Low Compression, running rough, backfire, Technical help please Options

[Don911]

I'll gather what I have tonight if I have time! Sorry for alert haha

[tazz9924]

So I have searched the forum (and internet) before posting...sorry if this a tired old topic.

Trying to narrow down the cause for some backfiring through the carbs and rough running.

Compression: #1-125, #2-90, #3-70, #4-85

Some oil around the air filter housing.

#3 plug fouled so all were replaced.

Carbs synched

Valve job completed.

Still: runs rough in lower RPM ranges especially when starting out and now I'm getting an occasional backfire through the carbs under acceleration.

Mech says it caused by low compression and needs at least a top end rebuild.

A lot of what I'm reading points toward...well a lot of things, but nobody says low compression causes the chugging from start and the backfire.

Agree? Disagree? Not enough info? Thoughts please...thanks!

Do a leak down test it will tell you exactly where the compression is being lost

[Ansbacher]

[quote name='dr914@autoatlanta.com' date='Dec 12 2018, 09:51 AM' post='2673251']
you say "valve job" did you mean vale ADJUSTMENT? If adjustment and you know that the adjustment is correct, and still low compression then certainly a rebuild. Carbs are very hard on a 914 engine.
So without decent compression trying to get your engine to run correctly, is probably futile, although with carb rebuild, adjustment, no intake leaks, dwell and timing and a good ignition system, it will run better than it is now,


Doctor 914,

Can you elaborate on what you mean by "carbs are hard on a 914". ? Very curious.

Ansbacher