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LeMans MK1 vs MK2 forks

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Robh View Drop Down
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    Posted: 13 Dec 2018 at 08:56
I have a 1978 MK1 LeMans that needs a fork rebuild. 
I am gonna need/want to replace the dampers, springs and stanchions. 
The MK2 got thicker material in the stanchions compared to the MK1. The dampers and spring differs but that going to be replaced anyway. 
Does anyone know If the MK2 stanchions Will give less flex and a crispier feel? 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Chris950s Quote  Post ReplyReply Direct Link To This Post Posted: 13 Dec 2018 at 09:16
I believe that a lot of people added a fork brace just above the mudguard to reduce the flex. Personally I went to Marzocchi 38mm forks and yokes, when the forks got bent, but these are getting hard to find these days. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Gianni Quote  Post ReplyReply Direct Link To This Post Posted: 13 Dec 2018 at 10:39
IIRC there is a difference in the outer diameter between Mk1 and Mk2 stanchions. From memory it was 34.7mm (Mk1) and 35mm (Mk2) but I may be wrong. The Mk2 stanchions were shared with the Spada (SP) and Spada SP NT (and probably the T3/T4, etc.)
 
The inner top thread is the same based on experience swapping aftermarket fork dampers around.
 
I doubt you would notice any difference just derived from the stanchion diameter. The Mk2 had different dampers as standard and again I suspect this was product line simplification as it meant parts shared with the SP, etc.
 
Just replacing old worn parts with new parts of the same specification should see a difference, though new parts are legendarily stiff.
 
If you want to stay visually standard there are many aftermarket internal upgrades which allow variable spring rates, variable spring and rebound damping etc. which are probably better and far more expensive than the standard stuff.
 
There are two generic types of fork brace - the bridge type that curves under/over the mudguard and bolts to the sliders at the mudguard mounts, and the handcuff type which clamp around the sliders. I tried both. The clamp-round the sliders type was dreadful, causing massive stiction and making it steer like an oil tanker, and was removed within 100 miles, the bridge type has been on for thirty+ years...
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Post Options Post Options   Thanks (0) Thanks(0)   Quote TheWrongTrousers Quote  Post ReplyReply Direct Link To This Post Posted: 14 Dec 2018 at 08:22
Morning all, I too am doing a fork rebuild my LM1. Judging by the sticky mess inside of my forks, the contents have not seen the light of day for a very long time. I am inclined to simply clean up the insides and put some new oil in. Should I replace the damper units  - does anyone have a view ? 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote c13pep Quote  Post ReplyReply Direct Link To This Post Posted: 14 Dec 2018 at 08:37
If it`s as bad as you say then I wouldn`t risk not replacing the fork internals, the bike deserves it

CHRIS
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Post Options Post Options   Thanks (0) Thanks(0)   Quote TheWrongTrousers Quote  Post ReplyReply Direct Link To This Post Posted: 14 Dec 2018 at 08:54
I guess you are right. I an see on Guzzi bits that you can get these air assisted dampers and fancy progressive springs as a super duper upgrade. I am wondering how much of a good idea are these compared to standard set up. Anyone care to share their knowledge and experience ?


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Post Options Post Options   Thanks (0) Thanks(0)   Quote Gianni Quote  Post ReplyReply Direct Link To This Post Posted: 14 Dec 2018 at 12:35
The oil in the forks is (generally) a lubricant but does inevitably affect the spring and rebound characteristics to some extent, depending on viscosity, temperature age and volume.
 
The designed damping is the oil in the cartridge damper. They can leak/burst and used to be relatively cheap to replace. Is there good resistance as you push and pull the damper rod or does it just flop out? Some of the replacement types can be rebuilt and the inner damping oil changed to your preference. I did this and it worked well.
 
The progressive springs can be an upgrade (especially the ones with a separate soft spring for dealing with minor bumps) but just swapping standard for progressive replacements does not guarantee anything - the effect depends on riding style, personal preferences and (ahem) body mass...  My experience here is based on riding other folk's modified bikes so no long term view.
 
I would avoid the air-type which just injects air into the body of the fork - all that does is stiffen things up and then leak over time (personal experience). Some of the German/Dutch/French aftermarket dampers do have more sophisticated compression and rebound damping which use a combination of air and oil to good effect (based on riding a friends T3).
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Post Options Post Options   Thanks (0) Thanks(0)   Quote TheWrongTrousers Quote  Post ReplyReply Direct Link To This Post Posted: 14 Dec 2018 at 12:42
That is really helpful. Thanks Gianni.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote TheWrongTrousers Quote  Post ReplyReply Direct Link To This Post Posted: 15 Dec 2018 at 09:16
And that brings me to fork braces. I have a tarozzi fork brace on the bike that I have recently acquired. It has come off along with most of the front end so I can sort out the front of the bike which was a mess. I feel disinclined to put the fork brace back on, largely because the years when I might ride a bike at such speeds the forks might flex and scare me are long behind me. 

I just enjoy pootling about these days. 

I suppose my question is, do I need a fork brace ? - does anyone really need a fork brace ?

 
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Gianni View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Gianni Quote  Post ReplyReply Direct Link To This Post Posted: 15 Dec 2018 at 10:00
See my previous but one post up this thread. I did not like the Tarozzi one but that was just my experience and preference.
 
I do think that, in the specific case of Tonti Guzzis, a bridge type fork brace is useful. We have linked brakes so there is likely to be a differential between the load on one side vs. the other under braking. Or only one brake is in use. The forks are quite skinny for the weight so a fork brace might ameliorate the effects of brake twist.
 
And yes there are lots of bikes with single discs but they are usually lightweights and there are not many that weigh in at over 500lbs.
 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote dan_s Quote  Post ReplyReply Direct Link To This Post Posted: 15 Dec 2018 at 16:01
You don't have to have a fork brace on a LM. Dave Richardson (Guzziology) recommends fitting one wholeheartedly. The best way imo is to try it yourself.
I found the tarozzi brace poorly made, bores for fork sliders were far from round. Crap quality may explain the fork binding aforementioned. I didn't read any complaints about Telefix braces.
With the original damper cartridges the fork was chattering over bumps, with FAC dampers (no air preassure added) it tracks very nicely.
Whether the original springs suit depends much of rider's weight
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Gianni Quote  Post ReplyReply Direct Link To This Post Posted: 15 Dec 2018 at 17:46

Ah, my post above should read Telefix and not Tarozzi (30 year old memories going down the pan). But I didn't like it.

The FAC jobs are good but I didn't know they were £200+/pair these days. I paid ~£70 for mine back in the day.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Chris A Quote  Post ReplyReply Direct Link To This Post Posted: 15 Dec 2018 at 18:35
I think that fork bracing really depends on the machine and the rider.. If you pootle around and the bike has steel fenders then the need will be less obvious.If the guard is plastic like the Le Mans or v 50 then a brace will be really noticeable even if you ride like grandad.A brace transformed my old V50..the T3 has less need of one.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Dukedesmo Quote  Post ReplyReply Direct Link To This Post Posted: 16 Dec 2018 at 12:47
No experience of LM1 forks but surely the thicker wall of the LM2 fork tubes must add stiffness? 

Don't know how much (if any) difference the wider track of the LM2 might have made to the bike although, presumably the OP is looking at just changing the forks?

I have a Tarozzi brace on my LM2 and am happy enough with it, can't say it was a huge transformation when I fitted it but the front end feels pretty good for a 40yr old bike.

I think forks on some modern bikes can be too stiff but that's never going to be a problem on an old Guzzi.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote TheWrongTrousers Quote  Post ReplyReply Direct Link To This Post Posted: 18 Dec 2018 at 08:02
Thanks to all for these words of wisdom
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