Fork springs mod: poor man’s hyperpros

I just came across this post by the legendary Stefano Bonacasa of the SWCI. It seems that by adding a second OEM small fork tube spring and washer to the OEM fork spring and changing the fork oil to 15wt similar results as Hyperpros can be had at ~$20USD.

Here’s a screenshot of the post from the SW-T FB post:




And here is a link to the front fork parts. See items 4 and 6:

https://www.partzilla.com/catalog/honda/scooter/2009/fsc600d-ac-silver-wing/front-fork

Maybe I am doing something wrong but I cant read the screenshot?

I did put 15w oil in my forks when seals were replaced. Helped some.

Now that's my kind of mod!

Is he suggesting 'doubling-up' on parts 4 and 6 and then put in 15w oil?

Sorry I can’t seem to manage a clearer screen shot of Steven b’s mod.

Loosemarbles, as I understand it the process is to remove the spring cap, spacer, spring, and empty the fork oil. Do a good job now. No sense in doing this half-assed. Then when reassembling you first drop in a new return spring and new washer.

15wt fork oil is then added to a level of 90mm. Pump the fork several times to insure that there are now air bubbles and double check that 90mm oil level.

After that install the original spring, spacer, washer and fork cap in the traditional manner. The new spring and washer will increase the spring height by an additional 25mm.

This same mod would probably work on a Forza as well.

That's how I figured it. As there is already a return spring and washer in there, I'd be doubling-up on those to increase the spring height.

That's kinda the same idea I had, when I replaced the spacer with two longer springs, extra washers and 15wt. oil/raised level slightly, over a year ago, it works very good, short spring could be better with oem spacers, may try it next winter if I'm really bored, , is riding season now  




Admin edit: Originally posted May 3, 2021 in this topic:
https://www.silverwing600.com/t12150-forks-bottoming-out

zrx212 wrote:

That's kinda the same idea I had, when I replaced the spacer with two longer springs, extra washers and 15wt. oil/raised level slightly, over a year ago, it works very good, short spring could be better with oem spacers, may try it next winter …

Damn! Senior moment. I knew I’d seen similar information “recently” somewhere. I’m sorry that I misplaced your earlier post zrx212.

Unfortunately with this new forum format it’s difficult to find this helpful information. I’ll try merge these posts into one topic.

Credit where credit is due. Hats off to zrx212 for first bringing this mod to light.

Thanks for your compliments  

I kinda like the variation of the idea where he places the new short spring+washer 1st in tube and then the rest of the OEM parts, it's a lot easier to push on solid spacer than a spring flexing   , in my case the extra spring was slightly smaller outside diameter, so I could not insert first.

IAC it would be a easy mod and in effect would add to overall spring action, instead of adding more spacers, kinda my reasoning when I did mine.

I have a monitor that is large enough that I could make out the wording in the image above and
it follows almost verbatim:


Front springs mod: poor man’s hyperpros A397aa10


Want to change the front fork springs?  Know that you have to spend around
120 euros but there is a CREATIVE way to achieve the same result by spending
only 20 euros using the same original springs.
Buying two springs and two washers.  Total around 20 euros, maybe even
less.

The Honda codes are
51411-MBA-003
51404-MBA-003

Transfer spring + washer= approx. 25 mm.

Once you have emptied the oil from the fork, insert the return spring, then the
washer and fill with SAE 15 oil leaving 9 cm of air, then insert the spring, the washer,
the spacer and of course the cap exactly like the picture.

Apologies for resurrecting this thread but I'd like a bit of info and advice. I'm considering doing this mod and can get the parts to order from David Silver spares for around £17 delivered plus a can of fork oil. On the photos that Tim provided above it shows the tightly coiled part of the spring going in first and on Stephen B's video it shows him installing the spring tight coils first and wider coils to the top. In the Honda fsm it shows to fit the tighter coils to the top so just wondering which one is correct and does it matter.

Check out the thread 'Fork spring direction' in the search bar.

Read it thoroughly and check out the You Tube video. It would appear that it makes no difference which way up you install the springs. I put mine in as per the FSM so that I didn't have to make the decision

Personally, I don’t think installing the spring up or down is gonna make a difference in your ride experience. But…

A theory goes that given the fork tube holds a specific level of fork oil before the spring is inserted, then if the spring is inserted tight coils down the fluid level will rise higher in the column vs than if the loose coils are down. That is to say there will be smaller column of compressible air to cushion the fork movement if the tight coils are installed down.


Perhaps one of our resident wizards can add more sense to this curious dilemma.

Good theory Tim. Hadn't thought of that.

I thought of the modification by Stefano Bonacasa.
Did some long research, but eventually I went for Hyperpro's.
A good friend pointed me to the company for more info. And he had many years of experiences with Hyperpro's.
I read all about the way they promote the Bonacasa method but I think that it was better for me to go with the Hyperpro's.
I went to my dealer for a mega deal, because I also wanted new tires so together with the tires, I had the Hyperpro's installed.
My god the difference is huge, riding in general is improved but when cornering and slow riding the differencein very noticeable.
Worth every Euro spend.
Greetings from the Netherlands

To put Tim's theory to the test we need to know the actual displacement of oil relative to each end of the spring using the oil level as a benchmark. It may not be rocket science but it's not far off

hello
I did this modification last winter
on the country road/motorway/in town the bike works great
but if you ride on cobblestone streets it's horrible
I'm aiming for hyperpro this winter

stefan

Thanks for all the feedback so far. I've just been looking at another of Stephen B's videos from last year showing his front springs mod https://www.youtube.com/watch?v=hMXjRO24s7Q  Not speaking Italian I set the video to show English subtitles to get a better understanding what he was saying. The translation is a bit hit and miss but you get the gist of it. In it he makes a point of saying that the fork springs as standard have the tighter coils facing up but he states that he always fits them facing down. Unfortunately he doesn't explain why he prefers this. The general opinions seem to be either way is ok. If I do go ahead with this mod I'll probably fit them tight coils down and see how it goes.

P-21179 wrote:

hello
I did this modification (Snip)
if you ride on cobblestone streets it's horrible
stefan

Hello Stefan and welcome to the forum.

I can’t imagine that riding cobblestone is ever pleasant. But is StevenB’s modification significantly worse than riding cobblestones with original suspension?

Which kinda begs the question: What can one do set up suspension for cobblestones? No doubt that’s probably going to be a discussion for another topic.

Gee, how does Vespa do it with those tiny wheels?

Hello Tim and all oders
The SWCI modification makes the small bumps felt in the steering wheel and it jerks here and there
you lose softness in the suspension
but if you drive on the highway it's a dream
but talk to stefano bonacasa by contacting him via youtube i did he answered right away

Stefan

There's a couple of things to consider in the great fork spring orientation debate.

One is that from a forces perspective, the orientation makes no difference. When you compress the fork, the tight coils collapse first (they have the lowest spring rate in terms of N/mm) and then the stiffer wider coils take over, so you get some progression of the spring rate. The tight coils collapse first whether they are on top or at the bottom.

The fork spring end diameter may play a part in the orientation decision; often times the tighter coil also has a smaller diameter, and that needs to bear directly onto the damper rod top, or against the washer under the spacer. You wouldn't want the coils to be able to slip down into the damper rod and jam for example.

The last point would relate to the oil and air-gap created, but I think that one cancels itself out. While the tighter coils to the bottom would displace the oil upwards more than the loose coils, the converse is happening to the air displaced by the looser upper coils, so the net volume of compressible air doesn't change with spring orientation. Or at least that would be my take on it.

I've got access to quite a few different Honda service manuals, and there is no particular pattern to the coil orientation.