Mod stock vfr700 fork?

86 VFR700

The fork bottoms really easy. Just a tiny bit of brake in a corner and it'll bottom out with a loud clunk on just about anthing. I haven't. Looked into the stock fork oil weight but would it be worthwhile to go little thicker to help with dampning?

Is it possible to change the oil withou taking the fork apart? Its recently had fork seals so id rather not pull it apart if I don't have to...

 

Have you tried adjusting the anti dive? It has 4 positions. Be careful with putting on brakes in corners. For road riding do any braking before cornering. Have you tried adding a couple of pounds of air?

 

First off, chuck those old softy springs and buy some heavier straight rate ones, Sonic Springs sells them at different rates according to your weight.
Adjust the antidive like Camo says and replace the oil with a heavier weight if you need to.

Or you could go totally nuts if you want to and race tech the forks with springs and emulators, or you could just replace the whole front end with an F2 that would give you true cartridge forks.

 

while we're on this subject....you bring up a good idea Dukie, with the racetech cartridge emulators....do you think those would work with a set of progressive rate fork springs? (more specifically, the ones from Motorcycle Suspension :: Motorcycle Springs :: Progressive Suspension ) ???

and does anybody know where a good aftermarket rear shock can be found for one of these 2nd gen bikes?

 

I agree that the correct springs and fluid will make a huge difference with those forks. Emulators are also a good idea, that's a fairly cost effective way to get a lot better damping.

A couple of things that I read above that concern me:
- The anti-dive is a bad thing. You actually want the forks to compress under braking. Keep the anit-dive at #1 (most amount of dive) and never change it. The anti-dive mechanism will not prevent bottoming nor will it cause the forks to bottom. It's a gizmo that was put on there because in the 80's people wanted knobs to turn.
- Don't just throw in heavier fluid. On the stock forks you should run 10w fluid. Going to 15w will only make things worse. To help with bottoming you should raise the fluid level (add more fluid) in the forks instead.

I hope this helps!

 

While compliance with the road surface is a desired trait under all conditions. Compressed forks reduce the trail making the steering very sensitive and many times less stable. Manufacturers have tried many techniques over the years to try and maintain steering trail under braking. The 700s had a system to increase the compression damping in an attempt to slow down fairly radical changes in geometry, there is a compromise. At any rate increasing the "anti-dive" does slow down the change in additude. It doesn't lock up the front end to any great extent.

Tire technology has changed a lot since the 80's The narrow front tires on these old bikes reduces the trail faster than the wider tires when leaned over.

The best handling might come from a transplant of suspension components from a newer bike.

Obviously there are many approaches to improving the front end sag that are valid. Many of us riding these older machines don't have the budget to remake them into a newer design.

 

A proper suspension setup will have you use all of the available travel during the highest braking forces. Having the forks compressed during turn-in is the best way to approach a corner. The anti-dive settings above #1 only hurt the performance of the bike. Settings 2 and above create longer stopping distances (yes, it's true!) and cause the bike to stay "stood up" going into a turn which hurts the handling bad. The anti-dive mechanism was a marketing thing to try and help sell bikes. You are right, we have learned a lot which is why you no longer find this feature on motorcycles.

 

JD, if I could ask, is it possible to modify the forks to remove the Anti-Dive system?

 

As far as having the suspension sacked out during braking, I'll be doing that if I need to avoid a deer or other obstacle in my path that I can not ride around. As far as entry to a street corner goes, riding the suspension stops is asking for trouble in my opinion (must work for you), nothing left to overcome bumps and ripples.

At least for me, the fun is coming out of corners and keeping a good cornering speed. In my road riding group we don't pass in the corners every one gets an entire lane. No reason to charge in on the brakes hard.

I try and keep a smooth line and avoid excessive geometry changes. I want predictability, x amount of steering input to give y amount of steering. I don't plan on using my brakes while leaning into a corner particularly near my apex. As the bike is leaned my emphasis becomes cornering traction. If I come into a corner apex and think I am a bit hot, I may drag the rear brake. I want to keep the front of the bike planted while have never mastered front end slides on a big road bike.

We used to have an expression "Asphalt is for racing and dirt is for growing potatoes." Most of my riding these days is on my offroad motorcycle. Way more fun per minute. No police, no oncoming traffic, no texters, just drive out my door. Funny how we change.

Telescopic forks somehow have been installed on 99% of motorcycles in the last 60 years. They are a mature technology and everyone who rides has them. Inertia will keep them popular. New technologies are typically expensive. Newer riders might be the most willing group to adapt to a newer design. Newer riders usually are not the most affluent, it will be pretty hard to introduce a successful new design.

 

You can't "eliminate" it because it's one of the caliper mounting points on that side. What you can do is disable it's function. You need to install emulators in order to do this BTW.

 

I never said the forks would be fully compressed! You assumed that - what I stated was that under braking is where you get the MOST fork travel. This is a fact, if not your suspension is seup dangerously and you WILL have problems when you need to brake hard.

Ok, quick lesson: by not applying the front brake going into a corner you are doing exactly the opposite of what you think you are doing. For you the bike is, in fact, going through a significant geometry change. When you enter the corner under neutral throttle and no brakes the forks are riding up high, basically at your rider sag point. This is about 25-30% of the total travel. When you lean into the corner the forks will compress. The amont depends on how hard you are riding but can be 50-75% compressed typically. That's a big change from when you entered the corner. The bike has to try and deal with corner entry and a big change in fork length at the same time - which is tough for it to do. What you need to do is apply the brake, then as you begin to lean start releasing the brake gradually such that reduction in braking loads match the increase in cornering loads. You start at (all brakes - zero lean) and end up at (zero brakes - all lean). If you had a camera on the forks you would see this as the forks compressing under brakes and not moving until you exit the corner. If you release the brakes too fast, or in your case do not apply them at all, you will see the forks pogo during the corner. The rear brake will not give you the correct fork action either, by the way, which is why it really is not part of proper cornering technique.

The facts ma'am, just the facts!

 

Makes sense. Thanks for the post.

IIRC, you upgraded a set of 37mm VF500F forks for Matt's bike using modern cartridges.

Is this something that you would recommend over Race Tech emulators?

I imagine that this is a pretty involved project, but I would be interested to hear your thoughts on this after completing the set for Matt's bike.

 

Please don't be condescending. As far as I am concerned, running the brakes into corners on public roads, reduces the safety margin. Save it for the race track.

 

I completely eliminated the TRAC anti-dive control system from the left fork leg on my old '86 VFR700. Anti-dive on one fork leg only was kind of a silly gimmick when you think about it IC and the darned thing just leaked constantly.

I removed the valving and simply fabbed up a small steel plate,welded the brake caliper mount clevis to a pin,set the pin in the hole I drilled in the plate,bolted up the brake caliper to set the correct depth of the pin so the brake caliper would line up properly in relation to the brake rotor,welded the pin securely on both sides of the plate,cut out a gasket to match my plate,put a bead of sealant around the opening in the fork leg and on my gasket,and bolted up my plate.
Basically all I did was make it a rigid brake caliper mount just like on any other bike.

I then installed a set of Racetech Gold Valve Cartridge Fork Emulators as well as a set of Progressive Suspension front fork springs and set the fork oil level a little higher than stock.

I rode the snot out of that bike for years after that. No more leaks and the bike handled beautifully.

 

Stosh, you just answered a question I've been pondering for a couple of weeks now. With you having DONE it, I now know that the Racetech Gold Valve Cartridge Fork Emulators CAN in fact be installed in a set of forks along with the Progressive Suspension front fork springs. How, in your opinion, does this combination actually perform overall?

 

Thanks Stosh. Any chance you have a few photos of this mod, in an old photo album?

 

It was a noticeable improvement over stock. The nicest thing about the Cartridge Emulators was that they were adjustable.
You could at least dial in your front suspension to a degree that you couldn't otherwise do with the stock forks.

Here's a link with some tech info that describes how those Cartridge Emulators work. Click me.>>>>>Damping Rod Forks

Nope. I never took any pics of that,never thought anyone would ever ask.

 

IIRC, the reason anti-dive was only on one side is that one fork handles compression damping, and the other fork handles rebound damping. Since it's a compress-damping function only, it only needs to be on the one side. And this split duty is ok because the forks are fully bolted together top and bottom.

I guess in theory the fork braces that link the top of the sliders would further add rigidity to the movement and distribution of the compression/rebound forces.

And camo, I'd really listen well to Jamie's advice on this one. I doubt we have anyone else on this forum that knows as much about motorcycle suspensions.

 

Not trying to be condescending, just sifting down to the facts. Even at moderately slow street speeds you can benefit by applying a little front brake going into a corner. The idea is to preload the forks to the point where they will be mid-corner. If you are going fairly slow this will mean you apply only a small amount of brake. This has nothing to do with the race track in any way, it's all about safe and enjoyable riding.

 

The damping rods control both directions in either fork. That is, if you want to call it that! I'm not really sure you should call what the damping rods do as "control".

You are correct, it's only the left side that gets affected by the TRAC system when the brakes are applied.