Racetech emulator install - 750 Maxim

Another day, another set of forks. I bought the cartridge emulator fork valves and new springs from Racetech. They have some great tech info on their site about how they work and why they're an upgrade from damper rods if you're interested. Basically they are a small cartridge that goes between the top of the damper rod and the spring and they emulate the damping found in bikes more modern than our antique XJ's.

They have a calculator on their site to select valves and springs although there's really only only valve available. There are multiple springs available, which increase in stiffness if you tell the calculator you are racing or weigh 400 lbs.

Here's what I received. The pair of valves comes with 3 sets of springs and two orifice plates. With your order you get a code that you type in at the website and it tells you the setup values for which spring, how much preload and how many holes in the orifice plate.



My setup called for 3 holes, which was the plate installed so thankfully I didn't have to drill tiny holes.



The valve nests into the 18mm socket on the top of the damper rod. It is not retained by anything but the spring pressure.



Unique to the 750 Maxim is the adjustable rebound. Racetech says to set this to minimum, which means the blocked port. Because the half moon hole for the adjuster rod made the valve sit just slightly off center, I drilled out the hole slightly. Original on the left, slightly drilled for clearance on the right.



You also need to drill new holes in the damper rod. The idea is the old orifices should not have any control so they are enlarged. Stock rod has 4 holes, and it calls for 6 holes total, 5/16". So two pairs are enlarged, one pair is drilled new.



Then it's assembly as usual, new seals, etc.



Since the cartridge valve is in the way, the rebound adjuster can no longer be used and must be cut off.



The cartridge can be slid easily down the tube and the instructions say it can be removed through the fork cap later for any adjustments.

When you get to the spring install, you have to set the preload as determined by Racetechs unique setup. In my case, there should be 15mm, essentially with everything in place and the fork fully extended, the fork cap is 15mm from being seated. The stock spring gives about 43mm of preload, but apparently the greater spring rate compensates for that. Here's a comparison of the stock, progressive wound spring and the shorter Racetech spring. Wire size is visibly thicker on the Racetech spring, but I didn't measure them.



To set the main spring preload, you can either cut your stock spacers, or make new ones from a plastic pipe that comes in the kit, which is what I did. They end up about a half inch shorter than the stock spacers. Racetech says not to use any air pressure in the forks.

They definitely feel stiffer with everything assembled. How much, time will tell. My main attraction to this tech was the idea of reducing fork dive under braking. If I get better pothole performance as well then great.

I used an All Balls seal kit. The upper seal/scraper has an external garter spring. Haven't seen that before, but they look like good seals.



So there's another set, ready to go. Unfortunately all I've got is the frame and forks and a pile of parts, so I've got a bike to build before I can test these out. I'll report back when I do, as I've got the other 750 with stock forks for comparison.

Pair of emulator valves are $199. Pair of springs are $150. I do wonder if I could have used the stock springs, but I guess I'll trust the suspension experts for now.

 

Nicely explained, written and documented. Thank you.

 

Excellent write up. Reference grade for sure.

Looking forward to reading your impressions of this fork setup vs. stock.

Also interested to see how the “all balls” kit stands up over time. They make various rebuild kits for my bike but, like everything, the reviews were mixed.

Congratulations getting your new setup!

 

One more question:
When servicing the front forks my service manual recommends that the “guide bush” and the “slide bush” be replaced (along with the oil seal and the dust seal). I also seen the bushings referred to as inner and outer.

Did you replace your bushings ? Or were they still in good condition?

Thanks

 

The new springs are the .80 kg / mm, which is the lightest spring they show available. I think they offer up to 1.30 kg / mm in increments of .05 kg. Their website lists the stock 750 Maxim springs as .46 kg / mm, but I also found info online stating the stock springs are .76 in the light section, progressing up to .98 so I'm not sure what is accurate, and unsure if this higher value includes some air pressure. I had a notion to test them both with a scale, but sheesh....who's got the time? The road test will be the deciding factor. I guess my feeling right now is the valves are a good value...the springs, not so sure.

I forgot to mention in the info above that the fork oil spec is also given by Racetech. They suggest 15W, and rather than a volume it gives a fill level as measured from the top of the fork with the spring removed. 140 mm in my case.

 

I did not replace them. This is the 3rd set of XJ forks I've rebuilt and I haven't replaced bushings in any of them. They have not appeared to be worn, or at least those are the lies I tell myself.

 

I fitted the same on my XJ900 several years ago along with Ohlins shocks on the rear . Suspension is now much more compliant and dive on braking was the biggest improvement from the emulators . Rides more like a modern bike now loves the twisties