help,rx1 w alpine turbo, started backfiring - sputtering

[sledheadgeorge]

Try disconecting the speedo sensor next to the drive bearing. If its defective or dirty it could act like that as well. Follow the line to the top of the fuel tank and disconect it there and try it.

 

[925rotax]

thanks ,i have a secound trx i will be taking out on friday for parts trial if needed, how would i bypass the unit, ill find on the resistance for test, apreciate all suggestions guys, really hoping to have running right by weekend!

 

[sledheadgeorge]

let us know how you make out

 

[925rotax]

i will

 

[925rotax]

just thought i would post what ive found. checked fuel punp pressure and fuel reg at idle =within spec . removeed coils and checked low and high side= within spec. checked tors to bypass=system was already bypassed by pevios builder, never checked fuel pump pressure above idle, installed a new pump and fuel p gauge, disconnected speedo senser . heading to the mountain tommorrow.

 

[925rotax]

got back from the hill and no change

heading up the trail and 20 mins in the problem cut in, sputtering backfiring drop of a cylinder, air fuel reads way lean,pulled choke full on and no difference, cracked the throttle w o t and pulls hard and release throttle and problem is back,0 - half throttle is where the issue is, wide open is okay once you build the rpms which is hard to do.only happens under load and once the motor reaches a certain temp, let it sit and cool down, start it and it runs great for 10- 20 mins and prob back again? disconnected the speedo and no difference,this is definatly a electrical issue at a certain temp.could this be the tps , but no codes?i think maybe the cdi? thanks

 

[rxrider]

If you one of the spark plugs quit fireing AFRs will read way lean because of the the high O2 content from the unburnt charge.

Where have you hooked up the pressure/vacuum signal line to the fuel pressure regulator?

 

[925rotax]

ill have to check rxrider, but nothing was changed at the regulater except a new msd fuel pump.apreciate any suggestions?

 

[925rotax]

hopefully i can explain this properly. the fuel reg i have is red and aluminum in colour w no visuable name.reg has 4 seperate brass nipple connections into it. 1- small connection w tube straight into the boost gauge. 2-from rider position, right fitting from tank into the regulater. 3-fuel pump to regulater. 4-fuel reg int 3 way tee to carbs and nx express noss system.

 

[925rotax]

started it up in the garage tonight and runs fine w no load, problem always cuts in at a certain engine temp under load? thanks RXRIDER for the info on tps specs, i will check readings w ohm meter tonight.

 

[sledheadgeorge]

Almost sounds like your intercooler is blowing off under load. Have you checked your clamps in the boot area?

 

[925rotax]

checked it for sure, even for cracks the problem cuts in at a certain eng temp under load, could even be at 1/4 throttle,not even building boost, i have even pressurized the intake turbo system up to 20 pds and no leaks?

 

[925rotax]

just got back from a ride with a swapped cdi, checked my tps and within the specs as well.unloaded sled, ran it 1/4 to 1/2 throttle for about 15 mins and the problem cut in,running on 3 cylinders, backfiring sputtering,air fuel running real lean. turned choke full on while about 1/4 throttle and seems t take some of the backfiring away and brings air fuel down to 13 from 17,will not kill the motor w choke full on,turn choke off and sled backfires and wants to stall? i have replaced the coils,checked in nose of sled for any damaged wiring, bypassed the tors, disconnected the speedo,checked the tps and is to spec,swapped out cdi unit,no cracked header, turbo flang to header flange tight, replaced fuel pump w new,leak tested turbo system to 20 psi,pressurized coolant system,swore about 20 times only does this under load and to a certain temp when cuts in. i did notice when this cuts in and i wot the sled builds up and pulls hard almost clears itself at wot, but when released goes back to running bad?

 

[rxrider]

Have you checked the coolant temp sensor?

Do you have good compression on all cylinders?

It may be possible to be on the edge on compression on a cold engine, when motor gets hot there is not enough compression to get the charge fired..... should blow oil out the crank vern... I'm sure it doesn't do that..... hmmmmm not likely your problem just thinking out loud.

Have you checked the rectifier/voltage regulator?

Have you checked you charging voltage?

Have you checked battery voltage?

What I can think of for now, hope you can find the culprit while you still have snow.

 

[925rotax]

looks like the problem was found, if not definatley would of caused one, heading out today and will let you all know, fingers crossed