I have a 2001 660R Raptor. It was running fine and on startup one day it ran like it was a 2 cylinder hitting on one cylinder. It backfires if you try to throttle up. Idles okay, a little rough but you cannot give it any throttle without stumbling and backfire. Here is what I have done: new coil, new CDI box, rebuilt carbs 6 times now, adjusted floats, cleaned and re-seated pilot jets, put meter on pickup coil and it falls in specs, timing is ok at idle - in the marks. One thing I have noticed is that sometimes the carb will not take gas? No gas in line and when I disconnect fuel line gas flows freely. If I blow in gas line to carb and reconnect it flows fine for awhile. I have replaced float needles and seats and checked vacuum break diaphram on carb. Any ideas?

 

Might try replacing the fuel line to the carb. Never seen it on a quad but have seen on other engines where the fuel line gets weak and under pressure it will collapse cutting the fuel flow down. I had it happen on a work truck once and after it sat idleing for a few mins would run fine for a few mins then do it again. Just a thought anyway [img]i/expressions/face-icon-small-smile.gif[/img]

 

I did replace the fuel line with a brand new hose and filter.

 

e brake? reverse limiter?

 

Can you clarify for me? The biggest problem is the engine backfiring with no power?

 

Check the emergency brake rev limiter. The same thing just happened to mine, it would idle fine but you could not give it any throttle without it backfiring and popping. It turned out the parking brake cable wasn't tight. We tightened it up and it ran fine. You can also disconnect the wire coming from the parking break i think. I am not positive if that works though so don't just go ripping wires out..lol

 

the low power could be lack of compression or back pressure. Do a test to check it and make sure your pipe isnt cracked or leaking alot.

 

Thanks, I will give the cable a look.

 

Pipe looks to be okay and tight at motor - compression seems to be okay. Is there anything else I should look at regarding the pipe or any other vac lines etc.?