2003 Viper 700 won't run properly/backfire/won't idle

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0203viper

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Dec 3, 2015
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kalamazoo mi
2003 viper 700. Good compression, spark on all 3 cylinders. Carbs were cleaned multiple times tried adjusting air settings - didn't help.
Swapped reeds, carbs , coils no luck whatsoever. Swapped fuel pump with a working one no difference. Cleaned out gas tank put fresh gas and blew out vent lines no luck. Replaced engine vacuum line and it didn't help much. Thinking I may have a stator issue? What else am I missing?

I can spray some gas into carbs and sled will start up and run but it will backfire and die shortly thereafter. If I can get to run for more than 5 seconds it backfires and doesn't sound good.

Thanks for any help in advance.
 

Check your exhaust for plugging. The pilot screws on a Viper (TM33 carbs) are fuel screws - open for rich, close for lean.

I would test your stator, but it shouldn't change by simply spraying gas.

Did you clean all circuits in the carbs including pilot jets, air jets and passages?

Flywheel and coils may be rusty or have some issue.

You may want to check your crank phasing.
 
Sorry I meant fuel screws I adjusted them anywhere from 1.5 turns to 2.5 turns and didn't change much. Still had a backfire. I cleaned pilot jets main jets and passages all were free and clear. I pulled the exhaust apart previously and cleaned it all and re assembled no luck. May try to replace donuts as well to see if that helps. I will test stator and see results. I have a spare one sitting right now I may end up installing soon. Would just like to get it running so it's ready to ride for next season. BTW it is stock single pipe exhaust with stock can.


Also, loosened throttle cable to see if that would help no luck there. Disabled tors and that didn't help either.
 
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in the past with my vipers theyve done the same thing and were getting too much fuel through causing the backfire.. whether that helps you or not just throwing in my 2 cents
 
Another thing that comes to mind is a sheared magneto key. Rare, but it is possible.
 
Is your fuel pump working? Maybe check the vacuum line that goes from the fuel pump to the block and see if it is broke or cracked. Sounds like a fuel issue.
 
Sled is running good mid and high range but doesn't want to idle still unless I pull the choke...pulled the carbs again and pilot jets are clean and not plugged any other ideas to cure this issue?
 
Where did you end up setting your fuel screws...? You said you blew through the pickup line...there's a fuel filter on the end of it inside the tank how does it look?

Sent from my E6560C using Tapatalk
 
does carb cleaner come out the little idle orfice hole in front of carb? if not that's where its plugged up....not only does the pilot jet have to be clean and be able to see light thru it, the passage ways also have to be clear or no fuel will flow.

if it runs better with choke lever then its pilot circuit related, STOP riding it as you will damage it!!!, the pilot circuit flows 2-3% fuel flow even at wide open and everytime you come down off higher rpm your leaning out the engine.

check out the carb clean 101 to see pics of what I am reffering to
 
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