You could just dump it all in your ultrasonic cleaner , get one they are excellent
dellorto carb manual
Download the manual, read it. Stripping and cleaning carb is one of the easiest jobs to do on a 2stroke bike.
Meccano is harder to get to grips with than stripping and cleaning a carb. Don't let it scare you - it really is easy to do... otherwise, I'd suggest selling the bike and getting a 4T, as any regular maintenance that is a necessity for a 2 stroke bike is gonna scare you, and you're gonna end up forking out hundreds in labour hours to the local bike shop for tasks that really you should learn to do yourself.
Grey residue is likely result of water mixed with 2T oil saturating / flooding your spark plug as you have water in the float chamber that is submerging the main jet (mainjet is in base of float bowl, and petrol floats on water), so when you open throttle, bike gets a lung full of water rather than fuel.
Flip up tank. Turn fuel off. Look down at carb. Either side of it you'll see 2x jubilee clips clamped over rubbers. Undo those. Grab carb... move it backwards and forwards and work it out from between the rubbers. Keeping it the right way up, undo big brass bolt in bottom. Bottom will then come off. This bottom part is the float bowl. Ideally, open the bolt over a glass bowl so that you catch the spilt fuel and can inspect it for signs of water or contamination.
If no signs of globules of liquid suspended in fuel, inspect the bottom of the carb that you removed for signs of contamination - dust, rust, dirt etc. Rinse it out.
The jets are small brass things with a hole in the middle and a flat-blade screwdriver cut - you'll see em. Take them out one at a time, blow thru them, rinse in boiling water. Put em back in again. Tighten em til they nip gently.
Put float bowl back on. Do up the big bolt to secure it in place. (Note, this big bolt has the main jet fitted in the opposite end of it).
Fit carb back in between the rubbers. Put the jubilee clips back on. Turn on fuel tap.
See if it starts. See if problem still exists.
CARB SETUP
Set it to rev at 2000 with the idle screw, then twiddle the air screw just to the left of the idle screw... turn it all the way in, then back out 1.5 to 2.5 turns, listening to engine. As you turn it, revs should increase slightly. Set it to a point that revs are at highest and smoothest. Now use the idle screw to tune it back down to around 1100rpm - 1500rpm .
in = increase
out = decrease revs
see more Aprilia RS 125 posts here
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Servicing The Fuel System
Here we’ll look at servicing the fuel system, checking the tank, fuel tap, fuel hoses and fuel filter are all working correctly as well as checking for any signs of leakage, deterioration or damage. We are particularly looking to make sure that there are no leakages coming from the fuel hose or fuel union.
Inspecting The Fuel Hose
Firstly you’ll have to remove the tank, carefully removing the fuel hose that is connected to the fuel tap. Here you will have access to check the fuel hose for any damage or deterioration, if there are any signs then you should replace it immediately.
Inspecting Engine Oil Hoses
You’ll want to check the engine oil hoses from the oil tank to the pump, then from the pump to the carburettor. If there are any leakages present then ensure that all the hose clips are tight and replace any hoses that are cracked or have signs of deterioration.
Inspecting The Fuel Tap
With the tank removed inspect the tap and underside of the tank for any signs of fuel leakage. If the tap body is leaking then a new tap will need to be fitted as no individual components are available.
If the tap to tank joint is leaking then follow the proceeding instructions.
If your Aprilia RS 125 is the model between 1993 to 1998, the tap is retained by a union nut; hold the tank union with a spanner to prevent it twisting, then tighten the union nut carefully. On 1999 to 2005 models, the tap is retained by two bolts; tighten the bolts carefully. If leakage persists then remove the the tap and fit a new joint O-ring.
Fuel Filter
The fuel filter is mounted in the tank and is an integral part of the fuel tap system. Clean the filter at appropriate intervals or if you suspect fuel starvation.
With the tank removed you’ll need to drain the fuel into a suitable container.
On 1993 to 1998 models, hold the tank union with a spanner and loosen the union nut. Unscrew the tap and union nut from the tank and withdraw the the tap and filter assembly. It is recommended to fit a new O-ring upon reassembly.
On 1999 to 2005 models, undo the two bolts securing the tap to the tank and withdraw the tap and filter assembly carefully.
Allow the filter to dry, then clean with a soft brush or low pressure compressed air to remove all impurities in the system. Check the gauze for holes, if any are found then a new tap will need to fitted.
