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hi guys,

having a bit of trouble with the FB. shes got a fairly tired 173 red motor and unfortunately I decided to drive her a bit too hard last time I took her out. now, the engine idles fine when turned on but when you press down the pedal the engine starts to backfire and get rumbly and there's no power. when you go back to idle it rumbles for a bit but does settle down to a nice if not a little fast idle. drivable, not too many strange noises apart from the backfiring, but still very concerning. with the air filter off there is a distinct gargling noise when you apply the gas rather than the usual hissing. my first though was a vacuum leak somewhere but Ive checked the obvious places to no success. any thoughts? plenty of fuel getting to the carby.

cheers,
james

timing?

had a quick play with turning the distributor, just rotated until it reached maximum revs, do you think a more sophisticated approach would help?

Next step is to drive it and if it pings, turn the dizzy back till it doesn't ping under load. But I somehow don't think that is going to solve your problems.

Just guesses, but:

Is she backfiring up through the carb (pressurised cylinder when inlet valve opens... 'zorst valve stuck, lifter failed, rocker jammed, pushrod bent. cam lobe worn, timing out), or is she backfiring through the 'zorst (unburnt fuel exiting the cylinder and igniting... Overfueling accelerator circuit, ignition breakdown, timing out)?

If you run with one plug lead off a cylinder (one cylinder at a time) does it still backfire (common system issue... Fuel, spark, timing) or does the problem go away (issue related to one cylinder... rockers, lifters, pushrods, lobes)?

hey, i too have a 173!!!
check yr points, and then check the rotor shaft for excessive play. mine ran good and then shit and then great and then shit depending on what it felt like on the day. all due to worn dizzy that no adjustment would sort as one rev of the motor would throw it all out again and burn another set of points. this would also alter the timing at revs due to the eccentric wobble of the loose shaft so it ran totally different at revs than at idle....solved it with electronic dizzy and now she runs sweeeet

hi guys, im in the process of pulling apart the dizzy to check all these things and have gotten a little stuck. im meant to "remove the securing screw and lift out the capacitor and low tension lead assembly" however the only screws (there are two of em) i can see, I cant get access at because they are under what's in the pictures above. anyone know what the next step is in this case? its a bosch distributor of some description. also, how does one check if the vacuum membrane is fine in the vacuum advance?

You do know thats an electronic dizzy yeah?

As for the vaccuum advance suck on the little bit of black plastic poking out of the side of the dizzy (where the vaccuum line connects too). If you can suck air in its got a hole in it.

Gees Wizz there fella, you certainly dont do things by halves!!!
"Read on the internet it might be the dizzy love, i'll just pop in the shed and yank it out for a look see"... the very next morning!
as DR pointed out, what you have is an electic/electronic dizzy already, no points to gap there so its not points messing the timing of the motor, and the shaft play could have been checked in the car by simply grabbing a hold of the rotor and moving it up and down or side to side to check for movement of the shaft off centre, mine had something like 5mm movement from one side to the other and so you could never set the points gap correctly, i think i may be telling your nanna how to suck eggs the way you have excecuted this swift operation, but you dont have any points to gap there.

once you reinstall it, set the timing with vacum line disconnected, not on, like my mechanic did.

SunnyTim wrote:sounds to me like you have some crap in the jet in your carby........and not the dizzy. Put the dizzy back in and get it running as normal, then swap a few plug leads around so it backfires through the carby - should clear the jet
Tim

worked a charm. still a little flat at the top end so might need just need to drive around to bit until it all gets cleaned out / drawn into the engine, but certainly a dramatic improvement (ie - its now fine to drive). and nope, had no idea that was an electronic dizzy, very new to this game. cheers for the advice everyone

on a related note, came across this while reading up on how a dizzy works:

http://www.youtube.com/watch?v=UYGU7mTwsZc

pretty through huh?

gah. went for a drive today and it worked for a bit then chonked out. same problem. looks like someone is pulling a carby out and manually cleaning out the jet and fuel bowl.

Have you got a fuel filter? If so does it need changing or fit one preferably before the pump to avoid clogging that up too.

wd40 clean of everything in the carby and shes running even more smoothly than before all the silly buggers began! replaced the fuel filter - is it worth having one on either side of the pump, i've seen it done but i wonder if it's not overkill? cheers again guys