need a bet of help

[Blue shadow]

Last year when I put her away running 18 psi of boost she ran fine .I had to remove the head so I put a new gasket on .Intake valve is set at .007 tho and exhaust is .009 tho .I put new coils on and spark plugs .Clean the carbs and reset the float bowls at 13 mm like she aways was.At Idle the fuel pump gauge reads 4 psi .I did not make no changes from last year.She idles at 13 A/F and if I take my time reaving her up she reads good to 9000 rpm at 12 A/F .Now if I hit her at full movement she would back fire at 4000 rpm and just die .The a/f goes about 16 to 18 when this happends .This is all done with the clutch off .Timing is set with a degree wheel at 110 on both intake and exhaust just like last year .thanks

 

[uphigh]

The backfire says not enough fuel. Revving up slowly and it runs ok sounds like the fuel supply is slow. Checked the fuel lines etc for blockage? Are you sure the carbs are set where you were last year? New fuel? Just some ideas. :exc:

 

[rxrider]

You run with no load on the motor, things will change with some load. Install the belt and run the track on a stand and see if it changes anything.

 

[Blue shadow]

Been working on the sled the last few days and hear is what I change .Put her back to the stock timing ,change coils,cdi ,regulater,carbs ,check all wireing,tps,leak down between 5 %to 7%,155 to 160 psi on all 4 clys,new plugs,she starts and idles fine but its a wall at 5000 rpm and backfires and dies . When this happends I shots it down and then drain the carbs to see how much fuel is in there and they are all full with the same amount in each bowl.The A/F hits in the 30 when this happends .thanks .I did try what you said RX rider but still the same.

 

[rxrider]

Your fuel pressure regulator working?
Have you tested fuel pressure under boost to see if it stays at 1:1 as pressure is rising?

I remember something funny, a few years back I forgot to remove a cotton rag I had put into the IC inlet to prevent dirt to get in there under storage (I had the sled in pieces all summer). Mine hit the wall at 4500 to 5000, I could ride it but it would not go past that rpms, nor would it produce any boost. When I tried to open the throttle she would fall on her face and die. Just a thought

 

[rxrider]

Any chance it's flooding? With the AFRs going sky high I'm thinking of too much unburnt fuel charge passing the O2 sensor fooling it to believe you're way lean. ???

 

[kinger]

I was going to see if you check the plugs are they soaked? Did you change the presure signal from the carbs? Or maybe a kinked line to the bowls?

 

[Blue shadow]

No kink lines,The plugs are black when I remove them after this happends.I am not running any boost just in the garage with the clutch off.No snow yet.Presure signal is in the same place. I will remove the turbo to make sure.The fuel presure is at 4.5 psi at idle

 

[HURRICANE]

 

[mulot30th]

One thing for sure.. this is a lean condition un acceleration.

I can duplicate this easily on a efi sled by leaning the 'accel pump' feature on the efi system.

 

[kinger]

Any work done on the exhaust? Sounds like donuts on a NA one although I realize you dont have that but you sure yuor header is back on correctly, etc?

Otherwise it points to the same issue skidoo'in it was having with his yamadoo. He had too much fuel pressure to the bowls flooding it out.

Problem is it worked fine before anything other mods this year over last?

 

[Blue shadow]

Nothing change from last year when I put her away .I just don t get it .I check every thing to do with fuel .

 

[nytrochris]

I had a problem after storage a few years ago and a mouse had built a nest in the belly pan and ate a few wires Just a thought!

 

[Blue shadow]

went over every wire and all is ok ,thanks

 

[kinger]

What haven't you checked?