Rightside up 80´s 46mm forks

mbha

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#1
(43mm, coldn't delete my post)
Hi!
I'm really having a hard time finding out some tech specs regarding plain old genuine 43mm forks before the upside down era.
I have a KX250 -87 and a CR250 -86. What is the recommended oil volume ?.
Is there any recommended settings that everyone in the world know of but me ?

//Many thanx
// Bengt

[This message has been edited by mbha (edited 03-11-2001).]
 

Jeremy Wilkey

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#2
Bengt,
I don't have a volume but I think you will find that 100-130 should work fine for either one.
Regards,
Jer
 

mbha

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#3
Thanks for the reply but I don´t understand how I am supposed to measure the level.
Perhaps you can help me out on this one, I tried to dissasemble the fork leg today to change the seal. I don´t know how to remove the inner fork leg. I tried to turn the nut at the bottom of the fork but it seem to be stuck with the nut and everything turns. Now that I have the fork leg loose from the bike i can pull up the inner leg so that the holes come up above the seals but no furher. This is about where my ideas are running out. I´m not suposed to be able to slide the inner fork leg this far up, right ?
What´s the trick ?
//Beng
 

Jeremy Wilkey

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#4
Run a aearch for instructions.. you will find my usd instructions. The concpet is simillar.
Regards,
Jer
 

mbha

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#5
I searched first but I can´t find anything appropriate to conventional forks here or anywhere else. Now I have searched again and nowbody seems to have talked about that.
So I still wonder why anybody would care about the oil level in the fork since there is no oil stick or level hole. the volume seems to be the only valid measure unit to me. And in order to take the inner (upper) tube out, do I unscrew anything at the bottom or at the top of the fork (steering head) ?.
//Bengt
 
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#6
I just purchased an 85 RM125. They have the 43mm units so this might help.

Pull the spring out and let the inner tube fully collapse to the bottom. The oil height is measured in milimeters from the top of the inner tube to the top of the oil. Raising your oil height will lower the number.Ex. If your oil height is 120mm and you want to add 10mm of oil your new measurement will be 110mm.
The recommended oil height for the RM is 170mm. Maybe try that and go from there.

To get the bottom nut off,put the spring and fork cap back on and zip it off with,I believe,a 14mm allen head and an impact gun.Or get the holding tool. Hope this helps.


------------------

Vester
96 RM250
"Let's see if an "A" rider tries it first.."
 

mbha

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#7
Thank you. Is this for sure the way ?
Just thinking that the spring and heavier springs would change the oil level and someone still thinking that they have one particular level doesn't.

Now the problem with diassembling the fork. I tried to unscrew the nut at the bottom of the fork with the fork leg still on the bike, clamped. I certanly don´t need a holding tool since there is nothing to hold !
But the screw turns with the nut and it doesn´t release, it turns with a sligt addition of violence but nothing more.
So I figured that something inside the fork leg turns as well, something that cannot be hold still from the outside since both the inner tube as well as the leg is still while turning.
clues ?
//Bengt
 
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#8
You're right, as your turning the nut your also turning the danper rod assembly that the nut/bolt threads into. Thats why you need a damper holding tool to stick down inside the tube and hold the damper rod assembly from turning while you unscrew the bottom nut.. or....you can use an impact gun ..air or electric will work. You have to take the fork off the bike so you can put your weight on the fork,compressing it and zipping the nut off with the gun. Compressing the fork will cause the spring to keep the damper rod from turning.

On the RM I'm currently working on, I had to go to extremes and compress the fork with a pair of tie downs to keep the damper rod from turning. If you have to do this, DO NOT! get your face or upper body anywhere near the compressed tubes. If the tie downs were to slip or give the results could be very bad!
Thats why it would be best to get the damper holding tool from your dealer,if you plan on keeping the bike. Unlike me I'm fixing this one up for resale...gotta save up for some knee braces.

So just try and use the weight of your body first to compress the fork. If this doesn't work I'll explain how I did it with the tie downs.

------------------

Vester
96 RM250
"Let's see if an "A" rider tries it first.."
 

mbha

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#9
Thanks for the extremely valuable and correct information you shared with me.
The reason I could pull out the inner (upper) tube until the holes and smaller diameter came up above the seal was because the nut already was lose. I only had to drag it out with a few solid bangs and the sealing and bushings came out as well. Now I have set the oil level to 140mm 7.5w putoline fork oil, remounted the inner fork assembly, change the seal and assembled the entire fork. Much thanks to your help. Thanks again!!!
//Bengt
 
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#11
Hi,

I too have a collection of old conventional forked mx bikes. My one comment would be that I too tried 7.5 wt oil and they were far too soft. I have been advised to use 15 wt. Any comments?
 

mbha

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#12
Yeah, 15w sounds a bit thick though but I´m using the 7.5w because it´s winter here, riding in snow with spike tires you know.
The temperature is between -5 and -15 celsius. A question though!
At the bottom inside the heavily debated nut I have a small copper screw head, that can be turned 12 clicks anti clockwise.
This is the rebound damping right ?
I did set it at 6 clicks to begin somewhere, does anybody have a better idea ?
(Honda CR250 1986, showa)
I can´t find any compression damping adjuster. Is there any or do I revalve/change oil/oil level something ?
//Bengt
 
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#13
Here's a good way to compress your forks while removing the bottom nut. Put your bike on a stand & remove the front wheel & axel. Install the axel back into the forks w/o the wheel and loop a tie-down around the lower triple clamp & onto the axel. Just cinch up the tie-down to compress the fork...simple as that.