Fork sludge cleaning

[ranxerox]

Great!  Thank you both.

[CDNRatMan]

  I used varsol (lots of it) to clean inside mine, swish it around, pump the tube up and down and yes try and get a pipe cleaner of a round brush down inside to get anything loose then I left them hang upside down overnight.

[outlaw]

The sludge that you talk about is the oil braking down, ( think how many times the spring will go up and down in the forks, ) + if you had a seal go it may take in water on the fork seal, what I have used in the past was a small bit of petrol, shake the forks up and down while pushing the tube in and out, leave to drain the crap out from the tube, then get a rag and wrap it around a stick then use that to clean it out, then put it back together, and ride it.     

[ranxerox]

Dipping into the knowledge well again, so many thanks in advance.

My right fork seal blew. Not sure why, but I reviewed the manual and got familiar with the process, including buying the tool on ebay.  A quick recommendation on that is the that the handle is basically a 2 foot 3/8" extension.   If you have a couple of longish extensions, then the tool you need to buy is the tip.  Cut's the price in half.

Anyway, on to the reason I'm here.

I disassembled the forks per the manual and I noticed a sludge  in the bottom tubes.  However, in the fork tube that had the bad seal, the sludge was drastically more, in amount and in thickness - goopiness.  I've changed the fork oil twice since I got the bike; the first time for maintenance, the second time to increase the viscosity.  Both times I used Red Line Synthetic.

So -

What is the sludge?

Can I prevent it from accumulating or better yet,  happening again?

What can I use to clean it out?  My first instinct was to hit it with a couple of cans of Brake Kleen, but I know that stuff can be too caustic for many parts.

Thank you again for all the help.