Series 3 Military 24v FFR 109 (1981)

can any one help me?

My engine developed a miss fire... under load.. has got worse!

I have a zenith carb which i known for its issues! so i have replaced! as the slow running screw would not effect the engines idol at all! so just scrapped it!


but the miss fire is confusing me! its hard as all the work im doing when im on my own so harder to diagnose untill i have a mate helping once in a while!

missfire -

compression tested 150 through all (i think was 150) but all matched!
changed the points
rotor
condenser! nothing!

Im hoping its just a plug or lead now! i have plugs on the way but leads are hard to come by being 24v screaned etc

any one have any ideas?

Paul ..Brighton uk

had this with one i had a while back cleaned the plugs cus they was coked up to hell due to the mixture(warped zenith) being so rich,the leads very rarely breakdown so i should whip the plugs out and give em a clean,if it turns out to be leads doubtful but...craddocks were breaking a few a couple of weeks ago so try them

con666 said:

I have a zenith carb which i known for its issues! so i have replaced! as the slow running screw would not effect the engines idol at all! so just scrapped it!

Click to expand...

is the slow running screw the same as the mixture screw? (the wee screw on the bottom of the carb, pointing towards cylinder 1ish i think) if adjusting this screw does nothing there may be an air leak on the inlet manifold. i've had trouble with leaks on the carb/inlet manifold before, just nipping up the carb securing bolts helped.

doobie said:

is the slow running screw the same as the mixture screw? (the wee screw on the bottom of the carb, pointing towards cylinder 1ish i think) if adjusting this screw does nothing there may be an air leak on the inlet manifold. i've had trouble with leaks on the carb/inlet manifold before, just nipping up the carb securing bolts helped.

Click to expand...

i could tek the mixture screw to both extremes fully in or totally remove mine and it med no difference whatsoever playing with the idle screw
with the zenith carb due to the location of the screws securing the 2 halfs they tend to warp allowing for a total screw up in its operation
easily fixed by splitting your carb open and using fine wet and dry on a dead flat surface to reface your mating surfaces by carefully working the two halves until you,ve got your flat surfaces back did mine ina bout 45 mins