Front end education.

[fintip]

I've never had to think too much about forks, have only put them on and taken them off without really much concern for their performance. (The XJ 650 Maxim was never going to be a beautifully handling machine, though I have to say it kicks the ass of my friend's '84 R100RS, so I never really complained. Before that, I didn't even know what carburetors actually were, much less fork design.)

So considering that an FJ will be my next bike, I've started putting some thought into front ends. I've started studying tire geometry and design. And I have started reading up on forks. (This was a great resource).

I just realized I have a slight gap in my understanding though; from the 87 to the 89 front end, I know the rim size changed to accommodate a different size tire, one which was wider but with a narrower sidewall and about the same diameter, greatly improving front end 'feel' and maneuverability.

What I am not sure of is the forks themselves. Was there any actual improvement on the forks? Is there any difference? They're both just damper rod suspension, right? Maybe they just were designed differently to accommodate the wider rim--is that it?

Can the older generation of forks take the RPM mod ('emulator') just as the newer generation can?

[RichBaker]

 The early bikes, pre-'89, had anti-dive on them. It's pretty much useless and adds complexity unnecessarilly. They can be be removed and drilled block-off plates installed (needs the drilled channels for fork oil to flow). They also have different spacing for the caliper mounts, so the monobloc calipers won't bolt-on, you'd need adapter plates.
They are 41mm, so the RPM inserts should fit and function correctly.

[Anti-Dive Dave]

The early bikes, pre-'89, had anti-dive on them...They can be be removed and drilled block-off plates installed (needs the drilled channels for fork oil to flow).

Hello - first off, my apologies for my absence on the site (I'm going through some dark places in my head, and haven't come out of it yet - I'm suffering from a shitty bout of depression  )

Aside from that...what else has happened since I been away?  Oh yeah...my FJ got reversed into by a truck (full side on, as she was parked sideways) - the guy knew the bike was there, as I was chatting to him before he got in the cab, fired up, and just shot back - later asking "what did I make that face for....why did I not shout out or raise a hand?"

I thought he would have stopped in time, or was taking it as close as he could get in order to pull out and make a turn. In less than 2 seconds, after the massive BANG sound, the bike was on the floor with a tipper unit hovering over it before I really knew what happened. But, he did say for a split second, his mind was on other stuff, and he just "forgot" it was there.  I guess shit happens, and that day, it happened to me.

Anyhoo - A question for when the Anti-Dive units are removed and the blank plates are on.....

Does it alter the fork oil quantity much?  I mean...how much "less" should I add to the forks when the anti-dive (AD) are removed.  Surely they hold a small amount, or, do they hold very little, that it makes no difference to the level when changing forks seals for example?

Sorry if it's a long winded question, with possibly a simple answer.

Basically - what level of oil (cc) do the forks take after the anti-dive is removed.  Do we put less in to compensate?

Would be a bugger to put the full amount in and then pop the seals (as maybe the each AD unit holds say....20 or 30 ml?)

The reason I ask, is that I am changing the fork seals soon, and don't have the anti dive fitted (They weren't fitted when I bought the bike)

Thoughts and suggestions...as usual...written on the back of a spare $100 bill and mailed to my address....

Thankees and handshakes all round.

[FJmonkey]

As an 86' owner with AD forks I can say that I saw no gain from it. They still dived, hence, worthless and added unsprung weight. At best a sales gimmick. They don't hold any amount of oil that you need to worry about. The concept is pinching off the fork oil when the brakes are applied. Most of the size of the AD unit is a cavity with a spring that moves a needle.

[Anti-Dive Dave]

Hello - crikey that was a quick return.

Sooo, erm....with no anti dive fitted (that is: removed), the fork oil quantity is the same and the fork internals are left as is (i.e with all that gubbins)?

All I gotta do then is drain the fork (either by screw or tipping upside down), pop the old seals out, fit new ones, top up from empty as per yammyha spesifeecayshuns and bobs yer uncle then? 

And you wrote the answer on the board!!! Was the wallet clean out of hundred dollar bills.

Sheesh!

Times are hard over here y'know......

[FJmonkey]

Very empty wallet, ditched the 86' forks for 89', put RPM valves in, FZR1000 front wheel on, new 17" rubber, braided lines, Blue dots, new master cylinder with lever, new bearings, new Galfer knock off rotors, new HH pads, promises of "love you long time" to wife....

[Anti-Dive Dave]

promises of "love you long time" to wife....

Hmmm.  You mean...she's still married to you despite the bike being the first love?  BLIMEY - she's one tuff cookie!

Remember, giving her a "gift" back does NOT involve saying: "come on dear...hop on the back and I'll take you for a spin n' show you where all the money went....."

[SlowOldGuy]

A/D Dave,
How did you "remove" your A/D units.  Did you remove them and put a simple cover plate over the ports?  Or, did you install drilled plates?

There are a few ways to bypass the A/D function, but blank plates that aren't drilled won't work.

DavidR.

[FJmonkey]

Hmmm.  You mean...she's still married to you despite the bike being the first love?  BLIMEY - she's one tuff cookie!

Remember, giving her a "gift" back does NOT involve saying: "come on dear...hop on the back and I'll take you for a spin n' show you where all the money went....."

Truth be told she kept me from selling it after I crashed it. I found parts years later to fixer her up and got back to riding. I then found the Yahoo FJ group and enjoyed it, till it imploded and Marsh created the alternative FJ group. I still read the Yahoo posts as they hit my email. She no longer rides with me but supports my addiction. I think she likes the times I am out of the house, Sancho might enjoy it as well.....

[fintip]

Can the pre-88 forks accommodate the post-88 3" rim as a straight bolt on?

I've never heard of adapter plates, but they look pretty cheap and straightforward; is there any disadvantage to using adapter plates? Are they a hassle for any reason?

In other words: Does one really need an 88 or later front-end, or could one just upgrade the pre-88 forks with the RPM catridge emulator, get a post-88 rim, and get some new calipers with adapter plates? Wouldn't that be easier? Any reason this isn't a good idea?

[fj11.5]

I'm after a set myself , but to save the hassle of adapter plates,  fzr400 rr front calipers bolt up to 84/87 Fj,s , twin pot , maybe not as good as blue spots , but better than the single ones your using now , , I changed my other 84 over to 89 with 3.5" rim , forks ect and blue spots, , like to keep this one closer to standard 

[1tinindian]

Can the pre-88 forks accommodate the post-88 3" rim as a straight bolt on?

I've never heard of adapter plates, but they look pretty cheap and straightforward; is there any disadvantage to using adapter plates? Are they a hassle for any reason?

In other words: Does one really need an 88 or later front-end, or could one just upgrade the pre-88 forks with the RPM catridge emulator, get a post-88 rim, and get some new calipers with adapter plates? Wouldn't that be easier? Any reason this isn't a good idea?

Why go through all that and end up having what would look like, a half assed, cobble job?
Switching out the fork legs are NOT a difficult operation.

The forks are one of the main reasons we have been suggesting an 89 or newer year model...as you're starting out with a better outfitted platform ready for modding, but anything is possible.

If it were mine, I wouldn't be happy with the overall look of the forks, with a capped off, no longer functional A/D and adapter plates for the calipers.

But, after all, it's not mine, do what you want.

Leon

[Anti-Dive Dave]

How did you "remove" your A/D units.  Did you remove them and put a simple cover plate over the ports?  Or, did you install drilled plates?

Hello Mr R,

When I bought the what-started-as-a-$250-needs-everything-replaced-bike, the forks already had the AD units removed, and plates already installed. (Have photos of the bike then, it looks like a insurance write off!)  But, for £200 Uk pounds, I couldn't argue.  Granted, it has cost me 3 times as much putting it back on the road. SHEESH!

And here's the honest part - the forks were not touched at all, and the bike has been ridden like that from day one.  (waits a bit whilst everyone reels back in horror  .  I mean, the bikes "damping" ability is pretty non-existant and I put that down to the leaky seals (clearly seen on the fork leg).

When the FJ was fixed up enough to try for an MOT (UK Government annual road inspection), he wrote an advisory (a pre-warning) to get the oil seals replaced as there's not much "bounce" left in the front end.  I put it off...and off....and off, and just rode the beast as is.

Now, I got me new seals to go in, and new fork protector/blade dust covers - I'm gonna have to do it (correction, I'm going to have to get someone to do it for me!)

I'm now curious as to what plates are fitted.  If they ARE indeed just cover plates, then I assumed the forks would just function as "normal" straight leg forks with no "holes".

Can I ask another ignorant question then?......what do the "drilled plates" look like, and why do they need to be drilled, if fluid is no longer required to flow through?  My sincere apologies for the lack of knowledge.......

[FJmonkey]

Can I ask another ignorant question then?......what do the "drilled plates" look like, and why do they need to be drilled, if fluid is no longer required to flow through?  My sincere apologies for the lack of knowledge.......

With the AD units your forks have two seperate systems. The dampener rod system and the AD system. The AD system attempts to control the dive by controlling the fork oil flow through it. If not blocked off properly the fork oil will not pass through the AD system and into the dampener system. This locks the hydraulics and would make your forks hard as rocks. If you are out of oil then the jury is still out on weather your block-off plates are drilled or ported properly. There are two ways to port the plates. Cross drill and then plug the drilled hole or mill an internal groove in the surface eliminating the need to plug a hole. Look at your plates to see if there is any evidence of extra holes or fasteners. If not then remove one and look for a passage to allow oil to pass from an upper hole to a lower one.

Here is one example, a little too complex but they get the job done.
http://www.ebay.com/itm/FJ1100-fork-anti-dive-block-off-plates-FJ-1100-1200-/280761718032?pt=Motorcycles_Parts_Accessories&vxp=mtr&hash=item415eb3d510

[Anti-Dive Dave]

Oh no! - the plates on my forks look nothing like those fancy things.  Mine are just...well...on the outside: just basic flat plates.  Nothing fancy.

I don't wanna take one off, as I'll have fork oil piss out everywhere (whatever is left in there - if anything!)  And how do I get the oil back in?  By removing fork cap.  Then, the bike has to be off the ground to relieve pressure on springs....and...and...not having the means to get the front end off the ground (just a side stand), I can't do it meself.

Partly one of the reasons I just left em as is.  The forks DO have some kinda rebound in them, and are not locked solid, so maybe thats good news?

I have pictures I can post (of the outside of the plates...oh, and the rest of the bike....not that anyone want to see a well travelled battered and bruised FJ), but I refuse to open up another account to flickr or photobucket, just to upload photos.  That's another email address the web has, and another inbox full of spam.

PLEASE, can the mods have "insert image" and then we have the option of browsing our computer to select pic.  Obviously, no boobs, bums, willies and next doors dog taking a crap on me lawn....


Oh, and Mr. Monkey - HOW MUCH for 2 bits o' aluminum?  JEEZUS H!!!