Topic: flushing forks

[octagon]

anyone tried using kerosene to flush forks before putting in new oil? would this be a good idea?

[MCRider]

Good idea-yes and no. I think the manuals may even suggest it. But without a complete teardown, there's no way to get it all out before filling as its sort of clingy. There can be goop in the bottom of the tube that kerosene would be good for dislodging.

So... if you do it, maybe let it sit overnight for as much as possible to drain out. Also, pump them after the wait to pump it out the drain hole.

As a practical matter a little bit of kero in the oil probably would be unnoticable to any but the most picky.  I'd have to take them apart though.

[Alan F.]

I usually strip forks down their individual parts, then blast everything with brake cleaner and set things to dry on clean shop rags.
One of the last things you'd want is to have a hole in the damper assembly plugged with dislodged crap when pumping the forks full of kerosene...
One side would ride stiffer than the other until if it dissolves and passes through.

Just my .02

[octagon]

good points. was hoping flushing and changing the fork oil will improve the ride on my 76 750k - the front end is pretty stiff and unresponsive - have a feeling the seals need changing as well, but i'm trying to block that out.

[paulages]

another tip- when simply changing fork oil i stuff a rag around the top of the tube and blast compressed air into the fork, which pushes more oil out the drain. I'd also not recommend using the kerosene without a complete teardown, but if you're going to this might be helpful for getting the kerosene out after the flush.

[octagon]

i pulled the 10mm drain plugs at the bottom of the forks and no oil came out - loosened the cap bolts at the top of the forks and thought i'd wait overnight to see if anything seeps out. guess this is another indication new seals might be needed.

[MCRider]

i pulled the 10mm drain plugs at the bottom of the forks and no oil came out - loosened the cap bolts at the top of the forks and thought i'd wait overnight to see if anything seeps out. guess this is another indication new seals might be needed.

Without disassembly, you have to pump the forks to get the oil out. WAIT! Don't do it yet. Take it out in the yard. When you pump the forks the oil will come squirting out the drains for many feet. Don't do it in the garage unless you have a helper holding a catch can and you just do one side at a time.

You probably realize, don't take the top cps off without raising the front end on a jack of sorts. The front will collapse with even one cap off, plus the cap will shoot up like a rocket. They don't need to come off or even be loosened.

[GammaFlat]

...was hoping flushing and changing the fork oil will improve the ride on my 76 750k - the front end is pretty stiff and unresponsive - have a feeling the seals need changing as well, but i'm trying to block that out.

Your remark is a little surprising to me...  I'm looking for ways to stiffen up my K6.  Is it possible that your forks are not "trued" or not straight.  By "trued" I mean not aligned.  Fork tubes are aligned by tightening the bottom triple and bouncing the front end up and down by "weighting" and "de-weighting" the handlebars.  After doing this, tighten the top triple tree.  Also, make sure you have the washers in the top triple (very often missing) because if you don't have them, your upper triple will crack. 

[octagon]

i didn't realize that about the front end collapsing - will do that tomorrow.
as far as i know the front end is straight - it handles going down the road - i've only had the bike a couple of months and just now am getting it on the road. it sat in a garage for ten years, one of those deals, mainly (i think) with electrical problems. i've only put a few miles on it. getting a tag tomorrow.

[fastbroshi]

I'm with those that suggest breaking them down to their individual parts to clean.  When I took mine apart the cylinders that sit in the bottom of the fork had to be pumped a bunch after spraying with brake cleaner.  I didn't believe the amount of crud that came out after I thought they were clean.

[octagon]

well i got maybe four ounces at the most of oil out of each fork - bounced the front til nothing would come out.
added seven ounces of 10/30.
the old oil was dark but it wasn't particularly dirty, no water.
doing some other stuff to the bike but hope to ride it tomorrow and see if there's a noticeable difference.

[MCRider]

Now that you've done it once, you can do it again if the 10W-30 doesn't suit you (a little harsh for my tastes).

Put a full teardown on the menu for winter. The lack of oil may mean it turned to sludge. When I cleaned mine I removed the damper rod from the bottom and was amazed what was in there even after I thought I'd cleaned it.

[octagon]

good point - i was thinking seals and upgrade the bearings. thanks to all for the advice.