vacuum | Moto-Abruzzo

19/10/2019

Tuono clutch cover – AP0610992

Well it was a long time coming … I mean a looonnnggg time. Try several years in fact. But was it worth the wait? Well I think so, but hey, I’m biased!

Here it is …. AP0610992, a gold(ish) Magnesium clutch cover from a Tuono (2006-2010). It seems they are harder to come by in an as-new state than the proverbial rocking-horse doo-dah. All the ones I’ve seen have either been mullered by over enthusiastic riding Gods (crashers) or are brand-new at silly Aprilia pricing.

I know the standard cover does the job just fine, but ever since I saw one of these on a Capo motor I’ve wanted one as well – it just looks so much better. And besides, the weight saving alone must be worth at least 10 mph on the top end – right? 😉

Swapping over only takes a couple of minutes …. 8xM5 bolts and a click clamp to remove. I exchanged the old one for a nice new Zero-Leak low profile Stainless Steel 11.3mm version – very snug! In fact the old one wasn’t really squashing the pipe onto the siggot anymore and could be pulled/pushed/rotated very easily, which makes me think it was no longer vacuum tight ….hmm. Anyway, the new one crimped up lovely and everything is supper-sealed once again.

08/10/2015

Check Valve AP8104251 – symptoms

Aprilia Caponord ETV1000 Rally-Raid AP8104251vacuum check-valve exploded view A couple of folks have asked what the symptoms where that prompted the replacement of the check valves (AP8104251). Well, for a while I’d had an intermittent ‘cough’ or momentary stumble when lifting the throttle off idle …. maybe once every twenty times or so. More than enough to make your heart skip a beat when you think she’s about to stall just as everyone’s powering away from the traffic lights! Other than this annoying habit, everything in the garden was Rosie. Or so it seemed.

I’d cleaned and rebalanced the throttle bodies and all the vacuum hoses and inlet rubbers were perfect as they’d been replaced – but it kept happening. In the end with nothing much else to go on, I’d pulled the check valves and found them both to have failed.

Since replacing them, I realise there were other symptoms – very subtle – and the sort of thing you adapt to without realising it.

Reduced engine braking. This was really noticeable within a couple of miles after the valves were replaced – Engine braking is certainly stronger now
‘Burble’ from the exhausts on overrun. This is greatly reduced, especially at low RPM
Eratic idle during warm-up. The idle became lumpy at 65°C then smoothed out again by 70°C – now stable throughout.

With a few hundred extra miles under the belt, it’s fair to say that the intermittent off-idle stumble has well and truly gone which is great of course …. but I do miss that bit of ‘Burble’ on the overrun! So if you have idle issues and any of these symptoms ring a bell, then take a moment to check the valves as well as the usual old favourites – IACV, vacuum lines and inlet rubbers. You might be surprised.

25/09/201527/10/2015

Vacuum check-valve …….. part2

The new vacuum check-valve (AP8104251) arrived yesterday and today, while the rain poured endlessly from a depressingly black sky I set about swapping out the bad one on the front cylinder. Just to be Boy-Scout ready, I’d also made sure to have some new hose and stainless steel click-clamps to hand – just in case! Getting the old one Aprilia Caponord ETV1000 Rally-Raid AP8104251 failed check valve out is a real trial of patience and dexterity believe me! Here is a pic of the old valve cut in half and you can see that the valve has broken up completely.

With the valve cycling anywhere between an estimated 11-73 times a second depending on RPM, it looks like the 0.5mm thick valve flaps suffer from fatigue and rips develop where the material flexes most. The valve doesn’t completely fail until the flap is ripped away as my other (rear cylinder) valve is testimony too. That valve flows in one direction but also a very small amount in the other and when Aprilia Caponord ETV1000 Rally-Raid AP8104251 valve stress test viewed end on, light can be seen through the valve flaps leading me to think that rips have already begun. So now another new valve is on order and I guess I’ll make a note to check these again in 15K miles or so, it’s easy and quick to do – simply pucker up and suck or blow! 😳

Oh and I’ve been asked a couple of times …. why not use a cheap Ebay ball-valve replacement? Well it seems to me they’re just not designed to cycle rapidly, a ball/spring valve may well be susceptible to the same phenomena as an engine valve train at high rpm – valve bounce/float. Of course in the real world it may make no damn difference what so ever and I’m just a sucker for buying genuine Aprilia parts! 🙂

UPDATE

Second (rear cylinder) valve replaced and all now in perfect condition. In this case the valve was leaky as it had a tear down one side – so a partial rather than total failure. It also seems that these parts were upgraded some time ago, this looks like it’s a modification to the plastic body …. on the old one the case is simply presses together, on the new one it is welded. Maybe they had instances of the cases coming apart in service, who knows.

04/09/201514/10/2015

Pucker up and suck or blow …. your choice!

Here’s todays little quiz ……

What’s this?
Where does it go?
How many are on YOUR bike?

20150830_142552

Of course the smarty-pants among you will scream out the answers to 1 & 2 in double quick time – it’s a check-valve or none-return valve and it fits between the throttle body and clutch in the vacuum line. Excellent stuff, spot on …… but question 3 …… one valve or more than one? Hmmm.

Here’s what Aprilia show in the parts manual (click for photo of matching engine) …..

The front cylinder throttle body port has nothing but a piece of clear hose and a bung – the manometer/VAC gauge test point. All the slipper-clutch hose/valve assembly is ONLY attached to the rear cylinder throttle body port and TPS port. This may well be fine and dandy for an 01-03 bike.

But if you have a Rally-Raid or an 04-onward bike, next time you’re under the fuel tank/airbox take a good look at the front hose …… my guess is you’ll have a ‘T’-piece and more black hose disappearing downward below the mire of cables and wires running alongside the frame. Now this might be no surprise to you, but it had me scratching my head for a while I can tell you! 😕

And this is what I’ve got on the Rally-Raid (click to enlarge)……

A second complete set of pipes AND a second check valve connecting to another ‘Y’-piece. Why do this? Well this is my hunch, guesstimation, call it what you will ….. the 01-03 Capo has I believe a clutch pack that is 43.6mm thick, the 04-08 is 44.9mm thick. A difference of 1.3mm – in other words the valve springs will be compressed an extra 1.3mm on later bikes and that means a little more spring preload for the vacuum system to overcome when getting the clutch to slip, hence the second set of connections to improve the vacuum – 2 cylinder are better than 1! Also, two sources of vacuum from cylinders running out of phase (60° remember) may well help smooth out the pulses you can sometimes feel through the clutch lever. It simply looks like Aprilia modified our blessed Caponords and just didn’t bother to update the parts manual.

So what’s all the hullabaloo, why rip this poor little thing from the Capo’s delicate innards? Well the long and short of it is that one of them is pooped, shot, completely knackered ….. where air should only flow one way, it flows happily in both. Looking at the defective duckbill valve reminds me of Daffy-Duck cartoons, the ones where Elmer Fudd rearranges his bill with a shotgun! No worries, simply order a replacement …….

……. Aprilia part no AP8104251 Just make sure you’re sitting down when you look at the price! 🙁

I’ll shortly open up a new page with some more 3D images to try to better illustrate how the system is operating at different stages and how to go about testing the valves and what to expect.

08/07/2015

Down the tubes

Boy doesn’t time fly. It only seems a few days ago (weeks really!) I got here and already I’m packing again to head back to the UK on the Capo. Other than a check over, the Capo’s as she came back – unwashed even.

But this morning, with only a couple of days to go, events took a turn for the worse. Off we went for a little run around and suddenly, out of the blue, she’s running rough at idle …. Cough, cough, snuffle and splutter. In all honesty, only one thing came to mind – vacuum pipes.

Anyway it didn’t spoil the day and we got home with no drama (she ran fine at higher rpm) and 15 minutes later the tank was lifted … and here’s the culprit. One split vacuum hose on the front cylinder. So for now a generic bit of fish-tank plastic line has been press-ganged into service and a couple of nice new silicone hoses have been ordered of Ebay – one blue, one red. Colour coded vac pipes for each cylinder!

After 12 years and with almost 80,000 miles now on the clock I guess it’s probably a job that was getting towards the top of the to-do list!

13/04/201501/11/2015

All things being equal

gauge It’s been a while since the Capo was serviced and one job has still remained outstanding – in fact it has been ‘outstandingly’ outstanding for the past few services since I lost my old Davida vacuum gauge set! Yes, the perplexing throttle-body synchronisation*. Truth be told, the Capo has been running just fine for ages, but it never hurts to check it once in a blue moon!

I wasn’t about to lay out a fair-sized wad of cash for another (excellent) Davida set or buy a Carbtune II again in a hurry, so I thought it was about time to go the Poundland route and build my own manometer for a few pennies and with a bit of scrap kicking around the barn. The nice thing is that there’s a mountain of info on the internet about how to do this yourself, just pick what suits your needs best and modify for your own bike.

So what do you need? Well just a sturdy board, door or wall on which to mount the kit, a length of 6mmID clear tube, a suitable liquid and a way to connect it to the bike. That’s the nut’s and bolts of it, but a simple addition will make the setup ‘user friendly’ as you’ll see later. Although the tube is straight forward, the liquid is a bit more controversial …. Some say coloured water, some 2 stroke oil, some EP90 gearbox oil …… you get the idea! I chose some good old Scottoil Blue. Why? Because it was on hand, because it is basically ATF and has a fairly low viscosity, because IF it gets ingested by the motor it won’t cause any damage and because it turns out (purely by chance!) to work REALLY well!

*Workshop manual page 4-18-00

Now for a bit of physics ……

OU-1970's-style First off, what kind of vacuum are we looking at from the Capo motor? From measurements, it looks to be somewhere in the range of 22-24cmHg (based on an erratic Carbtune II) per cylinder measured against atmospheric pressure …. Now that’s not much for a mercury manometer – barely the length of a sheet of A4 paper. A nice compact manometer then, except that unfortunately mercury is almost impossible to get hold of because it’s deemed way too dangerous for us potato-heads to use safely. So what does this mean in terms of manometer height if we use liquids of a lower density? Well…..

Mercury 22-24cm (Ideal!)
Water 299 – 326cm (free-ish and known density but hard to see at a distance)
Light oil 345 – 376cm (coloured – easy to read, density varies on type of oil)

So here’s our first problem …… measuring each cylinder individually will require a water manometer at least 3.5m tall and an oil one even taller, clearly not exactly practical or compact! The solution? Well the Capo comes to the rescue …..

Being a twin, the Capo simply needs a differential setup – that is, measure both cylinders against each other, not against atmospheric pressure. In theory they should cancel each other out if perfectly balanced and so the manometer would read zero. Any imbalance will have the liquid slightly higher in one tube and lower in the other …… so by measuring differential pressure we don’t need a manometer anywhere near as tall, but remember, even small differences in pressure will make big changes in liquid level, so the manometer still needs to be quite tall. In the end I built mine on an old wardrobe door – a total height of 155cm, with about 60cc of Scottoil filling about 40% of this. With hindsight, it’s about twice as tall as it needs to be, but hey you live and learn!

Putting it to use …..

With the Capo nicely warmed up after a little ride, the tank lifted and the manometer plugged into the Capo’s vacuum ports, she was fired up again. The oil level in the tubes drifted apart and settled at approx. 9.5cm (equivalent to approx. 0.6cmHg), a gentle nudge of the screw for the front cylinder on the throttle body saw the level drop to just below 2-2.5cm (approx. 0.15cmHg) – comfortably within the 0.5cmHg accuracy quoted by Synchromate and oodles better than the 2cmHg per division of the Davida gauges. So that’s a £2 rig versus the commercial £70/£170 rigs ……..

….. and one other thing, this was without ANY damping (valve/jet/cotton wool etc.) in the line because the Scottoil works perfectly well as its own damper. It pulses gently by no more than about 2-3mm in the tube but is viscous enough to respond reasonably quickly to changes in vacuum. Oh and that addition I mentioned …… simply two small sealed containers greater than the volume of oil in the manometer, one placed in each line. Now if either vacuum line should come adrift the container on that line acts as a trap to capture the oil before it can get swallowed up by the motor!

So ultimately it’s cheap, self calibrating with excellent resolution around the balance point ….. but not exactly portable! And so in typical MA fashion, the mind wanders off to thoughts of a compact electronic version. Powered by the bike, self calibrating – kind of like this one!