Back fire!!

[REBEL GT TURBO]

Right im gettin some hold back/judder in low revs if i slam my foot down and keep it down i get a LOUD bang from the zorst! Sounds cool but im guessing im over fuelling it?? my mpg is pretty s**t too! Plus the AFR goes over to 16/17 red for a split second it then clears and hammers it:cool::burnrubber:

If this is the problem whats the way to solve it??

Cheers.:)

[Os8472]

Timing out abit maybe, breaking down aei, crank sensor

[Trevhib]

Boost spike kicking in the over boost switch?

[SCHWARTZ]

what cam and turbo? how much boost? what jets in the carb? do you have the over boost circuit still in operation?

[REBEL GT TURBO]

standard cam, t2 turbo running 1bar of boost not sure what the over boost thing is??

[Trevhib]

Have a search. It's a pressure sensing switch that's fitted to the turbo-to-intercooler boost pipe. When it senses a specific boost level above that of the standard pressure (around 16psi as OE IIRC), then it cuts the ignition temporarily which produces a huge back fire as unburnt fuel ignites in the exhaust AFAIK.

[REBEL GT TURBO]

No its no the over boost trev! could it be the air corrector thats not right?? i think all the jets are standard or at least i was told they were when i bought it!

[tiff_lee]

AFR goes to 16/17 that's lean right?

[stuTHC]

AFR goes to 16/17 that's lean right?

No. That's VERY lean! Something is gunna pop lean!!

[tiff_lee]

Well that's what I thought so surely it can't be overfuelling and in which case what causes the backfire?

[J8TRO]

The night before ND i found the end of my mixture screw had snapped off, luckily it was still in the carb base and when i took it off i could knock it out with a pin. Anyhow, i put what was left of the mixture screw in the carb to at least get it running and took it very slowly to Mallory where i got it sorted.

With wide open throttle (WOT) which i only did once to check the fueling, it leaned out big time and back fired massivley! not good.

Take out your mixture screw to check its ok and still has the O Ring, also check your Idle jet for bits of crap and iff you can chuck some carb cleaner through it.

[REBEL GT TURBO]

On WOT mine is 13.5/14 so its not leaning out! its just sometimes when i boot it say from 2nd into 3rd it holds back for a second AFR shoots round to 16/17 then it goes ok and goes to 13/14

I'll try giving the carb a clean out!

[bigdur]

13/14 is lean on WOT!

[SCHWARTZ]

13.5-14 at WOT is lean and is where the damage will be done. afr's at WOT should be 12-12.2. Could be the acc pump jet not working/adjusted properly

[REBEL GT TURBO]

whats the acc pump? sorry if i sound stupid!;)

[REBEL GT TURBO]

u mean acceleator pump jet! damn whats wrong with me!:o

[J8TRO]

Take off the lobster and look down into the carb, as you operate the throttle, additional fuel is thrown into the carb which you will physically be able to see, do this without running the engine.

If its not chucking in fuel it would indicate being at fault.

[tiff_lee]

Well I guess the acc pump would explain the 16/17 when you floor it but being lean at WOT would need some carb fettling to sort.

As for the acc pump I had snags with mine it should be a nice squirt (ohh) of fuel rather then a dribble....