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.

https://www.youtube.com/watch?v=DurkqMf7bBw

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. :)

LOL... I seen this vid on you tube before here...
I was almost going to post it here till I realised it was yours...

PS.. arn't the damping rods tiny....

,

I am becoming internet famous, I better practice my diva routine...

those damping rods are almost comically tiny, but they do suit the size of the fork tube diameter well...also tiny. Pretty stout little buggers though. I was pleasantly surprised to see piston seals on the ends of them as well. I almost tore the forks down completely to see if they had serviceable bushings or not, but then I came down with a case of laziness and decided it could wait for another day.

:tup:

Looking forward to see how forks & rear shock perform! :tup:

I am 100% confident in the forks. I did fork valves in two previous bikes, and once you get them tuned in they make a world of difference. Combine them with a fork brace and the right preload and you would have one heck of a front end. The fork brace is my next project.

We share the same experience. Nothing but good. Once set just forget, unless some drastic weight changes. Just don't get fat like I did. :hehe:

Honestly, even with weight changes - getting fat or adding luggage as examples - truly isn't that big of a problem. Even if they do require a little re-tuning, by the time you get your valves dialed in the first time you have a pretty good understanding of the potential adjustments needed. Assuming they are even needed in the first place. Even with 90lbs of crap loaded on my back of my Goldwing, I never had to adjust the front. The rear on the other hand...

I sent mikesxs another message in regard to his fork valves. It would be pretty sweet to have a cheaper option for this upgrade. Being able to use his valves would make this a sub $100 upgrade.

Fork valves
 

Did you hear back from mikesxs if his fork valves would fit our hawks?

Not a peep. Tried 3 times now and never heard back.

Fork valves
 

After doing some internet research, I think you are correct that the mikes valves will fit our 35 MM forks. Ive ordered the valves and will report back on the dimensions when they arrive.

I am definitely curious about them. Looking forward to what you come back with. If you can, try posting a couple of pictures of the valves as well so I can see if there are any differences between the two.

Saw this thread this morning and was inspired to play with mine. Made it this far before a headache took over my life for the past few hours now. What can we buy/do to make this style better? I’m going to add that Valvoline Max Life Synthetic ATF and figured I would snap a pic and ask before I buttoned them back up.

You have them a part this far..so put the right stuff in them..
dirt use a 5 weight oil... But if you are a road only rider the ATF
will do as the slow fork action won't matter so much..It might even help..
A 20 weight would be better...

The only way for me to get an idea of what could be done would be to see the internals, which would require further disassembly. They look like a cartridge style fork, which means they would already have a valve system installed. If that is the case, then the only improvements that could be made is different valves, or changing the shim stack to adjust deflection rate.

Sounds expensive ;) Thanks for the reply, the more YouTube I watched on it the more I figured out it’s cheaper to just buy used Honda forks. I added the 250ml of tranny fluid and went for a ride. The steering seems over sensitive but the smoothness is pretty cool. Wish I hadn’t waited 8 months to do it ha! The original oil looked mostly clear but sure wasn’t providing the best ride. Thanks Mega D!!

Fork valves
 

I got the sxs fork valves from mike and they measure 23.70 in diameter and look just like the ones that megadan posted, ill try to post some picture when I figure that out. :tup:

Excellent! That means this can be done for a MUCH lower price now. Thank you for taking the chance and confirming my suspicions.

The main curiosity I have about these valves are the slow speed ports. Those are the tiny little holes on the top of the valve close to the spring and adjuster for the valve. The YSS valves have 4 holes, which means they offer much softer slow speed damping by allowing more fluid to bypass. Less holes = more resistance to flow = firmer slow speed.

I guess now would be a good time to post my initial impressions of the valves that I installed.

5 turns of valve preload was actually a bit too firm for the high speed compression damping. Not harsh by any means, but rougher than I desired, so I turned them back to 3 turns. The 4 ports for the slow speed is just about perfect in my eyes.

After roughly 50 whole miles on the bike thanks to winter showing up again, I can say that it was worth every penny. There is a rather rough stretch of ignored cobblestone road that I like to travel down that is filled with lots of bumps, lumps, and even mild whoops. I took my last Hawk down this road many times, and so I figured it would be a good way for me to judge any difference in how the forks perform. As I already expected, it is a huge improvement. The new bike feels much more planted and under control. Combined with the fork brace this bike responds almost immediately to steering input. The wet noodle feeling of the stock front end is almost completely gone.

One change I do plan on making is running a thinner fork oil. The rebound is actually a little bit too slow for my liking with 15 weight. Now that I can tune it independently from compression, I think I will go down to a 10 weight oil.

The rear shock is kind of a wash at this point. It is definitely better in terms of handling my weight on rough surfaces. I need to play with the damping settings, but as a whole I would say it was worth upgrading. I do wish it had a little bit more rebound damping, but it is also not a pogo stick either.

Fork valves
 

Thanks Mega Dan for sharing your shock valve adjustment experience, I will start there. Learning of your mods and those of other members have allowed me to make some truly amazing modification to my bike. I can wait for winter to be over so I can continue to improve:thanks: the ole Hawk

Mikes xs valve 27-1086 only has one bleed hole near the spring it measures 1.50 mm.

If the Mikes valves have a firmer spring, then my adjustments might not translate to yours very well. The best thing you can do is start with their recommended base setting and adjusting from there.

Once you get them installed I know I would love to read about your experience with them.

If you haven't done so yet, then I highly recommend the fork brace mod done by Wamey. Link http://www.chinariders.net/showthread.php?t=19349

The fork valves and brace combined is almost indescribable compared to a stock bike, and with the Mikes valves now being a possibility, then a massive upgrade to the front end of the Hawks can be done for less than 100 bucks, including fork oil.

Ok, so that would be one big difference. the nice thing is, that can also be changed/modified if desired. Simply drill more holes as desired to "soften" up the slow speed damping.

While doing some research on this mod I found some additional info that piggy backs on the mod Megadan has done. it is on an external website TS500/XS500

Hopefully this assists!

Good post and thanks for sharing. Great detail for people that might not grasp how it works.

Fork valves
 

Megadan do you have a measurement on those rebound holes?

Nothing definitive since I had no reason to measure them the last time they were out, but an educated guess just by looking at them I would say very close to the same 1.5mm that you measured on yours.

looking at the instructions on the MikesXS website for the valve the following is included

Enlarge the Holes in the Bottom of the Damper to 8.0mm. (5/16") diameter and drill additional holes as shown so that the damper rod has 6 holes ( 3 sets of 2) as shown. The holes will have to be deburred and chamfered inside and out after the drilling is complete. New holes must be spaced lengthwise at 10mm. (7/16") and must be at 180 degrees to the last set of holes so that the rod is not weakend. No other modifications are required.

Also found this info (http://www.xs500forum.com/index.php?topic=240.0 this has pictures, the text is below)

The Damper valve/Cartridge Emulator
Race Tech lists an emulator part number for the ‘75/76 XS500 at $170. (Dec 2011)
Because they are only $48, I took a chance and ordered the Damper valve set from XS650.com . (MikesXS.com for you Americans)
As the name suggests, this site caters to the XS650 model, but because the later XS500 and ’77- ’84 XS650 all have 35mm forks, I thought they shouldfit. (Note, I have a ’76 XS500C. Some earlier 500’s have 34mm forks . I’m not sure if the emulator that I used will fit 34mm forks.)

These damper valves are essentially knock offs of the Race Tech Cartridge Emulator. Mine came with the flat washer installed incorrectly and no instructions. (See photo)

The washers are easy to relocate. A quick email to XS650.com resulted in the document being emailed to me next day.
Take apart pic here:


You can see in this pic the small plate with has a hole in it. This hole allows compression damping for slow fork movement. The spring holds the plate down with a force that is adjustable with an allen head screw. The flow of oil during fork compression is from right to left.


This pic shows the plate lifted from the emulator body. This is the open position, which would happen when you hit a pothole, ie: the damping would be far less.


With the screw, spring, and plate removed, we can see inside the emulator. Visible is a thin steel washer-shaped one-way valve which is held up by a weak spring. This is the bypass valve for rebound damping. During fork compression the flow of oil is upwards thru the emulator, so this washer valve is closed.

During rebound , the oil flow through the emulator is downwards. The washer valve is pushed down by the flow and opens up a huge hole for oil flow, so virtually no restriction. In other words, the emulator does not affect rebound damping . I’ve pressed down on the steel valve with a plastic rod to show how far it can go down .

Installation
When taking apart the forks, I managed to totally strip the head of one damper retainer bolt. (The bolt at the very bottom of the fork.) I had to drill the head off. And I mangled the bolt head on the other fork. (Lesson learned: don’t substitute a hammer drill when you need an impact driver! )

It initially looked like the damper tube was not compatible with the emulator!

It turns out that the top part of the damper tube is a cap which pulls off easily.

I checked the fit of the emulator to the top of the damper tube-perfect!

Normally the tapered end of the fork spring fits over this removed cap. But to allow enough clearance around the emulator valve , the spring has to be flipped, so that the large end of the spring is at the bottom, against the emulator.

The next step was to drill out the damper tube. The compression holes (the larger holes) in the damper tube are about 1/4”.

These need to be enlarged to 5/16” and a third pair of holes need to be added. Making all these large openings removes any restriction here, so now all compression damping is controlled by the emulator valve.


I installed new fork seals while everything was apart. A 1 1/2” ABS drain pipe, made very slightly smaller with a belt sander , makes a great seal installer.


I installed the damper parts and fork tube, and new damper retaining bolts and copper washers at the fork bottom.
BTW the fork damper bolts available at XS650.com are too big-it cost me $3.92 to find out.
But because Yamaha uses the XS500 damper bolt/washer on many other models, you can still order them through your dealer.


The emulator spring tension determines what size bump will pop off the plate to allow for lower damping. In other words, what size bump do you want the shocks to absorb vs transmit to your arms?
To adjust the tension, back off the screw so that the spring is loose. Slowly tighten the screw until the spring is just held in place. This is the start point for counting turns. I tightened the screw 2 and ¼ turns, then tightened the lock nut. Then dropped the damper into the fork tube , spring upwards.

Dan, how did you tighten the bolt into the dampening rod? Is it reliant on the pressure of the spring once the whole thing is put together?

I have a tapered wood broom handle that I use to hold the rod and get the bolt snugged up, and then once the fork is assembled completely I go back and tighten the bolt down. Once you have it snugged up the spring tension is usually more than enough to hold everything together to get it tightened the rest of the way. Getting it started is usually where people have an issue with the damping rod turning in place.

I should also update one bit of info. The YSS Fork valve rebound/low speed compression holes are 1mm.

1mm seems very small.

There are 4 of them, which gives it almost double the are of the mikes xs valve.

So I just blew out or lost all dampening in my front forkkkks today. No oil everywhere just sag almost to the almost all the way to the bottom of travel now. Is there a. Iner seal i blew or what not? I'm going to do the SSR fork valve stand spacer for sure since do hard trail riding. Is there any videos I can watch or a basic fork removal video looks pritty straight forward think i have a good idea on doing the ssr valve and spacer it's just the removal process and installing everything back.

I just orded Mike's xs valves I will let everyone know how it goes and what adjustments I make once they are installed.

HI Dan,

Stupid question did you loosen the bolt at the bottom of the fork before releasing the top cap so that the spring applies tension, enough to release those bolts?

Yes, it is easiest to crack those bolts loose before removing the caps.

Anyone found better looking forks for the Hawk 250?
 

I hate how skinny the original Front forks look so i want to replace them wider ones. Any suggestions?

I know this is an old thread but I am planning on doing this to my hawk over the winter. I ordered the yss valves. I have some 15weight fork oil on hand. After reading Dans complete write up I'm thinking mayhe I should get 10 weight or go with atf which I hear is about 7.5 weight. From the guys who have done this what's your recommendation on the oil weight and amounts to start with. I was going to simply spill and fill with 200ml of 15 weight. But having found this awesome upgrade I'm going to try fork valves. I'm not new to mechanics but am still learning bike suspension. Hawks been fantastic to work on though.

So I installed the yss fork valves and drilled extra holes just as Dan did in his video. I left my cartridges at their factory settings. I used 5mm spacers as my factory preload spacers were 2" long which really surprised me. I refilled with 200ml 12.5 weight fork oil (I split it 50/50 with 10w & 15w oil as I was undecided which one to use). My rider sag is almost perfect with the stock spacers, valve and 5mm bushing. I haven't got any saddle tine other than a rip around the yard but immediately you can tell it is impressive over stock. They no longer nose dive on braking and when you slam the front end down it actually dampens the blow. Can't wait to go for a real ride and see how it handles.