Cold start on aprilia 650 1999 model a problem. I know only the one carb is chocked.is there a way to choke the second carb as well? if I smuther air intake at box it starts very easy

check float level height on carb

WHEN YOU GIVE A CARB CHOKE, IT RESTRICTS AIR FLOW AND GIVING THE ENGINE MORE GAS INSTEAD OF A REQUIRED MIXTURE... USUALLY THIS IS FOR STARTING IN COLD TEMPS. UNTIL THE ENGINE WARMS UP AND YOU RETURN THE CHOKE BACK TO NORMAL. THAT IS ALL THE CHOKE DOES.... IT DOES NOT MAKE THE ENGINE RUN BETTER BECAUSE YOU THINK IT WILL.

if too rich adjust choke leaner
if too lean, adjust choke righer.

from 1920 to about 1988 , usa, 70 years we did this.
no more. well we do, but most dont now.
i still have 1 twin carb motor cycle and one single carb VW 1968.
both restored.
also the chock heater must work and the choke spring not old.
the old bi-metal spring that is old become lazy,/crazy. kick it to the curb for best experiences.
if water heated choke the water actually must flow here.
if not, it will fail.
there are 3 common types.
electric, needs 12v.
water, needs 180F hot water actual flow.
and exhaust choke stove heater. (a small horror this, dont ask)
there are others, but would need carb name and p/n

Sounds like the unit has sat, and carb gum, Try draining the carb bowl and re-filling. There is a screw at the base of the bowl. Also make sure when cold choke is closed. And it opens fully after 3 minutes. Check battery voltage on choke coil.

sounds like you left old gas in it to long the jets inside the carb are plugged you need to take it apart and clean it

weak mixture,dirty fuel,air leaks on induction manifolds,jets blocked,fuel tap filter chocked,float needles sticking,fuel level in carb incorrect,thottles not opening together,air leaks at exhaust pipe joints,

Check the choke opperation is working correctly ,and that nothing is fouling the chock sliders .Theses bikes don't like too much air in first starting .and rel;y on a near neat fuel supply .it could be a case that the choke is not sutting off air supply enough..If you richen the mixture you could cause to much fuel to enter the engine a wash away your oil lubrication .,causeing the engine to over heat ,and in some cases cause valve burn outs .

If your bike starts even for 5 seconds you should investigate your fuel delivery system.Check fuel pump,filter,try spray carb cleaners like Gum Out.Most importantly make sure your choke is working.You got your ignition (spark) it is most likely fuel related.Good Luck.

Yes its getting too much petrol , you will have to check the float pin, better to clean the carb.

Hi brownboots,

Have you tried using the choke to start it when its cold?

Secondly the air-fuel mixture may require to reset, but before you do tht after a spin , remove the plug and examine it ....it should be brownish and dry!
Also make sure the saprk plug is of the correct type per manufacturers specs.

Hope this would help.

Knight.