mis-fire at 2000rpm

[vw moses]

i get a carb. pop at 2000rpm-it's like a backfire then goes away? what can cause this? I have duel hpmx 40 magna-spark dist-i cleaned the carbs in&out still happens-magna spark&wires brand new??

[udidwht]

Check the points.
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1972 Westy Hardtop/Type-4 2056cc
96mm Biral AA P/C's~7.8:1CR
Headflow Masters New AMC 42x36mm heads w/Porsche swivel adjusters
71mm Stroke
73 Web Cam w/Web solids
Dual 40mm IDF Webers - LM-2 - 47.5 idles/125 mains/190 air corr./F11 tubes/28mm Vents - Float height 10.45mm/Drop 32mm
Bosch SVDA w/Pertronix module (7.5 initial 28 total @ 3400rpm)
Bosch W8CC plugs
Pertronix Flamethrower 40K coil
S&S 4-1 w/Walker QP 17862
3 rib 002 Trans
185R14 Hankook tires

[vw moses]

it dosen't have points elec.type ing.

[77charger]

are the idle jets clear?
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Click to view image
Bugpack 4 seater rail
2275 built by me
Auto linea alm case,82 dpr crank wedgemated by DK machine
cb 5.4 h beams,12 pound DPR f/w,Slr xv294cam,cb straight cuts,hpmx 44s,40x35 heads ported by brothers machine

[vw moses]

yea,I think so I shot everything with b-12 carb. cleaner&blew out the emls. tubes with air-compressor--i didn't take out idle jets or idle screws(didn't want to change settings) It backfires out carb POP_POP then dosen't do it again until i rev. it up. ar. 2000-2500 pop Hiss? i'm thinking cross fire on the wires,but I don't know!
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Youtube@vw moses
73 thing-gone
66 beetle-gone
62 beetle-gone
57 beetle-gone
convertable-beetle-w/bugspray & screamer dist.(019) gone
"Where There's a Will There's a Way"
63 one of a kind beetle. 57 dash,double rear window--sweet!

[MURZI]

I just tuned a 1776 with those carbs...seems as if the empi clones like more idle jet. I would up at 55/130/200. You should richen the idle circuit and run at least a 125 main.

This weekend I will be tuning a 1850 with a 2241 and empi carbs as well.
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62 vert
2276
Tim’s welded heads
45 Dells
A1 sidewinder
Fk44 cam

[vw moses]

Thanks for the heads up--the carbs come with 52/115/200 i'll change to your recommendation 55/130/200 I didn't know the jet size would cause the pop&cough! must be "STARVING" I'll let you know-now back to ordering & waiting!
_________________
Youtube@vw moses
73 thing-gone
66 beetle-gone
62 beetle-gone
57 beetle-gone
convertable-beetle-w/bugspray & screamer dist.(019) gone
"Where There's a Will There's a Way"
63 one of a kind beetle. 57 dash,double rear window--sweet!

[MURZI]

I'd try 125's first. Did you try to adjust mixture screws out? Set float levels to 10.5mm??
_________________
62 vert
2276
Tim’s welded heads
45 Dells
A1 sidewinder
Fk44 cam

[vw moses]

I didn't adj. idle screws--I did tweak the floats according to Weber carb book 10mm up 30mm down, Already ordered mains&idle jets(55+130) they shouldn't starve now. But We'll See.I'll report the results
_________________
Youtube@vw moses
73 thing-gone
66 beetle-gone
62 beetle-gone
57 beetle-gone
convertable-beetle-w/bugspray & screamer dist.(019) gone
"Where There's a Will There's a Way"
63 one of a kind beetle. 57 dash,double rear window--sweet!

[MURZI]

Before you change idle jets, I would remove them and clean them. Turn each one in until the rpm drops and then come out 1/4-1/2 turn. Do this on each one, and then do it again.....
_________________
62 vert
2276
Tim’s welded heads
45 Dells
A1 sidewinder
Fk44 cam

[77charger]

Theres no setting for idle jets they just screw in thats all.The mixture screws are what take some adjusting but even if they are off slightly they wont cause a miss.

Starting at 1.25-1.5 turns out from lightly seated should be good enough to get a good start on tuning them.
_________________
Click to view image
Bugpack 4 seater rail
2275 built by me
Auto linea alm case,82 dpr crank wedgemated by DK machine
cb 5.4 h beams,12 pound DPR f/w,Slr xv294cam,cb straight cuts,hpmx 44s,40x35 heads ported by brothers machine

[MURZI]

[FreeBug]

ok, i am going to work off of some assumptions here: The engine has some miles on it and has always worked fine. You change plug wires, and now it is lean in the idle/progression circuit. Could it be that to change the wires you took out the carbs, and developed a vacuum leak between manifold and head? Quick to check.

[Quokka42]

Yeah, that's it - vacuum leaking out all over the place... Seriously though, backfiring is usually lean mixture. Check for leaks and check your jetting in that order. BTW, you should have pulled all the jets to clean the carbs - they're really good at catching stuff and causing the engine to lean out.
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There has only ever been one man who was perfect, and they nailed Him to a cross.

[vw moses]

Ok,Before I take off carbs. I'll start,(does Idle OK) and shoot some starting fluid at base&intake gaskets--the carbs are brand new w/maby 10 miles if that on them; If that.When I took em down everything spotless(got 2 fuel filtere 1 bf-elec pump-1 bf-tee) When the new jets come in everything will be b-12 w/air comp. shot(I'll won't forget to "HOLD de jets Tight") I'm pretty sure it's getting the jet sizes right' Cuze my mtr. isn't stock(has some goodies that probally need more gas to Excite! Thanks for the feedback!
_________________
Youtube@vw moses
73 thing-gone
66 beetle-gone
62 beetle-gone
57 beetle-gone
convertable-beetle-w/bugspray & screamer dist.(019) gone
"Where There's a Will There's a Way"
63 one of a kind beetle. 57 dash,double rear window--sweet!

[aerosurfer]