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10K views 18 replies 3 participants last post by  Pedro CH 
#1 ·
I've bought my RD03 about one year ago. I've got it ready for the 2016 and this year I've ridden more than 26000 km on it, one third on unpaved roads and muletracks in Italy, Balkans, Turkey and Georgia.

What really disappointed me about the bike is the air intake system, in a shitty place where a lot of dust enters (even mud can enter as I have experienced at the Cow Adventure!).

So I was looking for a solution, I've tried a filter skin, it was not bad but in Turkey I rode up to 3000 masl and I was costantly at 2000 masl and the engine was running to rich, so I had to remove it and the filter was filled quickly.

I've seen pictures of snorkel that was used on the RD04 marathon and I got interested on it.

This bike redirected me to Boano:
HONDA XRV 750 Africa Twin - 1992 DA COLLEZIONE Moto e Scooter usato - In vendita Monza e della Brianza

I've asked him and he can do it but in order to do it, a lot of things must be changed, as the bigger tank and the longer airfilter (I don't want to have the bigger tank and the longer airfilter, because it would be impossible to find a spare airfilter in case mine brokes). Moreover the price of this is more than 2000 €. No way.

From this website I got some informations and the owner even sent me some detailed pictures of a german guy that builded one alone:
AFRICA TWIN MARATHON - HOME

I've opened a topic on the italian Africa Twin Club and people helped me a lot on finding more informations:
Modifica Airbox Rd03/04 - Modifiche / Accessori - Moto Club Africa Twin Italia

One of them has even explained with a high precision technical draw how the airbox is modified:
View attachment 106521

Then another one redirected me to the german ebay were an air intake was being sold:
HONDA XRV 750 Africa Twin "Rallye Luftfilteranlage mit Sitzbank" RD04, HRC. | eBay

Africanqueens has something on their shop, I've asked them twice what was it about but I've never got an answer.

So I decided to build an air intake on my own, using fiberglass (I can't work and weld alluminium).

I've did some fluid dynamic rough calculations in order to compare the resistance of the original snorkel and the one I was building in order to have an idea about the cross section (Mine has a height around 20 mm, the original one was higher)

I've bought a used airbox from ebay and as soon I've got it, I've started the work. I've done the fiberglass directly on the tank, putting Cellophane in between (nothing sticks to cellophane, but be aware that there can be diffusion and some resin can pass through).
To form the channel I've used a foam covered with cellophane:
View attachment 106529

Water Yellow Drink Food


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I still have to finish it by putting a round border at the entrance, some L profiles + a foam in order to make the seal on the airbox and a rubber tap for the tank screw hole.

The seat has to be modified aswell.

Right now with K&N airfilter and arrow PD the bike runs fine, the minimum is not affected by the new air intake, when the needle works, the bikes runs lean (the higher rpm the leaner it is) and I was surprised because the max jet is working fine and the bike runs up to the limit rpm. The noise of the airintake is very loud and gives the bike 10 "psychological" HP more. :D

Next step will be to implement a low density filter foam on the air intake, in order to find the best compromise (Then maybe I'll have to use a smaller max jet).
 
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#2 · (Edited)
Excellent job! Thank you for sharing with us.

You are right for the airbox of RD03/RD04. If you are looking for more HP you never have enough air.:(

So, I experimented with different air filters.

Wire Cylinder Auto part Waste container Filter


I took the best results with Twin Air, much better than K&N.
You can take an old air filter and put Twin Air foam around after clearing the paper filter. Very easy and cheap.

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Maybe it's better to try it first and then play with carb jets.

Please keep us informed.:thumbup:
 
#3 ·
Hey mate!

What I'm looking for with this modification is to reduce the amount of dust/mud that reaches the airfilter, that's why I hope to find a nice compromise with the sponge into the air intake, so that I have to change much into the carbs.

I want to keep the filtration as original as possible in order to not compromise the engine life (90k Km and right now it is consuming around 2-3 dl of engine oil every 10k km) .

A foam air filter is nice for offroad but it is not as effective as the original one regarding filtration.
 
#5 ·
Pedro: Thank you for initiating this thread and sharing your progress. I am experiencing similar issues and am looking for better filtration setup/configuration. In order to maintain a narrow profile with the panniers, I decided to remove the side panels. Recently, I have been experimenting with a pre-filter at the intake port by creating a box made of a common household air filter found at any hardware store or Family Dollar store. I'll attach a few photographs of my recent trip and results. David
 
#8 ·
Pedro: Thank you for initiating this thread and sharing your progress. I am experiencing similar issues and am looking for better filtration setup/configuration. In order to maintain a narrow profile with the panniers, I decided to remove the side panels. Recently, I have been experimenting with a pre-filter at the intake port by creating a box made of a common household air filter found at any hardware store or Family Dollar store. I'll attach a few photographs of my recent trip and results. David
Your Idea is similar to something I've tried just before starting building the snorkel:
I've rotate the original snorkel of 180° (So it was pointing inside the bike) and I've closed the left part of the chassis with duct tape (Including the part between mudguard and chassis, on the left).

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I tried it under the rain, the part under the seat and the intake were completely dry after a 10 km ride. The bike was running fine, at very high rpm and full throttle it was a little bit rich. But I didn't like the fact that I couldn't properly test this possible solution till the next dirt ride, so I've built the snorkel.

A nice and easier solution is to remove the left side cover and to build an air intake that takes air from the front and it is completely sealed from back and sides.

Something similar to this bike:
OnlyBike - Africa Twin Transafrica
 
#6 ·
Result of running rich in higher elevations and off-road in desert terrain.
(Mojave Desert; Utah & Colorado)


common household furnace filter being used as a pre-filter: (new and used)




During a recent two month, 5,000 mile trip, I had to order three OEM air filters while on the road.
 
#9 ·
Pedro: Thank you for your reply. I like your idea of rotating the intake port hose to under the seat and sealing the sides with tape. Apparently, this setup failed to provide a better filtration system. Perhaps a combination of this method with the furnace pre-filter formed to the space under the seat may be a cleaner, suitable, less complex, less intrusive solution. I will test this and report results in the future. I may also consider extending the intake port with a common flexible hose to a cleaner area with a pre-filter. More to come.... (Btw, I understand the R/R may fail due to excessive heat. How long (km's) have you been running with the R/R mounted on the inner fender and under the seat? You may want to ensure the R/R does not get too hot, without proper ventilation. Just an fyi...) Thanks again for sharing your progress and thoughts. (I would consider your snorkel solution, but I am extremely happy with my rally fuel tank, Kahedo/Touratech seat, Bagster tank cover and Bagster tank bag.)
 
#10 ·
For rotating the intake, you have to cut away the internal curve. So be aware of having a spare one in case it doesn't work well. (I tried this because with the spare used airbox I've got also an intake.

Regarding the voltage regulator, the main problems are the connections that burns up due to many Ampérés. There is an easy solution to this:
1) Use a non standard muffler, the original one is huge and gets really hot (And it is close to the R/R connectors)
2) Leave lights always on

I've ridden 26000 km this year, in some points the ambient temperature was 45 ° C and I rode a muletrack up to Didgori in Georgia (No 4x4 could pass there, 1st gear, a lot of clutch "abuse", ambient temperature was around 42° C), both oil and water temp passed 100° C...No problems or signs of burning connectors.

I was regularly checking the connections every 1000 or 4000 km, depending on my mood :D

small tip: Under the righ side cover you can place a lot of stuff, on my long trip I had the two original footpegs, a spare voltage regulators, all levers (clutch/front brake/gear)
 
#12 ·
Cheers mate!

Be aware that after this work the resistance of the air intake will be bigger and so the bike will for sure run rich.

Boano does a simplier works aswell:
- Bigger foam air filter (as Marathons have had, so he also modifies the air box in order to be able to mount the longer air filter)
- Reduction plate for the diameter after the filter (when original bikes have a mesh) in order to keep the original jetting

Good luck and happy holidays!
 
#13 ·
Pedro/Forum Members: Does anyone have experience with the K&N Airforce Pre-cleaner offered at Rugged Roads?
K&N Airforce Pre-Cleaner - Rugged Roads

Also, if someone has an image of the upgraded RD04 Marathon air filter, please post the image to this thread. Thanks in advance! David

>Boano does a simplier works aswell:
- Bigger foam air filter (as Marathons have had, so he also modifies the air box in order to be able to mount the longer air filter)
- Reduction plate for the diameter after the filter (when original bikes have a mesh) in order to keep the original jetting<
 
#15 ·
Regarding the pre filter air foam: I've never used the one of K&N but it can for sure be good if you use a k&n filter (the bike runs a little bit leaner with k&n filter)

I used an home made filter skin during the trip (made with a collant) and it helps a lot keeping the airfilter clean.

I'm just wondering how can you mount the filter with the big red sponge around it: does it fits in easily?

Btw with the "tank" snorkel I will have already a pre filter foam in it and maybe I will also use a filter skin on the entrance, I'll post pics before Christmas when I'll do this work.
 
#19 · (Edited)
Hey mate!

Thanks for sharing.

Today I had some time and I've finished the airintake:

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Here you can see the thickness of the sponge (it is the less dense I've found):

Sea cucumber Flatworm Organism Echinoderm Sea cucumber

Ignore the two side (I had cutted it like this in order to avoid it to being sucked into the snorkel), the thickness is just in the center and it is around 15 mm.
I started with a thicnkess around 150 mm.

I'm very pleased beause the bike is running very well, I don't think I will have to adjust any jetting, may it is a little bit lean I would say but I will test it more tomorrow when the ambient temperature should be around 10° C.
 
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