Forks and the "Joe Minton" mod

Kevin Werner

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I have done most of the Minton mod on my 81 forks but a question in my mind comes up. In the mod oil volume is increased to decrease the air volume in the forks. Thus as the forks compress the trapped air becomes a progressive spring. However, later XS650s have a preload adjuster that does not seem airtight. Will I be pumping fork oil out through the adjuster?
 
No, the adjuster is sealed into the fork cap with an o-ring. I've never had leakage problems with them on several different fork sets with the Minton Mods (and more oil).
 
No, the adjuster is sealed into the fork cap with an o-ring. I've never had leakage problems with them on several different fork sets with the Minton Mods (and more oil).
Thank you, oil level 6.5 inches from the top of the fork tube fully compressed?
 
I go 6". That's about 6.5 ounces of oil in the leg. The original spec calls for just under 6 ounces but that's not enough. These forks just plain work better with a little more oil in them.
 
The cap itself is sealed but I'm not so sure how well the adjuster is sealed. Your correct that the air space becomes a progressive rate spring, but it is anyway, by decreasing the available air volume you've just increased the spring rate.
 
The increased oil level only functions in the last 25% of travel. It’s an especially good remedy for brake dive. I have preload adjusters and it works fine. My fluid setting is 130 mm.
 
The cap itself is sealed but I'm not so sure how well the adjuster is sealed. Your correct that the air space becomes a progressive rate spring, but it is anyway, by decreasing the available air volume you've just increased the spring rate.
The adjuster cap sliding shaft has an O-ring but that area is subject to severe corrosion. I spent some serious time and effort cleaning up the adjuster restoring it to smooth action on several sets of forks.
You can (should) disassemble the adjuster by driving out the pin that acts as a stop against the ramps in the cap.
Keep in mind any work on the stock forks is bandaiding a crude, marginally effective system.
If you are hotrodding and after "modern suspension action", 70's 80's low budget tech is poor starting place. Sez the guy who's ridden a lot of miles on modded XS fork internals, including the minton mods on madness, and resto that had the mike's cartridge emulators.
Chief problem with all these is the lack of adjustability. The fork action you want cruising a smooth road in cool weather is quite a bit different than when trying to keep up with Chaves in the Ozarks at 85F!
 
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The fork action you want cruising a smooth road in cool weather is quite bit different than trying to keep up with Chaves in the Ozarks at 85F!
I would try to keep up with Chaves 35 years ago, now I am just happy to really enjoy the powerband of this motor at pace comensurate with my slightly rusty skills. (Yes that means back of the pack!)
 
I have RaceTech emulators in my Eleven Special and custom straight rate springs provided by Traxxion Dynamics. That forced the need for a fork brace that I sourced from Tkat before he retired. Even with 20 lbs of brakes on that thing, it's obvious that the tire makes better contact with the road. It was tuned for cornering on smooth pavement with switchbacks. It did not work well on broken Mississippi roads. Backing the emulator adjustment screw out one full turn fixed it. It soaks bumps up just fine now. This is a bit of a spendy option and there isn't much more you can do with stock fork other than 2 lb rotors from 650 Central. All spendy.

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North Carolina high speed sweeper.
 
The adjuster cap sliding shaft has an O-ring but that area is subject to severe corrosion. I spent some serious time and effort cleaning up the adjuster restoring it to smooth action on several sets of forks.
You can (should) disassemble the adjuster by driving out the pin that acts as a stop against the ramps in the cap.
Keep in mind any work on the stock forks is bandaiding a crude, marginally effective system.
If you are hotrodding and after "modern suspension action", 70's 80's low budget tech is poor starting place. Sez the guy who's ridden a lot of miles on modded XS fork internals, including the minton mods on madness, and resto that had the mike's cartridge emulators.
Chief problem with all these is the lack of adjustability. The fork action you want cruising a smooth road in cool weather is quite a bit different than when trying to keep up with Chaves in the Ozarks at 85F!
This year for the Ozarks I'm bringing an R1 with XS650 decals, so I can keep the last guy in sight haha
 
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