Carb Blowback ?

[brettLo]

Hey,

Just wanted to ask what causes carby blowback ? is it just excess fuel in the carb ? or something worse?

Im only asking as sometimes when i start my bike it puffs some whitísh coloured smoke out of the carb, so was just wondering what i can do to stop this or what causes it ?

 

[android90]

BUMP ... I would love to know this answer.

 

[twisties]

Yep, me too!

 

[android90]

Come on tech experts we know that you would love to educate us about this subject

 

[DHZ_XR8cing]

Your timing is out or your valve clearances need to be done and if I was a betting man I would say that
your valve clearances are out.

 

[eichkay]

most engine backfires result from an improper air to fuel mixture which causes unburned fuel to explode outside the combustion chamber.. rather common on china bikes as the carbi's are setup rather rich...

Its not harmful and it generally happens when kick starting on the wrong rotation of the stroke , ie kicking it over half way up the stroke

 

[android90]

Cheers guys ,in glad that I got a AKUNAR CAM and port job and valve clearance redone as mine had blown smoke out carby b4 .. my bike should be ready to pick up tomoro

 

[brettLo]

Hey guys

Thanks for all the replies. My bike does it on the very odd occasion, not often enough for me to really worry about it I guess. Just thought I'd ask the question.

Thanks for the responses, it's highly appreciated as always.

 

[rumble]

most engine backfires result from an improper air to fuel mixture which causes unburned fuel to explode outside the combustion chamber..

Inlet valve clearance issues.... Generally fuel cant ignite outside the cylinder unless the intake valve is open slightly or leaking

 

[brettLo]

Inlet valve clearance issues.... Generally fuel cant ignite outside the cylinder unless the intake valve is open slightly or leaking

Hey Rumble,

So to stop this from happening all together, id have to recheck or redo my valve clearances ?

 

[android90]

Hey Rumble,

So to stop this from happening all together, id have to recheck or redo my valve clearances ?

I'm NOT "Rumble'. but the answer is YES mate

 

[Cactus Jack]

^^^ It's always a good idea to check valve clearances to eliminate them as a cause of blow-back , back firing or carb misting ... Sometimes an intake valve or seat can be bad ~ ie bent , out of round etc ... It'll be interesting to see what you determine to be the fault ...

There's some info here and in heaps of other vintage MR threads ...

http://www.miniriders.com/tech-talk/22786-backfiring-through-carby-popping-noise-solution.html

 

[brettLo]

^^^ It's always a good idea to check valve clearances to eliminate them as a cause of blow-back , back firing or carb misting ... Sometimes an intake valve or seat can be bad ~ ie bent , out of round etc ... It'll be interesting to see what you determine to be the fault ...

There's some info here and in heaps of other vintage MR threads ...

http://www.miniriders.com/tech-talk/22786-backfiring-through-carby-popping-noise-solution.html

Hey Cactus Jack,

Does sound interesting, thanks for your post and the link ill be sure to check it out!\

At this stage its not a major concern as it only seems to do it on a rare occasion.

 

[brettLo]

I'm NOT "Rumble'. but the answer is YES mate

haha its all good android, I was quoting what Rumble had said to me ... My apologies if I caused any confusion