missing/backfiring at cruising speed..kads or burnt valve?

risk

I'm running dual kads and 009 set at 32 deg total advance on a stock 1600dp...No balance tube and the carbs do have the check balls in accel pump tube..
checked and re-checked the valves..
replaced plugs, wires, cap, rotor, points, condenser and coil...
sooo here's my issue...

When I got the carbs they had sat with some water/bad gas in them on a baja.. cleaned them out/ rebuild kits/ new floats and they ran fine for a while...

I have cleaned these carbs out numerous times and the issue keeps popping up.. it used to clear out after a while, now it's doing it all the time.

Runs good on acceleration or wide open throttle, but when you let off to cruise or just maintain a speed it starts missing and backfiring. When I unplug #1 or #2 spark plug wire there isn't much change at idle, but when I unplug #3 or #4 the engine wants to die.. I am assuming that my problem is in right side carb.... but could it be a burnt valve or something else I've overlooked?

carcrazed · Posted: Wed Mar 04, 2009 6:44 pm Post subject:

Had the same problems with my Kads. I had to rejet them. Also...check the squirt adjustments, they might be loading up the carbs. Did you go to lowbugget.com? He is an expert and has a trouble shooting guide to Kadron's. Maybe check your idle jets and make sure they aren't plugged.

www.lowbugget.com
_________________
1965 Herbie Replica. 1776cc dual Kads.
1961 Beetle 33,000 Original Miles

"Just When you think you are getting ahead, you're always wrong."

Max Welton · Posted: Wed Mar 04, 2009 9:02 pm Post subject:

You could find out if the right carb is the problem by swapping the carbs and seeing if the problem follows the carb.

You can rule out valve problems with a leak-down test.

Max
_________________
1967 Type-3 Fastback
Under the Knife https://shoptalkforums.com/viewtopic.php?f=24&t=151582
Home Stretch https://www.thesamba.com/vw/forum/viewtopic.php?t=767836

skills@eurocarsplus · Posted: Wed Mar 04, 2009 9:13 pm Post subject:

if it was a burnt valve, it would do it non stop, all the time. burnt valves are not intermittent problems. as far as pulling the plug wires while running, small dual carbs generally run on 2 cylinders at idle, my ICT's do that too. are you running a balance tube?

Max Welton · Posted: Thu Mar 05, 2009 6:57 am Post subject:

Idling on 2 cylinders comes from the firing order of the engine. The two that fall out with dual single throats are 1 and 3. He's having problems on 1 & 2.

Any chance that side is running rich enough to foul the #1 and #2 plugs?

Max
_________________
1967 Type-3 Fastback
Under the Knife https://shoptalkforums.com/viewtopic.php?f=24&t=151582
Home Stretch https://www.thesamba.com/vw/forum/viewtopic.php?t=767836

risk · Posted: Thu Mar 05, 2009 8:01 am Post subject:

after doing some more reading lastnite i pulled the idle jet on that side to find an insect wing lodged inside.. ugh!! I guess it got in there somehow and was just never blown out during cleaning. Embarassed

made me feel like a real moron

thanks for all your responses!!

hutton65 · Posted: Thu Mar 05, 2009 8:18 am Post subject:

at lest you didn't have a rat get into your engine compartment and ruin your freshly painted engine tin! makes me wonder why I let my wife have a cat.........


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