Hi all

Thinking of changing the oil in my forks to a heavy grade. The drain plug is at the bottom, so do I take the cap off the top to fill the forks?

I have a 87 model with 20k on the clock

Thanks

 

Yes.
Interestingly, I've always thought that to stiffen the front you put in heavier oil. Last time I did my forks the shop owner said it's a big no no. The reason is that on older bikes the springs are usually soft & saggy, sogoing to a heavieroil only causes the forks to sludge & react slower. The result is then loss of road contact over bumpy roads. Sorry don't mean to thread jack but I thought it may be an opportune time to discuss the idea.

 

Mate I am open to any input.

The reason I posted the question is that I hit a hard bump on the weekend and the forks bottomed out. Under hard braking the nose does dive a bit also.

From what I have read the forks on the CBR are a bit soft.

Thought that I might be able to stiffen the forks a bit without going to the extreme of replacing the springs.

Thanks again.

 

The ideas I've put forward may not be correct. It's what I did & it seems ok to me but I'm no pro. You may find that just replacing your oil improves things anyway. I had an ex race rider once tell me to put spacers inside the forks to compress the springs. I think that only lifts the front & reduces the travel??? See what some of the others on the site think. Good luck.

 

I would go for the new oil first and see if it helps (not "heavier" oil)...probably you have to replace the forksprings, as bluebeard says "they are usually soft & saggy" on these old bikes.
I resently bought me some new forksprings ( Hyperpro)i plan to change the coming winter.
My bike also drops down a lot when breaking, so with new springs and oil it should be solved...hopefully.

 

To change the oil, open those plugs at the bottom and bounce the front end with the brake applied. To refill, you need an engine hoist or some such device to pull up the front and and completely decompress the springs, otherwise you will have a big nasty problem on your hands when those springs fire out of the tubes. Try some progressive rate springs if the new CORRECT fluid doesn't seem to make a difference. The springs may indeed be sagging. New OEM=High dollar.

 

Ok I will replace the old oil with the correct oil and see what happens.
So the springs will fire out the top of the tubes.
If I lift the front wheel off the ground are the springs still under pressure when you take the top caps off?

thanks

 

They are probably under some pressure but not much. There is always some degree of preload, if not, there would be a lash in the fork and that would be dangerous.

 

Release weight from your front wheel first (you may jack up the front part of engine) then remove top end cap of forks. You may use right size of box wrench and hold the wrench as you are revolving the top end cap because fork spring give force to the cap. One time, I did not hold the end cap and the cap flew off and hit my fresh repainted fuel tank. Now you may remove the drain bolts on the bottom of the fork and drain old oil. I suggest you to remove front wheel, so that you can pump the forks easily. In order to drain oil completely, you need to pump the forks 5 to 6 times. If you really want to drain completely, you may need to remove the forks from your bike and remove springs from the fork and hold the fork up side down and pump it several times. Stock fork oil is 5 weight, and I am using 10 weight. Forks work fine and more stability on front. I also dropped front end about 15mm. More stability on hi-speed turn.

 

I put 15weight oil in my forks. Put a floor jack under the engine when it is on the centre stand to lift the front . There should be preload when you take the top caps off . Bleed out the air before you undo the drain plug .measurementof oil thatyou take out of each fork i think the left fork holds more oil. To check the sage in the front the forks theyshould be at the top with out you on the bike and only dropwhen you get on. You can put spacers in the forks to reset them. I thing theoil amount is 450 to 480ml .