Ok, This Front End Sucks

[inanecathode]

After a long while ruminating on the subject, I've decided the vision front end sucks. This is an 83 front end, and it still sucks.

I already installed progressive springs, AND a one inch spacer on each side. It still sucks. It's ridiculously squishy, and soft. To get the right sag, i have to add too much air into the forks and risk blowing out the seals, so i have NO air in the forks. Even with that, I have gone through fork seals like h2o goes through stators. I just cant seem to keep the oil in the damn forks. They're in there straight, tubes arent nicked, fully seated, all that noise. Still, its puking like a frat pledge, all over my formerly good front freaking brake pads. Now i have slippery front pads with a master cylinder that needs a rebuild badly, and ballooning front brake lines. It works, sort of.

It's not so much the brakes as it is the obscenely under-speced front forks. I'm probably heavier than the test rider they had, and i have the fairing, and i have the bags, and i have the rear shock that jacks all the weight up to the front. Maybe that's it, but i'm looking for like 3/4 to an inch sag and i'm getting more like three. Obviously i cant keep air in the front end as it's either ineffective and not enough, or effective and enough to shoot the fork seals into low orbit. I understand i've a special case that might rule the stock front end pooched anyway, but im still looking for a solution.

1) Fix whats there, put in magical-super-stiff-fork-springs, and magical-heavy-duty-fork-seals, new brake pads (grrr), rebuild the master cylinder, steel brake lines

2) Replace whats there with oddly-bolt-matched-yet-much-beefier-forks, different master cylinder, steel brake lines.

Or a mix of the two. I'll probably be replacing the stock MC with a much smaller version. I had some success with a buell MC on another bike, i'll have to see what bore sizes i'm looking at is and figure that out. I havent found yet a front end that would bolt up ok. An xv920 has 36mm (one mm bigger) front forks, with i imagine longer fork tubes and beefier springs, but that'll give me a funky top tree, and probably way too tall of a front end.

It seems better to just fix whats there, but i'm not entirely convinced there is a spring that will work for what i'm trying for here. I dont know if its the yzf600 rear shock that's jacking the weight up to the front end or what but it's sagging so bad, even with progressive springs (from a different bike) and huge spacers.

Halp!

[fret not]

Sounds like you have the wrong springs. 

Back in the 70s when air caps became popular on the MX bikes we sold a LOT of fork seals.  Usually the seals would work well enough with air pressure but when the pressure was reduced the seals would puke oil all over everything.  It seems the pressure actually helped the seals do their job, but wore them out prematurely.  Adding air pressure to the forks is a good idea IF you also have a plenum to deal with the extra volume, much like the external reservoirs for shocks. 

[inanecathode]

I'm having trouble finding where to get the 'right' springs (i want heavier than normal anyway, dont care about progressive), and also braided brake line kits.

[Walt_M.]

Have you considered going to the Seca Turbo front end? There are several on ebay right now. I got a set this week for cheap and am going to do some measuring. A plus is they use tubular handlebars, maybe. If I get any useable info I will pass it on.

[supervision]

 My stock springs have been stiffened, by shortening them!  Don't take away too much or you will get coil bound, but you can get close and not hurt a thing. When you finish make sure your ned spacer zero pre load, cause you don't want to take up any of that the spring travel.  CHEEPNEASY

[Walt_M.]

Took some measurements and it looks like the turbo forks will give about 10 mm less trail making for quicker steering. Also, unless I modify my steering stops, the fork tubes will hit the fuel tank at full lock. If I keep the 110 front tire, the quicker steering may be ok but I will have to modify the steering stops. I am going to try it for the thicker tubes will stiffen the front end and I think I can use my fork brace too. I'm not sure I would try it if I had a longer shock though.

[Night Vision]

110 front tire? that's a fatty!

[inanecathode]

Uh, well. I think i'll just have to first find the right fork springs. The ones i have i think are from a gl500 or maybe a xv920, not sure, but they are progressive. I wish there was a place that just had a bunch of different springs you could choose from, instead of 'stock' and 'progressive'. The fork seals are definitely pooched, have a good rivulet coming from them after cleaning them once. I hope i can save my brake pads, maybe they're not totally soaked through.

So, i need help finding the following:

Heavier (not stiffer) fork springs (preferably progressive)
GOOD fork seals (i have some that might be OEM, not quite sure but they sure look like fork seals)
New brake lines (i guess braided, but new lines would be just as good)

I can find the right master cylinder (not going to rebuild stock, it's a dumb size on the bore for dual disk, not the feel i want, really). That should get the front end sorted. It's really not a 'quick' steering problem (btw, really? quick steering? I guess i've never noticed it steering 'slow') or a fork stiffness problem, its just jelly soft springs and weak damping (weak damping, i have to up the weight of oil in the front, its got 5w in it, it needs more like 12 or 15).

[QBS]

Check your fork tubes for surface imperfections.

Get them squeaky clean of all oil.  Then lightly drag a nylon stocking or its equivalent over the tube surfaces.  If the stocking gets snagged you have discovered a surface imperfection that is probably not the only one.   Even a few of these imperfections will render a fork seal "leakey".

Try removing the imperfections with very fine sand paper, (think wet sanding).  The objective is to polish the imperfections away.  Keep checking with the stocking until no snagging occurs.

[Tiger]

..... i have to up the weight of oil in the front, its got 5w in it, it needs more like 12 or 15). 

There is part of the problem mate...15w is 'stock' on a Vision :P

Sum of all parts carry the Galfer Stainless Steel braided brake lines...

www.pyramid-parts.com carry good aftermarket fork oil seals/dust covers, front brake pads, steering head/front/rear bwheel bearing kits, etc...

                8) ...... TIGER ....... 8)

[pullshocks]

I agree the stock setup leaves something to be desired.  But I don't have it in me to mess around with swapping
My upgraded springs from Race Tech didn't get here this week(thanks to United Parcel Service) but hopefully next weekend I'll be able to tell you there is a vast improvement.  I am also installing their cartridge emulators.  (Assuming the UPS driver can actually be bothered to get out of his truck this time)

Funny thing about the seals--despite leaking copious amounts of oil (so much that there was hardly any left in the right leg) there was still air pressure in the fork

[fret not]

Inane, you can get inexpensive custom braided steel brake lines out of Canada.  I got one from their eBay listing.  Just search in MOTORCYCLE PARTS for BRAIDED STAINLESS BRAKE LINES and a bunch of listings come up and a couple will be from the Canadian place called Rennsport.  A custom line is less than $40. with shipping.

With the braided steel line your original master cylinder might work well because the brake line doesn't expand like the OEM rubber ones.  The braided steel lines provide a very firm feel to the brake lever.

It's not cheap but you can get just about any configuration of front fork springs from several shops that specialize in suspension.  Roughly about $90. new.

[pullshocks]

+1 on the braided lines, although when your brakes are soaked with fork oil even the braided lines don't help... 

I got mine from Fiat Doctor at a very good price.  I haven't seen any posts from him lately but you could try to PM him

[akvision]

First thing came to mind..

progressive springs,,, slightly longer spacers and heavier oil.. 15W and proper new seals.

sorry I missed you on my last trip out to the hills.

Jim, akvision

[motoracer8]

 The probblem with Vision forks and all other damper rod forks of the era is they have too much compression damping and not enough rebound, if you put lighter oil in the forks to reduce compression then you have no rebound. Stiffer springs just make things worse.  I have installed Rev Tech gold valves in several damper rod forks over the years all with good results.  The best improvement I made to an old Honda Elsnore that I used to ride in AHRMA events, I have them in my Vision, they are a worth while investment for any damper rod fork, and the compression is adjustable.  The stock fork springs are ok once the ride hight is adjusted and compression is set the forks work pretty well.  Cartridge forks they will never be, but with real compression valves you can get close.

  Ken G.

[johnclemens]

I would suspect bad bushings. If these are worn they allow the fork tube to deflect as it slides.
Thus the seal gets pushed on one side and that leaves a gap on the other side. Then the compression pushes oil past the seal. These are easy to change when the fork is apart.
Assuming they are just leaking and not really BLOWING out. meaning the seal lip inverts or the seal comes up out of the fork leg. In that case I would suspect too much oil or your not getting the retaining clip seated correctly.

When racing a stock bike with stock forks we settled on 15wt with progressive springs. I ran the 83 caps but did not put any air into them.
Granted this was with no fairing and I am(was) 150lbs. ::)
Oil level is very important.
to set oil level, Take the cap off, take the spring out, compress the fork tube ALL the way into the fork leg, then fill the tube with 15wt till its 6 inches from the top of the fork tube.
Also buy Yamaha fork seals if you can get them. The aftermarket ones can be shite.

[Lucky]

These are easy to change when the fork is apart.

John, can you provide details on R & R of the bushings?  (a lesson?) i don't think many of us have done this job...

also, specs on them, how to tell if they need replacement & where to get 'em?

[QBS]

Motoracer8, thank you for your comments and observations regarding the built in excessive compression dampening in our old school forks.  For years I have been really irritated about the harshness during sharp compression of my '83 front end.  But I just passed it off as too heavy oil.  Besides, in every other way their operation was quite satisfactory for me.  At 88k miles my factory seals don't leak, they hold my 6psi air for literally decades, rarely bottom out and even then only under the most extreme circumstances.  Bottom line: they're not broke so I won't fix them.  None the less, the harshness on compression still bothers me.  Now, I at least know why.  Thanks again.  You old time racers are worth your weight in gold, almost.

[johnclemens]

I looked in the service manual and it appears the forks don't use any bushings...
I thought they did. They slide up and down against the fork tubes. so if the fork tubes are worn then they have to be replaced.

Best way to tell is without oil and spring you see if the tube has ANY movement front to back.
You can tell with the fork on the bike if you know what to feel for. You remove front wheel and fender. then grab the bottom of the fork leg. try to move it front to back. if you feel any movement its worn.

[VFan]

Also buy Yamaha fork seals if you can get them. The aftermarket ones can be shite.

I've come to be of the same opinion. It's not worth spending the time to replace the seals with cheap replacements.

VFan