Hawk/Enforcer Fork Valve upgrade. - Page 2

Megadan · 06-26-2018, 04:20 AM

I figured I would cover this in a separate thread in order to focus more on this particular mod/upgrade. This upgrade may well work with other bikes that have similar style forks, such as the Magician, but somebody would need to measure the inside diameter of the fork tubes for me to verify.

It is well known that these bikes are not known for their great suspensions. In an ideal world they would come with 43mm off-road oriented long travel forks, but then they wouldn't be the cheap fun we know and love.

The biggest weakness of these suspensions is two fold; 1. Dual rate fork springs with a very soft initial spring rate combined with very little fork preload. 2. Damping rod style forks.

The first one creates a condition where the bike has too much sag in the suspension relative to the total travel of the forks. Depending on your weight, you could easily be taking up more than half of the suspension travel available in the front forks, and this makes them very easy to bottom out. Thankfully, this problem is easily resolved by making your own preload spacers to set the proper rider sag. For the Hawk and Enforcer, this total laden sag (weight of the rider suspended on the bike while vertical) should be around 2-2.5 inches, and no greater than 3 inches.

The second problem can actually make the situation worse with the former. Damping rods just don't function in the correct way to properly dampen the suspension. For a more detailed explanation of why, I invite you to read this article: http://www.racetech.com/page/title/E...%20They%20Work

The simplified version of that is - Since damping rods rely on orifice holes to regulate the flow of oil alone, they have an inherent weakness. During low speed compression the holes flow a large volume of oil easily, and as a result can allow a large degree of travel with very little control - this is most easily evidenced with extreme nose dive under hard braking or coming down after cresting a hill that unloads the suspension. During high speed compression, like a sharp bump, the oil cannot flow through that same small hole fast enough to provide adequate compression, and as a result makes those high speed hits very hard. In the real world, these two situations should be reversed. More control on the low speed compression, while better compliance on high speed for comfort and control.

What Fork Valves or "Cartridge Emulators" do is exactly that, reverse those roles by taking the compression control away from the damping rod holes, and in turn giving it over to a valve - just like a cartridge.

I am happy to report that my experiment in installing the YSS PD238 fork valves was completely successful. This opens the door for people that want to improve their Hawk or Enforcers suspension without potentially spending a ton of money on a fork swap and dealing with all of the headaches that come with it. Below is a video where I cover what is required and how to set it up.

I would like to note that the adapter can also easily be aluminum. As long as they are around 23 to 23.8mm O.D. and at least 5mm thick, they will work.

Also, the valves only alter the compression dampening. The rebound dampening is still metered by the damping rods upper orifice holes, but can now be adjusted by changing fork oil weight. Since the compression damping is valve controlled, the weight of the fork oil has very little to almost no influence over it any more. This allows you to really dial in the suspension.

As far as the source to purchase the YSS Fork valves, I have yet to find a U.S. distributor, but they can be found and purchased on ebay or through the UK website wemoto. https://www.wemoto.com/parts/picture/ys-pd238 Roughly the cost is around or a little over $100 for the valves.

There is a potential cheaper second source for a similar style valve, but I have thus far been unable to find the specification on the outside diameter of the valves. They are for the early XS650, which used a similar diameter fork spring to the Hawk. At $60 a set, they are much cheaper, and they are shipped within the US, so if you feel like doing some leg work you could give these guys a call and try to find out the diameter. As long as they are less than 24mm in outer diameter they should work. https://www.mikesxs.net/yamaha-xs650...hoCmyEQAvD_BwE

I honestly can't wait to get the bike out of the road and start dialing in.

06-26-2018, 04:20 AM	#1
Megadan Join Date: Apr 2017 Location: Omaha, NE Posts: 8,008	Hawk/Enforcer Fork Valve upgrade. I figured I would cover this in a separate thread in order to focus more on this particular mod/upgrade. This upgrade may well work with other bikes that have similar style forks, such as the Magician, but somebody would need to measure the inside diameter of the fork tubes for me to verify. It is well known that these bikes are not known for their great suspensions. In an ideal world they would come with 43mm off-road oriented long travel forks, but then they wouldn't be the cheap fun we know and love. The biggest weakness of these suspensions is two fold; 1. Dual rate fork springs with a very soft initial spring rate combined with very little fork preload. 2. Damping rod style forks. The first one creates a condition where the bike has too much sag in the suspension relative to the total travel of the forks. Depending on your weight, you could easily be taking up more than half of the suspension travel available in the front forks, and this makes them very easy to bottom out. Thankfully, this problem is easily resolved by making your own preload spacers to set the proper rider sag. For the Hawk and Enforcer, this total laden sag (weight of the rider suspended on the bike while vertical) should be around 2-2.5 inches, and no greater than 3 inches. The second problem can actually make the situation worse with the former. Damping rods just don't function in the correct way to properly dampen the suspension. For a more detailed explanation of why, I invite you to read this article: http://www.racetech.com/page/title/E...%20They%20Work The simplified version of that is - Since damping rods rely on orifice holes to regulate the flow of oil alone, they have an inherent weakness. During low speed compression the holes flow a large volume of oil easily, and as a result can allow a large degree of travel with very little control - this is most easily evidenced with extreme nose dive under hard braking or coming down after cresting a hill that unloads the suspension. During high speed compression, like a sharp bump, the oil cannot flow through that same small hole fast enough to provide adequate compression, and as a result makes those high speed hits very hard. In the real world, these two situations should be reversed. More control on the low speed compression, while better compliance on high speed for comfort and control. What Fork Valves or "Cartridge Emulators" do is exactly that, reverse those roles by taking the compression control away from the damping rod holes, and in turn giving it over to a valve - just like a cartridge. I am happy to report that my experiment in installing the YSS PD238 fork valves was completely successful. This opens the door for people that want to improve their Hawk or Enforcers suspension without potentially spending a ton of money on a fork swap and dealing with all of the headaches that come with it. Below is a video where I cover what is required and how to set it up. I would like to note that the adapter can also easily be aluminum. As long as they are around 23 to 23.8mm O.D. and at least 5mm thick, they will work. Also, the valves only alter the compression dampening. The rebound dampening is still metered by the damping rods upper orifice holes, but can now be adjusted by changing fork oil weight. Since the compression damping is valve controlled, the weight of the fork oil has very little to almost no influence over it any more. This allows you to really dial in the suspension. As far as the source to purchase the YSS Fork valves, I have yet to find a U.S. distributor, but they can be found and purchased on ebay or through the UK website wemoto. https://www.wemoto.com/parts/picture/ys-pd238 Roughly the cost is around or a little over $100 for the valves. There is a potential cheaper second source for a similar style valve, but I have thus far been unable to find the specification on the outside diameter of the valves. They are for the early XS650, which used a similar diameter fork spring to the Hawk. At $60 a set, they are much cheaper, and they are shipped within the US, so if you feel like doing some leg work you could give these guys a call and try to find out the diameter. As long as they are less than 24mm in outer diameter they should work. https://www.mikesxs.net/yamaha-xs650...hoCmyEQAvD_BwE I honestly can't wait to get the bike out of the road and start dialing in. __________________ Hawk Information and Resource guide: http://www.chinariders.net/showthread.php?t=20331 2018 Hawk 250 - Full Mod list here. http://www.chinariders.net/showpost....62&postcount=1 2024 Royal Enfield Shotgun 650 https://chinariders.net/showthread.php?t=34124 Last edited by Megadan; 07-01-2018 at 04:42 AM.
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