Gen II Fork oil tip from Duken4evr

FZ1inTX

Adminstrator
I found this on the other site and thought it was interesting and should be shared here. I'm sure Duken will not mind as he was enthusiastic about us sharing his map packs as well.

This is an interesting take on fork oil... Never looked at it this way before.

Duken4evr said:
Well I completed the oil change. The bike has 11,000 miles on it. The fork oil did not look too bad at first really, until the cartridge emptied out. I could tell when that happened. The nasty black stuff came out Still, the oil looked a helluva lot better than the stuff that comes out of my dirt bike every winter service

Put the Maxima 85/150 (5 weight - green color) in the compression leg and 165/150 (10 weight - clear color) in the rebound leg. Used Traxxion's handy fork spring compressor tool and retaining clip thingie. I was able to do the compression side myself as the cartridge rod on that side slides in very slow, as it is, um, the compression side Mrs. Duke helped out on the rebound side as the rod just drops right down in there - no compression. This requires two more hands - one to put the clip tool in and one to hold the rod extended so the clip tool can be put in.

Helpful tips if you do this:

1) Once the cap is removed from the cartridge rod and the spring is out, always handle the forks from bottom or the inner slider can and will separate from the outer leg with predictably messy results. I learned this the hard way with my dirt bike forks awhile ago. No need to repeat that again

2) Pay attention to setting your clickers when putting the caps back on. If the fork cap is threaded on too far, you will have no adjustment and it will be jammed on full stiff. If the cap not threaded on far enough, your clicker will run out of clicks on the tight side before fully seating. Some fine tuning while threading the cap on before locking things down with the jam nut and it will be dialed.

3) A length of rubber tubing that fits tightly over the threads on the cartridge rod is handy, particularly on the rebound side, for holding the rod fully extended while the spring is compressed and the clip tool is put in place during the reassembly phase.

4) Make sure to stroke the cartridge rod until the air is purged out and it does not "skip" and the damping is consistent. The compression side quickly came online with a few strokes, but the rebound side took a few more pumps to do so in my case.

5) Start with the compression side to get your flow going, as it is a bit easier due to the non disappearing act cartridge rod. I of course started on the more difficult rebound side!

I went with a touch over 4" (110mm) of oil level. It measured 3.75" stock. I know from Lee's postings that the last inch of travel is a hydraulic anti-bottoming deal, but I never used the last 1.5 inches of travel. Figured I would drop the oil level a touch. Stock forks tend to be undersprung and overfilled in my experience. At least the FZ1 is properly sprung for the average rider. After today's ride, which involved hitting some bumps at speed, I had about 1.25" of unused travel left per the hi tech zip tie measuring system in place. Seems good to me as I am using almost the full travel, definitely .25" more than before. I am not a heavy braker on the street, but I did go over some bumps at speed

The forks felt better. I was able to relax my rebound to 11 clicks out from 8 out, (compression is at 11 out, 3.5 bands showing on the preload) and it felt fine. The forks felt about as good as the Penske in back, which is pretty darn good. It felt balanced front to rear. Very nice. Good enough for my street riding that is for sure. Even before the fork fiddling, I would have to be going way into the trying to keep up with the hottie on her Duc 1098 go to jail impound the bike zone before the handling started to fade. The FZ1 is one fine handling bike really.

The ride today involved a mix of canyons, one in particular with washboard bumps (Peak to Peak out of Nederland for the locals). Some taken pretty fast - touching 100 mph here and there, as well as freeway, etc. The forks did nothing "noteworthy" and were pretty transparent. While going fast (100 mph or so) over rolling bumps, they felt like they came back at me less fast, yet they were fine in the ripples. This is good.

All in all, while this does not compare to a full revalve, it is a worthwhile incremental improvement type of mod that does not cost anything extra if you are going to change your fork oil anyway. I would not do it if you have fresh oil in your forks, but if your FZ1 has 10K miles on it or more on the fork oil, get the compressor tool from Traxxion, two bottles of Maxima fork oil, have at it and ride around knowing you have different weights and colors of fork oil in your FZ1's legs

Don't forget to pump your front brakes to take up the slack in the pads when all done

And after his first longer ride with some adjusting, Duken followed up with this:

Duken4evr said:
Went for a 350 mile ride today. The difference between the last ride and this was was setting the forks to 4 bands showing (loosened up from 3.5) on the preload and taking one click of rebound out of the Penske shock.

It really rides like Daddy's Caddy now. 90 mph on the concrete slab used to beat me up a bit. It felt like 65 mph today. The bike is flat out working great now.

I would now say the oil swap mod is less than night and day, but more than an incremental improvement. The forks feel really good for spirited street use at this point, and of course the Penske rocks. My butt was hardly sore at all today. The harshness is just gone.

As delivered, my '06 had a "harsh" personality. On/off throttle and the suspension, particularly the OEM rear shock, was harsh. Now it is more powerful and smooth in every way. 80-100 mph cruising out in the wide open high mountain meadows of Colorado feels easy and natural. She just flows now
 
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A response to this from Lee @ Traxxion

Lee is quoted with this response:

Lee@Traxxion said:
It's worth a try. The stock compression valve assembly is an orifice damping style of piston so the 5 wt oil or lighter in the left fork might help for bump compliance.

The 7 wt oil or possibly 10 wt might help on the rebound side (right fork) so you can relax the adjuster setting a bit. I'm sure with it turned in so far, the slow speed rebound damping is way slow and I wouldn't be surprised if the front tire was scalloping or wearing strangely.

It's fairly easy to get the high-speed rebound damping close but getting the slow-speed rebound damping correct at the same time is a tough job when you have a single valve assembly and only one needle for slow speed oil-flow adjustment.

That's our Duken for thinking outside of the box.
 
And some wisdom from Lee about our Gen II forks...

Interesting stuff and it really makes sense!

Lee@Traxxion said:
RaceTech probably only sells a rebound kit for the Gen2 forks because that is the only type of valving that will work in those forks. Let me explain...

Btw, this is top secret sheeot and you are all sworn to secrecy.

Yamaha wanted both rebound and compression adjusters at the top of the fork leg on the Gen2. Probably someone in their marketing dept thought it would be a good way to save some money and impress some potential buyers. You know, that whole MotoGP tech that we've read about. Anyways, since there is no adjuster at the bottom of the fork leg for compression damping (dumb down cost saving move by Yamaha design dept.) then the only way to maintain compression damping adjustability would be to locate the compression valve on the cartridge rod that moves up and down inside the cartridge body. That way, the adjuster can be moved to the top of the fork leg just like normal rebound adjusters on forks.

Here's the problem with using a typical "compression" valve mounted on the cartridge rod. Aftermarket compression valve pistons are different than rebound valve pistons. Rebound valves have a piston band because it generally slides up and down inside the cartridge body. Normal compression valve pistons have O-rings on their circumference. They are not designed to slide or move at all. So, how would you expect to make a compression valve work that slides? Shouldn't it be a piston that has a band on it? Well yeah it should. There already is a piston that has a band on the circumference but it's named "rebound". Now, how can we make that rebound valve piston damp for the compression stroke? hmmmmmmm... Why not invert the rebound valve piston so it provides damping during fork compression? This my friends is how it's done. One rebound valve assembly kit is all that is needed for the Gen2 forks.

Don't even ask me what shim stacks work best. I can't share that information. I've probably already said too much but the questions presented needed to be answered.


Ok, now back to your RaceTech product discussion....
__________________
Lee
 
So, I'm wondering how much is a rebound valve assembly and what it consists of. I guess if we compare the blow-up of each fork leg for parts, we can determine what makes them different and buy those? But his (Lee) supposed secret is shimming them so it would be a bit of trial and error I suppose. I should look into a bit more research and see if anyone has already figured this out without spending a ton of money.

Thoughts? It makes sense to me.
 
Both forks are rebound assemblies. In order for Yamaha to have the compression adjustment on the top of the fork, they basically invert the rebound piston and "BAM" you have a compression assembly.
 
Both forks are rebound assemblies. In order for Yamaha to have the compression adjustment on the top of the fork, they basically invert the rebound piston and "BAM" you have a compression assembly.

This is not what is stock in the forks. Traxxion took the stock forks apart and found them to be very different. To better the stock compression side, you buy the rebound stack, invert it and replace the compression side. Lee is also quoted here:

A1. The Gen2 forks do not have a fixed compression valve assembly with an O-ring seal at the bottom of each cartridge.

A2. The sliding pistons attached to the ends of the cartridge rods are very different. The rebound valve assembly is typical of Kayaba and other top level brands for rebound valve assemblies. The compression side is not the shim stack and checkplate type. It is an orifice style piston with no shim stack at all. Basically, it is good for low and medium speed damping but poor for high-speed damping due to inadequate oil flow volume capabilities.

A3. The non-shim stack side of the rebound piston has a spring loaded "check plate" design. The stock compression piston does not use that design as I mentioned in A2 above.

The common aftermarket upgrade using these Gen 2 OEM cartridge bodies is to use a rebound valve assembly pair. The rebound side is normal except for a special shim stack because it is performing all of the rebound damping for the front suspension. The aftermarket compression damping side is also a rebound valve assembly but it is inverted to create damping during fork compression. The rebound fork leg has no compression damping and the compression fork leg has no rebound damping.
 
This is not what is stock in the forks. Traxxion took the stock forks apart and found them to be very different. To better the stock compression side, you buy the rebound stack, invert it and replace the compression side. Lee is also quoted here:

Hence I was generalizing.
 
:wow: I'm going to have to read that S-L-O-W-L-Y to try to understand it. I think I'll still just change the fork springs, but I'm not sure what to do with oil weights. I know the stock fork isn't the best, but it seems worlds better than the rear shock.

I think I'd like to do the R1 conversion someday, for the fork and the brakes. I'm just focusing on the rear shock and fork springs for now. :confused:
 
A syringe is a good example. The needle is the orfice much like the holes in the compression piston. If you press the plunger of the syringe slowly fluid flows. Press harder and faster and the flow is limited for the orfice and force, but adding even more force does not increase the flow much. Put on a larger needle, and the flow can be increased.

Does this help?
 
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