Hitchcocks Forum

My Electra X has started puffing out black smoke out of my exhaust pipe on accelerating. Also has sooty/black plug. I know this means rich mixture. It is an Electra X, Mikuni and K&N filter. So what can cause this problem?

A sudden rich mixture is hard to explain, in Australia it could be a blocked air cleaner. Broken piston oil ring perhaps, oil pump return not working properly, allowing wet sumping. Other opinions will come along soon.

Leon,



if it's black smoke it won't be anything to do with the engine oil. Uncleared wet-sumping is usually white smoke, and it usually clears up after a few minutes.



The carburettor needs checking for blocked airways, though it could also be the needle and main jets unscrewing themselves and dropping down into the floatbowl, effectively raising the needle and making things richer on acceleration. Also check the float needle valve isn't sticking open, though if that happens you'd usually get petrol pouring out of the overflow pipe on a Mikuni.



A.

Adrian: Quite right. My mind started off as thinking petrol and wandered to oil; it`s an age thing --- I think; now what were we talking about?

I had exactly this symptom, just prior to a rocker shaft seizing.

Rocker, not rocker shaft.

Hi guys,
I think the clue might be in the "When accelerating" phrase........Didn't the Electra X have a CV type carb ?...I can't remember just how the piston/diaphragm unit was damped ( Remember the SU Carbs had that oil dashpot as part of the chamber top ??)..but if the piston assy. were allowed to rise further than it needs to then that would give a rich mixture, but only when accelerating....At a steady throttle demand position it would balance-out....
Just thinking outside the box so to speak---- I'm probably 100% wrong !!

Cheers Count Johnny, not a comforting thought. I think I will check the carb first. Thank you for the comments everyone.

Yes it sounds like a carburettor problem that's the first thing i would check. I have an electra x but mine as a Dellorto carburettor.

Graham, as a matter of interest which Mikuni carb do you have fitted? The VM32 is an obvious choice, though other types have been used successfully.



The Electra-X rockers are a different design compared to the classic version, I have never heard of any problems with them, but you could always check the rocker feed line for any debris.



Watsonian-Squire's decision to use the PHF32 Dell'Orto pumper carb for the original Electra-X go-faster kit was a bit left-field, but I love the look of the things, and they are a superior instrument to the bog-stock Mk1 concentric our hosts favoured. Only the W-S mounting arrangement was a bit odd IMHO. The biggest improvement for the Dell'Orto is to replace the fiddly cold-start lever with a cable operated one using an old-style choke lever on the handlebars, if this hasn't already been done.



A.