Front Fork Rebuild

[osteoderm]

Hugh's tutorial is great, but my '74 fork internals look nothing like the "early"-style Hugh shows in that post. My dampers are as shown in post #8 above. Rubuilt my forks twice again this morning, test-driving between each, with the damper washers, rod, and piston is various configurations. I can only seem to make it worse, not better.

 

[tzimmerm]

Ok, to be precise, here is the order of the parts as they came out of my forks when I dissassembled them-

But it doesn't make sense to me that the little spring would be just stacked above the the longer one. I assembled one with the small spring sandwiched between the damper and the lower fork like this last night-

But it ended up shortening the over-all length of the assembled fork by about an inch and a half compared to the other yet-to-be-disassembled fork. One of the seals looks pretty good, and neither leaked in the 3,000+ miles I rode last summer with fresh fork oil added, so I’m thinking at some point someone replaced the seals, and perhaps re-assembled them incorrectly. I looked online for exploded views and re-read every fork thread I can find, and I can not find any info specific to this. I have both new seals in the fork lowers. I just need to tighten them up and add oil and I can throw them back on the bike. I just need to know which configuration is correct for 77 forks. Any help would be appreciated.

 

[650Skull]

This might help read the whole thread.... http://www.xs650.com/threads/35-mm-fork-damper-rod-diameter.44545/ ......Note 5twins post #10

 

[tzimmerm]

Thanks skull! I did not read this thread before, and correct me if I’m wrong but it would appear that perhaps my forks have NOT been previously dissassembled, but maybe someone pulled a shadetree fix and added the smaller valve springs at some point. My question now is this- when they are being called “valve springs” are we talking like the actual engine tappet adjuster springs?

 

[DogBunny]

The parts manuals call it a rebound spring. It should be assembled like your second picture, on the damper rod.
Some people call the damper rod a valve -- it does act as a valve, it has holes that fork oil flows through as the forks travel, dampening the action.
Do a search for the "Minton Mod" while your forks are still disassembled. It is a simple modification that will significantly improve handling.

 

[5twins]

Your forks had to have been apart in the past because someone added that little top out spring. '77 forks didn't come with that. The spring on yours doesn't look like an original top out spring, it looks longer. It could very well be an engine valve spring. The original top out springs are about 22mm long. They compress about half way when the forks are assembled so that lowers them about 11mm. Your added springs are probably too long if they're shortening the forks an inch or more. I would cut one in half and use half in each fork.

I like the idea of adding a top out spring to the '77 forks. They "clunk" upon full extension in their stock form without one. I also like the way this lowers the forks internally by about 3/8". I usually raise them in the trees a little bit anyway but this does the same thing without having to.

 

[5twins]

One more note - fork springs should be installed with the tight wound coils on top. Don't know why, that's just the way the manual says to do it. And if you want to stiffen up the fork springs without having to buy new ones, cut new top spacer tubes 1" longer than the originals.

 

[tzimmerm]

Lots of good info! Thanks to everyone. It looks like no matter what I decide to do, it comes down to a matter of preference. I’m not even sure if the main springs are stock or just very badly worn out, because without the extra springs in there, even with the spacers there would probably be a little extra room in the tubes. I might just put them back together with the springs I have now on the dampers and lower the front end the 1 1/2 inches. Or just put them back together the way they were. I don’t know if I want to switch up my rake geometry after learning how to ride and getting used to riding the way they’ve been. Is lowering the front by that much going to make a drastic change in handling? On the mintin mods- I have thought about it and it seems to me Maybe the reason the 77 was recommended to use 20 weight oil was BECAUSE it didnt have damper springs and it DOES have the beveled holes on the damper. There seems to be a lot of variables with the forks, and I’m not anywhere near “performance tuning” in my goals with this bike. The thought has occured to me that if (when) I ride a newer, modern motorcycle, this bike will probably feel like a sluggish dinosaur. I’ve experienced that with cars; going from driving cars like a 70 fleetwood, 79 continentals, and a 73 hearse to an 05 6 cly olds Alero made it seem like a race car. The point is I’m not really worried about “maximizing performance” on this bike. My time and money are better spent on keeping it roadworthy and rideable. I also don’t want to make too many changes to the stock parts so I can retain as much of the “original survivor” status as possible for whoever may buy it from me in the future. (Hopefully that’s not for a long time.)

 

[5twins]

Measure the free length of your springs. Stock '77 springs were about 472mm long. Dropping the forks 1 1/2" could be a bit much. The slight lowering many of us do only amounts to about 1/2" at most. Like I said, I'd just use one of your longer top out springs cut in half.