Can the old style front forks be improved????

[Imack]

I got two old bikes 250 elsinore 1975 and a 1983 Husky CR250.
I have been trying to figure out to to get any shock absortion when the bike lands in the front wheel, but seem like there is nothing other than the spring force. The internal piston gets some pressurization, but I think that the design is not meant to use hydraulics in the up direction. Does anyone have a good clue on how to improve this area????

 

[2strokerfun]

A stiffer spring and slightly heavier oil?? I think you are right about the fluid is mainly for rebounding on these.

 

[Bultaco206]

A stiffer spring and slightly heavier oil?? I think you are right about the fluid is mainly for rebounding on these.

Increasing the amount of oil is your best way to help overall compression. The weight of oil is your rebound.

 

[Imack]

But you are forgetting some...!

A stiffer spring and slightly heavier oil?? I think you are right about the fluid is mainly for rebounding on these.

As you know most of the oil is under the piston, as the front wheel hits the ground, the piston strts going up, oil on top of the piston starts flowing through the tube orifices to enter the lower chamber. The only holding the oil against the advance of the piston is air.., so on high impacts the suction force produces cavitation which is like another spring, but in essence there is some hydraulic dampening untill the upward force exceeds the cavitation negative pressure. That is the main reason why the new bikes have the inverted shocks...!
There is a world of difference as you may have experienced

 

[2strokerfun]

Try this tip from Rick Siemen (adding air to old-style forks). Don't know if it works, but what the heck:

http://www.superhunky.com/mar01rsForkCaps.html

 

[wirefryer#85]

I went with progressive rate springs and a heavier weight oil to take the ouch out of landings.

The guy who does my suspension rebuilds also put in a piece of PVC pipe in each fork to 'firm' them up. I have no idea how long they are exactly or where in the assembly they are (I think they sit on top of the spring)

I've never messed with the air pressure, don't really have a need to.

 

[Vince Stokes]

I dont know if there is a Ractec Cartride Emulator that fits but
if so its a great gadget,gives you damping that works on big hits and small.

 

[Imack]

Guys, I think all these solutions will work somewhat.!

What I have been thinking is to incorporate a plunger inside the piston tube that partially blocks the oil passages. Then portrusion inside this tube could be used to control the height of the plunger in relation to the oil passages. The lower screw could be used with a nut holding the tube to the outer housing, then changing the space between the bolt head and the nut, will cause the screw to portrude more inside the piston tube, therefore moving the internal plunger somewhat across the oil holes...! What do you think of this idea for an adjustable dampening of the front forks????

 

[dirt bike dave]

What do you think of this idea for an adjustable dampening of the front forks????

I think it will not work as well as Race Tech Cartidge Fork Emulators and will be alot more work.

The emulators are also very adjustable, but you do have to remove the fork springs and fish them out. Not perfect, but if RT has them for your application it will greatly improve your forks. JMHO.

 

[originaldirt]

Yeah, "what he said" ! Emulators, are the way to go. They make old forks work close to new forks.
OriginalDirt

 

[Shadowpillar]

would this work well for dual sport bikes like the DT175? Improve the ride on the roads? (especially around here...)