Scooterotica

If you want this carb to work:

1st. Remove the gas filter from the carb's bowl cup. That alone increases the flow to the float bowl by 20%

2nd Replace the carb bowl cap cover and needle for the cosa 200 model. The cosa 200 needle is wider and has a better gas flow

3.On the cosa bowl cap drill this hole: http://picasaweb.google.com/Vespisti1/V ... 8492565714

to 2.3mms (use imperial -inches- size equivalent). Drill it from top to bottom so you don't damage the needle's seat

4.pass a dril bit of 1.9mm (use the imperial equivalent) to this hole

http://picasaweb.google.com/Vespisti1/V ... 5842472546



The problem of the SI is gas flow. This mods take care of it.

If you need a main jet over 128 -130 you have insuficient gas flow due to the design limitations of the carb body. For instance: The hole shown in the second picture is the one that takes the fuel from the carburator bowl to BOTH jets. It's width size is 1.6mms or "160" in tems of the SI jet sizes. Besides, it is like 15mm long. That is the reason why it restricts the fuel supply to the jets.

Note1 : Don't do mod number 4 if you dont do numbers 2 & 3 first or your gas bowl can dry out at speed.

Note2 : Once you do number 4 you will need to down jet 5 to 10 sizes dependig on were you started. Y went from 135 to 125 after I made this last mod.

Use the P/PX 200 air filter. This filter chokes the carb a little at high speed and creates the needed fuel progression that this carb would not have otherwise. remember this carb do not have a needle and progression over half-throttle would not work well without the PX filter.

The T5 SI 24/24G carb and filter has the bigger T5 filter wich does not create this condition and is VERY VERY VERY hard to set up for this reason.

Avoid the use of SI carbs without its filter You need it for prigression. You also need it becaise it catches the gas that the engine splits up out of the carb under sudden acceleration, and then enriches the mixture for a more powerful pick up.

Look at the COSA. They have a much better foam air filter inside the frame but they still use the PX filter. Now you know why.


taken from http://www.sip-scootershop.com/communit ... 09810.aspx

when you have done this gadge let us know thi outcome i keep mi eye out

UPDATE....DON'T drill supply hole without the the rest, carb worked as normal initially but after a week for some reason deteriated, started flooding(borking stuttering) on the throttle and starting scoot became a nightmare....onwards and backwards

Do you think you may have damaged the valve seat when you did this mod? Perhaps a new valve needle may help as the old one may have become moulded to the old narrower seat?

i know what ye saying diablo, but i did,nt drill the needle supply hole, i drilled the float bowl supply hole to the main jet and idle jet done it like a surgeon, i also had the 3mm float bowl packer on of which won,t seal when float bowl cap is placed on top of it and screwed down it needs a good sealant and not maybe the one i used as there were bits in the bottom of the float bowl, not a good sign and possibly added to the issue, so onwards and backwards...I,m trying to get hold of a cosa float bowl cap, but as rare as hens teeth....

Ah ok.
Sealant wise I guess one of the potable loctites might be suitable or maybe a homemade gasket?
Quite interested in this myself as I have a dyno donkey 210 motor I've just put together with a std carb.

H,POOL GADGE wrote:3.On the cosa bowl cap drill this hole: http://picasaweb.google.com/Vespisti1/V ... 8492565714

to 2.3mms (use imperial -inches- size equivalent). Drill it from top to bottom so you don't damage the needle's seat

How come 2.3mm Gadge SIP recommend 2mm :bouncing:

2.3mm,s the float needle supply hole....

UPDATE...... drilled float bowl supply hole 1.96mm(measured drill by vernia), gotta cosa float bowl cap from sip, of which does take the 5.2mm needle and the needle supply hole in comparison to px cap is way bigger, the standard px 24/24 cap won,t take the oversize needle, but i reckon you could reme it out and therefore drill the needle supply hole 2.3mm to accept the 5.2mm needle it,s a big needle when compared to a px needle like, i also took the gauze out of the float bowl cap filter, any way road tested it and i had to come down from a 128 to a 124-125main and idle jets gone richer but leaving that as starting scoot is a pleasure more 1st time kickovers like it! thrashed me scoots head in for about 10mile and no sticky piston(as sip call it)so all good would recommend it....

Just about to do this mod, anymore pointers.