Fork dismantling question

[pinholenz]

I am struggling to get the bottom damper bar out of my forks -  and Haynes is not helping. The book recommends using a 1/2-20 bolt and a couple of nuts to create an extension bar to fit in the damper hex inside the lower tube. What is a 1/2-20 bolt head?.

A 19mm bolt is too big. Can anyone tell me what size bolt to use please?.

(Intuition  tells me that it would be the same as the spring retaining hex at the top of the tube - which happens to be 19mm)

Cheers.

[The Prophet of Doom]

1/2-20 is one of those ghastly imperial things.  1/2 inch (12.7mm) 20 Threads/inch  Head is 3/4 inch (19.2mm) flat to flat


Hard to get stuff like that except in Lyberia, Myanmar and one other country (all three being too busy fighting wars to start measuring things properly)


Nearest I could find was an old 1/2 inch galv bolt that measured 18mm flat to flat. Did the job OK
I don't do it like that any longer as the whole Haynes double nut / tape thing is a pain in the arse.  Easiest way is a rattle gun on the bottom bolt if you have access to one.  The torque will undo it without having to poke anything down the tube.


Good intuition PinholeNZ

[pinholenz]

A couple of hours fiddling and I have finally got the first damper out - more by luck than science. I managed to jam something down the tube to just hold the damper sufficiently to get the securing bolt loose.

My 19mm bolt should have worked but it was a fraction oversize and too tight a fit. And the  fitting on the damper was shaped like a socket wrench, not 8 sided like the securing screw at the top of the fork.

For the next removals I have some 12mm threaded rod about 750mm long. The nuts for this happen to 19mm. I have two nuts at each end tightened against each other and this will form the extension into the tube with a wrench at the top end to hold it while I work at the bottom to loosen the 8mm hex bolt. I am sure that this is old hat to you seasoned wrench-monkeys, but this is the first time I have ever replaced fork dust seals.

Boy, were they knackered!

Thanks POD

[jefferson]

A little file work on the flats of the 19mm should have worked to get it down to the right size, but as pod stated, use an impact on the lower allen bolt before removing the cap and spring and you won't have to worry about holding the damper rod.

[pinholenz]

After draining the oil, can the bottom allen bolt be removed completely before the cap and spring are removed? Thanks

[The Prophet of Doom]

After draining the oil, can the bottom allen bolt be removed completely before the cap and spring are removed? Thanks

Wouldn't you just scuff it all up from the spring metal rubbing on the damper metal?

[jefferson]

No real need to drain the oil before hand. The oil will drain when you remove the bolt and then you can slide the leg off.

[admin]

A couple of hours fiddling and I have finally got the first damper out - more by luck than science. I managed to jam something down the tube to just hold the damper sufficiently to get the securing bolt loose.

My 19mm bolt should have worked but it was a fraction oversize and too tight a fit. And the  fitting on the damper was shaped like a socket wrench, not 8 sided like the securing screw at the top of the fork.

For the next removals I have some 12mm threaded rod about 750mm long. The nuts for this happen to 19mm. I have two nuts at each end tightened against each other and this will form the extension into the tube with a wrench at the top end to hold it while I work at the bottom to loosen the 8mm hex bolt. I am sure that this is old hat to you seasoned wrench-monkeys, but this is the first time I have ever replaced fork dust seals.

Boy, were they knackered!

Thanks POD

glad you got it working.
I could be wrong but I think you might just need a 17mm allen socket and long extention  to hold these
I've done them a few times but, haven't in a number of years now
think I bought the socket from my regular mac tool guy, wasn't too expensive.
-R

[MikeScoot]

I'm about to do mine, so this thread has been very helpful. I now know;
The XZ550 damper rods have a 19mm hexagonal recess in the top end which is used to stop them rotating while the hex-headed bolt is removed from bottom of the fork leg, thus releasing them (damper rods) from the fork leg (slider). A 19mm bolt head will be too tight to easily fit into the damper rod's recess, so it (the bolt head) needs to be very slightly smaller than 19mm or it will not fit easily.
Off to the hardware store tomorrow with calipers in pocket. :-)

[Walt_M.]

When I did it I used a 3/4 inch hex bolt with 2 nuts jammed together for the socket, I'm in the US and they're plentiful. it does require a lot of force to get them apart as they are locktited. I did ruin the hex on 1 with an impact gun and had to drill in out so I recommend you don't do that. Good luck.

[kevin g]

I just had mine apart.  I used a spark plug socket that has a hex on the bottom.  I have two different ones that have a 3/4" hex and just measured them at 18.7mm.  I used three ratchet extension with the first one put through the socket end so the hex went into the damper rod and it fit perfectly and viola, the bottom bolts came right out.

[MikeScoot]

Thanks for the tips fellas. Well armed with info. now :-)