I got the car back from the mechanic yesterday, he replaced the first gear syncro and did some welding on my heat exhanger. I was getting a backfire when I shut done and a little decel popping from the leak. He also said he adjusted my carbs (44 webers on a big bore 1.7)

Now I don't get the popping sound but I get a giant backfire a few seconds after I turn of the key/engine. Advice?

So, is this a carb issue - too rich? an exhaust leak, or am I just screwed.

bump

Ken:

IMO if you have a stock 1.7 ,( bore ,stroke,& cam) you are way over carbed. Most guy's that use 44's have at least 2.0 or bigger. I have a 1.7 also
i have Weber 40's with no problems. I think you are to rich,when you shut it off there is a still a load of fuel in the intake side of the engine and it gets lit off. Resulting in that back fire ,. Now why is does that will be up to someone who knows 44's much better than I .
I would start by astablishingif the tune of you engine is correct and dead on. Also pull the plugs and see if they are wet,or black, if the back fire only occures when you shut it off that sugests ,to me ,idle jets may be to big. They are very easy to pull,( if the same as the 40's) and check size . then post . We will get this streighten out . Dave

P.S. I was assuning the back fire is comming out the carbs???? for it to be intake issue.
In rereading your post it seems to be on the exhaust side ,if so that says way to rich on the main jets and idle side .post the sizes you are running and the venturie
size,we will get ironed out.

You know... I'm kind of paranoid once in a while, but I would be very leery of a carb back fire when you shut down. A carb backfire can light your air filter on fire (and then the rest of your car).

On old motorcycles any way; if your carb backfires the best way to put it out is to kick the engine through; that will suck the flames into the engine & extinguish the fire. An exhaust detonation is generally louder and more annoying and embarrassing, but not threatening. I'm certainly no expert, but IMHO; your exhaust can handle unbrunt fuel, your carbs cannot.

Did he use new crush gaskets when he put the muffler back on?