Recently changed my fork oil and the stuff was like sludge due to the grime it contained. Did not bother with fork seals as these were not leaking. Suspension performance has improved. How often should this be changed?

 

its covered in the owners and service manual,50k, but, in reality, i think, the environment you ride needs to be considered when figuring your service intervals.

i changed my fluid twice in the last year and the second time, there was an insane amount of sludge from dirt/dust in there.

 

I went 10 years and 30,000K...that was too long, the oil that came out was black and smelt like swamp water.

 

Last winter i changed my fork oil and i couldn't believe what came out,had never change it before.So i decided to replace it again in 2 years when i change my break fluid again.that will put between 10 and 20,000 + miles on the fork oil.At that point i will determine a routine interval to change out the oil.The 50,000 mark that harley recommends is for complete disassembly of the fork tube(off the bike)and clean, inspect and replace any worn parts.they do not have a specific interval for oil change.Thats why from 2013 on there is no fork drain.They don't want you to just change the oil,they want a complete inspection.

 

For pre-2013 bikes, e.g. 2007, is there an easy way to change fork oil then?

 

https://www.hdforums.com/forum/sport...s-install.html
Just follow this without the spring change part.

 

Thanx!

Any reason why you say: "Compress the forks fully before adding new oil."

 

That's only necessary if your putting different springs in as you have to do the level by measuring. If your keeping the stock springs just fill it up with the amount of oil specified in the service manual for your model.

 

See HOW TO videos on youtube. The air gap at the top is critically important to get exact as it acts as a spring assist and bump stop. Too much or too little will cause big issues with ride and handling. Best way is to measure directly with a Turkey Baster or similar device. Mark distance on it (provided by service manual) with marker measuring from tip. Insert to mark and suck out excess oil until it sucks air. I would not rely on oil quantity as some old oil will be left in forks throwing the air gap out of wack using oil quantity added. To measure air gap you need to fully compress fork and only have certain parts in fork during measurement. Service manual should mention which components are in fork at time of measurement.

I have 20,000 miles since last fork oil change and old stuff smelt really bad and was consistency of mud. Used Lucus synthetic this time round.

 

I always recommend 20K between fork oil changes for cruisers and 50K for baggers

It's not that crucial to do it that often