Fork Service recommendations?

[4corsa]

Dropping my 2003 Le Mans w/ 20k miles and Marzocchi forks at The Spare Part Co. in Philly (Guzzi specialists) this Saturday to have them change out the fork oil (has not been done in at least 9 years, as neither I nor the previous owner have had it done). There are no leaks, so the seals seem fine, and they recommend leaving them alone.  I'm happy with the way they work for me, so not looking to change cartridges. I saw another post where fork oil weight was discussed (5, 7, 10). I was planning to have them replace it with same. This is not something I know a lot about,  so if anyone has recommendations for anything to discuss with the mechanic, etc., kindly let me know.  Thanks in advance!

[docc]

I learned (from this forum), early on, that lighter oil performs better in our forks, so I chose 5 "wt."

Then, I learned (from this forum) that 5 "weight" can vary widely between manufacturers and even between one manufacturer's different products. After taking in Peter Verdone's discourse, and published tables, I chose BelRay 5W High Performance fork oil based upon its rating in centiStokes. This measure is vastly more accurate than "weight."

http://www.peterverdone.com/archive/lowspeed.htm

http://www.peterverdone.com/archive/images/content/motorcycle/PVD-ISO-Viscosity-Data.gif

Perhaps, most important (and biggest gain) with forks is to be certain your springs and preload reflect your rider weight and riding style. Factory springs are notoriously soft. Springs are also fairly inexpensive and super-easy to change during the oil service. I used Traxxion Dynamics to spec my springs and preload spacers and they are spot-on.

[audiomick]

Not quite on topic, but related: mine has a blown fork seal. Not just a drip, it lost (apparently) the entire contents of the left fork leg on the ground overnight after the last time I rode it. It has, according to the speedo, about 70,000 km on the clock.

I'm still tossing up about what to do. On the one hand, there is a place about 80 km away from here that is a "fork specialist", specifically Öhlins, but I gather he'll do any forks. On the other hand, the workshop that I use as needed has no doubt done forks, and can no doubt do a servicable job.

I was more or less happy with the fork's performance. As far as the "too soft" springs go, I currently weigh 65 kg, so I don't need particualrly hard forks.

So what should I do? Go to the effort to take the forks to the specialist, or just have them done by my "tame" mechanic? I do like to have things perfect, but on the other hand, I'm not going to be racing it or anything demanding like that.

I could have a go at it myself, but I don't think I'll find the time (it's already 6 months since the seal went), and I don't have the experience to evaluate the wear on the internal parts as to whether anything needs replacing.

I'd be interested in a "vote", what is the sensible thing to do, weighing cost and effort against advantages.

Edited 14 hours ago by audiomick

[4corsa]

2 hours ago, docc said:

I learned (from this forum), early on, that lighter oil performs better in our forks, so I chose 5 "wt."

Then, I learned (from this forum) that 5 "weight" can vary widely between manufacturers and even between one manufacturer's different products. After taking in Peter Verdone's discourse, and published tables, I chose BelRay 5W High Performance fork oil based upon its rating in centiStokes. This measure is vastly more accurate than "weight."

http://www.peterverdone.com/archive/lowspeed.htm

http://www.peterverdone.com/archive/images/content/motorcycle/PVD-ISO-Viscosity-Data.gif

Perhaps, most important (and biggest gain) with forks is to be certain your springs and preload reflect your rider weight and riding style. Factory springs are notoriously soft. Springs are also fairly inexpensive and super-easy to change during the oil service. I used Traxxion Dynamics to spec my springs and preload spacers and they are spot-on.

Thank you docc, and how do you feel about the results? Did you notice any difference - are your forks more compliant or firmer?  Will you use the same Belray 5W?  

Just now reading in Guzziology p.572 "Starting in the Piaggio Era" owner's handbook call for either a viscosity of Fork 5W or Fork 20W. I'd recommend you start with 5W and I can't imagine going heavier than 10W unless you're trying to create damping where there isn't any in drum-brake loop-frame forks".

[4corsa]

...also beginning to better understand your choice for Belray 5W. According to Verdone, "most cartridge type forks use a viscosity of 16 cSt@40°C". Not sure what that's based on, but according to Belray's website, the 5W has a viscosity rating of 19.1 cSt@40°C. What's interesting to me is going to just 7W increases the viscosity all the way to 32.4 cSt@40°C, and 10W only slightly more to 34.9.

[docc]

1 hour ago, 4corsa said:

Thank you docc, and how do you feel about the results? Did you notice any difference - are your forks more compliant or firmer?  Will you use the same Belray 5W?  

Just now reading in Guzziology p.572 "Starting in the Piaggio Era" owner's handbook call for either a viscosity of Fork 5W or Fork 20W. I'd recommend you start with 5W and I can't imagine going heavier than 10W unless you're trying to create damping where there isn't any in drum-brake loop-frame forks".

Yes, indeed the more accurate cSt measure varies dramatically with the "weights" of common fork oils.

I am extremely pleased with my suspension set-up (YMMV). Yes, my target cSt is about 19.x while the typical "7wt" pushes into the 30s.

The 19.x gives me much more compliance and responsiveness from these forks. Again, I changed my springs, raised the forks in the triple trees 5mm, adjusted my tire pressures 35psi front/ 40psi rear (with selected tires/sizes for my rim widths), and changed the rear shock/spring rate/preload.

[4corsa]

14 hours ago, audiomick said:

Not quite on topic, but related: mine has a blown fork seal. Not just a drip, it lost (apparently) the entire contents of the left fork leg on the ground overnight after the last time I rode it. It has, according to the speedo, about 70,000 km on the clock.

I'm still tossing up about what to do. On the one hand, there is a place about 80 km away from here that is a "fork specialist", specifically Öhlins, but I gather he'll do any forks. On the other hand, the workshop that I use as needed has no doubt done forks, and can no doubt do a servicable job.

I was more or less happy with the fork's performance. As far as the "too soft" springs go, I currently weigh 65 kg, so I don't need particualrly hard forks.

So what should I do? Go to the effort to take the forks to the specialist, or just have them done by my "tame" mechanic? I do like to have things perfect, but on the other hand, I'm not going to be racing it or anything demanding like that.

I could have a go at it myself, but I don't think I'll find the time (it's already 6 months since the seal went), and I don't have the experience to evaluate the wear on the internal parts as to whether anything needs replacing.

I'd be interested in a "vote", what is the sensible thing to do, weighing cost and effort against advantages.

When you refer to "fork specialist (Ohlins) would you per chance be speaking of Markbilt near NJMP? If so, he is the GOAT, and top Ohlins service center in the northeast. He prepped all my track bike suspensions, and upgraded the valves / cartridges on most. The improvement was always very significant.  If you're planning to keep your bike for a while, its worth going to an Ohlins service center, and yes, they typically work on non-Ohlins suspension. Only issue may be that they are very busy this time of year prepping race bikes for the season.