strange engine problem, intermittant stalling and back firing

Anthiron The Baja Rejuvenation Begins

4,936 posts · joined Oct 2003 · 18 Apr 2008, 1:34 pm

#641540

in the last cpl of days my engine has developed a nasty habit of backfiring on decelleration and then revs dropping to a stall, but only sometimes. i might drive to work and it will be fine but on the way home it will do it. ive replaces the points, condensor and done the timing again for these. ive tried revving the engine up and putting my hand over the carby to suck anything through that might be blocking a jet. ive tried cleaning the carby up with carby cleaner and spraying down the throat while engine is running.

usually is i start the engine from cold it will run fine for at least 10 minutes or so before the problem surfaces.

im a bit hesitant to dismantle the carby as last time i rebuilt it i noticed that the threads in the alloy were worn to the stage where next time the screws probobly wont bite anymore.

but im running out of other ideas.

anyone have a suggestion?

the coil wouldnt cause this would it?

Nicko

62/60 model bug eye baja bug, (Full Build in Progress)
1974 Chevrolet Luv
1970 MK2 Ford Cortina GT
1979 Yamaha RX125 Two Stroke tracker project.
2004 Harley Davidson Sportster XL Custom

Sides Veteran Volks Folk

2,220 posts · joined May 2007 · 18 Apr 2008, 2:11 pm

#641545

This is gonna sound really dumb, but my sister's bug had the same symptoms once... turned out to be an intermittent short where the wire from the condensor plugs onto the coil. The thing there didn't have any insulation on it, and had gotten a bit bent or something so sometimes it would short on the fan shroud.

Once finally found it I just bent the terminal back and put some insulation on it, and she was all good again (the car that is, not my sis - she was still a pain 😉)

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Joel Now containing 100\% E-Wang

9,368 posts · joined Feb 2006 · 18 Apr 2008, 3:00 pm

#641553

classic symptoms of a blocked idle jet

next time it starts doing that if u can pull over and pull the idle jet out and see if theres any crap caught in the hole its only a tiny hole about 0.5mm so the smallest bit of rubbish can block it

and problem is that most aveage fuel filters dont catch the really small stuff that does it
i started using metal efi filters and the problem has never occured again

Anthiron The Baja Rejuvenation Begins

4,936 posts · joined Oct 2003 · 18 Apr 2008, 11:13 pm

#641627

to get to the idle jet in a 30pict ive got to pull the top off the carby. im pretty sure if i unscrew those screws one more time they arent going to bite in the alloy when i try to screw them b ack in.

i guess ill give it a go though.

62/60 model bug eye baja bug, (Full Build in Progress)
1974 Chevrolet Luv
1970 MK2 Ford Cortina GT
1979 Yamaha RX125 Two Stroke tracker project.
2004 Harley Davidson Sportster XL Custom

Joel Now containing 100\% E-Wang

9,368 posts · joined Feb 2006 · 18 Apr 2008, 11:56 pm

#641630

u shouldnt have to pull the top off
the idle jet on pretty much all solexs is on the right hand side below the auto choke
some of the earlier ones just have the idle jet mounted to the cutout solenoid

Bizarre Moderator The artist formerly known as blue74l

12,785 posts · joined Aug 2002 · 19 Apr 2008, 8:11 am

#641635

vacuum leak?

Futue te ipsum!!!

Anthiron The Baja Rejuvenation Begins

4,936 posts · joined Oct 2003 · 19 Apr 2008, 9:27 am

#641652

oh im thinkiing of the idle air jet.

yeah its in the cut off solinoid i think in a 30pict

62/60 model bug eye baja bug, (Full Build in Progress)
1974 Chevrolet Luv
1970 MK2 Ford Cortina GT
1979 Yamaha RX125 Two Stroke tracker project.
2004 Harley Davidson Sportster XL Custom

geodon Wolfsburg Wizard

478 posts · joined Aug 2002 · 21 Apr 2008, 2:16 pm

#641925

Do 30PICT's have a cut-off solenoid??
Certainly not the -1 (1300) or -2 (1500 split Kombi)
I thought only the 34PICT's had them, but I could be wrong. I know what I'd rather work on! The 34's suffix should have been changed from PICT to PRICT.

I'd go with a vacuum leak. On over-run the throttle shuts & the wheels keep turning the motor so the vacuum goes v high & any leak will suck in lots of air to lean off the mixture = stalling.

cesiumfrog Seriously Crusin Dubber

161 posts · joined Apr 2005 · 21 Apr 2008, 3:45 pm

#641933

yep...idle jet would do it..esp if the o-ring that seals it is stuffed or, like dub74L says , bit of crap in the idle cicuit.....from memory two tapered needle screws on passengers side of carbie one idle speed ( bigger one)the other idle mixture (smaller one)

Bizarre Moderator The artist formerly known as blue74l

12,785 posts · joined Aug 2002 · 21 Apr 2008, 7:35 pm

#641969

If it was idle circuit i doubt it would idle

My reason for saying vacuum is the carb is under decent pressure on decceleration and this will accentuate any problems

"usually is i start the engine from cold it will run fine for at least 10 minutes or so before the problem surfaces."

This masks the leak problem as the choke starves the air so the car runs ok.
When the choke comes off - too much air and the car stalls

Also where are the threads dodgy??
I would start looking for leaks there.

For $10 get a can of carb cleaners and spray away
Check the throttle bushings and gasket
Try the manifold head gaskets as well.

For what it is worth
I had my 34Pict rebuilt the other day.
Never had a FRESH rebuilt carb.
NEVER had a car run so smooth.

Futue te ipsum!!!