3D Print Project for SP airbox lid

[SouthCoastRich]

An RS lid has the intake portion waisted, whereas an SP lid maintains the same cross section for the same length of intake.

I see a few images of "modified air box lids" which just hack of the waisted part off. This will mess up a lot, and carburation, because basically it's literally like junking the airbox, the upper carb intake can just vacuum in the air from the atmosphere, and the air gets drawn through a small proportion of the filter.

My plan is to take my airbox, and cut away the waisted piece. This doesn't have to come out in one piece to I'll think on dremmel angles and number of cuts later.

Next will be to 3D print the missing portion in the SP cross section - which is handy as that's the same as what'll be there. I'm thinking of the stay for the filter and this may get incorporated into the design. With that part fabricated some form of RTV silicone will join it all up.

Well, that's the plan.

[4l04ever]

You would need to use an adhesive which is petrol resistant, as RTV could get affected by the petrol vapours coming back into the airboxes.

I modified my R airbox lid by getting some round plastic tube and warming it up and squashing it oval, then fixed this in place of the standard tapered R inlet tube.

[SouthCoastRich]

Thanks, that's saved me some considerable pain down the road, I can just imagine it. "Bikes started fuelling really bad all of a sudden" No one would think the airbox fallen apart internally!

Yes, I think Gavin has something like yours too. It'll be my fallback option 

[bulldogboy]

This is mark one and 2 air box lids from the dyno, ive got an SP lid if you want the dimensions?

[SouthCoastRich]

Last pic looks like quite a restriction like the R box. Can you take a couple of pics from your SP one looking through the tunnel from both ends?

ive got an SP lid if you want the dimensions?

Might well take you up on that if the pics don't show the whole story - thanks 

[bulldogboy]

ill take some pics tomorrow took me 2 years to find an sp lid, theyre rocking horse shit.

[SouthCoastRich]

Thanks 

Rare for sure - hence the plan to 3D print rocking horse shite 

[SouthCoastRich]

I've removed the R/RS tunnel. In practice this is a lot harder than I thought. The angles are very difficult and in some instances it's better to go in through the aperture to get a 90 degree cut. The other issue is I have a single speed dremell and that tends to melt the plastic rather than cut it. However, the job is now done and thanks to pics from Gavin on an original SP lid I think we're good to measure up for printing. Out of interest the side of the tunnel you can cut off it straightforward enough (for those skilled in the use of a variable speed dremell) but the moulding on the upper surface (lower in the picture as it's upside down) also needs taking back. Getting the right diameter tool for the radius of the corners is super important.

I'm not sure this is going to be an easy repeatable process!

[bulldogboy]

Top marks for trying though how you going to join the 2 sections? Just get a good join then use sealant?
Or include a lip on the print for the new bit so it overlaps the bit on the lid?

[SouthCoastRich]

Here's the tricky bit in a picture of what needs removing to keep the profile the same. In practice I doubt this make much difference but I'm trying to get as close as possible to the SP lid.

[SouthCoastRich]

Top marks for trying though how you going to join the 2 sections? Just get a good join then use sealant?
Or include a lip on the print for the new bit so it overlaps the bit on the lid?

I'm sure there'll be manual sanding on the part and more on the box. After that I'm trying the superglue & filler trick. I can go over a bit on the outside of the tunnel to seal in. Well that's the plan!

[bulldogboy]

Look up "gold label" pond sealant, you can get it in black, its designed for welding butyl pond liner together.
Its really rubbery, it sticks like shit to a blanket, but retains some give, and suppleness , would not only bond but fill in any minor gaps.

[SouthCoastRich]

I've ordered some QBond - which is supposed to be the ticket for areas that may have petrol fumes.

My Dad's taken the piece off my tonight and will work some 3D magic... we'll see what he comes up with 

[SouthCoastRich]

Here was the cut plan. Ended up using electrical tape to get cuts 1, 6 & 7 straight.

[Warwick]

Quite a bit of work really, innit? Wouldn't it be just as easy to make a mould from the larger section and use that to make a new plastic or fibreglass extension piece to extend the initial full bore section to replicate the SP intake? I guess 3D printers render such approaches somewhat old skool, maybe? I don't know enough about them to be honest so it'll be good to see what you come up with. 

I'm curious though if anyone else has actually done any dyno comparisons between the R and SP box lids since we did some brief stuff back in 2006/7? It looked then like there was a possibility of very small gains using the SP lid, but we were testing all sorts of other stuff at the time too and such very small differences between runs could easily be within the normal range of differences between run readings really (we didn't rigorously test just the difference between R and SP lids alone), so I'm curious if anyone has done anything since then that shows a clear gain with the smaller R/RS carbs just by changing to the SP upper airbox lid? I don't recall seeing anything, but I might have missed it of course. 

I must admit that I feel kind of guilty thinking about all of the perfectly good R/RS lids that have been ruined over the years by people hacking at them to try to 'derestrict' them based on my reports of those dyno sessions back then...