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Discussion Starter · #1 ·
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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it sounds like it is definitely lean, stock jets and a slip on would cause that and make it run hot. are you getting the carbs back in the boots correctly they are a real bear and can slip out easily when you are installing the air box. there is a water pump it is by the oil filter on the right crank case, it has the tubes from the radiator connected to it and they can go out. check to make sure your timing is still correct. it is possibly to jump time or have the chain so stretched it is no longer in time. ( see the manual in the sticky for the procedure) check your valve adjustment. i have not had the slides out of mine but digger talks about some clips that can be tricky, did you get those in correctly. as far as the parking brake find the wires on the parking brake lever that come from the handle bars and go under the hood ad unplug them that will bypass the revlimiter. if it was the reveres rev limiter you should see the light flicker. it could be electrical but i think it would have dried out after a few days but if your are going to abuse your machine in that kind of mud you need to add some dielectric grease to each connection to keep the mud and water out.
 

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Discussion Starter · #3 ·
Yeah the carbs are snug on the boots. I will need to check the radiator hoses this week and the water pump. I am ordering bigger jets to get those correct..
My parking brake is unplugged and lever is gone. going to try grounding the rev limit this week.. then adjusting the floats... then finally check valves.. this sucks.. just gotta do step by step to slowly eliminate everything..
 

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Pull the carbs and check the float height. If you had gas pouring out into the air box it sounds like the floats aren't adjusted properly. If the floats aren't adjusted correctly you will either get too much fuel or not enough depending on how they are set. With a slip on exhaust it should still run and ride with stock jets but it will over heat very quickly and do some serious damage if not addressed.

Valves are something I would have checked at the start, a couple thou over spec on the intake will make it run lean.
 

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My raptor did that too. Had a DG slip on. Header would get red sometimes and backfired a lot especially on deceleration. I got some bigger jets and also repacked the exhaust and not it's great. Also sputtered a little before and now it doesn't. I would suggest bigger jets and check for a hollow exhaust


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Discussion Starter · #6 ·
Update: Grounded the Rev sensor wire and most of the backfiring stopped.. it backfires with anything over 1/2 throttle and only a few pops, not too bad. I then upped the Jets to 150/155 and pilots to 25. It ran wayyy better! still some slight backfiring when u rev it hard. Drove it around but it bogged out like it was running out of gas if you gave it 1/2 - 3/4 throttle... took it back apart AGAIN haha i moved the needle clips to the 3rd position (they were at the 5th or top clip mark, plus i discovered they had some random tiny spring in one side(looked like a spring from in a pen).. and the stock shorter spring in the other side, I put my new brass needles and springs in) and that made it way more torquier and it improved a lot. Just need to take it out on a straight away to see if it still bogs out at full throttle.. I was just testing it in the yard. Running way better, not 100% perfect but at least i can ride again! I have not touched the mixing screws.. not sure if i should... one looks like its turned 1/4 more than the other.
 

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I also Have a problem, While riding my raptor 660 cuts out, My vapor display goes dark and 2 seconds after it goes on again,almost like a kill switch, can It maybe be a faulty connection somewhere?
 
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