Need Help with 73 Front End Swap

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nanoonanook

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Hey all,

I want to replace the front end of my 73. It has the 34mm forks and they are pitted and rusting.

Ideally I would like to replace the entire front end -- clamps, forks, etc. etc. Hope that someone can chime in with a couple of bits of wisdom for me.

- What is the head stock width / length that I need to look for? Is there anything else that I must take into account?
- I found a list of makes & models with similar fork width, however it does not seem to factor in the head stock width and length..... so, has anyone swapped out with something else... which make and model?

I hope to pick up something soon so that I can get my ride height and hard tail sorted out.

Thanks!
A
 
Well... lots of views but no replies. So that either means a) I'm a dork and its a simple answer or b) we're not sure.

In either case, I thought I'd document what I'm attempting so others can have a reference of, I hope, what to do.

I picked up an entire front end assembly from a 1980 XS650 and I have just ordered a set of tapered bearings. Upon rough fitting, it appears that the new neck length is about 1/2" longer than the stock 73. I need to use a caliper to check the width of the neck still, but it appears to be nearly identical.

Once I've fitted the new tapered bearings, I will take another measurement to see where I stand. My hope is that is will all fit perfectly, but realistically I expect to need a spacer of some sort, or possibly even the use of a third cogged nut.
 
This was the first time I saw this thread. There are many frontends that get put on the XS650. Sportbike, Springers, most anything has been fitted. A bit of searching for different forks on the xs650 should have gotten many hits. Like if you scroll down to the bottom of the page you will find a list of simular threads.
The first few years 70-73 used a shorter neck. In 74 they did a total over haul of the frame. Adding bracing and strengthening the frame. A longer neck was one of the changes. All the years used the same loose ball bearings and races. So all the stems were the same diameters. The 74 up stems as you found are a bit longer.
There are several ways to fix it. The easiest would be to shim above and below the bearings. Get the stem in your 80 trees shortened and rethreaded or swap the stem from the 73 tree into the 81 tree.
Swapping stems would be the one I'd use. Easy to do, grind out the welds, press ouit the stems, swap, reweld.
At the top of the stem where the upper bearing rides is turned to fit the bearing only far enough to fit the longer neck. The bearing won't fit far enough down the stem to seat. That is without turning the stem and rethreading or using enough spacer under the lower bearing to move the stem lower in the tree. This might move the tree low enough so the fork stops on the tree will miss the stops on the frame.
That's why swapping stems is the better option.
Leo
 
Thank you Leo! What an excellent - detailed - reply! Thank you! :)
As I'm very sure you can tell, I am very new to this scene and have jumped in with both feet. I have tried a number of searches, but didn't find exactly what I was hoping to find.

There is no doubt in my mind that the answer to my question was already on the forum... it is a WONDERFUL resource.... however, being so new, without a dead-on specific thread, I don't know enough to know that the answer is staring me right in the face. I appreciate your patience.

Now that I am getting some true wrench time and have been trying some things out, it is beginning to make sense. How does the saying go.... You know what you know, you know what you don't know, and you don't know what you don't know. Hopefully I'm moving up the spectrum!

Anyway, I've already parted out the 73 parts, so I'm working with the 80. I will go the shim route as you suggested. I need new fork stops anyway so I will weld some on when I get the hard tail.

Thank you again for your feedback!
A
 
Warning: The more you know, the more you realize you don't know.

My goal is to learn more and more about less and less until I know absolutly everything about nothing...
 
Just to update the tread. I have replaced the loose bearings with tapered bearings.

For the spacer --- for the time being --- I have left the lower fork loose-bearing cup in place and put the removed lower bearing cup from the bottom of the neck, upside down on top of it to see how the longer neck fits into the frame. It is close, but there is still a bit of play in the lower bearing. I am going to pick up some thin washers to try to get the correct spacer height (so that there is no play in the neck). Once I know the height, I'll get a proper spacer made up.... somewhere... not sure where yet.

I'll post the needed spacer in case anyone want to put a 74+ neck into a pre-74 frame.
 
The one thing that can come into play with spacers is that the stem is only the right size for the bearing for a short distance. It then tapers to make it easier to install and remove the races. If the spacers lift the bearing enough so the new bearing is up on the smaller part of the stem it will have to much play.
Leo
 
Well, good news. I have been shimming up the bottom of the 1980 steering unit and have found that a 14mm spacer will do the job. By raising the spacer a bit more and making sure the collar nuts (not exactly sure what they are called, but they are the cogged nuts at the top of the neck) are fairly tight, all play in the lower end of the steering post is gone. Everything looks and feels great.

I am having a stainless spacer made up (to replace the flipped over lower race and random washer that I'm using to determine spacing). The dimensions are as follows:

14mm thick
48mm O.D.
30.5mm I.D.

For anyone in the future who is replacing a pre- 74 steering post / triple clamps with a newer xs650 unit, please consider:
1) The 14mm speacer width requires that you remove the lower steering post race, but keep the rubber.
2) The loose ball bearings are replaced with tapered bearings -- There may not be a difference, but I can't say for certain as I am using tapered bearings.

A
 
nanoonanook--I've been contemplating the newer fork swap that you're doing for a while on my '72. I changed out the swingarm to an 80's version for more length--better handling but not sure on the forks. I know the newer forks look nicer but do they really improve the handling compared the the older forks?? That's the question that I can't find the answers to. Anyone have feedback on the handling differences? If the improvement is minimal-- then I'll probably keep the stock set.
 
A lot of cycle magazines and rider evaluations of the period had good things to say when the forks went from 34mm to 35mm. Also, the earliest forks (70-71), had steel lowers and looser bushings, with a weaker (torsionally wise) fender mount. These guys were performance evaluating, and were very critical of the xs's handling.
 
It's possible that the 36mm forks and tree from a late'70's xs750 triple or possibly the 850 triple would be a direct....I say direct swap for the early short necked 650's. Jury has been out on this for a while.
 
I have a set of forks from an XS1100 standard. The upper tubes are 37 mm. The Stem from the where lower bearing seats to the top of the stem is 8 5/16 inches.
I have a set of 75 34 mm forks and the stem is 8 7/8 inch measured the same way.
Does anyone have an early stem to measure?
The XS1100 stem has tapered roller bearings on it. I would think they would fit in the races that come with the tapered roller set for the XS650. So I think they would bolt on to the early bikes by just using the races from the XS650 kit.
There is one difference that may or may not make it workable is the offset. On the XS650 trees there is a just under 2 inch offset from the center line of the fork tubes back to the center of the stem. On the XS1100 tress the offset is 1 3/8 inch.
This will increase the trail by 5/8 inch. The stock trail on the XS650 is 3.9 inches, adding 5/8 inch makes it 4.525. This may make the bike handle a bit differently. I think a bit harder to turn, a bit more stable at speeds.
I plan at some time in the future to try the XS1100 fork on my 75.
The larger tube diameter makes the forks stiffer. As with any tube the larger the diameter the stiffer it will be. With forks this helps keep the front wheel pointed where it needs to be. A smaller fork tube flexes more during turns, this allows the front wheel to not turn as far as handle bar inputs. A larger tube diameter lessens this flex.
Leo
 
DanW -- I can not comment on the change in ride as my bike is in about 500 pieces right now. My reason for the swap was due to the poor condition of the original front end. From everything that I have read, the newer front ends are more stable.


XS Leo, I sold my front end... sorry. I have an old pic with a measure on it, but it is not conclusive as I show 9.5", but I didn't include where I took the measure from! Oops. I'm sure someone will chime in.
 
The XS1100 standard used a regular fork with the axle straight under the fork. The XS1100 Specials used a leading axle fork, one with the axle out on the front of the fork.
I don't know if they used different trees with the different forks. I quess you could research that on a parts fiche at a seller like boats.net
I think the XS750 and XS850 did the same, standards used reg fork, the Specials the leading axle.
The XJ 750 Maxims used a leading axle, at least on my friends 82 XJ750 Maxim.
My XJ 650 turbo Seca used a reg fork.
Some were air adjustable, some had adjustable damping as well.
My XS1100 forks have caps with plugged air fittings. They could easily be replaced with air valves.
Leo
 
nanoonanook, I have been reading your thread with much interest. I have a 1972 XS-2 which I am customizing and I want to fit a later XS650 front end mainly for better parts availability here in England.
Just for clarification, where exactly does the spacer you had made fit? is it in the frame neck under one of the bearings?, on the lower yoke (triple tree) under the lower bearing? or above the top bearing?
Dave.
 
+1 grind press swap the stems, I have done it a couple of times, or use an XS750 "standard" fork AFAIK it is plug and play but the tubes are a bit longer (1"?) No matter how big the fork IMHO the early frames are still "whippy" compared to the better braced late frames.
So as always when modding, the whole bike should be considered in your "goals"

Back in the day road racing my CB900F at Road America a guy had an H2 750 that really made some horsepower, he had grafted some big wing? front end on the notoriously flexible H2 frame, I'd pass him every corner he'd take it back every straight. He finally tried to match me through the corner, I last saw him headed out into the woods riding a tank slapper.
 
Hi Wickerman,

First, I must say that gggGary has MUCH more experience than I probably ever will with respect to 650's. What he is suggesting makes perfect sense to me and he has the experience to back it up. IF that works for you, it is very much worth considering.

That being said, I do not have a welder and am not a the stage where I am confident enough to do what he is suggesting on my own project. In time perhaps, but I am not building a bike that is designed for speed or performance. My goal to is have a piece of eye-candy that I can putt around town (I live in a beach-resort type town) on and go out for a beer on.

O.K., so now that you know where I'm coming from, I'll answer your question. When you take the triple clamp off the top, and pull the lower triple clamp through the steering post you will see the lower 'loose bearing' race at the bottom of the steering post. The spacer that I have replaces this lower bearing race and sits in the same spot. To use my numbers, you MUST replace your old-loose bearings with new tapered bearings and races. They are about $50 from Mike's XS.

Good luck!
A
 

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