Hitchcocks Forum

Right, I wuz riding Effie into work this morning & noticed that she wuz back-firing a little on the overrun?

She's a 2008 Electra EFI with a K&N style air-filter and free-breating exhaust, both supplied by our hosts.

She is also still running on the standard Indian ECU, will that make the engine do this? Also slightly jerky acceleration from standstill.

Reading all the horror stories on this site has maybe got me worrying a little too much but on the open road she runs sweetly, though not as sweet as my 2004 Kawa W650 which is an absolute delight to ride!

That's usually an air leak into the exhaust, most likeley at the head, and/ or a weak mixture.

I thought slight backfiring on the over run was an endearing characteristic of Enfields

Thanks guys - The bike was so quiet and used to snuffle along with the old restrictive original cat-equipped monster silencer that maybe I didn't notice it doing that before.

It sounds like a REAL motorbike now! (but the backfires are also louder!) and I can't quite stretch to a power commander yet and was worried something else was amiss.

You can still get reversion of the exhaust even with a tight exhaust system. That's where cold air is sucked up into the hot exhaust and expands rapidly with unburnt fuel ignited. Which produces rude retorts on the over run.



The oem ECU is a Keihin system so it's not rubbish, however I have fitted the Dynojet Power Commander V (PCv) and now this week the Autotune AT-200. Which means I can now see the air-fuel ratio (AFR) on the laptop from its Bosch wide-band O2 sensor. Basically the AFR is all over the place at idle and on the over-run i.e. very, very rich 7s & 8s and/or extremely lean up in the 19s and 20s. It is simply not being controlled.



Using the AT-200 to fix the idle mix to a sensible value (the 0% and 2% columns) seams to have made the occasional loud bang disappear.



Dynojet's basic Autotune instructions are here so you can see what I info can see on the laptop https://www.youtube.com/watch?v=AOi9NHRv7jE



And there are a number of discussions and videos out-there on using the AT-200 to cure banging by controlling the idle/closed-throttle mix.



Before fitting the PCV I partially cured the reversion by ensuring the exhaust system was tight, part of that was the 50s free-flow system but using the copper ring exhaust seals instead of the cement biscuit gasket which crumbles away, *and* by raising the idle a little by turning the brass idle screw a little anticlockwise. The jerky running I put down to the oem ECU, it went away with the PCv.

May I add that Hitchcocks' dynamometer-developed map for the PCV is quite different to the oem map. Fitting a non-stock exhaust is quite sufficient to throw the oem map way out and the oem narrow-band Lambda sensor can only adjust the AFR in very broad strokes i.e. it cannot do it. This is where Hitchcocks' PCV kit comes in, and they're the only place that has RE-specific maps for it developed in house (ok Dynojet has one but it is out of date).



Having fitted another exhaust, you may well need the PCV now.



Most dynamometer tune-ups are for maximum power on sports bikes. I had a chat with a couple of places that run dynos here. They don't pay much attention to puttering cruise and idle/over-run. That's where the wide-band sensor on the AT-200 comes in as it can adjust the mix for the next induction (oem narrow-band can't do that).

I spread-sheeted the base map and there are a couple of sudden big peaks and troughs which the AT-200 is trying to smooth out.
Still a work in progress.