Observations re fork oil change and steering head

[Gio]

Some of this should probably follow previous threads, but here are some observations made on my 2000 V11 during recent service (57,000 km) :

 

1. Fork oil change

 

Stock forks with 120mm (+11) spacers. Drained vol (springs in place, 400ml per leg last service) R=380ml, C=390ml over 2 days. Re-filled with 400ml of 10w again - R will only take ~350 at first but 400 if allowed to settle, and in fact settles at a visually lower level than the C leg)

 

(Ratchet - I know you will give me some stick for doing it this way - do you measure the volume of oil per leg needed to acieve equal air gap of 100mm ... enquiring minds ?)

 

2. Steering head inspection

 

I had been experiencing a little head-shake (even with Mr Bitubo cranked up to +10 although I don't think there is any oil left in there) and found the 32mm head nut very loose. Bearings seemed ok - a little doubt re the top set so replaced that one and tightened with a 32mm wrench ~1/4 turn.

 

(Canadians - you can get a very nice Filzer 32mm cycle wrench from MEC for $18)

 

Test ride was satisfactory. Felt a little firmer up front and no head-shake. New tires next.

 

Gio

[Guest ratchethack]

Some of this should probably follow previous threads, but here are some observations made on my 2000 V11 during recent service (57,000 km) :

 

1. Fork oil change

 

Stock forks with 120mm (+11) spacers. Drained vol (springs in place, 400ml per leg last service) R=380ml, C=390ml over 2 days. Re-filled with 400ml of 10w again - R will only take ~350 at first but 400 if allowed to settle, and in fact settles at a visually lower level than the C leg)

 

(Ratchet - I know you will give me some stick for doing it this way - do you measure the volume of oil per leg needed to acieve equal air gap of 100mm ... enquiring minds ?)

No stick here, Gio. But as I've posted before, setting the air gap is the preferred method, despite the fact that the Guzzi manual calls for the volume measurement method (400 ml. per leg).

 

When the forks are being assembled on the factory floor, there's no latent trapped oil in there to start with. Presumably, there's only a tiny amount of assembly lube in there. In this case, the 400 ml volume method is the quicker, easier, preferred way to go, whether it's the Luigi's at Marzocchi or the Luigi's at Mandello doing the filling, it doesn't matter -- it's-a molto bene presto veloce. Capice?

 

The problem arises when it comes time to re-fill after servicing and draining the old fluid. Despite repeated right-side-up and upside-down pumping gyrations, and even hanging upside-down overnight, as you know per above, Gio -- it's VERY DIFFICULT to get all the old oil out. It's really a hit-and-miss proposition by my experience, and it's not at all consistent side-to-side. If you then put in 400 ml on top of whatever remains trapped behind in there, the danger is that you're over-filling the forks -- and more'n likely, significantly, and very unevenly at that (ask me how I know ). Just a few mm makes a noticeable difference in the air spring effect, and you can be off by as much as 20 mm or more this way!!

 

It's for this reason that the preferred RE-FILL method is by measuring the air gap (aka "Luftkammer", 100 mm according to Wilbers). Of course it's very important to pump all the air out while filling before you measure! NOTE: Unlike getting the oil out, it's EASY to get the air out by pumping. This method accounts for any unknown volume of oil that may have been left trapped in there, ensures proper balance, and provides an air spring effect that's accurate, known, and 100% predictable.

2. Steering head inspection

 

I had been experiencing a little head-shake (even with Mr Bitubo cranked up to +10 although I don't think there is any oil left in there) and found the 32mm head nut very loose. Bearings seemed ok - a little doubt re the top set so replaced that one and tightened with a 32mm wrench ~1/4 turn.

IMHO, depending on what you mean by "very loose", this wouldn't be a likely contributor to head-shake, unless the forks were rattling-loose, as would be determined by grabbing the fork lowers and shaking them fore-aft. I've torqued my steering head bearings up twice to 20 ft-lbs. in 31K miles. Some will swear it has to be 15 and some will say 25 ft-lbs., but the manual doesn't specify and I've always gone 20 on every bike I've owned. Both times on the Guzzi it took more than 1/4 turn. I think one time it took 1/2 turn, if memory serves. There's never been any notchiness in the bearings, nor as much as any trace of head-shake, speed wobble, neuritis, neuralgia, nor the heartbreak of psoriasis.

 

If there's no oil in the steering damper, she's-a morto .

[badmotogoozer]

Yup - I've had this one too. Started getting some shake and noticed the tell - tale sign of loose head. (hit front brake, clunk)

 

Same thing top bearing done in. Don't know if it came loose and toasted the bearing, or if the bearing toasted and allowed the nut to loosen.

 

I've replaced a ridiculous number of bearings in a bike with 12K kms on it <_ very few of which in the rain.>

 

cheers,

 

Rj

[Gio]

Ratchet

 

Re steering head - no detectable play in forks but reckon I could tighten the 32mm easily by hand between 1/4 and 1/2 turn from memory (ie probably 1/2 to 3/4 turn required to tighten) ..? My test is a local hill which I can coast down hands free without any wobble. I was also experiencing some shake under hard acceleration. With the new bearing a 1/4 turn past finger tight did not impart any resistance to the steering.

 

Re fork oil - I do agree with your recommendation re the air gap method but having drained out almost the 400ml (380/390 anyway) put in last time, I took the easier route and re-filled w 400ml. With hindsight this may have been a mistake.

 

Did you record the volumes required for each leg using this method ? - I would be interested to know how close (or not) to 400ml they were? If one knew these volumes they would be a better guideline for the re-fill method.

 

Gio

[Guest ratchethack]

. . . having drained out almost the 400ml (380/390 anyway) put in last time, I took the easier route and re-filled w 400ml. With hindsight this may have been a mistake.

 

Did you record the volumes required for each leg using this method ? - I would be interested to know how close (or not) to 400ml they were? If one knew these volumes they would be a better guideline for the re-fill method.

 

Gio

Gio, I applaud y'er care in measuring wot came out and recording it. However, unless you put back exactly the same volume that came out AND you ALSO knew without question that the volume in there to start with was CORRECT, I'm afraid it was a wasted effort, my friend.

 

More'n likely, as I explained above, you've over-filled, just as I did my first time doing this. There's simply no way to know how "close" to 100 mm Luftkammer you got by adding 400 ml without measuring the air gap. The good news is that you can measure it easily enough and make adjustments with about 15 min. of careful, low-trauma effort. I find a turkey baster works perfectly to draw off the excess -- that is, if you can "safely" explain the taste of baked turkey that has a hint of 125/150 synthetic -- or in y'er case, 10 wt.. . .

[docc]

I'm ready to put some more spunky springs in my Marzos. They came out of some Ohlins and I'm banking on there being something better than my 47,000 miles stockers. I'll go by the sag and set up the preload accordingly. Yeah, 'wingin' it,' I know.

 

Is the Luftkammer measured with the springs in the juice?

[Guest ratchethack]

I'm ready to put some more spunky springs in my Marzos. They came out of some Ohlins and I'm banking on there being something better than my 47,000 miles stockers. I'll go by the sag and set up the preload accordingly. Yeah, 'wingin' it,' I know.

 

Is the Luftkammer measured with the springs in the juice?

Docc, I'd be surprised if springs from Ohlins fit the 40 mm USD Marz forks, but then I've been surprised more'n a few times by such coincidences as this.....do you already know if they're the right dimensions, key dimensions being OD and (o'course, spacers could make this a non-item:) free length? Do you know what rate they are?

 

Ausgezeichnet! Luftkammer is measured with springs out and forks fully blocked up in "bottom-out" position. This puts the fork scrapers against the fork lower castings.

[docc]

Nah, I'm ashamed to say I don't know poot about these springs. Andy felt they'd fit and I thought they'd have to be more substantial than my originals. I'm 165# in street clothes and the spring rate isn't bad , it just ain't good.

[Guest ratchethack]

Nah, I'm ashamed to say I don't know poot about these springs. Andy felt they'd fit and I thought they'd have to be more substantial than my originals. I'm 165# in street clothes and the spring rate isn't bad , it just ain't good.

Docc, you may be on to something here. It's worth pursuing IMHO. As far as I know, the pathetically weak springs offered by the factory on my Sport, which I estimated at .6 kg/mm by comparison on my workbench against springs of known rate, would be among the lowest-rate of any springs installed on such a (ahem) substantially gravitationally-endowed (ahem) bike as the Guzzi. IMHO, they'd be the correct rate for someone closer to 140 lbs. In previous Forum discussion, we've also determined that apparently, the same forks have been equipped with higher-rate springs in Europe, possibly by Guzzi, but then again possibly only by Marzocchi.

 

FWIW, before you investigate, this might help. I just sent the dimensions of the stock springs to Skeeve yesterday. The free length is 293 mm, OD is 35 mm, wire dia. is 5 mm, and there are 23 coils.

[Skeeve]

...As far as I know, the pathetically weak springs offered by the factory on my Sport, which I estimated at .6 kg/mm by comparison on my workbench against springs of known rate, would be among the lowest-rate of any springs installed on such a (ahem) substantially gravitationally-endowed (ahem) bike as the Guzzi. <_ ...>

 

FWIW, before you investigate, this might help. I just sent the dimensions of the stock springs to Skeeve yesterday. The free length is 293 mm, OD is 35 mm, wire dia. is 5 mm, and there are 23 coils.

 

Yoiks! Those are some pretty pathetic springs indeed! Doing the math, it looks like about 9 coils would have to be cut from the 23 [and an appropriate spacer crafted to recreate the 293mm [11.5"] OAL...] to bring the spring rate up into the vicinity of the 1.0kg/mm [55.8#/in] deemed best for normal-sized N.A. males from the estimated .6kg/mm [33.5#/in] stockers.*

 

Ride on!

 

 

*: Fun thing about the math; since the wire dia. and OD are the same on both sides, they drop out, and since one of the means/extremes is unit (1.0kg/mm), you just end up multiplying the number of coils by the .6 to end up w/ the new number of coils needed. Whee! Of course, I'm probably wrong, and I'm going to have to check my back-of-an-envelope estimate against a proper spring-rate calculator - thanks for the numbers, Ratchet! - but for right now, it seems likely. This calculation is of course ignoring important other considerations like spring bind, etc...

[Guest ratchethack]

Skeeve, right or wrong, thanks for sharing your findings. I never did the calculation because I wasn't too keen on the idea of shortening the stock springs, which among other challenges, would've involved figuring out how to heat-bend and grind the new end of the spring so it'd sit something close to square inside the stanchions without riding heavily against the stanchion ID under normal operation. Y'er findings fit my general expectations. The other thing to think about with such a substantial shortening of the spring is if the new rate would actually be able to go the distance of the available fork travel, which is 120 mm. With such a short spring, as you noted, it'd be more'n possible to coil bind it long before running out o' fork travel. F'er my purposes, the convenience of new Wilbers progressives from Todd E at $133 USD eliminated all the problems and worked a treat.

 

BAA, TJM & YMMV

 

It was a good thought, though.

[Guest ratchethack]

Hey Skeeve! It just occured to me that your Guzzi is an '03. Mine's an '00. I know that my fork is a 40 mm USD Marz, and I'm reasonably sure about the rate of the stock spring per my bench estimate.

 

Next item: I'm almost certain that your fork is NOT the same as mine -- and I'd be even more certain that your stock springs ain't the same as wot came with mine!

 

Just checkin' in with a little follow-up, lest we unintentionally join the infamous Leapers to Conclusions Club. . . . .