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03 660 idles fine, backfires n stalls w throlle

Yamaha YFM660R Raptor (2001-2005) - Yamaha ATV Forum - www.bluetraxx.com
Tried asking on raptorforum and barely anyone is active on there...

OK Background..

2003 Yamaha Raptor 660R

Bought this thing and it was running OK.. (was leaking oil like crazy out the case put gasket and sealant on to fix that problem...check!)

Problem B4...when at constant throttle in 2nd or 3rd gear it would all of a sudden act like it was running out of gas and throttle would start cutting out then it would slow down and stall out.. only way to get around this was when I just feathered the throttle at higher speeds (IE.. BRAAAAAAAAAPPPPPPPPP = no throttle response and stalling.... Brap, Brap, Braap, Brapp = ran fine with minimal power loss at high speeds) I figured the carbs were all clogged up because that's what it felt like. Also it would leak gas out the carbs.. and the air filter was soaked in gas Def thought they were clogged..

Went riding in mud and it overheated and kept stalling...stalled going thro 6-8" deep mud puddles...got out of woods then wouldnt start.. sooo

Cleaned carbs, put new gaskets (surprisingly they were pretty clean) But the Black Plastic Slides were like sort of melted at the bottom edge (needle end) which stopped them from coming out completely and would stick.. I put everything back together and tried running the quad.. now idles fine, but backfires like crazy with any throttle... took them back apart and decided to sand off and wet sand the melted edges so they were back to smooth and slid out smoothly, put a lil wd-40 on the plastic as well... fingers crossed.. put back together and the quad again idles fine, but backfires like crazy when any throttle..Ran a tiny bit better than last attempt tho..

-Has brand new oil, filter, swapped the spark plug (it was black... but its weird because it feels like its starving from no gas

-Only noticeable mod I see is a Brothers White R4 (looks like) slip on exhaust. (Not sure if this needs to be jetted? All Jets are currently stock) 140/145

-Last time it was running ok, we went through a ton of mud and shallow water (nothing was submerged) and I made it home but it started stalling out every 2 seconds in the yard, then just wouldn't start at all and we had to tow it to the garage.. the Overheating light was on, the coolant reservoir was empty, but when I added coolant it just filled the reservoir (like there was some in the lines) Couldn't feel coolant in the radiator when I stuck my finger in the top hole.. added some directly there as well.. filled half.. Maybe a clog in the lines? is there a pump that pumps coolant through that could possibly be bad? Have not seen coolant leaking anywhere.

I'm thinking it overheated, backfired, which caused the melted slides.. Maybe it needs to be re-synced?? But now I don't know what to do...and its starting mud season...

Was doing a little research and some people are saying if it idles fine but throttle makes it backfire and bog out it could be electrical? They mentioned either the parking brake wires or the reverse switch sensor causing the rev limiter to freak out? Previous owner cut the wires and removed the parking brake lever completely..but the part on the rear caliper is still there. I need to find and check the ground on the reverse sensor.. ill try grounding that thus week.. but I feel there is a bigger problem... or maybe just needs to be synced...


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