Forum

[grunda 12]

apparentley on the over run my 500 electra fires fuel in the exhaust pipe causing a small bang and a blue flame out the end of the silencer i find this all amusing i also thought it may be a bit rich putting too much fuel in unburnt firing in the exhaust any way lets have some expert opinions as i can now get back into the shed the carb is an amal concentric with the fully open downpipe have looked at the plug and the colour is correct so lets see? atb paul also down pipe is sealed by gasket and silicone air filter is s&b

[John L]

Paul -
Classic sign of the exhaust drawing air in somewhere - these leaks can be very difficult to trace sometimes....

[Alan R]

Hi Paul---With the bike warmed up and at idling speed, try blocking the outlet with a ball of rolled-up cloth held there firmly whilst checking the two main joints for leaking ie at the cyl head and where the silencer and downpipe meet....soapy water is good for this----- There you are then, a sensible answer and NO passes/hi-jacks.

[PeteF]

Yes, it's sucking air in somewhere.
This is a problem with carbs, when you close the throttle there is quite a vacuum in the inlet so some petrol is sucked into the engine but not burnt.
Modern injector systems close the fuel feed completely when you close the throttle until the revs drop to tickover speed.
This is one reason injectors tend to be more fuel efficient and produce less immissions.

[Alan R]

THE BLUE LAMP -------------- "Evenin-all!!" (Thumbs into serge jacket lapels---- bends the knees slightly)---- "You know it's a funny old game, this Policing business. Why only the other day a young Yorkshire lad, beside himself with worry about an old Electra X he'd recently bought, asked for my advice regarding a bit of a back-fire his bike was doing....My years in the Force immediately came to the rescue and I reminded him that it's a WEAK mixture that's slow burning and will only be ignited by a hot exhaust pipe...and that in itself is probably a product of the said weak mixture....I took him to one side, gave him the obligatory cuff-around-the-ear ( we could do that in the 1950's), suggested that he actually richens the main jet a tad then sent him on his way---with a promise that his Dad need not know !!---- As I said, Funny old game this---------- 'evenin all!!" (Salutes and fades into the night background)--cue the mouth organ music---------

[grunda 12]

thanks guys !!i tried the exhaust system for leaks ,covered the silencer end with a rag and it stopped the engine so i,m nearly sure that the exhaust is well sealed ,also checked for a weak mixture as the down pipe has turned blue a possible indication to weak mixture although the plug is a reasonable colour ,i might try altering the needle setting by a notch to richen it up a bit more or adjust the mixture screw ,i just thought i,d plumb the depths of knowledge on here to see if i was blinded by the blue flame because i was standing too near it ,as sometimes even the most stickler types like myself miss the obvious ,anyway its only done 350 miles since the rebuild so i need to hit the road and get some more in thanks and evening all!!paul.

[Alan R]

Oi !!! SONNY !! Now look 'ere }----Mixture screw is for pilot jetting, needle position is mainly mid-range whilst main jetting is for top-end. SO, if I wer yew I'd UP YOURs by approx 5%. Now run along and don't let me catch you scrumpin old Ma Coggins apples again !!!!------------- gertcha !!

[grunda 12]

hi alan ,the flame appears with the pop only occasionally when there are no revs being applied on shut down i.e throttle closed so i,m not too sure about up jetting as when throttle is closed main jet is not in active service so to speak i also forgot to mention that it only does it after a long run of wide throttle openings i,e down the bypass trapping on then shut down for roundabout bang flash anyway i,ll tweak a few things tomorrow and report back atb paul.

[Beezabryan]

The Infanous Enfield does it regularly on over-run.... Am I bovvered AM I BOVVERED NO 'cos it wakes up the dozy cagers who're getting too close to my rear end .... I'm not fussed about it as the thing runs fine the Micarb is set up OK. It ain't broke ergo it will not get mended

[STU]

Yeah Paul my Electra does the same. It came with the WS Highway Kit and popped and banged a bit from new, but since I fitted our hosts full Goldy system it does it more, louder and with blue Flames!
However, I also got more performance and noise, which as Bryan says is sometimes a good thing.
I think that it is all to do with it being designed as a lean burn motor and then we go and put big carbs, free- flow filters and exhausts (particularly the header pipe) and blank off the PAV system.
If it is not so offensive that you could just live with it? Sounds like a 'real' bike...