I've been having some issues with my 74 Spider. It backfires through the carbs. I took it to an Alfa shop near me and it still runs pretty badly. Here's what I'm currently seeing.
- First, it doesn't want to start. It takes 20-25 pumps and lots of cursing to get it going.
- Once it is running, it runs pretty badly until it warms up. When cold, at idle it backfires through the carbs multiple times per minute. If you rev the engine at all it backfires more, mostly through the carbs but sometimes through the tailpipe.
- Once it is warms up and your on the highway, it runs much better. On the trip back from the shop to my house it only backfired a couple of times over an hour or so on the highway.
- After about 30 minutes of standing it was easy to start and while it didn't run great, the backfiring was noticeably less.
- When I removed one of the carbs, the cover plate that covers the throttle spring and is between the two throttle plates fell off.
- Also, on one of the cold start mechanisms, it looks like one of the pistons doesn't move as freely and the little "finger" attached to the gear that moves the piston up and down broke off. (The cold start mechanism isn't hooked up)
- One of the idle jets is not held very tightly by its holder. I could easily turn it and pull it from the holder.
- I decided to check the fit of the throttle plates to see if there was a gap that could be causing an air leak. I looked down each barrel of the disassembled carbs to check the gap and could see light around the plate each time.