What fork oil to use?

[katt]

What brand grade to use if i want softer shock operation in California.

How much exactly to put if i remove old oil completely?

[90GTVert]

Measure what comes out and put the same back in or measure height and do it that way. Not really sure what these things have stock. Just try light fork oil from a local dealer I suppose.

If you haven't seen this, it may be of interest :
www.youtube.com/watch?v=yWrSLBBWEjw

[ThaiGyro]

Hey katt, Have been working on my Yamaha Mio to improve it's front end handling. Being an old racer, I get impatient with non adjustable damper rod forks. I see three things that could be an altered, but more information is needed.

You say you want softer. Softer damping or softer spring? I see why you are thinking oil change, but most OEM forks have super light weight oils, meaning softer to begin with. Like vert said...no idea what's is there.

As a super general rule, lighter riders would tend to enjoy lighter viscosity, heavier people heavy oils. The range in my mind being 5wt for light weight, up to 15wt for big boyz.

In case you have not heard this: You can mix oils to get nearer your better viscosity! Two considerations. First, they should be from the same manufacturer...and be of like blend. I use Ohlin's here in my big bike, but mix their 10wt equivalent with their 15wt. to make 12.5. It is fully synthetic. Synthetics and "fish oils" as some call OEM fluids are not happy together.

If you are trying to fix "bump" damping, (that's the initial hammer into service that your forks feel) There are also things you can ply with, assuming you don't mind pulling them apart.






The above shows a damper valve. Many older dampers, had a "shim stack", or multiple valve pieces that fit together at the top of the damper rod. The idea being more surface area of the valve, to slower the bump impact and obviously less would allow quicker response/movement.

So what you have is internal hard parts working in some equilibrium with the oils. There is no steady state reality, riding style, temperature and rider weights all effect a change in feel.

Then...there is the spring. Another complication. They have a single rate that is a compromise. Scoots can carry rider/passengers cover far too big for the available little spring.

If you are near Redlands, CA, go see Ed Sorbo at Lindemann Engineering. Best suspension shop I have had the pleasure of working with.

[katt]

May 20, 2018 20:49:55 GMT -5 ThaiGyro said:

If you are trying to fix "bump" damping, (that's the initial hammer into service that your forks feel) There are also things you can ply with, assuming you don't mind pulling them apart.

The above shows a damper valve. Many older dampers, had a "shim stack", or multiple valve pieces that fit together at the top of the damper rod. The idea being more surface area of the valve, to slower the bump impact and obviously less would allow quicker response/movement.

So what you have is internal hard parts working in some equilibrium with the oils. There is no steady state reality, riding style, temperature and rider weights all effect a change in feel.

I cannot afford shops at moment got to figure it out myself.

Yes now when i go over uneven road whole scooter jumps up like there's no springs at all, i like the shocks to lower the bump impact to some extent.

I live in Los Angeles, ride during the day, my weight is 175 lb , i ride mostly 30-40 mph, what oil weight would you recommend?

Seen this video and i got a question, are scooter shocks supposed to fold that much as road bike shocks in the video, can someone with properly adjusted shocks try zip ties and tell me how much your fork travel? I doubt mine moves more than 1/4th of its length.

[ThaiGyro]

Sounds like you may have some "stiction" problems going on inside, but you can jump off that bridge after more checking.

The first thing to tune in any suspension, is "sag". The general thinking for road bikes and scooters is that you are looking for sag of 25 to 30+ percent of total travel. The attached shows up to 33%. Personal preferences. (That means percent of fork travel or rear shock travel) If you do have stiction issues, it would likely show by checking fork sag...your sag differential might be inconsistent, meaning internal problems. If consistent...good! You can move froward.

Look at this quick guide from RaceTech mid 90's. Good place to start!

racetech.com/articles/SuspensionAndSprings.htm

I weigh just a few pounds less than you. However, I am not near my scooter until Saturday. I can measure my Yamaha sag and let you know.

[ryan_ott]

You may need to look at your forks carefully and check that they are straight, if they are straight there may be a chance your forks are overfilled with oil and they can’t compress. If this is of any use... I have decent Paioli forks from a Aerox in good shape. I have about 13-16mm of sag. During normal riding I use 50-60% of travel. Hard braking I use 70-80% and can’t bottom them out. I’m using factory amount of10wt.

[katt]

Did my fork job today used Maxima 15W oil even though my old oil was less than 100ml from both shocks so i had no i had no idea what level to use i set it to 55mm when folded.

By the way my shocks are nothing like on 90GTVert video they way more inferior its this one the picture, which is probably most common cheapest Chinese scooter forks out there surprised no one know the oil level for them.

Is there some rule of thumb about minimal oil level like "damper valve should have no air underneath it when shock is decompressed"?

I kept the old oil seals and dust covers since brand new pair of this shocks goes for $40 on ebay and i have not seen a pair of oil seals cheaper than $20 plus $10 for new dusters and $10 for oil adds up to price of new shocks and makes no sense.

Here's a better video.

Before i serviced i bottomed out when braking zip tie was just 10mm above dust seal, perhaps this was another reason i were getting front wheel locked so easy when panic braking.

[katt]

Took it for a ride and it was bit stiff so i took out some oil, being lazy simply did it without taking off the forks just removed top cap and springs then folded and pumped out excessive oil, its not like i know the precise level anyway so i got to experiment with different oil levels.

This stock Chinese fork travels 100mm all the way to to triple tree before it bottoms out, however limiting factor that only gives it 80mm travel before it virtually bottoms out into a plastic panels of the scooter mainly this one that split in two (see pic below) .

Front fork folded all the way to triple tree (springs removed).


Simple fix is to remove that broken panel however another problem are this two attachments to the fork that hold speed cable and brake hose that will touch rear plastic wall behind the wheel the more your tire is facing sideways more it will push into the the plastic. Nothing that cannot be fixed by simple modification though.

[AtariGuy]

Bookmarked this thread, probably the best starter info i've read on forks. If anyone has any further reading/research, i'm all ears

[katt]

May 21, 2018 21:04:40 GMT -5 ryan_ott said:

I have about 13-16mm of sag. During normal riding I use 50-60% of travel. Hard braking I use 70-80% and can’t bottom them out. I’m using factory amount of10wt.

I only started noticing front sag when i sit as far front as i can (like on the very tip on the seat) and i sag goes away when i accelerate from the full stop and don't return until i brake, do you have any free sag?