and prior to cutting...
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Evo back together with an extra three degrees of genuine rake. Two things when raking the front end; 1. never use raked triple trees because then will reduce your trail to a dangerous minimum, 2. Raking your front end will put your handlebars closer to you and a little lower..
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Compare it with this pic taken a few weeks before and you can see the extra rake and extra space between the front wheel and the bike...
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Shaun is happy with the new set up... chopper handles better in the corners and is more stable on the road.
Chopit'nrideit... Prof

Joc
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Joined: Sat Jan 09, 2021 8:44 pm
Location: Neales flat
Interests: Choppers nd bobbers nd guitar

Re: 3 degree cups on an Evo...

Post by Joc » Thu Jan 21, 2021 6:21 pm

Great work prof front end handles th corners nd bumps much better. Thanks again Joc.

Prof
Founder, Choppers Australia
Posts: 6018
Joined: Sat Oct 22, 2005 3:54 pm
Location: Willunga, South Australia
Contact:

Re: 3 degree cups on an Evo...

Post by Prof » Fri Jan 22, 2021 9:22 pm

And the extra 3 degrees doesn't hurt low speed riding. Bike manufacturers could sure go out a bit further and produce a safer and nicer bike.
Chopit'nrideit... Prof

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