Author Topic: OEM Fork Spring Mod  (Read 993 times)

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Offline Concurious

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OEM Fork Spring Mod
« on: July 18, 2019, 08:20:23 pm »
Hi Everyone,

I have been lurking on the forum for a few days now and thought I would join prior to buying a bike (hence the username). I love the idea of getting a Concours (c10) and having something to putz with but not break the bank. I am especially drawn to the idea of modifying the stock springs by cutting them, I previously had a Kawasaki ex500 and that was a very popular mod, and I remember trying to convince some folks on adv rider that they could stiffen the suspension in their dual sport if they tended toward street driving by cutting the springs.

What I am curious about, is whether or not anyone has tried to cut the stock springs, and add a cheap cartridge emulator (The Harley knock offs on ebay for 41mm shocks). It looks like they run about $60, and I was thinking that the emulators in conjunction with cutting about 7in out of the springs (creating a spring rate around 1.0kg/mm for a post 94 spring) and a heavier weight oil, would create a pretty aggressive front end setup on the CHEAP. I apologize if the subject has been brought up before (I couldn't find it), and if anyone sees any issues with my idea please comment. I am going to look at a couple bikes this weekend and I am excited to get my hands dirty. I loved my last Kawasaki, but it was also woefully under sprung at the front end.

Please let me know if anyone is using the knock off emulators and if they would recommend them. I will continue reading, and look forward to getting my hands on a new bike this weekend.

Thanks,
Concurious
Current Bikes:2002 Concours, 2016 Zongshen TT250
Past Bikes:1983 Yamaha Vision, 1991 Kawasaki ex500, 2006 SV650S, 2003 Kawasaki Super Sherpa, 2005 SV100S

Offline Bud

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Offline Concurious

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Re: OEM Fork Spring Mod
« Reply #2 on: July 19, 2019, 06:06:02 pm »
That's embarrassing, sorry I didn't notice that there is a current thread about the same topic. Thank you for providing the link. I have a bike that I am very excited to look at tomorrow, and hopefully I will be riding it home. Can't wait to dig into it, it seems like there is a lot of potential to make this a very capable bike!
Current Bikes:2002 Concours, 2016 Zongshen TT250
Past Bikes:1983 Yamaha Vision, 1991 Kawasaki ex500, 2006 SV650S, 2003 Kawasaki Super Sherpa, 2005 SV100S

Offline Bud

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Re: OEM Fork Spring Mod
« Reply #3 on: July 21, 2019, 07:38:32 pm »
 :great:
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Offline connie_rider

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Re: OEM Fork Spring Mod
« Reply #4 on: September 01, 2019, 05:53:15 pm »
Soo, did you get the bike?

Ride safe, Ted

PS: Removing 7" is too much.
      Would be very stiff, and the gap between the winds is not enough to allow full fork travel. (ie; Spring bind)
      Here is another discussion;  http://forum.cog-online.org/concours-c10-zg1000-general-chat-and-tech/front-fork-springs-2006-c-10/msg650861/#msg650861
     
« Last Edit: September 01, 2019, 06:05:53 pm by connie_rider »
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Offline Daytona_Mike

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Re: OEM Fork Spring Mod
« Reply #5 on: September 04, 2019, 05:15:28 pm »
Order the Sonic 1.1 or 1.2 spring kit  depending on your weight and riding style. Definitely get the inexpensive emulators but you will have to drill holes in the emulsion tubes  :)  That is a good time to replace seals and  slides
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Offline Concurious

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Re: OEM Fork Spring Mod
« Reply #6 on: September 05, 2019, 05:18:32 pm »
Connie Rider, I did get the bike! So far I have been enjoying it as is, and will hold off on mods till winter. I will have to read more, for some reason I thought that Steve in Sunny FL recommended cutting 7in, and that allowed him to have an effective spring rate of something like 1.0 or just shy of it. It would not hurt to start with an inch and then cut progressively more as I test it.

Daytona Mike, I am sure the Sonic Springs would be better, but in this case I am looking for good enough. My motorcycle hobby takes a back seat (financially and priority wise) to projects on my house. Anything that I can do for "free" might actually get done, and I have had some success cutting the springs on a Kawasaki ex500 before so I am happy to try again. The emulators seem like icing on the cake, I am going to try cutting the springs first and if that improves the brake dive I might stop there.
Current Bikes:2002 Concours, 2016 Zongshen TT250
Past Bikes:1983 Yamaha Vision, 1991 Kawasaki ex500, 2006 SV650S, 2003 Kawasaki Super Sherpa, 2005 SV100S

Offline Daytona_Mike

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Re: OEM Fork Spring Mod
« Reply #7 on: September 05, 2019, 08:23:19 pm »
Understood. You will definitely  cut down on the brake dive for sure.
Normally aspirated engines have perpetual turbo lag
2000 Red C10 1052 kit 100+HP  + way more torque.
2008  C14 Silver Dammit Full AreaP- Flies are put back in SISF_Flash
2011  KLR650   688 piston ported and polished
2011  KTM 530    This thing is FUN!!

Offline connie_rider

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Re: OEM Fork Spring Mod
« Reply #8 on: September 05, 2019, 08:28:08 pm »
Concourier, I'm pretty sure that Steve removed 5".
Calculations showed that as max removal without having spring bind.
I used 4" and was able to set my bike up for 35mm spring sag.

NOTE: When cutting, remove the material from the tightly wound end of the spring.

I also used his suggested settings on the emulator.

NOTE: The Emulator does not effect brake dive as as much as cutting the springs.
           The Emulator is primarily for adjusting the ride. {by adjusting the damping}

Ride safe, Ted

PS; Daytona, knows far more than I on suspension.
       I'm a rookie, and just telling you what I tried.
       Whatever he corrects on my thoughts is best...
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Offline Douglas

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Re: OEM Fork Spring Mod
« Reply #9 on: November 19, 2019, 02:40:15 pm »
I cut the springs on my C10 in 2003 after seeing my buddy Art put in Sonic 1.2. His springs were still too soft. Physics class in undergrad taught me the linear spring equation that dictates length of spring is directly inversely proportional to resistance. I have since forgotten the equation as that was 1998 and Physics class is not just remembered in principle. But in practice, if you measure the coil diameter, and divite it into the distance travelled, you will find there is enough room for half the original spring, even after subtracting some of the travel for sag setting. In practice you will find there is virtually no need for sag. I also found that the correct oil for this spring was 80w-90, or perhaps 75w-140. I've forgotten which I used on Mike Dionne's bike. Either way, it was still just a tad too thin of an oil. Important note is that you must use emulators if you do this or else your compression damping would be way too hard. The final result is that the spring is capable of bearing the weight of the bike...something that it can not do stock. Obvious question: Which half the spring do you use, soft or hard? Hard end. That's the loosely would end with greater gaps between the coils.

Minimal necessary tools:
 Micrometers
ruler
gray pcv pipe
flat washers with large ID to put between spring and pvc
needle nose pliers to remove cotter pin and preload adjuster
deep socket that fits the spring cap
hex bit sockets
air gun
....
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Offline Lee

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Re: OEM Fork Spring Mod
« Reply #10 on: November 19, 2019, 09:29:26 pm »
"In practice you will find there is virtually no need for sag. I also found that the correct oil for this spring was 80w-90, or perhaps 75w-140. "

Could you explain this recommendation please.

Offline connie_rider

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Re: OEM Fork Spring Mod
« Reply #11 on: November 20, 2019, 01:45:44 am »
Clarification question;
You sed; Obvious question: Which half the spring do you use, soft or hard? Hard end. That's the loosely would end with greater gaps between the coils.

I assume you mean to keep the hard {loosely wound coils} and cut your material and discard it,,, from the soft {tightly wound coils}…  In my case. I removed 4" of the tightly wound coils..

Ride safe, Ted
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Offline Daytona_Mike

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Re: OEM Fork Spring Mod
« Reply #12 on: November 20, 2019, 11:41:56 am »
I ran emulators and Sonic 1.1's. ( I weight 245lbs)  . I tested a lot of shock oils and ended up running 50W Spectra shock oil. Anything thinner  and my rebound damping  was too excessive. .
That bike to this day with the ZZR rear shock still  handles fantastic ( in conjunction with  the Meanstreak rear rim.)
Normally aspirated engines have perpetual turbo lag
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Offline Lee

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Re: OEM Fork Spring Mod
« Reply #13 on: November 20, 2019, 04:41:55 pm »
Douglas: Would you please specify your personal weight. Also did you really not need to compensate for sag or did you pre address this issue by your Gray PVC length in your setup?

As well, curious about your oil weights recommended. That is pretty far afield from Racetech emulator recommendations. Not being critical just curious. I have used 50 weight and now use a mix to 37 weight. Would like to understand your oil recommendation. Once I get this below sorted I may go back to heavier oil experiments.

Currently running emulators less than 1 turn, 4 holes in emulator plate instead of one, oil at 37 weight , stock springs cut to use hard widely spaced coils, and I weigh 285. My sag is not yet up to snuff. Will lengthen pipe inserts next go round to correct.

As aside, I removed my fork brace. Found I could not get it to operate without unduly stiffening fork action in practice. This with it working shimmed and checked unloaded without wheel for binding. Then when completely assembled still no binding. However with bike weighted on road brace affects fork action. This determined by its removal and reassembly several times now. I plan to plastigage it torqued properly one tube at a time. Feel there is an issue as yet not understood in the setup. Suspect it to be in the fork tube stanchions themselves setting up some kind of twist between stanchions and fork brace. That binding fork travel with bike is in use. Yes it is a early model fork that requires shimming. I think fork in action is causing pivoting on shim somehow in use.

Ted, if you are reading this you may remember I was concerned sometime back that brace was altering my suspension experiments unduly. It was. I will repeat my early experiments as time allows then go back to figure and resolve brace issue if possible.

Very curious about these outside box oil recommendations above 50 weight. I am planning to set up a test road course to look into it next season. Got a loop not far from my house where can run one weight then run home and change to another.

Ain't retirement grand! Yeah I know need to ride more tinker less.......Do try to mix both though. Thx all for input!
« Last Edit: November 21, 2019, 01:44:11 am by Lee, Reason: typos »

Offline connie_rider

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Re: OEM Fork Spring Mod
« Reply #14 on: November 21, 2019, 12:58:12 pm »
Daytona_Mike, can you clarify something?
NOTE: I am not arguing.  I'm in agreement with you.
           Just confused by your wording.

You sed; I tested a lot of shock oils and ended up running 50W Spectra shock oil. Anything thinner and my rebound damping  was too excessive. .

I think that adding; thinner/lighter weight shock oil would allow the shock to move quicker and you decrease damping??
                             thicker/heavier weight shock oil would allow the shock to move more slowly and you increase damping??

In this article from Race Tech they say that there is a hole in the tube that controls rebound damping, and the only way to adjust rebound is by changing oil viscosity. {See Rebound Damping at fig 3-18 and 3-19}
This Race Tech Article should be read/studied by anyone that is interested in adjusting their shock.
  It has a VERY good explanation of how a shock like this works and what the Emulator does.
   NOTE: It does take some study to begin to grasp.


https://www.racetech.com/page/title/Emulators-How%20They%20Work

Ride safe, Ted
« Last Edit: November 21, 2019, 01:15:03 pm by connie_rider »
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Offline connie_rider

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Re: OEM Fork Spring Mod
« Reply #15 on: November 21, 2019, 01:09:44 pm »
I do have another question though.
   I don't recall that a C-10 shock has a hole in that area of the Tube.
       Does anyone know if there is a hole or not?
       If no hole, what acts as the {rebound} orifice in a C-10 shock?

Ride safe, Ted
« Last Edit: November 21, 2019, 01:15:29 pm by connie_rider »
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Offline Lee

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Re: OEM Fork Spring Mod
« Reply #16 on: November 22, 2019, 07:15:53 pm »
Ted,
To answer part of question. There is no rebound damping orifice at the top of damping rods in the two sets I have (87 and 99, I believe) from air assisted C10 forks. As it would be a very small hole compared to compression damping orifices perhaps it is not needed in this circumstance as parts do not seal that travel of oil enough to warrant drilling that orifice. The damping seal is gapped and may be gapped enough as compensation by design suspecting. There by one less hole to drill for Maw Kaw's subcontractor. Refer to fig. 3.8 and you will see how seal ring gap might be the answer. Just a thought.
Oh regards to you and thanks for posting as always!

Offline Lee

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Re: OEM Fork Spring Mod
« Reply #17 on: November 22, 2019, 07:30:26 pm »
A second to Ted's recommendation on RT Bible and website. I have personally learned a lot from it on suspension works. Their reference has helped me immensely tuning for brake dive, road conditions in my part of world, and my riding weight. It, for me anyway, took rereading to grasp nuances and overlaps in function. They were very nice on phone with tech as well. That even though I identified as a second hand owner of one of their first emulator sets.

Offline connie_rider

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Re: OEM Fork Spring Mod
« Reply #18 on: November 22, 2019, 09:15:03 pm »
Thanks Lee.
What you said makes sense to me, and also makes Mikes heavier viscosity Oil seem the best option.

Ride safe, Ted
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Offline Lee

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Re: OEM Fork Spring Mod
« Reply #19 on: November 23, 2019, 05:23:49 pm »
Of note:

I am checking rebound damping by first applying brakes in curve to compress front end then releasing at normal point in apex. Watching fork rise speed as viewed through fairing down forks. This is dynamic and can be done at different speeds. Anyone know a better way, I am all ears?

I check brake dive and rebound similarly on straight.

Also using a loosely closed zip tie for monitoring full suspension compression. Right now am not getting full 5.5 travel range as I believe am carrying to much oil in forks limiting full compression. Will remove some oil 10ml at time to correct and tune this factor.

Got to get sag set properly before returning to above tests. It is a process. But it has its rewards.

Offline connie_rider

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Re: OEM Fork Spring Mod
« Reply #20 on: November 24, 2019, 12:48:29 am »
I am checking rebound damping by first applying brakes in curve to compress front end then releasing at normal point in apex. Watching fork rise speed as viewed through fairing down forks. This is dynamic and can be done at different speeds. Anyone know a better way, I am all ears?

XXX Check your  rebound damping by compressing the front end and observing how fast it comes back up.
You basically want it to rise almost as fast as you take the weight off the bar, without pogo-ing.
Video's on how to do this are on You Tube.
https://www.youtube.com/results?search_query=basic+motorcycle+suspension+setup+
Here is one with adjustable rebound damping.
  {NOTE: A C-10 does not have an adjuster, and the only way to adjust rebound is with oil viscosity}

https://www.youtube.com/watch?v=sz0z5IgVGSg

I check brake dive and rebound similarly on straight.

XX This may work for fine tuning, but you must first set as the damping as the video indicates.

Also using a loosely closed zip tie for monitoring full suspension compression. Right now am not getting full 5.5 travel range as I believe am carrying to much oil in forks limiting full compression. Will remove some oil 10ml at time to correct and tune this factor.

XXX You do NOT want to use all your travel while riding or under hard braking.
          My guess would be that max is about 80%-90%.
       ie; If you use all of your travel in normal circumstances, there is none remaining for sudden shock loading.

Got to get sag set properly before returning to above tests. It is a process. But it has its rewards.

XXX Did you ever find a cap that allows preload adjustment? This would help sag etc setting a lot.
« Last Edit: November 26, 2019, 12:34:22 pm by connie_rider »
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Offline Lee

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Re: OEM Fork Spring Mod
« Reply #21 on: November 24, 2019, 09:48:24 pm »
Never found a set of adjustable fork caps when looking last for early C10. Will just cut some new spacers accordingly as I plan to be in there soon anyway.

I am not getting even 80% travel so will have to adjust some. I have too much oil in there compared to stock spec. So have some room to maneuver.

Thanks for tips.

Offline connie_rider

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Re: OEM Fork Spring Mod
« Reply #22 on: November 25, 2019, 02:30:42 pm »
Hoping many that are more informed on suspension can chip inhere.
I'm guessing.

Know how to do spring/shock modes but not overly knowledgeable on tuning/damping adjustment.

Ride safe, Ted
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Offline Steve in Sunny Fla

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Re: OEM Fork Spring Mod
« Reply #23 on: November 26, 2019, 03:27:56 am »
OK, setting the wayback machine here. I first heard of cutting the springs from Douglas. It works and it's cheap. I don't remember, 5 or 7", I'm thinking 5". I also think I ended up with about the same setup and Daytona Mike, I had racetech emulators, iirc blue springs, 4 holes in the blowoff plate as a form of high speed damping, and oil did end up being about 35W. Working from an old / faulty shoulder supported computer, so YMMV. Steve
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Offline Lee

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Re: OEM Fork Spring Mod
« Reply #24 on: November 26, 2019, 01:18:42 pm »
Thanks Steve. I have "used" early emulators. Do not know about the springs as there is no blue left to/on them. Wish I knew how to compute spring rates. Seems I never have enough talents to ride the face of this earth with aplomb !