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"poping" small backfires (video linked)

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bajachris88 The international telephone dialing code for Antarctica is 6

6,661 posts · joined Apr 2005 ·

#876397
hmm. whats ur timing at? no single ignition lead in the incorrect position?

Just given the way it kicked back when trying to start, either a hint ignition is too advanced or a spark is going to a cylinder when its not meant to be.
mind you though, during running, too advanced ignition should pop in the intake, hence if its poping in the exhaust i would be checking the 1-4-3-2 sequence.
(ô_!_/ô) (ô_!_/ô)
69' baja: kombi box, thing spindles, irs, disc front, type 3 rear drums, 2 inch lift kit, 31x10 rears. 👍
New engine in process: 94mm p&bs, 74mm C/w chomol Crank, 35.5x39 SP heads, turbo. Wierd combo, hopeful torque monsta!

Bizarre Moderator The artist formerly known as blue74l

12,789 posts · joined Aug 2002 ·

#876398
certainly sounds like a lean "miss" to me.

pull your plugs and see if all of them are white

You are either under jetted on the idle circuit, blocked idle or a bad leak some where
Futue te ipsum!!!

vwbugsrule Slammed & Awesome Dubber

84 posts · joined Feb 2011 ·

#876419
leads are in the sequence 1-4-3-2, compression of the motor is 130psi per cylinder, spark plugs are black. What should my timing be for this year model beetle?

Joel Now containing 100\% E-Wang

9,368 posts · joined Feb 2006 ·

#876421
You've got timing way out on that.
Is that a vac only dizzy?

vlad01 Compulsive Aussie Vee Dubber

4,270 posts · joined Jun 2010 ·

#876425
what the hell happen in the end of the video? looks like it just abruptly locked up.

71 notchback,
Past owner of, 70 NB, 73 SB and 72 FB TLE

bevoracing Officially Full-On Dubber

327 posts · joined Jan 2009 ·

#876462
Mate, that engine isn’t kicking on all 4 any time throughout that run. Listen to it hissing as you crank it over, that’s not right. Do a compression test, all the plugs out, crank it and test each cylinder. My bet, you’ve fly cut the heads and not had the head face cut too. One of them is sitting up on the barrel’s fin castings and not sealing on the top of the barrel. I’ve seen it before. It blows out and sucks in, causes popping and missing etc. You get a similar effect with a valve out of adjustment, not closing.
My money’s on a leaking head, place your bets.
Good luck
Tony
Country Buggy King & Link Pin Overhauls, Type 1 & 2 King Pins, General Machining.
http://forums.aussieveedubbers.com/viewtopic.php?tid=74138
My car is KO813

vwbugsrule Slammed & Awesome Dubber

84 posts · joined Feb 2011 ·

#876470
Joel: yes its a vac only dizzy, big dizzy for the 40hp.
Bevoracing: ok, so what do i need to do to fix that? i did a compression test, it holds 130psi on all cylinders. All that has been done to the engine is: Pulled apart, clean up, and put back together.

matberry Moderator Go hard or go home

8,114 posts · joined Mar 2006 ·

#876485
Not a compression leak IMO, but not running on all cylinders either. Set timing to 32* total advance, I think 7.5* BTDC for the 40hp dissy. Double check your valve clearances and timing is my suggestion, carb tune won't go astray, neither would tailpipes. No exhaust leaks??
Matt Berry Motorsports...air cooled advice, repairs and mods Ph 0408 704 662
OFF-ROAD,CIRCUIT,DRAG,STREET,ENDURANCE

vwbugsrule Slammed & Awesome Dubber

84 posts · joined Feb 2011 ·

#876488
no no exhaust leaks, new gaskets all round. On the dizzy, there is a line marked on the outside rim, that is where the rotor is meant to be pointing on TDC right? pretty sure it is from what i remember ❓

rob53 Officially Full-On Dubber

385 posts · joined Jan 2007 ·

#876506
That's right but it's not guaranteed to be there if the distributor drive gear was not installed correctly. Check if the rotor points there when no 1 is at tdc. From the video, it sounds as if only 3 cylinders are firing.

As Matt said, try setting the timing to 7.5 degrees btdc. Also have you checked the spark on each plug?
Thats not rust, it's ah ... orange primer ... yep that's what it is ...

Joel Now containing 100\% E-Wang

9,368 posts · joined Feb 2006 ·

#876513
rob53 wrote:That's right but it's not guaranteed to be there if the distributor drive gear was not installed correctly.
Doesn't matter how far out of alignment the dizzy drive is installed, the rotor will always line up with the #1 notch but the trouble is then things like the vac can hitting the fuel pump if it's too far out.

vwbugsrule wrote:On the dizzy, there is a line marked on the outside rim, that is where the rotor is meant to be pointing on TDC right? pretty sure it is from what i remember ❓
Well there is probably the main source of your issues, the early vac only dizzys are timed at 7.5BTDC and some are even 10BTDC so make sure your pulley is the right one and has 7.5BTDC

If you have it at TDC that's why it's so doughy and popping.
Check it with a test light.

bevoracing Officially Full-On Dubber

327 posts · joined Jan 2009 ·

#877043
Mate, there’s just something silly going on there. You’ll have to start double checking everything, even the new stuff. Start with the coil, cap, rotor, plug leads, plugs etc. I’ve seen brand new coils, leads & plugs that just don’t work. Double check, everything.
Then, try taking the carby and the fan housing off, remove the rocker shafts, so that all of the inlet valves are shut at the same time, then put your mouth on the manifold and suck, see if you can find a leak.
There’s something wrong, it’s just a matter of finding it, double check everything until you do.
Now you know why mechanics seem to charge a lot for some jobs and not others.
Good luck, make sure you let us all know what it is when you find it, we can’t wait. It all looks great by the way, well done.
Cheers
Tony
Country Buggy King & Link Pin Overhauls, Type 1 & 2 King Pins, General Machining.
http://forums.aussieveedubbers.com/viewtopic.php?tid=74138
My car is KO813