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92' xr600 forks on a 79' xr500...?

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Hey there everyone. I'm new to this great site due to a recent pick up of an 79 XR500 in decent shape. I've been soaking in all the info and searching everything I can. I'm pretty new to dirt bikes, although I can wrench on anything.

I've tried searching and as much information as I came across nothing directly answered my question. From what I gather my steering stem dimensions are 26x47x15 upper and lower and is the same as the stem on the 79-84 xr500r. Is this correct? Also I have a chance to get a 92' xr600 complete front end and can't find the dimensions for it. I know the forks are bigger but if i swap trees and all should it fit? If the stem is the same and the bearings are different could I just use everything off the xr6 front end including the stem and then use the xr5 bearings on the "new" fork stem. I'd love to get a disc brake and get rid of the 23... thanks for any advice.

-Eric

Edited by PCDirt

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yes yes yes

Just that simple.

Way better forks, disk,21" wheel, all 13 years newer parts.

It's a beautiful thing.

did the 600 go USD?

Edited by MindBlower

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Post this on the XR600-650 board for lots of specific help from lots of guys that have done it.

Here's my 85 Xr350 with 2001 CR125 front end.

WP_000002_zps98a34771.jpg

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Nice bike MB. So it looks like I should snag up this front end. I shouldn't have any problems with the stem? If I post this in the xr600 forum will I get flamed for double posting? Thanks for the help guys.

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They probably haven't read this since they didn't reply, probably won't flame you anyway. Even if they do, it hurts way less than one good crash :D

You can google allballs and look at their steering swap bearing charts for the two in question. If the bearings are the same, it will probably swap with OEM bearings. If not, you probably need conversion bearings. Not a big deal, just a few bux.

If you figure out the bearings, and the distance between the triples are the same, indicating same stem length or pretty close, your 90% done. If not, there may be some tricks you have to play to get it to go. Finally, you may or may not alter geometry, which may or may not be good. That is where hearing from someone who's done it would be good. It's not something easily measured, calculated, or researched. In short, at the extremes, if you end up with little or negative trail, you have instability at speed, and if you end up with way too much trail, you end up with it not wanting to turn tight. I am suffering the latter, no problem on street, not real bad off road, and it's temporary, as the rear end goes up a few inches next modification. I closed my eyes, shot first, asked questions later, by necessity. Try finding any info on an SP250!

The last 10% can take some time to sort out, but it's not rocket surgery. It is the minor details like steering stops, cable lengths, getting a fender on, head light brackets, stuff like that. This can be almost nothing to do, or it can take up as much time as the first 90%.

In addtion to posting there, you can try to search the forum. Searching can suck, so if that fails, try googling some phrases followerd by site:thumpertalk.com and you only get returns from the forums.

Let us know how it goes, and let us know if you hit a bump and get stuck. Sometimes it's simple, but takes a different mindset or random thought to come up with the simple idear.

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Thanks a lot for the advice. I will look on the allballs site. Hopefully I can pick up this front end this weekend. I know once it's sitting in front of me it will make a lot more sense. I will keep you posted as to how it goes. Here are a few pics of the animal.

Cleaned it up since I first picked it up.

Here she is.

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20130704_201430.jpg

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Nice, you have a very good foundation to build on. I forgot they had twinshocks later than the yammy DT's. That will make it simpler to match the rear up with the new front. Just buy longer shocks with the right springs, if needed at all. Mine is major surgery to really do anything to really improve the back mono. Original version zuk full floater with all the linkage above the swingarm.

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Usually only need the bearing swap to run USD. XR 'should' be a straight bolt on. Unless on that old a bike they used different specs for the stem or bearings. From mid 80's at least, all the same.

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Thanks guys. So over the weekend I picked up the front end. Hopefully this weekend I can start on it. I think the main difference is the 79 used those ball type bearings and the XR6 stem has the tapered roller kind. Looking on all balls site, those"tapered roller type" are "upgrade/replacements" for the "ball type". Also, using their fork conversion chart there is a part number for a bearing to make them compatible. I emailed them since it seemed only the lower bearing was different but they told me I needed 2 of part number 99-3511-5. I'll probably try and verify this with the bearings I got with the front end since the guy was going to use it in an unfinished project and bailed. So it might have bearings I could use(doubt it). If it's a direct bolt on, i'd be a happy camper.

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Those look like they have decent chromes. He's got the triples on backwards :D Is the stem the same length as the 79?

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Those look like they have decent chromes. He's got the triples on backwards :D Is the stem the same length as the 79?

Yeah the rim is in great shape and the brakes are decent. As for the triples, maybe that's why he sold it and couldn't fit them on his cafe he was building. :jawdrop:

Haven't checked the length of either stem yet, as I've been working doubles since I got it. When I do, what is ideal besides being the same? longer shorter... guessing longer is better... which I think would be the case if any.

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if they are close or the incoming is longer, you might be able to make it work. if the new is much shorter, youll have to press out your stems fom the triples and use the original. from what other fellas said, it sounds like it will match.

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On my way out the door this morning I got a rough measurement of the stems. The new stem is at about 10 inches and the old one coming out is about 8 1/4 long.

What's the process for pressing the bearings? Take it to a machine shop or somewhere with a press...? Won't I have to get them pressed regardless? Or is that only if the bearings on the new stem don't fit the old frame? Or in the case that I have to transfer the old stem onto the "new" forks ill need to press the new"conversion" bearings from all balls.

Thanks again for the replies/advice. Just want to get a better understanding before I start on it this weekend.

EDIT - I realized you said press the stem and not the bearing. So I guess the only reason I would need a press is to press a old stem(if it were longer than the new) into the new triple. Sorry, i'm sure i'm probably being confusing.

Edited by PCDirt

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Sounds like you will need the original stem. My RM stem was only 1/8 inch off and it caused me enough trouble getting it to fit the SP. I tried to press mine out cold, the one in the RM, put several tons on it and it didn't budge. I didn't have to get it out, I had another way, so I gave up easy. You want to press them both out, then press the original stem into the replacement lower triple.

You won't want conversion bearings per se. You will need bearings that would work as if you were keeping the original front end in the bike. It would be easiest to just retain the loose ball setup. They last a long time as long as they are greased. The ID of both bearings will "see" the original stem, and the OD will see the races that are pressed into the steering head/frame. Good to lay an old towel town under the steering when working with the loose balls. If your not on a concrete floor, you might even get a sheet down.

The race for the loose balls on mine was a slip fit. The tapered roller bearing, a press fit. My SP had a taper on the bottom, loose balls on top. RM was all loose balls. Lower bearing going onto the RM stem felt like a pretty light press, but I was using a hydraulic jack, so that can be deceiving. I used my old fence gate, a 12 ton Jack, sockets, pipe, whatever I had laying around. A messy shop is an asset!

IMAG0414731035134.jpg

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Oh, check and make sure the stem is not welded in if it's a cast iron triple. Mine was on the SP, and that weld goes DEEP.

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I guess at this point I just need to start spinning wrenches and see what i'm working with. Being stuck at work doing these doubles is killing me. I found some pics of my 79 triple/stem online since mine is still together. Let me see if I understand this...the new stem wouldn't work since it would stick out farther (on top) and the treads would be to far from the triple hence not being able to seat the mounting nut? Also, when you pressed the stem, it presses from bottom to top, bottom triple first -then through the frame-then through the top triple? I guess I'm over thinking it. They are probably all different in design in one form or another.

79xr5stem.JPG

79xr5stem1.JPG

79xr5stem2.JPG

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They are usually pressed into the bottom triple only and the top is secured by a bolt to make the hole pinch it just like the forks are, plus the bolt that goes into the top. However, even easier (much easier) in the pic, it looks like the bottom is held on with the pinch bolt. Probably loosen the bolt and it will slip right out.

The donor forks appear to be pressed on the bottom. Maybe the top is too, I can't see a pinch bolt, but I've not seen that before (only worked on Yammies and Zukis).

It will make more sense when you get it apart. You can also look at the OEM section of the TT parts store and if the bikes are listed, look up the parts for a nice exploded view. Click "view full size image" or something like that and you get a larger pic you can print.

The 79's stem tapers in some between the bearing surfaces. That's how most were. The donor looks like it's straight. If swapping stems won't work, and if the donor is straight, it might work with a spacer and pressing the bearings further onto the shaft.

You would have to decide on higher handlebars, lower forks (higher front end) or split the difference and put a spacer for each bearing. The other option using the donor stem is the machine it to be more like the original stem in length, threads and distance between bearings. Hopefully the 79 stem will just work.

Oh, I was told on the RM stem I used (and failed to press out) that it presses down, the long way out. If the pressed area and the hole is straight, not at a slight taper, it should go either way. On the donor you have, it would be a long way to press if it is indeed a straight shaft, as it appears to be.

Looks like we have things to consider, once you get a better look at the donor, and maybe a couple of options.

Edited by knudsen

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Thanks a ton Knudsen, Your advice/posts have made it way clearer. Is there a reason I shouldn't just use the donor front end/stem and just use a spacer like this one?

I found this informative write up on the stems. It seems I would only need a press to press the stem out of the lower triple IF I need to use it in the new front end. I won't know for sure till I get in there. Besides the geometery of the bike being slightly off and the front end being higher, what negatives could come from using above said spacer? It seems like to do it right ill probably find/make a press so I can keep the original stem.

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