Topic: filling empty fork tubes

[cafe2be]

I put the forks back on my 750f after rebuilding them. Put on -2 fork tubes from cycle x. Used progressive springs. Had to chop 1" off the spring in order for it to fit. How much fork oil do I use? and what is the best way to fill them? I read, jack the front end up, take off the caps, let the bike down compressing the tubes. Fill with oil, lift up and place caps back on.

[modzsquad]

Did you just put new seals in?   Either way just jack up the front so the forks are fully extended, then fill with fluid ( automatic transmission fluid was called for my bike then i filled , my bike called for 6.5 oz of fluid per side. the hard part was screwing back on the covers...because the springs do have to be compressed back inside of forks, about an inch. Hopefully this helps!

[Popwood]

Just went through this with my '75K. Amount can vary depending on year. I refilled with Honda suspension oil before putting them back on. Very ease and screwing caps back on a breeze. But if they are on already, use the jacking process referenced above. And yes, you have to press the caps in hard and start them by hand to make sure you get them started correctly. But do be sure it's jacked as much as possible to make it as easy as possible.

[razor02097]

hmmm if its a rebuild I read you needed to have the springs out and the forks compressed.  I think it had something to do with the forks being completely dry.  I dunno.

I do know to do a fork oil change you do as mentoned above.

[MCRider]

I put the forks back on my 750f after rebuilding them. Put on -2 fork tubes from cycle x. Used progressive springs. Had to chop 1" off the spring in order for it to fit. How much fork oil do I use? and what is the best way to fill them? I read, jack the front end up, take off the caps, let the bike down compressing the tubes. Fill with oil, lift up and place caps back on.

From what you're saying we can assume the forks are dry? And the tubes are back on the bike, no need to lower the front end, besides it sounds dangerous. Support the front end with the tubes fully extended.

How much? I'd start with 1/2 to 2/3 required amt, and test ride it. By shortening the tubes and not taking measurements beforehand its trial and error at this point. If the ride is a little bouncy add a little oil.  Do not overfill. The ride will be harsh and potentially dangerous if you do.

Collapsing the tubes is done when the tubes are off the bike, the springs are out, and you use the "measure from the top" method of filling.  That is, clamp a dry assembly in a vice, allow the tube all the way into the leg without the spring. Pour in the amt required by the manual, the low end of the range.  Pump the tube slightly to get it all in.  Measure down from the top, I think for the CB750 should be about 4.5 inches but don't quote me. Make sure both are the same. Install springs and install the legs.

I'd be curious to know what Ken at CycleX would say.

[cafe2be]

Hey guys, this is for my 77 750f. The forks are bone dry. New seals, new tubes, fully cleaned legs inside. Reassembled and put back on the bike dry. I am going to the honda dealer today so going to confirm with them. I read online that the tubes should be fully compressed, add oil, fully extend the tubes and put spring and caps on. This helps to circulate the oil?

[ColinMc]

Wait...so you CUT progressive springs?! You do realize that is a HUGE no no...if you didn't cut them exactly the same, and even if you did...egad. To each their own I guess.

You could just get a set of nice linear springs that are shorter that you can then "preload" with spacers and get much much much better handling. But if money is tight making what you have work is key. I just hope those springs aren't even a half a mm off in where you cut them.

 Ideally you do the fork oil with the springs out if you can by level, if you do it with the springs in you can do it by volume with a syringe. Measure out the exact amount and put the exact same amount in each fork.

[MCRider]

Hey guys, this is for my 77 750f. The forks are bone dry. New seals, new tubes, fully cleaned legs inside. Reassembled and put back on the bike dry. I am going to the honda dealer today so going to confirm with them. I read online that the tubes should be fully compressed, add oil, fully extend the tubes and put spring and caps on. This helps to circulate the oil?

The only reason to compress the legs is to use the "measure from the top" method for your oil level. And the springs must be out. Pretty difficult to compress the leg all the way while it is on the bike unless you have the front end suspended and raise the lowers up to thier bottoming position. Very cumbersome, you still have to keep the fork compressed while measuring. While filling, you pump the tubes a little to get all the oil disbursed so you can get a good measurement. This is what the track guys do.

If you are going to use the fill it and forget it method, which is poerfectly fine for street bikes, no need to compress. Just fill each tube with equal amounts per the manual, put the caps back on and then pump them. The oil is going to circulate fine.  Since you have shorter tubes, you'll need less oil. Better to start with too little than too much and have to suck some out.

That's why I said start with 50% of the manual amount and ride it. I'll bet you end up with 75% of the manual amount. Trial and error.

[cafe2be]

hey colin, I thought it was strange too to cut the springs. I was told to do this by cycle exchange. The springs that were cut were pretty dead on. I spoke to another guys on this forum that said he had done it and they were fine. I cut 1" off from the tightly wound section.

[cafe2be]

thanks for that advise MC. Definately not going to be a tracker. Just cruising on the streets.

[MCRider]

hey colin, I thought it was strange too to cut the springs. I was told to do this by cycle exchange. The springs that were cut were pretty dead on. I spoke to another guys on this forum that said he had done it and they were fine. I cut 1" off from the tightly wound section.

Personally I don'tr see any problem cutting the spring. Sure just do it as accurately as possible.

You've already compromised the suspension by shortening it. If anything were a no-no, that would be it. Many people dont like things I've done either so to each their own.

Keep the speed down and watch those potholes.

[MCRider]

You know...I'm thinking about this wrong. Just because your tubes are shorter doesn't mean your travel is shorter. You'll still have the same amount of travel. The danger will be putting the fender or tire into the lower triple tree. You ought to check that just so you'll know. Jack the bike, pull the springs, and raise the wheel assembly as far as it will go.

And with that in mind, you're likely to use the same amount of oil as a stocker. I'd still use a little less and add as needed.

[cookindaddy]

I did it recently just the way it says in the Honda service manual and it was a piece of cake.

I had replaced the seals and caps and checked the spring length per their spec. Mine were bang on length. I cleaned everything with solvent like they suggest, let dry and put it back together.

They recommend a specific amount of Honda ATF. I used a lab graduated cylinder, 150 cc I think it was and screwed the cap back on. Yes the cap needed to be pushed down a bit to get the thread started. I did the filling off the bike with the fork held with a rag around it, loosely in a bench vise but I guess you could do it on the bike with the front wheel jacked off the ground? Honda does not suggest any compression of the assembly, just pour the oil in.

The bike rides beautifully now, much better than before. One side had been leaking. Tight as a drum now and it feels great.

[MCRider]

Plastic baby bottle works good (has cc on side) or a Ratio-Rite from the MC store. Graduated vessel designed for pouring holds about a quart and has cc on it.

[crazypj]

Honda don't specify oil level but really, that's more important than amount.
You need to cycle forks through entire range before checking (pump them up and down)
 I usually start about 6" from top, forks compressed, springs out then adjust oil level 1/2" until it feels right.

PJ