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Author Topic: C5 fork oil changes  (Read 165 times)

barenekd

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C5 fork oil changes
« on: October 17, 2014, 10:09:02 PM »
somewhere in the deep dark past, there appeared and Olde Wife that said all C5s had to have the fork removed as there was only one way to dump the odl oil out and that was through the top.
I always thought this sounded kind of ridiculous as I've never seen a bike yet that needed to pull the forks off to change oil. The idea seems to persist as a friend of mine mentioned he hadn't changes is C5 fork oil because of that.
Since I do have a shop manual for REs I figured maybe I should check this out.  I never really looked at the C5 before because I didn't have one. The first line in the book for C5s, after taking the wheel off, which isn't necessary on the leading axle forks, is to "Remove the allen screw from the bottom tube and drain the oil." Where these guys got the idea that you have to take the forks out is beyond me. It's pretty much the same way you drain all the old English bikes. Some of them had an extra plug to do it. I guess I'll have to post this and get another Olde Wive's Tale abolished.
So you can go out and do your oil change in short order. You'll sure like the ride better! Don't forget to pull the plug on top of the forks first. You might want to wrap a rag around the bottom of the forks when you unscrew the allen bolt. Mine sprayed oil all over the place  when I undid the first one, but I still had the top cap on.
Bare
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2011 Black Classic G5 (RIP)
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JVS

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Re: C5 fork oil changes
« Reply #1 on: October 22, 2014, 12:42:03 PM »
Hi Bare,

The C5 fork top has a 12mm hex cap as seen here:



Even if we remove the bottom allen screw, there is no way we can refill the oil from the top. Because this is how the 12mm cap is:



It is next to impossible to unscrew it. It is a reverse thread, but I have been unable to take that 12mm cap out. And you won't believe it, I have a B5. Same forks as the C5  :(

If one can't open the top cap, the only way is to remove the fork leg, remove bottom allen screw with an impact wrench, drain oil, and refill from the bottom again. Either way we do it, we need to remove the fork leg. Or a more radical way is to drill a hole in the top 12mm cap.

You can see more pics taken by Ducati Scotty at the following link.
https://picasaweb.google.com/117537683488075584374/EnfieldFork?authkey=Gv1sRgCIuiwMCp4ZfToAE
Sons continuing wars, our fathers were enemies


barenekd

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Re: C5 fork oil changes
« Reply #2 on: October 22, 2014, 08:51:43 PM »
Yup, looks like the refill could be an issue. I'd figure out something if it were mine though. Maybe just get a bunch of moving blankets and lay it on its side and fill them from the bottom. Or drill out the 10mm hole if leaking wouldn't be a problem. Have to see how the top is sealed.
Bare
2013 Moto Guzzi V7 Racer
2011 Black Classic G5 (RIP)
I refuse to tiptoe through life only to arrive safely at death
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mattsz

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Re: C5 fork oil changes
« Reply #3 on: October 22, 2014, 09:08:24 PM »
What would happen if we drilled a small hole in the center of that 12mm hex cap?  Is an "airtight" seal needed there?  Maybe we could then drain the oil from the bottom, and refill from the top just by removing the cap screws...

barenekd

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Re: C5 fork oil changes
« Reply #4 on: October 23, 2014, 06:19:16 PM »
Or increasing the diameter of the hole in the triple clamp so you can get that cap out.
2013 Moto Guzzi V7 Racer
2011 Black Classic G5 (RIP)
I refuse to tiptoe through life only to arrive safely at death
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mattsz

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Re: C5 fork oil changes
« Reply #5 on: October 23, 2014, 06:24:01 PM »
I'd probably start with drilling the caps; I wouldn't want to mess with trying to increase the diameter of the two holes in the headlight nacelle enough to remove the caps...

But if drilling the caps adversely affects the function of the forks...

Arizoni

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Re: C5 fork oil changes
« Reply #6 on: October 24, 2014, 04:13:17 AM »
Although you would have to remove the top plugs to do it, I think the best solution would be to drill and tap a 1/4-20 UNC threaded hole thru the center of the 2 plugs down in the middle of the hex wrench hole.

After cleaning off all of the chips and cutting oil the plugs would then be reinstalled.

After putting the forks back on the motorcycle I would fill the forks with the right amount of fork oil and then use a round head, 1/4-20UNC sheet metal screw to plug the threaded hole.
To keep things pressure tight, the screw threads and the underside of the screw head should be coated with some Ultra-Black RTV sealant.

I know this sounds like a bit of work but quite frankly, I'm surprised Royal Enfield didn't do this.  It would sure make it easier for the Royal Enfield mechanics world wide to change the front fork oil without having to go thru the major surgery of removing the forks.  The change also would not affect the existing forks design (assuming nothing bottoms out on the underside of that plug within 1/8 inch of center).
Jim
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JVS

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Re: C5 fork oil changes
« Reply #7 on: October 24, 2014, 08:24:27 AM »
I will one day have to use a drill on those 12mm top caps. What about the G5? Isn't it just unscrewing the plugs on the nacelle and re-filling? Those plugs do have an o-ring, even on our C5s and B5s (As seen in the first picture in Ducati Scotty's hand). Good enough for an adequate seal?
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Arizoni

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Re: C5 fork oil changes
« Reply #8 on: October 25, 2014, 12:46:27 AM »
When I changed the fork oil on my G5 it was just a matter of unscrewing the top plugs on each leg and pouring in the new oil.

They were sealed with a O-ring similar to the one in the photo above.
Jim
2011 G5 Deluxe
1999 Miata 10th Anniversary

azcatfan

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Re: C5 fork oil changes
« Reply #9 on: October 25, 2014, 12:33:34 PM »
When I changed the fork oil on my G5 it was just a matter of unscrewing the top plugs on each leg and pouring in the new oil.

They were sealed with a O-ring similar to the one in the photo above.

Same traffic on the older iron barrels, I'd say the idea of tapping a fill hole should be good.
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mattsz

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Re: C5 fork oil changes
« Reply #10 on: October 25, 2014, 06:20:48 PM »
When I changed the fork oil on my G5 it was just a matter of unscrewing the top plugs on each leg and pouring in the new oil.

They were sealed with a O-ring similar to the one in the photo above.

So, is it that the C5/B5 top plugs are larger, and don't fit through the hole in the nacelle?

barenekd

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Re: C5 fork oil changes
« Reply #11 on: October 25, 2014, 06:53:34 PM »
The plug that hold the springs down is the culprit.

Quote
Or increasing the diameter of the hole in the triple clamp so you can get that cap out.
You might be able to do this with a Dremel and their drum sander, although the drill, tap and plug would be a reasonable alternative.
Bare
2013 Moto Guzzi V7 Racer
2011 Black Classic G5 (RIP)
I refuse to tiptoe through life only to arrive safely at death
http://www.controllineplans.com