A few questions of changing fork oil

[DimitriT]

I'm getting ready to change the fork oil on the 750T. This is my first time doing this job.

I have a quart of 20 weight Castrol oil, a quart of 10W-30 and a quart of kerosene.

My plan is to leave the forks on the bike, drain the oil, flush with the kerosene and put the 209cc specified in the manual per fork. The manual suggests 1:1 20w mixed with 10w-30. Does this sounds ok? I'm a rather large rider (250lbs).

Have I missed anything?

The bike has the air fittings (see pic below). The manual says to remove the cover from the air nozzle, release the air, and then remove the fitting. But the fitting is not a hex head. How do I remove it?

 

[8trackmind]

The bike has the air fittings (see pic below). The manual says to remove the cover from the air nozzle, release the air, and then remove the fitting. But the fitting is not a hex head. How do I remove it?

Loosen the upper triple clamp bolts and take it out with an adjustable wrench. It shouldn't be very tight. It'll seem like it takes forever to get the whole thing unscrewed, but be carefull on the last few threads. If you let the spring eject it out, it may bugger up the threads making it a bitc# to started when you re-install the caps.
I run straight 20wt Belray fork oil in my bikes. Rides kinda choppy but handles way better.

 

[DimitriT]

Thanks 8track that's exactly what I was looking for.

Did you bother with the height measurement of the fork oil level
or did you just measure out the oil in a bottle?

I think I may just measure it in a bottle.

 

[Nessism]

My only comment is to question the need to wash the fork inners with slovent. If you do so some of the solvent will remain inside. Just dump the oil refill with new.

 

[DimitriT]

My only comment is to question the need to wash the fork inners with slovent. If you do so some of the solvent will remain inside. Just dump the oil refill with new.

That's a good point. Maybe the solvent step was for the case where the forks were off the bike.

 

[8trackmind]

Thanks 8track that's exactly what I was looking for.

Did you bother with the height measurement of the fork oil level
or did you just measure out the oil in a bottle?

I think I may just measure it in a bottle.

No problem.
I measured it out with a cup because I changed to progressive springs.

 

[Clone]

I would go with only fork oil or a transmission/hydraulic oil, as they won't foam, engine oil will foam and your damping will suffer.

 

[saddlewarmer]

changed fork seals on the 82 gs850l today. put atf in it. your fork cap just unscrews, long screw there. you can do the oil depth easy. picked up a tip. find an old spray bottle, take the top spray piece off, measure the oil heighth you want on tube coming out the bottom and cut the tube to length, fill your fork with oil, stick the tube in the fork tube, have a container handy, and pump till it runs dry. do the same on other fork. they should be the same heighth of oil in each fork tube now. hope that made sense.

 

[KGB]

Dimitri,

I used straight 20 weight bel ray in my 1000 and 1100.
No air, not a big job.

As stated be CAREFUL when unscrewing the air caps
as that spring under neath will propel it self and/or the cap into
a place it will take a long time to find. Like the corner of a garage or
a lawn...........

No springs just oil ?

The Triumph is next.

 

[DimitriT]

No springs just oil ?

Just oil. The stock springs on the 750T seem good. No bottoming and good ride. There are actually two springs per fork on this bike. An upper and lower seperated by a washer.

 

[ratgs81750l]

two springs...is common

two springs...is common

the upper spring is an air spring, the bottom is your mechanical/dual rate/progressive...depending on application

 

[Steve]

the upper spring is an air spring, the bottom is your mechanical/dual rate/progressive...depending on application

How can you call a steel winding an "air spring"? :-s
In the earlier bikes, the "progressive" nature was accomplished by actually installing two springs with different rates. They were separated by a washer to prevent them from coiling into each other.

In fact, there is an "air spring" in every set of forks. Whether you have air caps or not, there is air inside. The caps merely allow you to add more. As the forks compress, the pressure in the forks rises, increasing the spring rate, and in a progressive manner. This is in addition to however many steel springs are in the tubes.

Dimitri,
Keep the kerosene for cleaning parts that have been removed, but don't use it if you are not going to disassemble the forks. Also keep the 20 weight Castrol and the 10w30 away from the forks. Some people have used ATF with success (and some bikes actually call for it), but I have heard that ATF has no particular viscosity number, and it might range anywhere from 3w to 10w. It is much better to use oil that is formulated for use in forks. Brand name does not matter that much. Many riders recommend 15w fork oil, and that might be a good place to start. I go for a bit more cushy ride (while still maintaining damping control) and use 10w. If you happen to be dimensionally-enhanced and/or ride rather aggressively\\/ , you might prefer 20w. In any case, the cost is minimal, so feel free to experiment, but do it with fork oil.


.

 

[DimitriT]

I went with straight 20 wt oil. I used the new oil to flush out as much
of the junk that was in there as I could (by pumping the forks) and once
it was all drained I added about 209cc of the new oil. I used the Castrol
20wt non-detergent oil. Don't know if this is the right oil to use but I
didn't have fork oil and I wanted to ride. It'll probably eat my seals and
cause my hair to fall off, I know.

The results were good. A small improvement in handling but a good improvement
in how it absorbes bumps. Before it would wallow a bit
over large bumps with a slight pull on the bars. Now the front wheel stays
on the road better over the bumps and the pull is gone. It also feels smoother
over small bumps at higher speeds. More comfortable.

 

[ratgs81750l]

i called it an air spring because it is a spring like you said on top of the washer to prevent "coilbind" and it is not surrounded by fluid so yes i called it an air spring if you want i copy and paste a breakdown i have on telescoping forks we used in school just to clarify smartass