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Discussion Starter #1 (Edited)
Hi I need some help! I just rebuilt a basket case predator bottom end and top end. It has web cams 600cc Hot seat big bore kit and a k&n Filter. that is all mechanically that I know that has been modded. my problem is I can start it and it idles fine but I cant rev it up???? if i hit the gas or even try to feather the rpm's up it will bog and die....If I can get the rpm's just right and then hit the gas hard it will bog and then rev out and backfire and just sound like plain crap and it runs really hot.. I cant figure this out the needle clip was in the 4th spot I tried to move it to the 5th and then to the 2nd and none of that helped. The carb is def clean I cleaned it twice just to make sure there is supposed to be a pilot screw which shouldnt have anything to do with after 1\4 throttle but where that is supposed to be there is something there but not that I can screw in or out??? not too sure what is going on there. please help I really would like to get this thing running right. It was my first rebuild. Also just want to mention that this thing is in time unless the Webcams are supposed to be timed differently than stock. Any help is greatly appreciated Thanks in advance!
PS: also has a Hot Seat Performance Slip on
 

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Discussion Starter #2
I was just reading another post about timing and is it possible that I am off 180 Degrees? And still be idling and runnning? I think I am going to try to go 180 Degrees and see what happens I will update as soon as i do it
 

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Discussion Starter #4
Its a 11:1 Pump gas so the fuel shouldn't be an issue I may have set the timing 180 out I have done that before to an 05 Predator that I used to have also as far as the jetting as many times as i have taken the carb apart i didnt record the jet sizes but this was at one time running the same set up so im not sure why it wouldnt run its just confusing because it emits all the symptoms of a fuel issue but im almost certain there isn't but im going to try to change the timing 180 toninght and I will def post results thanks for the reply!
 

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Discussion Starter #5
well switching the ignition timing 180 didnt work actually it was running almost identical. Im not really sure where to go from here hopefully some one could point me in the right direction
 

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Discussion Starter #6
When i hit the gas it from idle it just cough out of the carb and dies sounds like a timing issue right? Is it possible that maybe i have aftermarket intake vales that are longer or something? I replaced the exhaust valves with stock one from polaris so I know those are fine
 

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Discussion Starter #7
well i pulled the clutch basket off and lined up all the marks on the timing chain just to eliminate that question! still the same thing...... I did notice that I can rev it up a little higher in rpms if i use the choke... Anyone have any ideas??? Any input at all oh and i took the carb apart again and the main is a 180 starter is a 42.5 and the pilot is a 50
 

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Discussion Starter #8
also blows black smoke out of the back of the muffler at high rpm when i can get it to rev out anyone? lots of views and no one helping.. come on lol
 

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definately need to change ur jets. im not sure on the sizes but sounds like u need to lean it out. the black smoke indicates too much fuel. check ur spark plug.
 

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Discussion Starter #10
definately need to change ur jets. im not sure on the sizes but sounds like u need to lean it out. the black smoke indicates too much fuel. check ur spark plug.

Yeah, I thought so because as soon as the slide starts to go up the engine starts to stumble. I ordered a Carb Rebuild kit for it so that will bring everything back to stock. Right now it has a 180 main and that could be my prob right there. If I lifted the choke all the way and then hit that gas it would rev up with a lot of black smoke. I was just kinds stumpped on this one because this same atv used to run the same setup... I dont know if the other owners had the timing advanced or what but it wont run with the jets that are in there now. I also ordered a jet kit for it because of the mods I will post back prob by this weekend to let you know the results Im waiting for the parts and will work on it this weekend
 

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Like you mentioned the obvious things are the first to check.
Spark is fine but you didn't mention the spark plug condition. With those kind of miles you may be looking at the injector fuel assembly or the fuel regulator or the ECU.
 

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Discussion Starter #12
I received the rebuild kit today and installed it got the same deal so i took it back apart and i noticed the needle jet was in upside down :x I dont know if that would make a difference but i turned it around and turned the pilot air screw out to 3.5 turns and it is getting better... The spot that it used to stumble at has gotten alot smaller but i still have backfiring. Now it may just be the main is too small?? The stock main is only a 150 and with the big bore kit k&N filter and web cams I would prob need to rejet? I should have a stage 1 and 3 Jet kit here on Saturday.... tomorrow if Im lucky.
 

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It is normal for many high performance exhaust systems to moderately backfire or pop when the throttle is closed from mid-to-high rpm. In fact, one should expect a well-tuned high performance engine to "pop" and "crackle" when the throttle is closed at high rpm. The popping is a result of the air/fuel mixture becoming very lean when the throttle is closed and the engine is rotating well above idle speed. It is also necessary that the exhaust system have rather open mufflers for this to occur.

Why This (normally) Happens:

1) When the throttle valve is in the idle position, fuel does not flow out of the main system (needle, needle jet, main jet). Fuel is only delivered to the engine by the pilot (idle) system.

2) The combined effect of the closed throttle and elevated engine rpm is to create a fairly strong vacuum in the intake manifold. This vacuum, in turn, causes a high air flow rate through the small gap formed by the throttle valve and carburetor throat.

3) Under these conditions the pilot (idle) system cannot deliver enough fuel to create a normal, combustible air/fuel ratio. The mixture becomes too lean to burn reliably in the combustion chamber. It gets sent into the exhaust system unburned and collects there.

4) When the odd firing of the lean mixture does occur, it is sent, still burning, into the exhaust system where it sometimes ignites the raw mixture that has collected ---- the exhaust then pops or backfires

Other possible causes:

Air Leaks:

Any source of fresh air into the exhaust system can create or worsen the conditions that bring about exhaust popping. The most common entry point is the junction of the header pipes and mufflers. Even a small air leak can dramatically increase the intensity or likelihood of exhaust system popping. A high temperature silicone sealant, as can be found in many auto parts stores, may be used to seal the pipe/muffler junction.

Lean Carburetion:


While exhaust system popping may be considered normal, it is certainly made worse by an overly lean idle circuit. Be sure that your carburetor's pilot jet is the correct size and that the idle air mixture screw is correctly adjusted before looking for other causes of popping. The procedure for adjusting the pilot circuit is covered in the Tuning Manual.

Ignition: If exhaust system popping is very loud, irregular and accompanied by loss of power, then you should suspect that the ignition system is not performing as it should. If, for some reason, the ignition sometimes fires at the wrong time, then exhaust popping can become very energetic (loud). Look for failing high tension leads (plug wires), failing ignition coil(s) and especially switches or connectors as possible causes.
 

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Discussion Starter #14
ok I got it running good... your gonna laugh at me but the needle jet was upside down lol yea go figure i changed it back to the 180 main and the jet needle that must have come with the jet kit that was in the carb before I got it now i just need to change the pilot jet because it spits and dies if i hit it hard off idle.. Oh and I had the carb boot upside down which tilted the carb up.... wow how stupid was that. the only reason i figured that out was because when i went to put the top engine mount back on it wouldnt fit because it hit the top of the carb. Well thanks for all your help!!! Oh and I took it for a small ride this afternoon and it is impressive!! I had a 2005 Polaris Predator 500 but this one with the 600cc Big Bore kit is just way way stronger....
 
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