Sometime way-back-when, I bought a used set of throttle bodies off an RTS Futura (51mm v Caponord 47mm) with the view of doing some tuning/comparison work on the Raid with the 3D printed hybrid velocity stacks (51mm diameter but Caponord height). What really happened though was far less glamourous and only involved a sturdy box and a shelf! But about a month ago I dug them out again and realised that I pretty much had all the ingredients required to do a full clean and rebuild. I had stainless steel 4x10mm and 5x12mm Torx screws on the shelf as well as all necessary seals. The ultrasonic cleaning bath would do the brunt of the work and I could send the injectors away for professional cleaning at a reasonable cost.
And so, with a plan to hand, apart it came. First the injectors were sent away for cleaning. The turn-around was quick and the total cost was about £30 including P&P. Thankfully both injectors got a clean bill of health. Next, the throttle body and associated parts went into the ultrasonic cleaning bath. I had bought the 6L version …. but when you take into account the smaller basket inside, the usable capacity is probably something more like 4 – 5L … just enough luckily, for the throttle bodies. If I was in the market for another one, I’d definitely opt for the 10L or maybe even try to stretch to the 15L for good measure.
It was amazing the amount of debris that came out of them … in the end they looked almost brand new again! The rebuild was very straight forward with all new ‘O’-rings and screws used. Pleased? Yes I think so. They are refurbished and ready for action which is the important thing. The only downside is that some of the mild-steel components are still showing a patina of rust. It would have been nice to re-plate them to give them that as-new look as well. For now I’ve cleaned off what I can and coated the parts for protection, but one day I’d like to have a crack at home plating … zinc, nickel or passivate of some sort might be interesting.
2x 4x10mm Stainless Steel Torx screws
4x 5x12mm Stainless Steel Torx screws
4x 10mm OD 2mm section Viton O-rings
2x 14.1mm OD 2.4mm section Viton O-rings
2x BS203 O-rings
1x BS008 O-ring
Just throwing it out there ……. If I were to offer these out as a bagged kit, would anyone be interested?
After January’s awful weather – snow, rain, sub-zero temps, earthquakes & landslides, it’s been a very nice balmy February! So much so, that the Capo has squirreled a good few miles under its belt – the last 300 of them with the new snorkel in place. And I have to say, I’m really chuffed at how it performs. No extra induction noise that my aged arthritic lug holes can detect and no detriment to performance even though it’s been nowhere near a dyno to tweak the mapping.
As I write, a swanky set of Futura throttle bodies are winging their way here, as are a nice new pair of Mk2 cam chain tensioners – AP0236253. The velocity stacks are now finished and ready to fit to the throttle bodies and so it just leaves the matter of swapping out the Anakee Wild tyres for a fresh set of Anakee 3’s and a DID ZVM-X chain and Ognibene front/rear sprocket set (courtesy of Motrag) and I think she’ll be ready for a damn good thrashing on Dr Dyno! 🙂
If all goes to plan, later this year the second Rally-Raid that’s currently being rebuilt, will finally get a motor installed. The plan is to use a big-bore motor …. an 1,103cc in place of the standard 998cc. The compression and valve timing will remain bog-standard Caponord (10.5/1 Inlet timing – 25°BTDC/37°ABDC and Exhaust timing – 57°BBDC/5°ATDC). However to accommodate the increase in air-flow, I’ve decided to use Futura 51mm throttle bodies instead of the Caponord 47mm items.
Meanwhile on top of this chunky aluminium marvel sits a pair of velocity stacks. These stacks vary in height (and diameter) depending on the intended tune of the engine. The RSV Mille of course is designed as a race-rep and as such wants high horsepower at high RPM – hence 57mm throttle bodies and very short velocity stacks. On the other hand the Caponord was tuned for improved low-end grunt and so has small throttle bodies (47mm) and tall velocity stacks to maintain good gas flow speed at low RPM. The Futura seems to sit firmly between the two!
Now of course I could simply use the medium height velocity stacks straight off a Futura, but I decided to go a different route and print a new pair of hybrid stacks – Caponord height BUT 51mm diameter to fit the Futura throttle bodies. Unlike ABS, Colorfabb Ngen (Co-Polyester) can’t be vapour polished with Acetone, so I’ll have to sand the venturi down with a variety of grades of wet-and-dry up to 2,000 grit and maybe finish it off with something like Quixx plastic polish – if it works on this stuff! Here’s a couple of pics comparing the original and new version – straight out of the printer!
Unfortunately 3D parts (unless made on high-end machines) don’t typically have the same strength as injection molded or machined parts – but they do make great ‘proof-of-concept’ parts! If these stacks prove to be a positive step forward, but not durable enough for the working environment, I can at least get the drawings to the machine shop and have them made in aluminium … but that’ll be a tad more expensive than 85p each off the printer! 🙁
Just had a spare half-hour to rub some 100/400 & 1200 grit paper down one of the stacks and all I can say is – WOW! This material rubs up lovely and probably a couple more sessions will see it through. All the print-ridges have gone and I can’t feel anything but a nice smooth surface that retains a print pattern that makes it look quite distinctive. 🙂
Just gave the Capo motor a service. No drama, everything went according to plan. I just thought I’d share a couple of pics of the inside of the airbox – with the modified breather – straight after the air-filter assembly was lifted. No cleaning, no Photoshop ….. just as it looks after 5,354 miles. The throttle butterflies, velocity stacks and idle air control valve (IACV) are all perfectly clean.
The extended drain tube from the airbox (down below the oil filter casing) held about a spoon full of oil when drained and what can be seen in the photo was only a light coating in the bottom of the airbox. One sheet of kitchen towel had that as clean as a whistle in a few seconds. Since doing this breather modification I’ve ALWAYS run the oil level to the HIGH mark on the tank. So without the tedious job of removing and cleaning out the complete airbox, it was a pleasure to simply replace the Athena air filter and button everything back together.