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Removing cap bolt from front fork of 850

Discussion in 'Norton Commando Motorcycles (Classic)' started by Joe Schlaberdowski, Oct 8, 2019 at 4:31 PM.

  1. Joe Schlaberdowski

    Joe Schlaberdowski

    Joined:
    Jan 1, 2017
    I decided to drain the front forks.and refill with hydraulic 20wt. (Power steering fluid). Going on short test rides there was a "not smooth" clunkyness. Took off the small screw at bottom of fork and started taking off the cap nut(bolt?) To drain faster and to refil. But the "cap" had a rod inside which started to come up with the cap; and something said "stop" until you find out. The oil that has dripped out already looks very thick and as if it's been in there since the last century, so not a bad idea to drain and replace, but just trying to be cautious.
     
  2. L.A.B.

    L.A.B. Moderator VIP MEMBER

    Joined:
    Nov 20, 2004
    Assuming the frame is supported?

    The damper rods are attached to the cap bolts so the forks need to be compressed once the cap bolts are unscrewed (raise the wheel and put a block underneath) so the cap bolts with damper rods attached extend from the fork legs.
     
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  3. Joe Schlaberdowski

    Joe Schlaberdowski

    Joined:
    Jan 1, 2017
    Just found a piece from L.A.B. on 25 Feb. 2009. But the advice about putting a wood block under the front wheel is a good addition. And I can see why.
     
  4. Jdub

    Jdub

    Joined:
    Dec 1, 2018
    I am told that the fork's internal damper caps wear over time and are the cause of the fork fluid passing too quickly and without correct damping. These items are not expensive and can change the character of the fork, so possibly worth looking into on rebuild.
     
  5. L.A.B.

    L.A.B. Moderator VIP MEMBER

    Joined:
    Nov 20, 2004
    Just make sure the frame is supported at the front end as there's no support from the forks once both cap bolts are unscrewed. I use a jack under the front Isolastic.
     
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  6. concours

    concours VIP MEMBER

    Joined:
    Dec 29, 2011
    I use a bottle jack under the from frame crossmember. Gently allowing it down to expose the springs/allow oil to be added. Note that adding oil is SLOOOOOWWWW.
    Or, it will overflow, and you will lose your volume measurement.
     
    Last edited: Oct 9, 2019 at 11:22 AM
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  7. Joe Schlaberdowski

    Joe Schlaberdowski

    Joined:
    Jan 1, 2017
    For all the above replies: Things to watch. Thanks guys. By the way, on jdub's comment about the caps wearing and a possible rebuild; is the rebuild easy? I know that's a relative term. Do that same thing day after day in a factory and it's nothing. First time if you've never seen it and maybe some time involved for the very average guy.
     
  8. L.A.B.

    L.A.B. Moderator VIP MEMBER

    Joined:
    Nov 20, 2004
    Yes. They are quite basic assemblies.

    Remove the fork spring, unscrew the damper cap, pull out the damper rod and piston(valve) then undo the nut to remove the valve from the damper rod. Edit: Watch out for the pin 067634 inside the valve.

    Maybe consider replacing the old damper assemblies with a set of Lansdownes from madass140.
     
    Last edited: Oct 8, 2019 at 6:15 PM
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  9. Joe Schlaberdowski

    Joe Schlaberdowski

    Joined:
    Jan 1, 2017
    Does madass have a web site?
     
  10. MichaelB

    MichaelB VIP MEMBER

    Joined:
    Jan 14, 2004
  11. Joe Schlaberdowski

    Joe Schlaberdowski

    Joined:
    Jan 1, 2017
    With the Cap Nut unscrewed and the
    With the rod and spring still attached to the Cap Nut can't I just pull out the whole damper assembly without undoing the rod attached to the Cap Nut? Wouldn't that be an easier way to refill the forks? With old oil having been in there so long would the damper assembly need cleaned in solvent? Also, is a slow drip from the small hole at the bottom of the fork leh sufficient to drain all the fluid from the fork?
     
  12. L.A.B.

    L.A.B. Moderator VIP MEMBER

    Joined:
    Nov 20, 2004
    Not really, as that would involve removing the wheel and unbolting the damper tubes from the sliders and you would still have to reinstall them before refilling the forks.
     
  13. kommando

    kommando

    Joined:
    May 7, 2005
    If you only undo one fork top nut at a time then the front end will always be supported by one spring, then its easier to compress the fork up and down and in doing so pump the oil out the drain hole. Fully complete the oil change including torquing up the fork top nut before staring the other side.

    If the oil is really old and is near to grease consistency then it all needs to come apart anyway.
     
    Last edited: Oct 9, 2019 at 5:27 AM
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  14. MexicoMike

    MexicoMike

    Joined:
    Jan 31, 2010
    Yep, back when I bought my Commando in '06, the bike that was in "Excellent condition - ready to ride across the country" (per the well-known seller of Britbikes who sold it to me), one fork had only rust in it, the other had some sort of black goo, possibly once known as fork oil. ;)

    I had to disassemble the forks completely and clean everything/install new kits. So be prepared for that if, as Kommando said, the oil looks more like grease. I would also add that even if it looks like oil, if it is extremely discolored, I'd do the rebuild.
     
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  15. Joe Schlaberdowski

    Joe Schlaberdowski

    Joined:
    Jan 1, 2017
    Beware of salesmen. Second on the bottom up list from lawyers. Yeah, ok. There are good salesmen just like there are good lawyers. But it's not everyday you find one of those good ones. When I was an owner operator hauling steel out of Pittsburgh (remember when the US made it's own steel?), we sometimes had to resort to diesel mechanics. Those garages HAD to do excellant work, and fast too. Because if not, their bad results would be broadcast on the CB all up and down the highway. True and trusted testimonials from the men whose businesses and lives depended it! So for the deisel garage, staying in business depended on keeping the guys on the road. It's probably getting to be like that with the classic bike community.
     
  16. jbruney

    jbruney

    Joined:
    Jan 5, 2019
    I have mentioned before how I hate doing forks right? I probably failed to mention how much better life is when you bite the bullet and overhaul them without pussyfooting. In the past now for me and glad I did. Seals & bushings aren't expensive and shall most likely be all you need to do for reasonable riding, though the stock springs are a tad squishy if you've got interesting road environments.
     
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  17. Joe Schlaberdowski

    Joe Schlaberdowski

    Joined:
    Jan 1, 2017
    After I give it a bit of riding I'll redo the forks. I'm thinking it's a cold weather job -- in a warm room.
     
  18. jbruney

    jbruney

    Joined:
    Jan 5, 2019
    If they don't leak then just drain, flush out the goo with some varsol(or your chosen solvent), & refill each side with quality oil (150cc- 5fl oz). Slowly. I use 30w.....others use various oils & play music to taste.

    Good fortune & happy trails.
     
  19. Joe Schlaberdowski

    Joe Schlaberdowski

    Joined:
    Jan 1, 2017
    Unscrewed the cap nut and took out the drain screw just on one side and let it drain (drip) overnight. Did NOT remove the cap nut by undoing the nut below it. Pushed the wheel up a little on a wooden block and moved cap nut and spring below just a bit to one side -- well, that's all it would go anyway. To refill I attached a stiff hose shaved thin on the end and flattened a little to the syringethe syringe is conveniently marked in cc's. The plastic hose (it came from the old rocker oil feed line I just replaced) screws on to the end of the syringe and the thinned and slightly flattened other end just fits past the spring. If you get it in the right place you can push the 20 wt power steering fluid in pretty fast without spilling it over the top edge of the fork tube. After getting things right, the fork oil change went pretty fast.
     
    jan nelder likes this.
  20. seattle##gs

    seattle##gs

    Joined:
    Oct 28, 2014
    the easiest way to fill the fork tubes is to block up the front of the motorcycle and remove the front wheel. Remove the big cap nuts, this will allow the forks to be raised and lowered by hand. Raise the forks about 2/3 of the way and fill with new fork oil. Pull the fork tube down and the oil will be sucked down to the bottom. Repeat untill the correct amount of oil is in the fork
     

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