Backfire

So she's been running just fine for the last few months. I even got her up to 75 on the freeway today. However, lately when I let off the gas in second or third and put a drag on the engine i get some mild backfiring. Suggestion? I'm hesitant to play with the timing since otherwise she's running so well.

It could be the mixture on the carb being a little rich or a leak in the exhaust somewhere.

It's fuel injected. I'll dial back the mixture a little bit.

I do think I have an exhaust leak somewhere. I just didn't realize that would cause backfires.
Thanks

Are you running the stock dizzy? Check your dwell on it, that can cause a backfire as well as an exhaust leak.

Oh yeah, do not hesitate to check the timming, you can be a bit off and it run great but will do some damage if not dead on. A friends bus is back in the shop with a chunk missing from his exhaust valve on his 74, not sure what caused it but thinking his timming was off.

meinvw wrote: Are you running the stock dizzy?

What's a dizzy?

At this point I'm sure I have the exhaust leak. I'm gonna work on that and then see what I need to do to the timing. Thanks guys.

peregrine67 wrote:

meinvw wrote: Are you running the stock dizzy?

What's a dizzy?

slang term for Distributor

Sorry, I should have known that. I've been out of the loop for too long.

Considering the previous owner put in a motor out of a 412 I don't quite know what stock is anymore. Stock to the bus? stock the 412? is there a difference?

well if its a 412, you'll want what ever is stock to the 412. just because its in a bus, doesn't nessecarily mean you should put bus parts on that 412 (unless they are the same motor, i have no idea). I wouldn't put VW parts on a baja with a subi conversion

Finding the exhaust leak should be too hard. You'll prolly see black carbon wherever the leak is.

Like in this pic of a snowmobile engine, the area around the leak will be covered in carbon

A 412 engine is a type 4 like a bus. The exhaust components should interchange. I have a type 4 from a Porsche 912 with VW 411 heater boxes and a 72-74 bus muffler.

if you have any Type 4 questions call Jake Raby at Raby's Aircooled Technology or Dave McCutcheon over at DTM Engineering. both are VERY knowledgable and can set you up with any parts you may need.

Okay I've located the leak but I need some advice on how to fix it. The muffler flanges on the driver's side isn't quite square with the passenger side. So if I tighten the driver's side down first it opens up the passenger side on the bottom like 2mm. And if I tighten the passenger side first the driver's side is open on the top about 2mm.
So what do I do? I know I could solve the problem with just a thicker gasket on both sides. The old asbesos one I took off was about a 1/4 inch thick but it fell apart and I can't reuse it. None of the parts stores had anything that I could make one out of either.
I was considing just making a ring of #6 copper wire and hammering it into shape but that seemed like kind of a ghetto repair to me so I wanted to bounce it off of y'all before I did it.