The importance of fork oil quantities

[Oldnick]

Some time back I posted about hard forks on my triked Valk. I had had them repaired and they were wrist-shatteringly hard. You guys talked me through why it was like it, and getting a bit of oiil out of the forks, and ounce at a time.

In the end I took out two lots of 25cc (1 ounce) and another of 35cc; so quite a bit. That last 35 cc took me over the hump on the comfort and lack of pogo sticking.

It's a different ride! Suddenly my cruiser is comfy and yet handles better than it didin many ways. No more hopping over little bumps on corners. No more hitting tiny bumps in a straight line and feeling like I was about to have the bars wrenched from my grasp. No more death grip when crossing railways.

So I just want to thank you all who helped me. It is an amazing difference. I may even take it up to 100cc to see what happens.

Nick

[98valk]

 

[Patrick]

Some folks think if a little is good, more has to be better.


But, I'm wondering what springs you are using. I found out years ago that Progressives like less fluid.

Its a lot easier to add fluid than take it away isn't it.

[Oldnick]

The guy who serviced the forks was pretty adamant that he used 10w and only the recommended amount. I reckon he's a pretty bike loving guy who also loves trikes and outfits. He went to a lot of trouble to hitch me up with a sidecar guy who builds leading link forks. The price scared me off...
 for the time being...   

So Yeah I  could see where the soft start Progressives would like less oil. I do not know what I have in my girl's forks. I do know that whatever I now have a sweeter ride.

Hah! Yeah I ended up using hose designed for mechanical pressure meters...very narrow (2-3 mm of), stiff walled stuff, to get down into the left fork. Took a few tries. The tube is so small that sucking the oil out with a syringe takes minutes.

Nick

 

Some folks think if a little is good, more has to be better.


But, I'm wondering what springs you are using. I found out years ago that Progressives like less fluid.

Its a lot easier to add fluid than take it away isn't it.

[Roidfingers]

So what is the easiest procedure to get some fluid out ? Mine seem very stiff. Would like to smooth them out a little.

[flash2002]

I did mine today, lift the front off the ground, unscrew the left cap and bring the bike back down till the cap come up. inside you will see a rubber bumper, pull it up and tie it to the cap. Look inside you will see 4 holes and the spring blocking the holes. I took a sharp pointer and stuck it in one of the holes behind the spring and push on the pointer to move the spring to the side. By doing that, the spring on the opposite moves enough to the side to clear the hole. All you need now is a small tube and some way to suck the oil out. The right side you don't have that problem. When you finish the left side, jack the bike back up and install the cap, do the same for the right. Do one at the time.

[Oldnick]

Yeah you maybe able to move stuff around as flash2002 says. I didn't get that    .

The advice on opening the fork top is right on the money.

For me the trick was very thin air/vacuum tube...stiff walled stuffwith a 3mm OD. You need to find the passage down into that left fork.

I used a 50ml syringe to suck out the oil. Its slow. Suck out as much as you can, then blow it into an accurate measure (I used another syringe)
 When you have enough in the measyre , blow the rest back into the fork.

Work 25cc at a time. Suddenly the ride will be .....nicer.

[Roidfingers]

how far down is the fluid from the hole? 3m OD. Dam that's small ID. I have a brake syphon. Could that be used?

[Oldnick]

mmm....6"? If you tyake the top off, you will see the plate and the oil is a little below that.

You may get away with larger tube if you can move the spring as described. But the holes themselves are pretty small. I found that a stiff pipe was best. I got mine from a place that sells hoses fro hydraulic etc work.

It's the work of minutes to get the top off the left tube and try to move the spring to free a hole. then you can see if you can use larger tube or not. i used a 60cc syringe, with a couple of different sized tubes silicoine-sealed to get down to the caplilary for the oil. as i say it's a slow process getting the oil out, but the whole process should take maybe 1/2 hour.

The right tube is just a tube. Easy and you can use a much larger sucker to save time and effort.

Nick

[Oldnick]

BTW I do not know if this was said, but undoing the lock nut and removing the tune cap nut frees things up a bit on the left side.

The tube I used is known as semi rigid vacuum tube, used for dash mount vacuum gauges and such.

Nick

[mark81]

Thanks for the info Nick. I know this whole process has been a headache for you, glad you finally got it sorted out.

[Oldnick]

I took the last 35mm out of the left fork today and gave some thought to what I would say if dsomebody asked how. Apart from what has been said so far:

- If you use the thin tube do NOT cut with sidecutters DAMHIKT. They pinch the tube and make things even harder.
- I did manage to move the spring a tiny bit. I found every time I have done this that the hole at about 10:00 on the plate, if you stand next to the bike facing forward on the left.
- if you lower the bike it lifts the top of the springs and the plate and it's easier to get to it with the tube. It will of course lower the oil and require more tube to extract it.
- my way of ensuring that I get the right amount out is to extract more, then inject the right amount into another syringe. The rest goes back into the fork tube.

Mine's a triked Valk, so I have no worries, but has anyone commentas on how to keep the bike stable on the jack?

[Oldnick]

So. Interesting. I only took oil from the RHS fork tube, because it's easier and it is the compression one that will feel the bumps as I hit them.. As I said, no more pogo sticks and death grip over railways. I tested the tirke with unequal amounts of oil, just to see how itr was.

Today I took the oil from the left fork...and the ride got bumpier! I can only think that when I freed up the compression, the slow release meant that I was simply not getting the tyre back down to the road on the rebound, so the wheel was simply "floating" over ripply bumps.

The ride is still heaps better, in that larger sharp bumps are absorbed far better, and the trike sticks like the proverbial brown stuff to the flat wooly bed cover, but (to me at least) it was an interesting exercise in suspension physics. Having one fork compression and the other rebound complicates things a bit. But it would be interesting to experiment withg different quantities or viscosities of oil in each fork.

To emphasise the importance of this stuff, I reckon I have gained 5-6mph on sharper curves, because of my increqased confidence in the front wheel not skipping out if there is a few sharp bumps on the way around. I seriously reckon my front wheel has jumped 4-6" sideways in the past on a hurried sharp bend or corner. A few of those can really spoil the "racing line"


Nick

[The emperor has no clothes]

So. Interesting. I only took oil from the RHS fork tube, because it's easier and it is the compression one that will feel the bumps as I hit them.. As I said, no more pogo sticks and death grip over railways. I tested the tirke with unequal amounts of oil, just to see how itr was.

Today I took the oil from the left fork...and the ride got bumpier! I can only think that when I freed up the compression, the slow release meant that I was simply not getting the tyre back down to the road on the rebound, so the wheel was simply "floating" over ripply bumps.

The ride is still heaps better, in that larger sharp bumps are absorbed far better, and the trike sticks like the proverbial brown stuff to the flat wooly bed cover, but (to me at least) it was an interesting exercise in suspension physics. Having one fork compression and the other rebound complicates things a bit. But it would be interesting to experiment withg different quantities or viscosities of oil in each fork.

To emphasise the importance of this stuff, I reckon I have gained 5-6mph on sharper curves, because of my increqased confidence in the front wheel not skipping out if there is a few sharp bumps on the way around. I seriously reckon my front wheel has jumped 4-6" sideways in the past on a hurried sharp bend or corner. A few of those can really spoil the "racing line"


Nick

And give you a racing stripe in your shorts. Does your trike have a rake kit ?

[Oldnick]

Haha! Yeah, it can be a bit.......startling.

Yeah it has a 6deg rake kit. I struggled with the theory of the rake kit until somebody pointed me to an article and diagram that showed how it works. To me _added_ rake would make steering even harder, but the geometry of the rake kit does exactly the opposite. Weird and a clever trick by somebody, sometime.

With the big Valk up front and a 6' Ford rear end and a 6.6' wheelbase, total length  about 8.5' or so, the girls is still a bit of a handful if pushed. I have not ridden other trikes to compare, but on a long twisty road I get a bit of a workout if I push myself.

One thing about that big bum, I have never even felt like she's lifting a wheel. So far the trike has not been the limitation

Nick