front fork issue

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Peter Restaino

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Hello to all. Im rebuilding my 1970 commando front forks. new stantions and all. I put in JS top cap upgrade. problem is after I put in the recomended 6 oz 10 wieght I feel during pushing up and down no damping effect on one and the other feels to dampen normaly. took it apart and checked for any issues and none found. the poppet valve looks correct . STUMPED
 
I used to have head-shake and twitchy issues with my 1973 Commando. I installed NYC Norton Fork Cartridge kit and the issues are solved.
It is an amazing transformation and I highly recommend this mod.
 
I did JS top cap and bushing mods to the stock damper tubes but the bike is not ready to try them. I must have something done wrong because it feels like I dont have oil in one but the other seems good. I find this really perplexing.
 
Air entering the damper tube from the top negates the hydraulic action of the damper because air passes through orifices much quicker than fluid and air is able to be compressed. Add some fluid and see if that helps, as Kommando implied...
 
Peter Restaino said:
I know I put 6 oz in and I took 6oz out when I took it apart
Click to expand...
Imperial or US? 180cc is 6,33 Imperial fluid ounces and 6.08 US fluid ounces so I expect you've probably put near enough the right amount in to begin with if you used US fluid ounces.
 
I put a tad over 6 us oz and it feels like nothing is in it. pushing it up and down with nothing bolted on it, just bare fork but the other one feels like there is dampening happening. I thought that I put the poppet valve on up side down but when I pulled it appart it looks right by a diagram from the manual but maybe my brain tricked me and so I will pull it appart again but first I will over fill it and see what happens.
 
The cartridge is a hydraulic mechanism. If it's not completely submerged, it can suck air instead of fluid. It should be obvious why that's a problem since air can be compressed and it's viscosity is very different than fluid...
 

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