forks

Hi. I have a 1986 VFR 750 and I need to do something about the forks. They bottom out way too easily and it's a dangerous situation.

I'm looking for some advice here. I guess my best options are either the Racetech cartridge emulators or trying install forks from another bike. Has anyone tried the Racetech kit? Does it work? With new springs, fork seals and bushings it would be around $300.

How about different forks, anyone done it? What bike did they come from and how much work was it? With new forks do you have to go with the 17" front wheel? I'm a machinist so making parts/spacers or modifying parts is not necessarily a problem. I'm trying not spend a mint on this.

I'll have some time this winter and I'll be painting my new upper and lower fairings as well. If anyone has some experience here please let me know.

Thanks

 

Have no experiens whit the Racetech kit, but I know the stock fork is soft. A easy way would be changeing to a hevyer grade oil, mayby new stiffer springs. Also the antidrive system linkage from the brake calliper seems to wear and get pleanty of play so you dont get full acction of it.
If you change fork, go whit compleat fork and wheel (I have Kawa -94 ZX9R Ninja fark and wheel on mine) and yes 17" is then the way to go.

 

The forks of my 86 vfr had the same problems,too soft springs and too heavy damping.
I installed Wilbers progressive springs #600-098-00 and the result is a much better steering (and breaking) bike.Look up their website.
Succes,and greetings from Holland.

 

The RaceTech parts work great - a total transformation of the front end. The bottoming resistance is greatly improved too, which is exactly what you are looking for. Stiffer springs are nice, but I've found that most people don't need them for the street. The RaceTech Emulators make the biggest difference.

Going up to a heavier weight of oil can improve the bottoming resistance but it also produces a harsher overall action. This is not what you want. The problem is the damping rod technology. It produces damping that is too soft on the big bumps (bottoming) and too harsh over the small stuff (poor handling), the worst of both worlds. Heavier oil makes this even worse. If you wanted to do something to help just bottoming resistance without hurting the already poor performance in other areas then you should consider adding more fluid to the forks. Raising the level will certainly help.

 

Try cable tying up the caliper with the antidive activator on so that the antidive is permanently engaged, if the fork action is improved you need to improve the compression damping (emulators) if not then the springs have lost their temper and will need to be replaced or have some preload added with spacers as an interim cure, that's the way i went on mine, mind you i ended up with a cbr6 front fork on mine after a car bike interface.

 

springs

Does the antidive mechanism actually work? From talking to people I was under the impression that the antidive device didn't help much even when it was functioning properly. Does anyone know if parts are available for a rebuild of the antidive?.

 

In my experience, the Anti-Dive mechanism was a fine example of Failed Technology.
Looked great on paper...
Years ago there were little block-off plates available to just eliminate the extra dead-weight (critical unsprung/moving mass).
I'm sure you could simply machine something yourself - don't forget a gasket or o-ring.
Correct springs for your weight & riding style, and a properly set-up fork is all the anti-dive needed.

I agree with all of the above advice.

Quick & dirty (read: budget) temporary fix would be:

1) Drain & refill the oil (likely worn out by now & overdue) with 1-2 grades heavier weight oil (10-20wt)
* I went with 10wt when I rebuilt my fork, wish I'd gone with 15-20wt; it's still too soft for my taste.
I ride the front end and work it hard, so I prefer firmish damping.

Drain/Refill:
> Back off Preload Adjusters all the way out to complete minimum to remove spring preload from the Top Caps.
> Remove the drain screws on the bottoms of each fork slider; pump out all oil.
> Set the bike on the centerstand with blocks or a jack under the engine block or header collector to support the front end off the ground to remove any remaining compression on the springs.
> Remove Top Caps from the tops of the stanchions (careful - the caps are still lightly spring-loaded; cover with a rag over the wrench to prevent injury.
> Refill tubes with appropriate quantity (either by height or volume).

* This is all easier to do with the fork tubes removed from the bike, but the above is the lazy way.

The oil amount is not hyper-critical; real-damn-close is good enough, especially since you're going to:
> Add an additional 10-15% extra oil (above O.E. spec) for additional bottoming resistance.
> Upon reassembly, crank up the Preload Adjusters to about 80% of Max. Be prepared to just max them out if still too soft.

* Be sure to also increase rear spring preload and damping accordingly for balanced ride-height/attitude and suspension action.

This will get you by on-the-cheap until you get around to a full rebuild with new springs, bushings, seals & Cartridge Emulators (DEFINITELY the way to go!).
When the fork is fully rebuilt with proper springs for your weight, you'll want to accurately set Static Sag for full suspension action.
RaceTech or another fork/suspension specialist can provide info & procedure.

I really don't see the need for the expense of replacing the front end with something more modern, unless you're intent on having a 17" front tire.
You'd almost certainly have to replace the brake rotors & calipers as well ($$), or most likely will need to fabricate caliper spacers to make the O.E. calipers work, which may not even be possible with different rotors.
There's a very good chance your O.E. rotors won't work on a different wheel, so factor in the rotors, maybe different calipers as well.
The O.E. fork will work just fine with a proper rebuild & Cartridge Emulators, unless you ride very hard or use it for Track Days (which doesn't appear to be the case).
You might consider an aftermarket Fork Brace (if you can even find one anymore), but it's not even really necessary for moderately fast street riding.

Modern, USD (Upside-Down) forks are stiffer, and frankly do work a bit better, but not that much better.
Stock USDs may not even work as well as a properly setup old-tech fork with Emulators.
At least, nothing anyone could notice on the street.

Now, if I recall, your '86 has an 18" Rear wheel, correct?
A 17" Front allows (requires?) a modern Radial tire; I believe that Rear 18's are only available in Bias Ply construction anymore - Mixing is a Major No-No.
Changing the Rear to a 17" is possible, but will significantly reduce rear ride height, upsetting the correct attitude, and I think the narrowest 17" Rear tires nowadays are about 150mm. Your stocker is what, 120mm?
Wider tires slow the handling too much, if it would even fit in the swingarm.

My advice is to do the above (replace oil for now; rebuild later), and save your $$.

 

while we are on the subject of forks.....

anyone know the stock spring rate of an 87 700 F2?

btw, I know it's a progressive spring, but I still want to know.

I know where I can get some springs for the forks, but they don't say how they are relative to stock, and they just give spring rate




*edit* nm, found what I wanted on the race tech website...they sell springs that would be upgrades for $109, bike bandit sells the same springs (less selection) for $89
that's how I'm fixing my suspension in the spring!

 

I really don't want to be a dick, but there are a couple of mistakes in this post:

1) The emulators are only rebound, not compression. Rebound is most of the performance, compression damping is left for more expensive (read: newer) bikes.
2) Springs do not [normally] get soft over time. Unless the material used is REALLY cheap the spring will remain just as it was when new. Honda's materials are decent enough that you never have a problem with this. People often blame the springs getting weak when it's actually the bushings wearing out causing excess friction. The compression loads can overcome this, but the springs have a more difficult time. This makes the springs feel like they a have lost rate.
3) Temper does not come into play when determining spring rate. This is a mistake that I've heard a few times. Nowhere in the spring calculations do you enter the material hardness - it plays no part. Temper is also not something that changes unless the part is subject to extreme temperatures, which fork spring are certainly not.

Yes, the anti-dive does work, but any setting other than #1 will reduce the braking power. You actually want the forks to compress under braking so that the transfer of weight to the front tire can happen. By the way, the modifications to the damping rods for the RaceTech emulators renders the TRAC system non-functional.

Again, please don't take this the wrong way. I'm just trying to make sure the correct information is passed along.

 

I have to say that while I still had the stock fork on my bike the antidrive did make a diffrence. Whit possison 1 it botomed, and whit posisson 4 it didn´t even it compressed much. I also had a lot of play in the joint betwen brake calipper and antidrive valve so I might have just used a antidrive possison that compares of posisson 2 if no play in the calliper valve joint.
I guess the antidrive was a budjet way to get less fork compression to the forks under brakeing before you could do it whit the fork valveing cheap enough whitout makeing the forks hash.
I have changed my forks for a USD fork from a -94 Kawasaki ZX9 Ninja, and it needed major work. I did go whit the compleat setup, forks wheel and brakes from the same bike. Mixing is dangerus if you dont know what you doing. I recomed to do so as well. And you can actually get 17" fronth wheel that firts straight the 86-87 VFR. Take one from the CBR 600 hurricane (87-89). It use same brake discs and speedo pickup. You get a better selection of tires, and I´m not talking radials here, than the oem 16" wheel. You should use a 110/80-17 tire only on that 2,5-17 rim. For the rear, if you go for radial tires front (as I did) the stock rear will handle a 150/70r18 tire (stock is 130/80-18). If you swamp to a 17" rear rim, the stock swing can take up to a 180/55R17 tire on a 5,5 wide rim, but then you need to move the chain line outwards, that might be a bit tricky, + get the rear brake tuorge arm outwards. I have a 160/60R18 tire rear on a custom PVM rim thats 5,0" wide whit the stock chain line and works ok. Still the wider tires do slow the steering, so I´m workin on getting my rear a bit higher to get the steering faster.

Sometimes I do wounder how my bike would handle as stock whit a deasent rear shock and stiffer front springs and litel heavyer weight oil. Last season I rode the bike stock I had a rear shock that was toasted (buoght a new one to next season) and the forks had never got new oil + I had a 120/80 front tire thet made the steering slow. I might put the stock fork on someday whit fresh oil and a new stock size tire and the stock wheel rear and go for a ride to see how it handle compared to the modified one I ride now.

 

I had TRAC on a Honda 500 interceptor, and Suzuki's anti-dive thingy on an '87 GSXR750.
Both proved pretty much worthless.
My FJ1200 may also have had an anti-dive mechanism, I can't remember.
If so, I was equally unimpressed.
The GSXR and the FJ both eventually got fully rebuilt forks with proper springs, etc., so any anti-dive hardware got "round-filed" (trash).
The VF500 I just remember fiddling with the TRAC to no apparent effect. I understood the concept, it just didn't seem to DO anything.

The lighter the suspension bits and wheels etc. are, the better the suspension works.

Good info on the fork/wheel/brake swap.
It certainly is possible.
I had forgotten that the CBR600/Hurricane front end & wheels are pretty much a direct swap.
The early 600's rims were fairly narrow, similar to the VFR's stockers.
I was not aware that appropriately narrow radial tires are available.

Still, I guess I've been riding pretty hard-core for quite a few years now.
I think I've come full-circle in my thinking.
I used to want to modify & "improve" things, now I tend to believe in keeping things fairly stock and simple.
Modern bikes and components offer much more capability than most people will ever need that well set-up stock stuff usually works quite well.
I consider a properly modified fork to be "tuning" rather than a modification; the main components remain O.E.

I also noted that the OP had mentioned having a budget.
I'm naturally frugal, and lean towards saving $$ whenever possible, so my advice was in consideration of maximum performance for minimum investment.

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As for raising your rear ride height, can you use shims at the shock's top attachment?
Some sort of machined spacer?
I don't know what the attachment looks like from the shock to the frame.

Try raising the fork tubes (stanchions) in the triple clamps; about 12-16mm should be in the ballpark.
You may need to go more, since the front wheel is now a larger diameter (from 16" to 17").

This should bring both ends more in line with original spec, and restore the correct geometry somewhat, but the trade-off is that you will lose a little ride height/ground-clearance.
You probably won't even notice it, especially on the street.

*If you raise the fork tubes, considering the front wheel diameter has increased, be careful of wheel/radiator clearance at full fork compression.

 

Thanks for putting me straight Jamie, I should have put a question mark after emulators as i am not that familiar with them and thought they emulated a cartridge fork and improved compression and rebound, as for the springs maybe temper was the wrong word to use, i went by the experience of the fork springs on a lot of the vfr I have worked on being compressed below the service limit leading to them going coilbound under compression, every day's a learning experience!! and every day's a bonus.

 

The Hurricane wheel only fit, not the forks what I know (even some campanys sell same stiffer springs for the CBR600 Hurricane and first gen VFR750/700) and the wheel is a strainght fit.
There is 110/80R17 radials awable from att least Dunlop, Maxxis and Avon what I know, that is the correct deminison for the 2,5-17 Hurricane wheel.

 

so, what can I do with my forks? I want to keep an 86 750 as total OEM as possible, already ordered fork seals cause I know they are busted, but I basically know nothing on proper setup or if I need to change the springs or anything else. You guys seem to know a lot on this issue, so a helping hand would be greatly appreciated!

 

order these: http://www.bikebandit.com/product/A5005197

 

now for the bonehead question of the day... how do I remove the shocks??? I just got this bike 2 weeks ago. Removed front rim, calipers out of the way, removed the bottom drain screw...now, do I have to remove the top cap? what size is it, 24 mm? the shocks are drained and now I want to inspect the internals, also need to replace the seals.

 

you really should have the manual handy when you do this. The first one, you'll want pictures and such for.

if not, just remember (write down) how everything went, and you'll be fine....best if you can find some one who has done this before to come and drink your beer while you do it.

however, if neither of those options are open:
http://www.motorcycle.com/how-to/how-to-replace-fork-seals-3442.html

that link helped me a ton, and plan for lots of time.

basically, it's remove the wheel and brakes, remove the handlebar assembly, loosen the top cap of the fork, loosen triple clamp, remove shock, disassemble, (do whatever, reassemble, put everything back in reverse order of how it came on (torque your bolts right) and then you are good to go.

a triple tree stand, or rafters or something, to get your front end up in the air, but not resting on the shocks are necessary.


*not sure about what size stuff is....sorry...don't remember...

 

thanks for the link, it looks like I'm in for tons of "fun"....

 

honestly, it takes lots of time to do the first one, the second one is cake.


figure it's a weekend project...it won't be....but then you can tell your wife it's going to take all weekend, and you are off the hook for dishes and yardwork.....once you are done you have to "test ride it"


something you might do is check local libraries for the manual! (seriously) I had to go to the next town, but they had the manual for the bike

 

btw, for me to do it all again, would prolly take 3 hours....

hell, just ride on over to Moscow, and I'll give you a hand