Dossing about with admission pipes.......

I was faffing with the admission tonight so I took a couple of pics. I've just gone from a home made admission pipe to one which holds the carb at a less severe angle. I'm trying to get smoother running at low engine speeds. I suspect the angle of the carb is to blame for this - but there may be other factors. Only one way to find out....
Here is the actual admission in my scoot :
https://www.flickr.com/photos/116877957@N08/13610383554/
Hemets/shopping are out ! I cut out the bottom of the bucket. I did the same for my gf's scoot - but I made a fibreglass bottom inside first - so she has a removable bucket-bottom. She can empty the contents of her handbag in there- but I can get at the carb without taking the whole scooter to pieces. I urge anyone with a Nitro/Ovetto/Mach G to do likewise !
The green bit of plastic under the collar is not pretty - but it stops the jubilee clip cutting into the rubber pipe.
There is a 5° plate under the reed box from RSE racing - The carb is mounted frontal - so there is a bit of the frame missing that holds the seat box on. This has been strengthened with the U shaped threaded rod you see.
Carb is an OKO 21 - but it will take a 28 or a 28 Del Orto VHST for nuttier configs. The connecting tube is a fibreglass home made construction - made to be as big as is actually possible. The theory is - if the diameter is big - the engine just 'sees' it as a part of the air box and not a longer admission tract. This would appear to be true - because (jetting aside) there is no significant difference using the open filter - or this. The purple connector adds a nice venturi at the mouth of the carb - and is flexible - but air-tight. It is in fact the front shock dust protector from a trail bike - cut down.
The intake is made so it will take a stage 6 big filter.
The pipe is an after-market second hand experiment. I like the angle of the carb. I don't like the lack of venturi. And it's not straight like the home made version.

This is the air box. It has been 'doctored' so it fits intake pipe.
https://www.flickr.com/photos/116877957@N08/13610014893/
It has a 23 mm intake hole. The entire thing is air-tight - but I added a big clip just to make absolutely sure.

This is the home made intake pipe:
https://www.flickr.com/photos/116877957@N08/13610032693/
It is fugly on the outside.....
https://www.flickr.com/photos/116877957@N08/13610022283/
but there are interesting things going on inside....... The final approach has been sculpted so it narrows - and re-directs things straight into the reed box. It works stupidly well if you mash the throttle - but does not want to know if you open 1/4 - it just splutters. The hypothesis is that the carb is at 45° and just dumps petrol into the admission. I might be wrong - hence the expoeriment. It could be that the venturi is just too pronounced. We will see.

https://www.flickr.com/photos/116877957@N08/13610370304/
here is the other end. It is flat. My welding bent the plate - so we had to quiksteel it & then surface that flat. This is without doubt the best admission pipe I have if you just want to burn off. Better than the Stage 6 - better than anything I have tried. But not if you want 'normal' behavior. Only full-tilt boogie will work. Reed box is Malossi VL14 with several flavours of reed. Thick ones for the big boys (MHR team 2 or Metrakit pro race), Thinner Malossi for the Stage 6 Sport Pro.

This may give someone some ideas. The other advantage is - any air box/filter makes noise. If you put it under the seat - you get less noise. And your wet-weather open-filter problems are gone.

 

Well there's a solution to my carb mounting problem and reed block dilemma for vision.if i do a copy..ile use alot of heat sinks on the parts that get welded.think a narrower one might help with port velocities. Looks good though..
maybe it would help if you did alot of spot welds and joined the dots..less heat build up.

 

Well I went on a run today with the big boys. Scoot was great- but I suspect it would have been even better with my home made pipe. Interestingly, there was no difference with the carb at a less steep angle. If anything it was worse. So I need to devote attention to the slow jet. I suspect it's too small and this is the cause of the splutter at 1/4 slow roll on. If you mash it it just flies.