Welcome to the forum! 1st - you're posted in the 660 suspension forum... I'll see if we can get you moved to 660 general or 660 maintenance - you may not get the visitors you need here.
BTW, charge your battery if you can - it sounds as if it's getting low (cranking speed is a bit slow) to me.
If it runs on starting fluid then you are simply not getting fuel through the carbs.
Have you verified that fuel gets TO the carbs? Do you have flow through the petcock? Open the drain screw on each carb. If fuel streams out, then the carbs have fuel and your issue is inside the carbs - either they are not cleaned well enough, the jetting is way off, or some other issue is going on... how many turns out are your fuel (pilot) screws set to?
If it still is the carbs, check and report back numbers on the jets and tell us what modifications the quad has (exhaust and air box mods)... then it's up to you to figure out since we can't see the carbs. check that both have fuel in them, verify that the fuel screw tips are not broken off in the carb throats, check that all orings and springs and spacers are in the correct orientation on the fuel screws and choke plunger... It should at least try to start and run - does your choke plunger work properly? Are your vacuum diaphragms intact (no tears) and mounted properly? Have you download the (free) service manual yet?
'01 660 Raptor, Burgard +2+1 arms, YFZ Shocks, LSR anti-vibe, CTR pipe, jetted, K&N
'01 Polaris Scrambler 400, K&N
'02 Honda 400ex, Big Gun pipe, jetted, K&N, Lonestar +2 A-arms, Lonestar anti-vibe
'04 Suzuki LTZ400
'16 RZR XP4 1000 Turbo
Last edited by QuadManiac; 08-05-2019 at 01:15 PM.