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Backfiring
jimmy - November 13th, 2002 at 10:37 PM

Running a type 4 in beetle with dual 40mm IDF carbies and a large exhaust, and getting a fair bit of back firing, what do you reckon the cause is?

vw54 - November 14th, 2002 at 07:16 AM

go get someone who knows what there doing, to tune the car properly for you.

Bizarre - November 14th, 2002 at 07:27 AM

As Dave said.....

Could be rich carbs, exhaust, valves, timing......
Is it backfiring or popping?
On acceleration or deacceleration?
What rev range?

bugboymatt - November 14th, 2002 at 07:59 AM

Quote:
Originally posted by vw54
go get someone who knows what there doing, to tune the car properly for you.


Bit harsh one line statment first thing in the morning !!!!!!!!!!!

Maybe the bloke wants to sort it out himself with a little help and guide lines from other veedubbers on here !!!!!!!!!!

I know what you mean to get it done properly by someone with more experiance than he might have. Always advisable.

If everyone gave one line statments like that no one would ask anything. Be no point if all your after is a little helping hand / ideas and ya get told to take it to somebody else !!!!!!!!!!!!

as blue says more info need to try to determine teh problem.

vw54 - November 14th, 2002 at 08:58 AM

Harsh

" Bit harsh one line statment first thing in the morning "

thats not harsh... its a bit hard to diagnose a vehicle over the inter net By saying this we might coax them into expanding more ... i could of said how long is a piece of string ??

Dasdubber - November 14th, 2002 at 02:53 PM

Don't think it causes backfiring, but check the seal between the inlet manifolds and heads - this can sometimes cause some tuning problems. Again not 100% sure, but clogged jets/inappropriate size jets may be responsible. Stuck floats, or maybe excessive fuel pressure (although you would most likely have leaks)....just thinking out aloud (may be totally off track).

Apart from the carb stuff above, playing around with timing might help?

Alan

KruizinKombi - November 14th, 2002 at 06:08 PM

Actually, although Dave was kinda blunt, I agree with him. If a person doesn't know where to start looking for the problem, they probably shouldn't try. Take it to a good mechanic and hover while he fixes it. Ask lot of questions while he works so that you'll have a better idea of what to try next time the problem occurs. :)

helbus - November 14th, 2002 at 08:07 PM

One quick thing you could try is look at the timing. If you have a timing light, check where it is now, play with it a little either way, see if that helps and if only gets worse, then set it back to exactly where it was and seek mechanical advise.

Although I don't want you to try it in this case, I have seen an amazing thing happen when kero was poured down a carby!!!!!!

Peter

70AutoStik - November 16th, 2002 at 06:26 PM

Crikey, how many fitted down the poor guy's throat? People use this forum to learn more about their VWs; I don't think this was such an outrageous question.

An appropriate answer is:

"Backfiring is usually due to a lean mixture for whatever reason. Leaking manifolds, gaskets, throttle shafts and blockages in the carbs' fuel circuits are the first places to look. If the problem is "popping," however, you need to look first at the state of your valves."

- Gives the guy some ideas of where to start looking, helps him to increase the enjoyment of his car. I myself learned a lot about cars by being sold a bomb and not having any money to pay for repairs. Our family mechanic was always happy to answer all my questions and even loaned me tools, he's also the guy who got me interested in VWs - another VW sort of person.

:jesus

[Edited on 16-11-2002 by 70AutoStik]

Quickbug - November 16th, 2002 at 08:10 PM

Also check your exhaust/extractors for leaks...

This is why one of my bugs backfires when u take ur leadfoot - sorry i mean left foot - off the gas...