is it possible to rebuild the shock on an mc21?if so any mods i should consider.i will also refurbish the front end,anything i should consider for this?I have the time now i am awaiting a pgm,so any help would be great.
What suspension do you have? SP, SE, R? They can all be rebuilt, but the rear shock is pretty hard. _________________ james
Its not how fast you go...Its how you go fast.
MC21 Rothmans
RS250
RC31
CRF250X
748R
Porsche (many)
http://members.rennlist.com/j911brick/rennlist3_002.htm
The consumable parts on the SE/SP shock (seals, etc) are all identical to the Honda CBR600 F3, I believe.
If you want to revalve it, you could ask Matt from Tyga for the NSR F3 shock valve/shim setup and duplicate it on your own shock.
Alot of times, you can get away with jest refreshing them with new oil and a fresh charge in the cannister. You will need to fabricate your own service valve or buy an aftermarket end cap for your nitrogen cannister.
If you want to service the shock yourself, you can pick up a high-pressure bicycle shock pump to charge the shock. I picked up a Fox pump for about $20 from Ebay that pumps up to 200psi. Works awesome!! _________________ Paul Herr
'88 FZR4/GSXR/YZF Frankenbike
MY BIKE PICS
Anything you do will be an improvement. About all you can do for the forks is emulators. Your better off to get at least SP forks. Maybe even CBR600 F3 forks will fit, but I'm not sure. SP rear shock would be a step up, but if you can do Ohlins all the better. _________________ james
Its not how fast you go...Its how you go fast.
MC21 Rothmans
RS250
RC31
CRF250X
748R
Porsche (many)
http://members.rennlist.com/j911brick/rennlist3_002.htm
I wouldn't put air in a shock. Nitrogen is used as it is affected much less by temperature (changes the pressure) and is dry so won't affect seals and internal parts.
I wouldn't put air in a shock. Nitrogen is used as it is affected much less by temperature (changes the pressure) and is dry so won't affect seals and internal parts.
Yes, you are correct. Nitrogen is better. But how much?? Let me see; ambient air is at least 75% Nitrogen in the first place. The thermal expansion differential between "pure" (actually about 95%) Nitrogen and dry air is so small it is virtually undetectable. As far as corrosion goes, yes, that is a problem. How much so? Well, I worked on aircraft hydraulic systems for the Air Force for almost 10 years. They used dry air for the last 50 years, and switched to Nitrogen a few years ago because some of their 30-year old aircraft were showing signs of internal corrosion on the landing gear struts (the landing gear struts use air on top the oil as the internal "spring" ranging from 1000-3500psi).
I dont know about you, but I service my suspension about once a year. Never had any problem in streetbikes or dirtbikes using "dry air" instead of nitrogen, and save a ton of money by it. Actually, I would bet good money that my suspension will last longer than most because I change the oil more often.
Price-wise, I can service my own shock for about $3, not counting the initial $20 for the pump. _________________ Paul Herr
'88 FZR4/GSXR/YZF Frankenbike
MY BIKE PICS
I am also experienced in gaseous and hydraulic aircraft systems. The nitrogen I use is 99.9% pure and dry.
It's actually around 78% in the atmosphere but it's the 21% of oxygen that is the problem and if you live in an area like the UK a lot of moisture.
I personally don't want to put 'air' in my £500 shock absorber and I don't think it's fair to advise others to do this either without explaining the advantages & disadvangtages. The only advantage being short term cost.
last time i filled a shock i took it on site with me, being a pipe fitter/welder and splicing into 12" gas mains there always plenty of Nitrogen around for purging lines so if you take you shock to your local pipe fitter chances are that you will fill it for free
if you live in an area like the UK a lot of moisture.
Yep! That could be a problem! Sorry guys, but I live in a desert region...
Oh, by the way, doesnt the normal air that gets trapped inside your forks bother you at all?? _________________ Paul Herr
'88 FZR4/GSXR/YZF Frankenbike
MY BIKE PICS
I now use only nitrogen when rebuilding the shock. I have used normal air before, but that was when I was a boy and didn't know any better. Having said that, it was apart so many times that I don't think corrosion had any chance to set in.
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