motovert outlaw 140cc caught fire!

[mso_elite_rider]

hi i got to have a half decent ride on with my new motovert outlaw 140cc motor and after a while the gears were stuffing up felt like they were jumping and couldnt select nutural very easy, and then i tried kicking it over for last time and i seen smoke coming from the motor and my air filter was on fire cannot see any damage from outside near carby. a friends dad said it may be the valve and it might be spitting fuel back into the carby. im not happy after spending $1000 for motor. any one have any ideas? im gona visit bike shop where i got it from see if they know anything. thanks

 

[mad man]

if it's new it would probably be under warrenty get them to deal with it

 

[mjc85]

Lol, flames should be coming out the zorst not the carb, mine throws blue backfires upto 30cm long

 

[jayde156]

its not suposed to shoot flames out the exhaust either.........

 

[mso_elite_rider]

lol thanks for replys yer ill try take it back to shop let them sort it out.hope its nothing big.

 

[mjc85]

The flames are just unburnt fuel igniting in the exhaust as the engine fires on the exhaust stroke as well as the compression stroke. Totally normal. The reason there is unburnt fuel in the exhaust is because of the poor port matching of the carby, head and manifold which lets fuel puddle up on the ledges which ends up not burning too well as it is not atomized properly. This is not really a problem but can be reduced by port matching the mentioned parts.

Most bikes backfire but you will struggle to see it in daylight, I can see mine they are blue and upto a foot long. If you rev right up and back off it does it pretty often.

 

[themountain]

Sorry but mine never does that.....backfiring is a sign of poor Valvelash...you should check that first...alittle bit more then to less!! otherwise you nick your Vave some day and thats not pretty!!

 

[jayde156]

and timing is critical

 

[Pittin]

I know 2 guys with those 150 pits and they bothe backfire to the shithous lol, I imagine its not good. Mine is yet to backfire good ole ducars

 

[mso_elite_rider]

ok how has my thread gone from it catching on fire to an exhaust backfiring. please has anyone got any ideas?

 

[Franky]

way out of tune.

 

[mso_elite_rider]

way out of tune.

care to explain?

 

[mjc85]

This is from Mikuni Site

Backfires in Exhaust

Note:

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.

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.
5) Completely stock Harleys do not do this until open-end mufflers, such as the popular Screamin' Eagle slip-ons, are installed. The exhaust must be both free-flowing and have an open exit for the popping to occur.


Other possible causes:

Air Leaks:

Any source of fresh air into the exhaust system can create or worsen the conditions that bring about exhaust backfiring. 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 backfiring.

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.

 

[themountain]

This is from Mikuni Site

Backfires in Exhaust

.

...are you dull..??? he said its not backfiring from the exaust!!! Check your Valvelash on TDC...maybe your intake valve hangs open whenthe engine ignites!!

 

[mso_elite_rider]

...are you dull..??? he said its not backfiring from the exaust!!! Check your Valvelash on TDC...maybe your intake valve hangs open whenthe engine ignites!!

again can you please explain this i have never touched one of these motors before. i went to motorbike shop today and they said its running to rich so its spitting fuel back into carby. i kicked it over to day and with in 5 sec fuel was comming out of the over flow tube my mate also said it was way too rich. can anyone help me with where the mixture screw is and which way to turn it. thanks

P.s got my new FMF Powercore 4 zorst system, cannot wait till motor is running right.

 

[pitmaster]

sounds like your float level is either

a) too high or
b) needle valve is stuck and the bowl is filling up to much (could be dirt not letting valve seat properly)

which would explain why you had so much fuel it caught filter on fire?????

 

[mso_elite_rider]

ok thanks i might pull apart carby tomrrow and give it a wash and clean, need new airfilter too. hopefully fix this problem and then need to figure out how come my gears are goign weird like not going into nutural eazy and jumps alot.

 

[epod]

Take it back

The gear box sounds like it is stuffed, but did you change the oil. As for tunning your carby all the info is on the net, it takes practice and trial and error before you really know what you are doing. Fix your float level and move the needle jet to best postion for quick throttle resoponse. Probably clip in the middle slot or second from top in your case you standard mikuni jets should be fine. Why it fired back through the carby i am not really sure have never seen this in 25years of biking. If you gear box is stuffed you better take it back to mojo and tell em to replace the motor, They should have given you at least 30days warranty. I can build motors with same spec or better than the mojo from $750 delivered. I can build any lifan with an all up shift grear box into a rocket ship. ( they are the most reliable,m I also don't mind GPX motors to modify.) The gear box problem will only get worse till it is unridable if you don't fix it now. Good luck.

 

[mso_elite_rider]

thanks for the info i have changed the oil about 3 times now but i will prob take it to bike shop where i bought the motor. hopefully i can fix carby problem.

 

[themountain]

P.s got my new FMF Powercore 4 zorst system, cannot wait till motor is running right.

...you should have skipped on the exhaust and bought a decend carby ....sorry , but Take it out and check the floatbowl...maybe something is clogged or broken...