Problems removing front forks on 77 xs650??

[XS650D]

I want to install a set off the Front fork Dampers (Mikes xs) on my 77 .I reviewed some
info before disassembling,(Made a tool on a long extention with a 17 mil bolt head to remove or hold the piston rod in place while removing the allen bolt at the bottom) problem is after getting everything apart i noticed that mine has a different setup inside the fork.Looks like a nut head with only 2 strait sides.How do i remove this and will i still be able to use the Damper kit as the pics on installation show the damper sitting recessed into the top off the piston rod which i usume is under this special 2 sided nut.Thx

 

[5twins]

I don't know if you'll be able to use the emulator but I can tell you how to get the '77 forks apart. As you noticed, the damper rod tops differ from the '78 and later ones. Yours are rather solid with 2 flats machined on the sides. Once out, you can notch out an old socket to fit down over them, but what to do now? Well, there is a hole down through the center and there is a roll pin stuck through the side .....

Get a length of 1/4" steel rod and hammer the end flat .....

..... then simply jam it down in the top of the damper rod between the roll pin and the side of the hole .....

Bend the top of the rod over so you can hold it from spinning .....

Once you have the damper rod out, you could make the special tool from an old socket but honestly, I never have. My bent rod has worked well multiple times for me.

 

[XS650D]

Perfect,Thx.Got a feeling the New Damper kits i got From Mikes won,t work with this Damper piston head design from a 77,guess i will know soon.My just do the Minton Mod while its apart.

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[5twins]

Yes, try the Minton Mods. I quite like the improvement they make. Also use a bit more oil that stock spec, about 7 ounces instead of the just under 6 stock amount. This really helps with the brake dive.

 

[grizld1]

Race Tech makes adapters for your damper rods. They're available from Traxxion Dynamics; call and tell them what you have. Cost is around $9.95/pr. Refer to www.race-tech.com for setup and tuning instructions, and remember that Paul Thede gave them to you free.

Another time honored way to fashion a tool is to apply the Big Friendly Hammer to a piece of galvanized pipe, and beat the pipe until it closes up enough to grip the flats on the damper rod tops. Hold the pipe in a vise while you do the needful with the bolts.

 

[XS650D]

ok thx Guys,got everything out ok,just eyeballed it and caut a 5/8" socket down in the middle leaving to outside edges,worked like a charm.The Damper definately dont fit,
i will call company above for a set off adapters.Thx
ps : i di consider taking the damper rods to a machine shop and enlarging the hole slightly but this sound better.I really wish Mikes/xs650 direct would state the years this kit fits!!

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[XS650D]

Traxxion dynamics said i need to order a whole new kit plus adaptor.Not happening.I have emailed xs650 Direct here in Ont Canada to see what they suggest or maybe send it back for refund.Probably cost me $100 to have a machine shop drill out the top off my stock Dampers and then im still not sure it will work correctly.For anyone with a 77 model year FYI.

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[XS650D]

5Twins,i looked at the minton mods and it sound like theres some confusion as to the correct amount off holes,size ect.Can u advisefor the 77 Dampers Thx

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[XS650D]

I measured the existing holes.There are 4 holes at the bottom 3/16" and 1 hole at top 1/16". ps :dont have numbered drill bits ie:45 ect

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[5twins]

Yes, the Minton Mods article is full of errors in the fork mod section. I explained them and the way I do it a few days ago in this thread .....

http://www.xs650.com/forum/showthread.php?t=45068

As I said, I quite like the results I've gotten with the Minton Mods, but that was using the drill bit sizes I mentioned in the thread above (#1 and #45). If you go with a 1/4" and 1/16", you may not get the same results.

There are some other things you should know about your '77 forks. They were the first year of the 35mm fork on the 650 and therefore may have been still sort of in the developmental or an experimental stage. For instance, Yamaha speced 20wt. fork oil for them. On the '78 and later versions, the spec was dropped to 10wt. Now, this could have been a case of Yamaha realizing that 20wt. was just too thick, or it could be related to the damper rod design, or maybe a bit of both. If you look at the oil holes on your rods, you'll notice they're beveled. An engineer buddy of mine said beveled holes flow better/more. The '78 and later damper rod holes are not beveled.

 

[XS650D]

ok i will go #45 top and #1 bottom holes. Regarding the
oil ,have u experimented with the thickness at all on 77 model year.I was running 10 weight before on stock setup with a 1" preload spacer.What weight would u suggest with this new set-up. I did previously try 20 weight and found the ride stiff but that was stock set-up.

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[5twins]

I've only tried and used 10wt. 20 seems awful thick for a street bike to me. The '77 forks I have are my spare set. They're sort of a "hybrid" with parts from the '77 and '78 & later forks combined. I have the Minton Modded '77 damper rods to which I added the '78 and later anti-top-out springs. You may have noticed your stock '77 forks don't have the top-out springs. They may make a clunking sound occasionally when they fully extend. It may not happen much when riding but you might hear it when putting the bike on the centerstand.

I also swapped in the slightly longer '78-on springs (482mm) for the stock '77 ones (472mm) and used the adjustable preload caps from the '78-on forks. The forks work well but they're still too soft with those stock springs. I'm going to try a 1" preload spacer. I like the stock springs. They ride nice and are progressive. I'd like to work out a way to make them work. It would save a nice chunk of change not having to replace them.

 

[XS650D]

Interesting info on the springs,Come to think off it mine does do a knocking noise when coming off the centre stand or at a hard brake to stop.Whats involved in adding the top out springs? to my existing set-up.I had a good look at the springs and they look to be a strait rate,same loop and thickness all the way thru.I measured them and there 19.25" Not sure if thats stock spring or not.Ill give the 10 weight a try.Thx

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[5twins]

Maybe your springs have been changed. At 19.25" (about 489mm), they don't match the length of either stock one I mentioned and both the stockers are progressive. As you can see below, the tighter wound coils at one end are pretty easy to see .....

Adding the top out springs is pretty simple. You just slip them on the damper rod before you drop it into the fork tube. Finding some may be harder. We discussed this a while back and figured that maybe old valve springs might make a suitable substitution, but I've seen no one mention trying them yet. But those absent springs may not be the cause of your noises. Without the springs, the "clunk" should occur at full extension, not when compressing the forks.

Be aware that adding the top out springs will lower your forks a little, but that's not necessarily a bad thing. An old time racer's trick that I have applied to many different bikes over the years is to lower the forks slightly by raising them in the trees. This is supposed to more firmly plant the front end and improve steering feel, maybe traction a little too. Adding these springs does it internally, without having to slide the tubes up. My "hybrid" forks are 11mm shorter than my stock '78 ones.

 

[XS650D]

Great info 5twins,were lucky to have u on the site!
Regarding the noise my front end makes,i believe your correct it was probably when the forks fully extended after being compressed hard.I am going to see if i can find a used set or maybe (as mentioned) a set of valve springs.Do u know if the valve springs are the same length and width to fit,(u may have old parts u can measure in your shop) I realize that the spring tension will prob be different but may work as u state.
Thx

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[grizld1]

Sorry for the delay--had to check the parts stash first. Late damper rods can be used in '77 forks, and I have a set, with topout springs and end bits, available--$40 US plus shipping as is or $50 if I drill and chamfer. But be aware that you won't get results that justify time and money spent if you use OE or OE replacement springs with emulator valves; for good results you need correct single rate springs. Brand new, OE and Progressive replacement springs are too soft even in the stiffer coils. I've explained why that setup won't work well elsewhere, so I won't repeat it here.

There's a limit to how much preload you can apply to fork springs; you need to be sure that coil bind doesn't occur within the needed range of travel. You can use this formula: (free length of spring minus preload) minus (number of coils times wire diameter)=travel possible before bind.

Send me a PM if you're interested.

 

[5twins]

Figuring out the fully compressed length of these fork springs is something I've been meaning to do but that formula just makes my head spin, not to mention the task of counting so many little coils, lol. I may just fully compress one and measure it.

I do happen to have some loose valve springs, top out springs, and damper rods laying around. I'll have to do some comparing. I think valve springs would need shortening as they are about 42mm long according to the shop manual. The top out springs are 22mm long. Since adding them to my "hybrid" forks shortened them by 11mm, that would seem to indicate they get compressed about half way when the fork is assembled. 11mm is near 7/16" and I'm thinking you wouldn't want much more drop on the front. 42mm springs compressed by about half would give you nearly twice that.

Using original top out springs or switching to newer damper rods and the springs might be your easiest solution. With the newer damper rods, you could use your emulators.

Something else I'll mention. You may have noticed in the damper rod pics that the '77 rods shine more. It seems Yamaha put a little more time and effort into manufacturing them, taking the extra time to finish them better. You can quickly polish the later rods in just a few minutes using 600 paper. Theoretically, this should make them slide easier and better through the bushing on the fork tube bottom, possibly reducing fork stiction a little .....

 

[XS650D]

Already returned the Mikes Dampers for credit.
And have drilled the 77 rods for the Minton Mod as per your specs. Maybe Griz will let go off those rebound springs he has as i cant find a suitable replacement.
Cmon summer!!

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[XS650D]

Found a valve spring of a small engine that fits perfect but its to long so had to cut it in half which has left me with each spring about 16 ml in length(yes a lil short),I grinded the cut end to a flat edge but have concerns that it could kink sideways a little in the fork tube because its no longer machined on both ends.It does fit pretty snug in the fork though.Should i insert the cut end facing up or down or will it matter.My fork tubes are new so i am being a careful.

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[5twins]

I think I'd put the cut end down so the top of the damper rod is hitting on the machined end of the spring.

I'm in the process of tearing down some "other" forks, some from an XS500 and an XS750 or 850 Special. They both contain top out springs but they are listed under a different part number than the 650 one. I have one out now and I can see it differs slightly. It's very slightly longer (24mm) and may be a tad stiffer because it has one more coil. The diameter is the same and it fits well on a 650 damper rod so I think this may be a viable swap. I can't see it making much difference in the way the fork operates but if you had none and needed some, I think these would work. I'm saving them.

The 500 fork spring is also interesting. It's not progressive and is about 490mm long. Maybe that's what someone stuck in yours?