MG Cali front suspension travel?

**MotoKuzzi** · 2nd August 2009, 20:02

The theoretical front suspension travel is 135mm on my Cali. The static rider sag is set at 40mm and the preload is wound out to 1 turn off minimum preload (4.5 turns max ). The max travel ( measured with a cable tie ) on my trip to Tauranga today ( 340km return ), over some fairly large bumps and the odd braking episode is 80mm. Would you expect under these circumstances the bike should be using closer to it's full 135mm? Any advice appreciated.

**SS90** · 3rd August 2009, 05:30

Do you still have the original "bitubo" internal dampers?

In theory they are a good system, but the do have a tendency to have internal seal problems.

By that I mean, there is oil inside each of the forks (I think 80ml), but that oil is only there to lubricate the fork stauncheons and bushes.

The dampening is controlled by internal (sealed) dampers.

While sometimes, the seals on the internal dampers leak oil the oil out of the damper, I remember seeing a few examples where the oil from the stauncheons was "sucked" into the sealed damper units.

the result of this is the oil level in the damper increases, and causes the damper to "hydraulic lock" at the last few cm of travel.

On one, I was able to simply unscrew the damper unit (a simple task, some of them are just screwed together, others are crimped, and as such a throw away item) and simply remove the excess oil.

It worked, and never gave a problem again!

I would suggest seeing how much oil is in your stauncheons (I think it's 80ml, but I 'm not 100% certain on that)

**Robert Taylor** · 3rd August 2009, 12:20

Originally Posted by SS90

Do you still have the original "bitubo" internal dampers?

In theory they are a good system, but the do have a tendency to have internal seal problems.

By that I mean, there is oil inside each of the forks (I think 80ml), but that oil is only there to lubricate the fork stauncheons and bushes.

The dampening is controlled by internal (sealed) dampers.

While sometimes, the seals on the internal dampers leak oil the oil out of the damper, I remember seeing a few examples where the oil from the stauncheons was "sucked" into the sealed damper units.

the result of this is the oil level in the damper increases, and causes the damper to "hydraulic lock" at the last few cm of travel.

On one, I was able to simply unscrew the damper unit (a simple task, some of them are just screwed together, others are crimped, and as such a throw away item) and simply remove the excess oil.

It worked, and never gave a problem again!

I would suggest seeing how much oil is in your stauncheons (I think it's 80ml, but I 'm not 100% certain on that)

Yes, I can 100% concur that this is very likely what is happening, the sealing system in those cartridges is indeed prone to failure ( especially also given distance travelled / age ) and will indeed suck the outer chamber oil and create hydraulic lock. There must be an internal air cavity inside them to allow for shaft displacement. This is actually quite dangerous so it needs rectifying asap. We have come up with a repair for these in the past as replacement of the units is very expensive.

**MotoKuzzi** · 3rd August 2009, 19:25

Thanks for the help SS90 and RT. I had a similar issue a yr ago and had work done on one cartridge, new seal and seal head from memory, perhaps the other side has gone now. I will start by draining the oil from each side into a measuring cylinder and see if there is a difference and go from there. How much oil if any should go into the damper unit itself? The manual specifies 70mls per leg of ATF but I'm sure the technician ( Gaudenz Gisler ) who did the seal repair told me he put more in than that.

**Paul in NZ** · 3rd August 2009, 19:48

Or - you can just bin the bloody useless things and put in some FAC's. While you are in there how about some progressive springs.

I can do mine (admittedly diff model n forks) in an afternoon.

FAC's are no better in intial ride but seem to last longer...

BTW - remember that in guzzi forks with cartidges, the oil is for lube only and a prick to put in, half it gets spilt anyway so expect some small differences.

**Robert Taylor** · 3rd August 2009, 20:34

Originally Posted by Paul in NZ

Or - you can just bin the bloody useless things and put in some FAC's. While you are in there how about some progressive springs.

I can do mine (admittedly diff model n forks) in an afternoon.

FAC's are no better in intial ride but seem to last longer...

BTW - remember that in guzzi forks with cartidges, the oil is for lube only and a prick to put in, half it gets spilt anyway so expect some small differences.

The oil is also there to set the oil level or rather trapped air volume. That sets the compression ratio of the secondary air spring. That sets the progression and is far more tunable than those god awful progressive springs.

**MotoKuzzi** · 3rd August 2009, 20:38

Originally Posted by Robert Taylor

The oil is also there to set the oil level or rather trapped air volume. That sets the compression ratio of the secondary air spring. That sets the progression and is far more tunable than those god awful progressive springs.

So could a larger volume of oil cause the problem I descibed?

**Robert Taylor** · 3rd August 2009, 20:38

Originally Posted by MotoKuzzi

So could a larger volume of oil cause the problem I descibed?

Absolutely

**MotoKuzzi** · 3rd August 2009, 20:41

Originally Posted by Robert Taylor

Absolutely

It's over a yr ago but I'm fairly sure Gaudenz put way more than 70mls in. I had the forks off the bike and he measured in what he thought it should be.

**Paul in NZ** · 3rd August 2009, 20:42

Originally Posted by Robert Taylor

The oil is also there to set the oil level or rather trapped air volume. That sets the compression ratio of the secondary air spring. That sets the progression and is far more tunable than those god awful progressive springs.

Funny you should say that....

I was just going to go back n edit my post. I fitted 'on sale' special price from USA - NOT local supply progressive springs and i reckon they are crap.

The original LeMans springs are shockers - much (much) lighter than the SP version designed to carry the vast barn door fairing and the LM springs collapsed so much the sustension would bottom out even with the feeble guzzi disk - NOT good...

I whacked in the SP springs with the original LM2 short ones and they were I think the best combo - I'm just too lazy to change back... I think the 2 piece spring idea Guzzi originally had with the 36mm fork was a good one - better than the prog spring one...

having said that - the prog spings in the TR6C are a definate step forwards over the sidecar one it was originally fitted with Gawd! There was more movement from the flex than anything else...

**MotoKuzzi** · 3rd August 2009, 20:43

I'll drain it tomorrow and check.

**Robert Taylor** · 3rd August 2009, 20:50

Originally Posted by Paul in NZ

Funny you should say that....

I was just going to go back n edit my post. I fitted 'on sale' special price from USA - NOT local supply progressive springs and i reckon they are crap.

The original LeMans springs are shockers - much (much) lighter than the SP version designed to carry the vast barn door fairing and the LM springs collapsed so much the sustension would bottom out even with the feeble guzzi disk - NOT good...

I whacked in the SP springs with the original LM2 short ones and they were I think the best combo - I'm just too lazy to change back... I think the 2 piece spring idea Guzzi originally had with the 36mm fork was a good one - better than the prog spring one...

having said that - the prog spings in the TR6C are a definate step forwards over the sidecar one it was originally fitted with Gawd! There was more movement from the flex than anything else...

Yes, I worked on heaps of these in the UK and well recall the dire front ends!

**Dodgyiti** · 9th August 2009, 23:24

FAC's are great improvements to the bitubo's. I love the adjustability with damping psi.
As for springs, the standard ones are pretty cheap to buy new. Tried progressive springs and concur they are not much chop, actually, plenty of chop.
My Calli did not use up all of it's long travel either. I never measured the stroke like you have, just noticed the squashed bug line was not as high up as I expected.
What kms are you at on it, if the back shock was leaking a few months ago and now the front is not performing perhaps it is time to refurbish?

**MotoKuzzi** · 10th August 2009, 19:45

So far what I've established is that one damper was indeed hydraulicing? i.e not compressing as far as the other and also noticeably a fair bit of crap drained with the oil from that side. Both fork legs had about 270mm of oil in them. ( I made a note in the hand book when I refitted them last yr ). Is it possible that amount of oil is needed to overcome poor spring performance? I have a mate who is an engineer with some experience working with race car set ups, looking at the dampers for me with a view to machining the suspect damper to accept a better quality seal to match the one done last yr. Replacement all round with better quality gear would be my ideal but unfortunately my motor cycling hobby is only affordable if I can either do the work myself or keep the existing set up going with sensible affordable quality repairs. Will give an update in a few days when my mate has had a look at the dampers for me.