Fork Oil Weight for 750 Breva

[Muzz]

Just a quick question to owners of Brevas or models fitted with the Marzzochi front fork. I weigh in at 164lbs, probably with all my gear about 180lbs. Just wondering if any of you about the same weight have changed the weight of oil and found an improvement.

I have always thought the front about right. The Sachs on the back are REALLY hard; I run them as soft as they will go and they are right then for two up. The compression damping is too hard and the rebound feels too soft. Replacing them is simply not an option $ wise. Not sure whether their performance alters the way the front feels.

Any comments welcomed. Bike rego due to go on on the 27th; I want to do them before hand before I go for the warrant of fitness.

[sign216]

I've just used the standard weight.  I did play w the pre-load moderately, but didn't notice a significant change in handling.

[Muzz]

Finding it hard to find a "standard" weight. Everything from SAE 5 to 20, with 10 being about average. Even saw one service which said you could use 10 in one fork and 5 in the other to fine tune the ride.

What weight are you Sign, and what weight oil did you use?

[Perazzimx14]

ATF is an excellent cost effective substitute for "fork oil". It is generally the equivalent as 10 weight fork oil.

[Muzz]

Thanks P. I used ATF on my one of the Hondas I had with good results.

Some "experts" (who would know ) have said that there are additives in fork oil that are not in ATF which help look after the seals. I had thought about ATF (I can get that free from my son's work - Guzzi content) but have come to the conclusion that I will splash out on a litre of fork oil (NGC)  

Good to know ATF is about 10 weight.

[luthier]

I have some 10 wt that is sold in agricultural places that service or sell milking machines. That's the oil they use and it's fairly cheap, maybe $20 for 4 litres.
I used to put it in the chaincase of my Norton for a smooth running clutch. Now it goes in my forks.

[sign216]

What weight are you Sign, and what weight oil did you use?

Muzz,
I'm 165 lbs without gear, and I used 10w oil.  My shop manual recommends 7.5w, but gives 5w to 20w as possible choices.
Joe

[Muzz]

Close to the same as me Joe.

Got hold of the holidaying Pete Roper, who suggested 7.5 I had looked at a Penrite site and they listed it. Sadly, it seems as if it was not an NZ site, as 7.5 is not available here. They do have 5 but I went for 10, as on their site they say from 10 to 20 for Guzzis. It's a full synthetic.

If it does feel too stiff I will get some 5 and do a 50/50 dilute.

[sign216]

My experience too.  Couldn't find the 7.5, so settled for the 10.
And...the 3 yr old fork oil looked as fresh as new oil.

[malik]

Muzz, do note that Penrite 10 is actually 7.5 - it's somewhere there in the fine print - or it was. I used Motul 10 wt on the V7C, with 150mm free space. Worked well for 60,000k & now again due for renewal.

[sign216]

Muzz, do note that Penrite 10 is actually 7.5 - it's somewhere there in the fine print - or it was. I used Motul 10 wt on the V7C, with 150mm free space. Worked well for 60,000k & now again due for renewal.

60k before changing the fork oil?  You are my leader!


I'll admit, changing the small block fork oil is surprisingly hard.  I mean wtf?!

[malik]

The first time I tried, I read all the guff on the net & went in well read, but with fear & trepidation. I found it to be surprisingly easy & straightforward & it took me only two hours, go to whoa. I was expecting worse.  This time, I shall have a socket cut down so it is flush with the fork caps. That will help make it a little easier.

Only 154,000 km on the V7C now - starting to think about getting hold of a new speedo. The odometer is expected to stop working in a year or two.

[malik]

So, changed the oil in the Classic's forks yesterday. The old oil came out black & scummy - looked like something out of a septic tank, so it was definitely due. The Penrite 10 bottle says it is now SAE 10. 150mm air space is just a little over 400ml. The job took around a couple of hours again. A straight forward task, with no real traps for the unwary. The front brake pads were fine, but the brake feel is now a little spongier - enough to warrant a re-bleed. I haven't felt a significant difference in the suspension feel so far, but as I've only ridden home from the Shed on suburban streets, it hasn't really been challenged yet. But I'm in NSW, so there's plenty of rough roads available for testing.

[sign216]

So, changed the oil in the Classic's forks yesterday. The old oil came out black & scummy - looked like something out of a septic tank, so it was definitely due. The Penrite 10 bottle says it is now SAE 10. 150mm air space is just a little over 400ml. The job took around a couple of hours again. A straight forward task, with no real traps for the unwary. The front brake pads were fine, but the brake feel is now a little spongier - enough to warrant a re-bleed. I haven't felt a significant difference in the suspension feel so far, but as I've only ridden home from the Shed on suburban streets, it hasn't really been challenged yet. But I'm in NSW, so there's plenty of rough roads available for testing.

How old was the oil?  Is the bike housed inside or outside?

Changing my 3 yr old oil, showed it was just like new.

[malik]

I previously changed the oil 17 months ago at 115,000km, and the bike sat for a while waiting for me to get around to replacing the clutch. That job done in April, I set off around the country with my other V7 on what turned out to be a 30,000km trip. At 150,000km on the way back, I noticed that the ride had become harsh on rough roads, so I changed to oil (at 154,000km). Although the bike (V7C) ad sat for a month while I rode the V7S, I did take it up the old Pacific Hwy & back (150km of twisty stuff) immediately before dropping the oil, which probably accounted for the  aeration in the old oil.

I bought the V7S in April last year with 4,000km on it, Although it now has 74,000km on it, the forks don't seem to give as rough a ride as the Classic did. But then the previous owner had installed a set of Racetech springs, so a better ride altogether. However, I'm wondering how much better they would be with fresh oil, so I plan on changing the oil on that one too. Today if I can find some fresh stuff at the shop. First a test ride up the Old Road this morning. Just have to do a before and after comparison,

BTW & for what it's worth, the local Racetech specialist has advised that fork oil starts deteriorating after 6 months.

I have noticed that fresh oil up front also smooths out the ride at the back. I don't seem to be able to pick where the real problem is. It may seem like it is a rear shock problem, but the rear suddenly gets better when the front is working properly.

My advice would be to change the oil in the forks more regularly than we tend to, and definitely before deciding to replace the rear shocks.

And we're not even getting into the effects made with different air gaps, differing oil weights & different pre-loads. I'm happy so far with 10wt oil & 150mm air gap.  Must be working OK - I'm getting an average of 20,000km out of a rear tyre. & 55,000km out of a front on both bikes.