Front Fork cap trouble

[Benjammin7]

All I wanted was to change my fork oil . . .
I did a little reading and decided I should really crack my forks open and clean them out a bit. I'm riding an 81 xs1100 standard with 24K miles. I wouldn't say it had been well maintained by the previous owner.

There was no air pressure in either fork. I had a heck of a time getting the fork caps off.

I'm thinking I might put in the progressive springs and figure while I'm here I might as well replace the fork seals (though they weren't leaking or anything).

I wonder if my fork caps are in too rough of shape to put back in. If I put in the progressives (eliminating the need for air) are there other fork caps I can use that will fit this model?

If this works, this will be a pick of my fork caps. Very corroded seal and I chewed the crap out of them with vice trying to get them off.

[bikerphil]

80-81 Standard will be the only caps that will properly fit AFAIK. Specials have a different thread and so do the early Standards IIRC.

[motoman]

If those are the original forks off that 81 Standard(Venturer1100), no need for progressive springs as they were already installed from the factory in that year and model only.

[skids]

I have an 81H and those forks (no air used) are the worst forks for bottoming-out when compared with the two 78E's that I have...

[MindWebs]

you might be able to find a different set of caps on fleabay, but another
route may be to locate a tap and die set to clean up those threads.

you'll have to look into prices,
it may not be cheap to get that size of tap and die.

also have a better way to add air and monitor pressure.
i can email that set of instructions if you'd like, it's a word document.
roughly $35 in parts needed, works great air gauge on handlebars to see pressure.
PM if intrested.

[crazy steve]

All the 'standard' forks used the same threads on the fork caps, so you could use the '78-79 type caps. But you'll need additional parts; the early caps have spring preload cams in them, so you'll also need the 'washers' (actually discs, as there's no hole in the middle of them, part 17 in the fiche) for upper spring seats. The '80-81 caps seat the springs directly.

You can't use any of the 'Special' caps, as the threads are different.

You're also missing the two o-ring seals for the caps, which is why they came off so hard. The PO used silicon sealer instead....

[bikerphil]

All the 'standard' forks used the same threads on the fork caps

Steve, I've tried screwing the early Standard fork caps in the later air fork stanchions and they didn't want to thread more than a half turn, something has to be different with them, and I have tried it with several different caps/stanchions.

[crazy steve]

That's interesting....

When I was rebuilding the '80 Special I sold, I used the later standard air forks on it and checked the caps against each other and tried them in the tubes; no issues. Granted, I can't be sure the forks I had were '80 or '81 (but I think they were '81 because they had the progressive-wound springs in them) but that shouldn't make any difference.

But then again, this wouldn't be the only time 'oddball' parts have showed up.....

[bikerphil]

I've got extra Standard fork parts from all years laying around here, I'm going to look into this further and report back.

[skids]

I tried to replace the air cap in an 81 with standard caps. I can't remember what the issude was but I think the threads are different. (or maybe not threaded into the tube far enough...the memory is failing me!)

[bikerphil]

Ok, here is the difference in the Standard fork caps, why they won't interchange. The 78-78 cap has 2 wider lips on it (red arrows) that prevents it from fitting down in the 80-81 stanchion. The thread sizes on both type caps are the same with a 1.0 pitch thread. Also note the depth difference of the threads on both types.

[crazy steve]

So if push came to shove, you could chuck the early caps in a lathe and turn those lips down and use them. I do remember someone reporting that they used the late air caps on the early forks, this would explain why....

[bikerphil]

Steve, yes, if you removed metal from those lips on the early caps, they should fit down, only thing would be there would only be half as many threads actually holding the cap down with the spring compressed. With the late caps, there may not be enough threads to let the cap fully seat. I'm going to try to make these caps fit with my spare parts, I will report back again.

[tarzan]

I would clean the threads up on the OP's caps, sand the wrench marks off and reuse them. It wouldn't take much work to get them functional and presentable.
Of course, run to the hardware store and get some o-rings that fit.

[bikerphil]

Here is the 80-81 cap threaded into the 78-79 stanchion. Notice that the cap will not thread all the way down ↓



Some material (0.075") would need to be removed from the 80-81 cap ↓



Picture of the 78-79 stanchion ↓



Picture of the 80-81 stanchion ↓



Notice the depth of the threads in the two types of stanchions, the threads in the 80-81 are further down than the 78-79 type.