Derbi Senda air filter issues, PHBL 24 carb

[fhol]

I have a Derbi Senda Xtreme Ltd. Ed. '17 with Airsal T6 Asso cylinder, Yasuni pipe and Dellorto PHBL 24 carb. Runs great!

To use the original airbox I had to cut the "hose" and install a bit of pipe in between - see pic - making it shorter. It was not a perfect fit - air tight though - but the rubber is under a slight stress. This seems to cause some cracks to appear over time. Ran it for a while anyways (cracks didn't go all the way through) but today when I checked, it was time to do something about it.

 

So I installed a small pod filter, temporarily. It is extremly tight both against the frame above it, and less than 1cm clearance from the pipe. Shock absorber is also in the way. Another BIG drawback is the noise with a pod filter - I would say twice as loud now!

Any smart ideas on how to connect the carb to the original airbox with some custom hose/pipe or something?

I would also appreciate tips on what kind of pod filter would fit better, maybe 90-degree bend, point it downwards?

Are there any pod filters that are less noisy than the one I'm using?

Mine (see pics) is a short stubby off-centered cylindrical one with a bit of foam and metal back plate. Maybe 8-10cm in diameter. Since it isn't perfectly symmetrical, I have rotated it away from the exhaust - but it hits the frame above instead and get bent there. Cracks coming soon I think.

[aeroxbud]

Pod filters are all noisy. They also increase your fuel consumption by making you run bigger jetting.
That's probably not a good idea to mount a lot filter there if you ride in the wet.
The metal pipe you have used is heavier and at the wrong angle. I would try and use some PVC pipe if you can find some of a similar diameter. You could then heat it and put a slight bend in it.

[fhol]

Apr 13, 2024 17:33:43 GMT -5 aeroxbud said:

 I would try and use some PVC pipe if you can find some of a similar diameter. You could then heat it and put a slight bend in it.

Sounds like an excellent idea! I will look into that, thanks!

(I used a metal pipe from an old vacuum cleaner because I was unsure about what sort of plastic would not dissolve in petrol fumes. The pipe is very thin/not heavy but hard to bend I reckon)

Still would like to hear about options for pod filter though, bent or something, as backup. If someone has a Derbi and knows what fits, that would be great!

[fhol]

I'm entering McGyver-mode now involving some chemicals, vacuum cleaner scrap, rubber and plastics. Wish I had a 3D-printer! I'll post some pics when I'm done with this madness.

[fhol]

Here is the old vacuum cleaner scrap, and some Multibond that is awesome for all sorts of repairs. It becomes rubbery and slightly flexible when it hardens.







I decided to put a thin layer of the multibond on the outside of the cracked rubber (not cracked all the way through) and hoped it will fix the issue - but for how long?

I also made a new pipe from the plastic handle of the old vacuum cleaner, replacing the very thin chrome pipe I used before. The plastic pipe had a little more diameter to it, so it fit the hose better, snug even without hose clamps. It seems to me that tightening with hose clamps is what puts some stress to the rubber, cracking it eventually. I will use those anyways, not tightening them too hard.

Experimented a little with the flexible plastic hose from the vacuum cleaner, but could not make it fit. Inner diameter too small. Yes I cleaned all the vacuum cleaner stuff like a madman before I used them, in case you wondered about that.



The red adapter came with another carb, (EDIT: actually came with the PHBL), a Dellorto PHBG 21mm "copy" from Naraku (crap quality, damaged inside when new, jets tightened too hard from factory, don't buy them - not a perfect clone either so repair kits for real PHBG won't fit - at least not the emulsion tube or whatever it is called). Anyways, red adapter fits on the air filter side on the 24mm PHBL carb too, but since they cut it, there is a tiny gap and tiny gaps are no good. Therefore I haven't used it.

Here is the end result (minus the hose clamps), which I was very happy with...



... until it was time to mount it. Even using a heat gun, it is a VERY tight fit directly on the 24mm PHBL carb. I ended up bending it too much mounting it, so the multibond cracked where the cracks in the rubber are, and the whole thing was just a waste of time.

Then I discovered tiny cracks in the rubber between carb and intake too, so I changed to the 21mm Naraku PHBG "copy" instead, with a different aftermarket intake that has the wrong angle for the hose to original airbox. Grrr!! However, with that rotateable rubber intake, the pod filter I have fits perfectly.

So that is where I am now. Temporary solution. I'm trying to find an OEM 847093 intake now, then 21mm Naraku + new airbox hose will fit without modifications. Going to buy new rubber for the 24mm PHBL, and maybe a 90-degree angled podfilter for it. I have a bunch of mopeds, so will probably use it on another one.

// Old McGyver-wannabe with a serious moped disorder

[fhol]

The absolute best solution - except if you get foaming inside carb because of the vibrations - would be an angled variant of this intake www.crash.no/trimdeler/innsug/derbi-gpr-senda-sm-insug-phbg.html with a clamp fit (not sure what the correct term is) and a carb that fits them, PHBG20AS for example. And to the airbox, some sort of flexible metal tube. No more rubber shit!

An angled such intake seems impossible to find. I think you need to manufacture it yourself. The straight ones are also super hard to find. The link above is the only place I saw one.

[fhol]

I managed to solve the issue using parts of two old original air filter rubber hoses/boots/pipes. Don't know what the correct term is in English.

First I tried with a podfilter attached to the rubber hose. That worked without stressing the hose, but the filter is crappy and the bike became way too loud.



After that I combined two old rubber hoses to get the correct angles and a very thin metal pipe from a vacuum cleaner. It is still super tight, but no stress on the hoses now compared to the initial solution that caused cracks because of the stress on it. I also used the red plastic 3D-printed adapter that shipped with the PHBL 24mm carb, to make the hose fit on it. Also wrapped the pipe in exhaust insulation stuff as it is so close to the rubber.





I'm happy with this for now. Looks like crap but... it works!

FYI, also tried with an aftermarket 90-degree air filter attached directly onto the carb. That didn't work, too little space for the bend (hits the spring). And no, I didn't repaint the bike from previous posts. This is a different one, same make and model, just moved the parts over.