Fork identification & rebuild help

[Muckroot]

Hello,

I have a set of forks I'm trying to rebuild and I've got a bit of a quandary. I purchased this set of forks with my XS650 under the assumption that they were XS650 forks but that does not appear to be the case! 5twins suggested in another thread that they may be from an XS500 given that the top caps secure with a circular wire clip instead of the screw in socket style cap, as well as the forks sporting what appears to be an 18" wheel. I've got a few more pictures and was able to get one of the forks apart with surprisingly just a couple Allen wrenches, a screwdriver, a knife, and a pair of needle nose pliers.

First, here's the forks semi-complete, with just the top triple tree removed:

Next, some shots of the rim:

some of the info from the brake caliper:

And most importantly, the forks themselves:

something I found very interesting is that there is no receiver for any kind of tool to hold the top of the dampening rod stationary while the bottom bolt is screwed in during reassembly (sorry for butchering the terms) Here is the top of the dampening rod, where on a set of 650 forks a big Allen bolt would fit in. It's completely smooth.

And lastly, the fork seal:

Here's what I need to know:
what do these forks go to?
where can I buy new seals and wipers for them?
are there any other parts that I should service in the forks while they're apart?
what is the correct fork oil capacity for these forks?
is a 650 brake caliper compatible with these forks or do I need to rebuild the caliper that came with it them? how can I measure the bearing rod(?) to find neck bearings that will fit these forks and the XS650 neck?

Also, how do I get the fork seals out? I beat the one up pretty good trying to remove it but had no luck. any advice is welcome.

Best, Muckroot

 

[stinky78]

hi MR, those fork seals are 33mm and the wheel is 18 inch, so definitely no xs650 parts, I had a link here somewhere to fork sizes for different bikes, here you go - http://organ-donor.org/motorcycle-data/fork-tube-diameter-list/#tube33 xs400 could be it, wheel size matches I think.

 

[timbeck]

I use an inexpensive seal removal tool. No mess and you don't beat up the lower legs....

tim

 

[5twins]

Some more info would help, like the fork tube diameter and better pics of the brake caliper. Get pics of the front side, the back you've shown doesn't tell us much. I can tell you those aren't 650 type brake pads, these are .....

Here's a late style 650 caliper .....

 

[Muckroot]

xs400 could be it

I think you've nailed it! I found a YouTube video of a guy rebuilding XS400 forks and every part he shows in that video looks identical to the parts I found in my forks, most noticeably the lack of brake caliper mounts of the left fork lower as well as the lack of the use of some long tool to hold the dampening rod in place from the top of the the fork while the bottom bolt is removed.

My next concern is even if I can successfully rebuild these forks will the tree that goes to these forks work with regular XS650 neck bearings? I'll measure the post on my tree and report with what diameters I observe.

https://www.mikesxs.net/yamaha-xs650-steering-stem-tapered-bearing-kit.html

better pics of the brake caliper

I'll get you those caliper pics and pad pics ASAP. if I can use a 650 caliper that would be fantastic. the caliper I've got has definitely seen better days.

 

[Muckroot]

Ok, so I gave measuring the tree a shot but I could only find a tape measure so I kinda eyeballed it. It looks like the bottom is 30MM, and the top where I assume the top bearing sits is 26-27MM. I'm headed to harbor freight for the weekly run so I can pick up a cheapo slide caliper and remeasure in about an hour.

as for the caliper, here are a couple pics. it resembles the caliper shown on the 650, but the pads look different.

the cup is locked up inside the cylinder, and im fairly sure it's missing a piece that sits in the cup to butt up against the back of the pad but I don't know for sure.

 

[wrenchjohns]

In a prior thread, you stated

I have no interest in building a wackadoo Frankenstein bike

and here you are. I recommend stop beating your head against the wall reduce the pain by getting the correct front end. Check the Classifieds here, check the online auction sites, good deals are available if you're willing to wait till "your deal" pops up.
john

 

[Muckroot]

Found my calipers, Here are more accurate measurements of the steering stem.
Will aftermarket XS650 neck bearings fit this stem?
A= 26mm in diameter B=30mm in diameter

getting the correct front end

I'd love to do that, but I'm trying to be thrifty and practical. Here are my pro's and cons.

Buying new springer:
Pros:
Would look exactly the way I wanted
Would ride decently
Would impress all the ladies (harhar)
Cons:
Have to wait 8-9 months to save up enough to even scratch the surface of cost.
prevents me from spending money on other parts of the bike to get it road worthy much much sooner

Buying correct 35MM XS650 forks:
pros:
Lots of reading material and data available for rebuilding.
guaranteed to fit neck bearings and has a huge aftermarket
Cons:
require more tools than XS400 forks that I don't already own
cost more money just to buy used forks than to rebuild XS400 forks
parts from XS400 front end may not fit XS650 triple tree or axle, such as caliper, wheel, bar risers, and tach brackets.
bigger than 33MM forks and not as skinny as I'd like them to be.

rebuilding 33MM XS400 forks:
Pros:
already own the forks, cheapest to rebuild
Already have triple tree rebuilt that fits these forks & has the tach mounted as well as a set of decent bars
already have all the tools to rebuild these forks
Skinnier than XS650 forks, more in line with the look im shooting for.
Cons:
have to find neck bearings that will fit. Might be able to use aftermarket XS650 neck bearings, might not.

I think I've got most everything on there. These forks will not be the easiest to work with. But they will get me on the road far faster and cheaper than any other option, and I think they'll look halfway decent to boot. I was really hoping I would only have to wait a couple three months to buy a springer, but they turned out to be waaaaay more expensive that what I had thought. So I'm going this route. If it turns out that I can't use these forks because the neck bearings just won't work, or the load bearing capacity is too low for a 650, or some other reason then I'm only out 7$ for the seal puller I bought (which I can use on the 650 forks anyway), plus whatever percentage of the 800$ I paid for the bike the XS400 make up. Overcoming challenges is Half the fun of building a custom bike. Looking cool riding it is the other half.

 

[5twins]

According to this chart, bottom 650 bearing should fit but not the top one .....

But, there looks to be a bearing listed (midway between the top and bottom 650 ones) that may work. Are you sure the top bearing goes where you've indicated and not on the section above the lower set of threads?

 

[wrenchjohns]

Update: the OE races are not interchangeable per Partzilla (which is a great resource) just look up the part, even if no longer serviced they show OE interchange between year, make and model. This does not mean that you can't find bearings to make it work. Don't forget, the length of the stem counts also.
john

 

[Muckroot]

So, looking at a set of XS400 bearings from dime city cycles, it would seem that the correct "d" measurements for the bearings are actually 25 for the upper and 30 for the lower. and both "D" measurements for the upper and lower are 48, same as the 650.
bearing-kit-steering-xj550-xs400-rd400.html

from the picture of these XS650 bearings it can be seen that 25 and 30 are the correct inside diameters for a stock stem
https://www.dimecitycycles.com/steering-stem-bearing-kit-xs650.html
but it doesn't verify the 48MM outside diameter for the races.

This chart from Allballs gives specs for the bearings shown in the pictures on dime city cycles for the XS400 neck bearing kit.
Those two bearings being the 99-3515 and the 99-3509
The ID and OD for the XS400 bearings sold by dime city cycles seems to match the ID and OD of the bearings for an XS650. The difference is the width.
the XS650 top bearing width is shown as 11, whereas the top XS400 bearing is shown as 13,
the bottom XS650 bearing width is shown as 9.5, whereas the Bottom XS400 bearing is shown as 12.

I don't think this is a deal breaker because the cups that the bearing races fit into on the XS650 neck are quite deep. They should allow for the bearings to fit properly. Is this assumption correct? If they stick out a mil or two is that a deal breaker?


will the length of the steering stem be an issue with only a 4.5 mil difference in the width of the bearings?

 

[Muckroot]

Are you sure the top bearing goes where you've indicated and not on the section above the lower set of threads?

I'll try and figure that out right now.

length of the stem counts also.

The info about the stem length should shed some light on which bearings would be ideal to use, the XS400 or the XS650.

Just knowing that both sets of bearings have the same ID and OD is a huge step, and would lead me to believe fitting XS400 trees to a 650 neck is completely doable.

 

[wrenchjohns]

xs2 Stem OAL 8 3/4" bearing to bearing 6 3/4" these are tape measured verynear .
john

 

[Muckroot]

Here's what I got. from what I can tell, the top bearing will end up sitting on the threads of the stem, which I measured at 25MM. that is, unless the bottom bearing moves the bottom tree down, thus lowering the stem as well. in these pictures I've got the tree pushed up into the neck as far as it will go. I would guess this arrangement would work, but it'd be a bit sketchy. Not a deal breaker for me personally, unless someone has info about this being dangerous or not working. I'm guessing this would work for a good while before problems started cropping up.
These are Millimeters btw:

 

[wrenchjohns]

One more thing to consider, any wobble in the top bearing gets seriously magnified at the wheel. The top bearing must fit it's mounting point on the stem cleanly but not an interference fit without wobble. My concern would be, if it lands on the threads are they going to hold up and not mash down with the inherent vibrations of this bike.
john

 

[Muckroot]

My concern would be, if it lands on the threads are they going to hold up and not mash down with the inherent vibrations of this bike.

Excellent point. I think what I aught to do from here is buy the 650 bearings and see how they'd fit, and if they land on the solid part of the stem then great! if not, then the stem just plain won't fit this bike, and I need to go about "converting" to the stock forks. plus I can hang on to the bearing I bought and simply use them for the stock tree. I'd love to make these forks work because like I said, they seem to be a fair bit skinnier all assembled than the stock forks are, but if they are dangerous then they aren't worth it. Thank you all for your input. any other recommendations are welcome!

 

[stinky78]

I wouldn’t want 33mm forks on my 650 I’m actually thinking of one day upgrading my 35mms to something thicker, 35s are noodly enough already without going down to 33, I would get a complete 35mm front end and sell the xs400 one on ebay or something, no point in spending money to make it handle worse.