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Message started by Armen on 01/11/17 at 20:06:20

Title: Forking around
Post by Armen on 01/11/17 at 20:06:20

So, once I read Gary's excellent fork fondling article, I decided I had to do mine.
Over the course of way-too-long, I bought the Race Tech Emulators, Race Tech springs, a good used front end (so the bike wouldn't be beached while twiddling the forks), all the seals, clips, allen bolts, upper and lower bushings, crush washers and whatever else I could think of.
There was an article titled 'Deslopping the Sliders' in Motorcyclist magazine in the 80's written by Joe Minton based on some work done by Pierre DesRoches (very good Kawi tuner). Around that time, the practice of using upper and lower Teflon coated bushings in forks was becoming commonplace. The good news is that the fork tube would be sliding on a slippery, replaceable bushing. The bad news was that the fit was often less than airtight when new, and got looser as the miles accumulated.
The gag was to remove the lower bushing from the fork tube, place a piece of shim stock underneath it, reinstall the bushing, and check the fit in the lower leg. The idea was to go up in thickness on the shim stock until the fork tube showed resistance when slid into the lower leg, then go down one thickness on the shim stock. I've done this on more than a few bikes. Sometimes no shim is needed (usually with new parts), and sometimes as much as .004" shim stock was needed.
The upper is a bit trickier. The upper bushing is pressed into the top of the lower leg, so a shim can't be fitted. The routine is to lay the bushing on the fork tube and dimple the outer surface with a center punch. The bushing and the fork tube are then reinstalled and checked of slop or binding. If there is slop, more center punching. If there is binding, then the dimples on the bushing are reduced by wiping them with a sharp flat file.
So, off I went.
With new lower bushings, the fit of the fork tubes in the lower legs was perfect. No slop and no drag. The uppers were another story. I could move the fork tube in the top of the lower leg. The bushings were removed and dimpled. The article also said to take a wipe off the edges of the bushing where it came together to allow the bushing to become a smaller circle. On the first go, the fork tubes bound up. I removed the top bushings and filed a little off the center punch dimples. The second try was perfect. No slop and no binding.
I modified the Emulators as per Gary's article. Different springs, more holes, different preload.
One fork tube showed slight wear marks. On bikes with a single disc and minimalist fork bracing, I've often stood on the pegs and looked over the bars at the front end while grabbing the brakes. You can actually see the front end rotate as you grab the front brake. i swapped the legs so that the less worn one would be on the disc side from now on. I'm hoping that with the more butch top clamp and the TKat fork brace, the front end won't twist as much or as easily.
In reassembling, I realized I had lost one of the washers that go under the fork seal. A 1/2" fender washer has a similar OD, so a bit of lathe work and I had a god substitute.
The whole mess went back together pretty easily. A bit of Race Tech seal grease on the ID of the fork seal. 10W fork oil (on another of my bikes, the 15W that Race Tech suggested was too thick) filled to 150mm from the top. As per Gary's article, I bought a set of pre-load adjustable caps, a nice touch.
I'm figuring that it'll need some tweaking, but I'm hoping it's pretty close. Gary is a bit heavier than me, so some of the specs that work for him might not work for me. Children won't die. I'll sort it out. It has to be better than the stock crapola.
Thanks to Gary for all his experimentation and thorough write-up.

In the pic are the Race Tech springs and Emulator. A fork seal/bushing instilling tool I made, the upper bushing showing the center punch dimples, seal grease, and some other parts.

Title: Re: Forking around
Post by Gary_in_NJ on 01/12/17 at 05:41:09

I do not think I can now lay claim to the best suspension on an LS650 - it would seem that you have set the bar much higher. I assume that the result of all of the effort at the bushing is to reduce stiction. There is a fair amount present in the LS forks. If I find a good set of forks on ebay, I may perform similar work. I'll be interested in knowing your stiction figures when you set your sag.

Interesting analysis on how a fork brace helps under braking loads, I've never even considered that benefit.

Title: Re: Forking around
Post by Armen on 01/12/17 at 07:38:35

haha
Somehow I don't think this will be an better than yours, Gary.
The purpose of the bushing twiddle is to tighten up the front end, not reduce the stiction. The play between the fork tube and the lower leg makes for a less solid front end. I used to think the front end stayed loaded in one direction until the bike shifted from accel to decel. One day I was riding an early Z1 Kawi (Flexible Flier) and noticed that the gap between the gas tank and the top tree was changing as I rode in a straight line. Just the variations in the road surface were enough to change the load on the front end and make the frame flex. So, any clearance between the fork tube and the lower leg would make for a wiggly front end.

Title: Re: Forking around
Post by Ruttly on 01/12/17 at 15:34:59

Stop it , you two have insulted my front forks enough. Now I'm gonna have to spend more money. Really I like how mine handle , yeah it's a cheap fork but it does just fine , the key improvement is a fork brace , it changes everything the fork does , especially when braking !

Title: Re: Forking around
Post by Armen on 01/12/17 at 16:37:37

Hey Ruttly,
The bushing flog shouldn't cost anything except fork oil, unless you change the bushings. Most manuals say to renew the bushings each time the forks are apart, but I think that is a bit of overkill. Just try the shim and center punch trick and see how it feels. If you've added a fork brace, this could be the icing on the cake for less wiggle.
Honestly, on most of the Pogo Stick forks I usually either do Progressive springs, or Emulators and straight wound springs. if you aren't really sensitive to fork action, just better springs will probably do for you.

Title: Re: Forking around
Post by Ruttly on 01/12/17 at 20:02:04

When I did the RYCA lowering kit the forks had only 809 miles on them so they are still new. Lowered , replaced seals , installed Progressive springs and chopped 1 inch off oem spacers and used my standard fork oil ,
Type F ATF. Added a Superbrace and upgraded front brake to Shawn's kit.
I just wish I would had the foresight to realize the frame needed to be deraked quite a bit , but the forks work fine and definitely good enough for this bike, have no complaints works well enough to ride fast on the edge of control !

Title: Re: Forking around
Post by Armen on 01/13/17 at 03:05:45

Hey Ruttly,
Any reason you are using ATF instead of real fork oil? IIRC, Dextron was the kind they asked for, not type F. Anyhoo, the bikes are usually happier with real fork oil.

Title: Re: Forking around
Post by Ruttly on 01/13/17 at 04:07:46

Had a bunch of it. It works well. Its cheap. I like a fork that feels good in the dirt as well as the road after all it is a tracker with dual purpose tires. If it was just a road bike I would have went with a 20wt fork oil.

Title: Re: Forking around
Post by Ruttly on 01/13/17 at 06:53:35

Besides all that I don't think it would even make a noticeable change until you got to a 30 wt with that inexpensive fork, money better spent on a fork brace ! ;D

Title: Re: Forking around
Post by Gary_in_NJ on 01/13/17 at 07:39:22

Ruttly,

I don't think you appreciate the function of the viscosity of the oil in a damping rod fork. Damping rods have major limitations that can not be fixed by simply changing the oil viscosity.

In the damping rod forks used on the S40 oil is forced through a fixed orifice at the bottom of the damping rod. This restriction is what creates compression damping. Forcing oil through a hole creates very little resistance to flow at low speed. Conversely, during high flow rates a lot of oil needs to flow through the damping orifice very quickly. Under this condition the fixed orifice cannot accommodate the flow and the fork becomes hydro-locked.

Increasing the viscosity of the oil only serves to quicken the rate at which the forks become hydro-locked? For a bike that is ridden on smooth surfaces and doesn't experience high-demand braking a higher viscosity can give the impression of improved damping during low-flow situations (because in the moment, the damping is better). However as soon as the road turns rough or during heavy braking the forks will loose all ability to dampen the fork movement. Compression will stop mid-stroke and worse, rebound will occur at very slow rate. This results in a bike that uncomfortable ride. Due to the slow rebound the front wheel contact patch rolls closer to the sidewall which can potentially cause the the front end to wash out, resulting in a low-side crash.

There are many problems associated with the way in which Suzuki set-up the S40 forks (don't even get me going on the 75mm air gap). I would caution you on using a oil viscosity higher than 20w in the forks.

Title: Re: Forking around
Post by Ruttly on 01/13/17 at 09:57:05

Dah !!!

Title: Re: Forking around
Post by Ruttly on 01/13/17 at 10:24:16

My point was it's such a piss poor fork that you wouldn't notice the difference until you got up to a 30 at fork oil. You guys are putting lipstick on a pig trying to get these forks to be something they will never be !!!
I did it right , I did it cheap , they work well for what they are. I wrote it all down spacer length I wound up with & oil level if you want to know !

Title: Re: Forking around
Post by Gary_in_NJ on 01/13/17 at 11:01:14

5E79787860750C0 wrote:
You guys are putting lipstick on a pig trying to get these forks to be something they will never be !!!

Well, until you have ridden a damping rod fork that has been modified with valving you have absolutely no basis for comparison. The fact is we HAVE converted the forks from a damping rod to a VALVED FORK. It's a completely different animal than a pig. It has all of the characteristics of a modern cartridge fork - the exception is that there is no external adjustment for compression or rebound. Also, the low-speed compression is fixed, but drilling the extra holes in the base plate adjusts the low-speed compression for a bike in the 300 pound range.

You may like your forks, but you'd love mine. Like I said, until you ride a modified bike you have no basis for comparison. I've done this conversion on my KDX200, CR250, GSF1100, VN750, SV650, FZ6 and now the LS650. It's a night-n-day difference.

Title: Re: Forking around
Post by Ruttly on 01/13/17 at 12:23:04

Like I said your going to make me spend more money !
My bike weighs in at 307 maybe 310 with a full tank !
How much $ ? What you take apart the forks to adj. them ?

Title: Re: Forking around
Post by Gary_in_NJ on 01/13/17 at 12:45:54

The process is well documented in the technical section.

Necessary parts: Racetech Gold Valve Emulators (GVE) @ $110-$125 and straight weight springs $110-$125.

If you have fork spacers I would suggest ditching those and getting a lower triple clamp off ebay and modifying it into an upper - investment @ $25 plus a few beers.

You already have a fork brace, so the complete job can be done for $250. For that sum of money you get compliant forks that are plush without being soft (no fork dive).

Has anyone in Ruttleyland done the conversion and would be willing to have him take your bike for a ride?

Title: Re: Forking around
Post by Armen on 01/13/17 at 18:07:10

Hey Ruttly,
I didn't post this as a way of wagging my finger and saying "You have to do this!". It was just a few notes about stuff I'm trying in case it might be of interest to someone. I get it that a lot of what I do isn't necessary. One is reminded of the story of one of Buddha's disciples asking "Master, why does a dog lick his nuts?" to which Buddha replied "Because he can!"
;)
If you are happy with the forks, leave them alone.
Having said that, you took a mediocre fork and made it worse. Cutting out 1/2 the travel, using dog squeeze for fork oil, and then complaining that the forks are crap, is a spectacular level of cluelessness. Kinda reminds me of a bud that couldn't understand why he had so many health problems, and when I pointed out that being 425 lbs wasn't a good long term plan, he went into a rant about that being irrelevant.
Again, whatever works for you.

Title: Re: Forking around
Post by Ruttly on 01/13/17 at 20:01:01

Well if I was starting this project instead of nearing the finish I would do it , I can live with some brake dive , I'm not sure how to ride without brake dive , kinda part of my style ! ;D

Maybe on the next project , we will give it a try

Title: Re: Forking around
Post by Ruttly on 01/13/17 at 20:24:38

Wow , didn't mean to upset you, pointing out that the forks are outdated , they are fine for my application. If I was building a cafe project I guess it would be a different story. I might have taken a different approach and just used a ninja or gsxr front end cause they just bolt on. Wish you could take it for a spin you might just like what this know nothing built

Title: Re: Forking around
Post by ohiomoto on 01/14/17 at 04:59:57

Too each his own guys.

We all own this bike for different reasons. Some because they like the look of the bike in stock trim. Others because they see a nice platform for builds. Some want performance, some want looks and some want both.

For me, I just wanted a simple "older" looking bike with "modern" reliability that I could build at a relatively low cost. If I wanted performance, I don't think I would have started with this bike. (Mostly because I don't want to spend the time, effort and cash to do it.) That sort of defeats the reason I bought it. But those are my reasons and I'm not going to judge others who are doing their thing on here.

I think it cool to see how someone else wants to do it and I appreciate others sharing their work. It might inspire me to do something I wasn't planning on doing originally.

That's one of the cool things about this community is the diversity of the members and the bikes we ride (even though they're all LS650/S40s). I say more power too you all. Do it your way.