Aprilia NS 1692 lives again! But I need some help please

[davidwheeler]

After only 37 years rebuilding, she passed her MOT yesterday so I have now had a little drive around and found some problems...

1  How do I keep the oil in the front suspension?   It must be 30 or more years since I rebuilt it and I do not recall any sort of oil seals.  The instruction book says fill it up till it overflows and that's it but it seems to pump out again in a few miles and I am back to pogoing.  Also, what oil to use please?
2  Third gear jumps out.  It did on my other gearbox as well.  (And on both my Lambdas!)  I presume the dogs are worn... Has anyone had them repaired?

[Scarpia]

the oil filling is a mystery to me too. (Mine's a second series with a dual pump on the reservoir). use normal (none synthetic) engine oil

If I pump the reservoir, at a certain moment oil pours out of the pillars and overflows as you say which is a mess and drips down the inside of the wheels. There is no apparent way of knowing when "enough is enough". I have no problem with "pogoing" though. There is a rotating adjuster at the top of the pillar but I never really could tell any difference in driving however I adjust it.My full sliding pillars were rebuilt in Sicily and are effectively brand new so perhaps there are seals worn on yours somewhere letting the oil leak?. At the technical control here in belgium they have a vibrating machine that pumps the suspension and gives a graphic readout and the aprilia supension performed better than many modern cars according to the MOT inspector. !
My gearbox is ok so no experience with repairs I'm afraid.

[davidwheeler]

Mine is first series and so differs from yours internally.  I have looked crefully at the drawing in the Handbook and cannot see any seals to be missing or worn and certainly do not remember any.

[ben]

   David
     There are no seals as such to cause leaks.However there is a small spring-loaded ball valve which I believe allows the damper oil to be pumped up through the central rod and out into the space above the damper piston.If this was stuck the oil would steadily accumulate in the lower chambers and spill out of the gap between the two halves of the spring dust covers. If you unscrew the lower cap ( T1 on tavola 17, p48 of your handbook) you should be able to see a slotted screw head by lying on your back under the pillar with a bright torch.Try poking something like a knitting needle (ideally a steel one like Gerry uses to knit your socks with) up through the hole in the above mentioned screw and check that the steel ball lifts off its seat. Or maybe unscrew it and clean it up but I have not tried this with it still on the car. (I assume your "T1" caps are in place and are sound.)
 The valve components are shown on p 96---Items 38-73165; 38-73170;  48023(the ball); and 38-73163.
  If this doesnt work or if the oil is leaking from the aluminium cover at the top of the suspension unit the passage-ways in the piston itself may be clogged in which case the only option is a major strip down! I dont think this is likely however. The pump action is the key.
   When you top up the oil, from the top, as per the handbook most of it will inevitably run out again down through the top bush but hopefully recharging it on the way through as it is porous.The bit in the middle that does the damping should be trapped.
  If the ball valve was stuck open I would expect the damper oil to drain out when the car was parked rather than be pumped out by the suspension as you drive along.
               Happy grovelling
                                         Ben

[ColinMarr]

As I remember it, there are brass ‘nipple’ fittings at the top of the pillars, onto which you screw the hand operated oil pump, which you have already charged with oil. Inside each nipple there should be a ball and spring non-return valve. It was messy, and had to be done every 1000 miles or so, but I don’t remember it being much of a problem. Maybe your balls are missing or not seating properly.

Dropping out of 3rd gear is familiar. The solution in the mid ‘60s was just to fit another gear box of which there seemed to be plenty! Not much help now I’m afraid. But some consolation perhaps from what I have read about with early four-speed Fulvia rally cars, where one of the jobs of the co-driver/ navigator was to hold it in gear!

Colin

[rogerelias]

As I remember it, there are brass ‘nipple’ fittings at the top of the pillars, onto which you screw the hand operated oil pump, which you have already charged with oil. Inside each nipple there should be a ball and spring non-return valve. It was messy, and had to be done every 1000 miles or so, but I don’t remember it being much of a problem. Maybe your balls are missing or not seating properly.

Dropping out of 3rd gear is familiar. The solution in the mid ‘60s was just to fit another gear box of which there seemed to be plenty! Not much help now I’m afraid. But some consolation perhaps from what I have read about with early four-speed Fulvia rally cars, where one of the jobs of the co-driver/ navigator was to hold it in gear!

Colin

[rogerelias]

OOPS PRESSED THE WRONG BUTTON

[davidwheeler]

I think you may have the right diagnosis, Ben.  It is not really possible to say when the oil drains out but there is a pair of puddles in the garage.  That may well explain why there is no damping action that I can detect.  I shall grovel this weekend.  I seem to remember that the spring is held by the bottom cover and that dismantling the upper half of the suspension can be done without any special tools??  I shall now scan in the picture in the handbook and enlarge it so my old eyes can see!
David

[Scarpia]

Maybe your balls are missing or not seating properly.

that's fighting talk where I come from Colin...

[ben]

     Diagnosis may have been right but suggested treatment not. I have now inspected some spare bits I have and find the crucial ball valve isnt visible or accessable from below. Thought I should log this in for accuracy of the record. Hope your investigations from the top are successful.
                             Ben

[ColinMarr]

David,

I take it that the aforementioned spring-loaded balls in the filler nipple are snug and comfy. (Sorry about that Scarpia, I didn't meqan to upset you!)

For a good and detailed description of the inner bits of the Aprilia front suspension, I suggest you refer to the 31 December 1937 issue of “The Light Car”. This describes how the “small valves (presumably the ones Ben refers to)…allow an easier upward passage for the oil, thus imposing a greater check on the upward motion of the piston than in the opposite direction…(which) controls the upward motion of the wheel due to road shock…”. As I remember it, these valves fit inside a sort of ‘cotton reel’ which is mounted on the rod that goes through the centre of the whole caboodle. Is it possible these have been put in the wrong way round? I don’t think you can get access to these without withdrawing the assembly upwards through the hole in the front wing, for which I think you do need special tools to undo the threaded sleeves down inside the top tube.

If you don’t happen to have that issue of The Light Car to hand, I have a spare photo-copy (which seems easier for me to find than my Tax Form P60 for last year!) and I would be happy to post it you. It must be a period copy too, because it’s on 10” X 14”” paper, which is bigger than A4.

Colin

[ben]

    The article you refer to Colin is as you say an excellent description of many aspects of the Aprilia. As fate would have it however I think the description of the damping action is back to front. The valve arrangment within the piston allows the oil to pass down through it relatively easily but restricts its flow more severely as it passes up.Thus as the wheel rises up over a bump the piston moves up easily but its movement back down is slowed down by the damper. Similarly if the wheel passes over a hole the damping action limits the degree to which it drops into the hole. I have harboured this concern for several years now but never had an occasion to unload it before!
    Further to my previous suggesions vis-a-vis Davids problem the more I study the design the harder I find it to see any way that oil can escape from the central damper zone. On the first series design the space below the piston and rod assembly appears to be completely sealed off. However if NS---- has a second series front axle the story may be different.
   The frequent topping up required by the maintenance schedule is for the benefit of the bushes that locate the stub axle etc and slide up and down on the pillar.
   I think I have only topped up my own car when setting off for Italy. That is 3 times in the last 44 years! Only joking---also before her M.O.T.'s.
   Incidentally Colin none of my comments about the Aprilia suspension are intended to denigrate the car in any way.I am one of Vincenco's most devoted disciples and would defend the claim that she is his greatest masterpiece to the death.
   Also I do not subscribe to the opinion that they are fragile.You probably missed the headline in Viva Lancia
                     APRILIA SHOWS INTEGRALE'S THE WAY IN LMC DRIVING TESTS
   because nobody got around to writing a report but second overall of the Lancias shows they are pretty robust even after 71 years.It also shows yet again how well the suspension works.   

[ColinMarr]

Ben,

O wise and clever man to have owned and enjoyed an Aprilia for 44 years! I am full of admiration and envy. I parted company with my 1939 Lusso in 1969 confident that I could always buy another one. Of course I never did and went on to enjoy Flaminia Sport, Beta 1600 Saloon, Delta 1500, Flavia Vignale, Aurelia B20 and now Fulvia Sport. But I still promise myself another Aprilia – one day.

I agree with you about the error in the Light Car article, which is otherwise brilliant. I guess I just read it to say what I expected it to say.

I missed the Viva Lancia! article you refer to – which issue was that?

Colin

[davidwheeler]

Here is one picture...

[davidwheeler]

...and here is the other