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Discussion Starter #1
So I just picked up a used 05' 660 Raptor. When I bought it and listened to it run the guy told me that it has some "sputtering and backfire" issues wen it is cold but clears up once it warms up, and indeed my first time out on it seemed to run ok once it was warmed up, though I was never really impressed with the response in the middle of the throttle range. Once it hit the higher end of the RPM though it really took off. My second time out on it however the sputtering and backfires never cleared up. It idles fine and never dies, it will loaf around in the low range of its RPM's just fine, but once you hammer on the throttle it just lays over and sputters and spits a lot till you can get it through the mid range and then it really screams in the top range of the RPM. I assumed from the beginning that it was a carb issue and that I probably just needed to pull them and clean them thoroughly, but now after reading I have seen issues regarding electrical and limiter stuff. As a side note I turned it off once this last time out and it would not respond at all so I pulled the battery box cover to dicover the ground wire busted completely loose from the Crimp on clip to attach it to the terminal. I reattached it as a band aid fix to get me through the day which is why I ask about the electrical.

Is there a more definitive way to determine if my issues are carb related or electrical? and does someone else have experience with this?

Thanks,
 

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Master of the Electron
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It's carbs. Try raising the needles one notch.

BTW, Welcome to the forum!
 
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Discussion Starter #3
Thank you for the response. I tried as you said “raising the needles”(lowering the clip from slot 3 to slot4) without much difference (maybe slightly worse now??) seems to spit and backfire slightly more now.

I ended up pulling the carbs completely out and tearing them down to clean them and see if I could identify a clear problem. Here is what I know:
1. Someone has done work on the carbs previously as the bowl screws were badly stripped. I replaced them with steel hex head.
2. The throttle cover is missing the seal. I read somewhere that it can pull air in from there and make problems. I ordered a new cover and seal.
3. I have no idea what jets are in it as I could not find writing on them, and I could not remove the main jet from the holder as they were extremely stuck, and the head on the right side was chewed up badly from someone else trying to remove it. I torqued on the left one with a flat head screwdriver while using an 8mm wrench on the holder after I soaked it with cleaner and WD40 to no avail.
4. The right side pilot seemed plugged. I removed everything (main jet and holder still together) and washed it all thoroughly with carb cleaner and blew everything out with air.
The fuel mixture screws were at 3-1/4 turns out on both sides and I put them back in at 2-1/2

I put it all together again and it seems to run exactly as before. I hoped the seemingly plugged pilot jet was the issue. It still idles fantastic, has good power in the very low ranges of the throttle but starts popping and spitting as soon as you go over 1/4 throttle the entire midrange has no power and continuously cuts out until the top end of the power band then it takes off like a raped ape.

I decided to just buy the parts to rebuild it so I bought a stage 2 dynojet kit and a titan rebuild kit off amazon.

It had a stock air box and filter on it when I got it with the lid on, but there are indications to me that it was ran without a lid and the filter is missing it’s seal to the box. I bought a K&N factory replacement filter and a pro tec Moflow lid for it (but do not have them yet)

The pipe looks pretty new, but OEM?? Not sure as I don’t see a name on it.

Any other advice?
 

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Discussion Starter #4
Oh and I am about 1,200 feet above sea level when I trail ride but at sea level in the sand.
 

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Master of the Electron
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Keep in mind when tuning:

pilot jets control 0 - 1/4 throttle
needles 1/4 to 3/4
mains 3/4 to wide open.

start with mains and work down.

if airbox is open you'll need 146 L / 148 R dynojet mains (160 L / 165 R Mikuni), dj needles around center, 25 pilots and fuel screws around 2.5 turns out. (All numbers approximate)
 
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Keep in mind when tuning:

pilot jets control 0 - 1/4 throttle
needles 1/4 to 3/4
mains 3/4 to wide open.

start with mains and work down.

if airbox is open you'll need 146 L / 148 R dynojet mains (160 L / 165 R Mikuni), dj needles around center, 25 pilots and fuel screws around 2.5 turns out. (All numbers approximate)
Bro I really enjoy reading these forums and finding your responses. Sir you are very knowledgeable on the raptor.
 

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Master of the Electron
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Thanks. Hope we've helped you.
 
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