Forum

[Smithy]

Hi

I've just bought a 2016 Classic EFI with 4000 miles on the clock. I fitted a Hitchcocks Gold star silencer which sounds great, however the bike is running very rich. There is black soot in the tailpipe and a friend of mine said it puffed out black smoke as I pulled away from his house.

Other than an expensive power commander does anyone know how to remedy this please.

[Alan R]

Hi Smithy----At this stage and without any other info to hand I'd say that fitting a silencer that has a much reduced back pressure is giving false gas flow readings for the EFI system ( Electronic Fuel Injection )..........Remember that your model was set up to meet Euro. Emission limits so any change from standard items will have an adverse impact unless you compensate for that change........With respect to the Dynojet Power Commander go to Pages 42 and 88 in our hosts catalogue where they will tell you that}----"Fitting It is essential when tuning the engine with different silencers and air filters etc "......( £295 + Post & VAT )..........As the bike has only done 4,000 miles it must still have lots of Warranty on it so I'd check to see if this new silencer voids that warranty first.................Sorry mate, I know this isn't the answer you wanted to hear but, in my honest opinion I'd re-fit the original silencer, run the bike and enjoy it until that warranty has run its' course....During this time save up your spare £££ and then buy the appropriate Power commander....

[Smithy]

Hi Alan

Thanks for the reply, I suspected that I would need to buy a Power Commander to cure this problem. Never mind it will be worth it in the long run as everything else about the bike suits me fine. I don't have the original silencer as when I bought the bike it already had on an aftermarket silencer that I didn't like the look of. Thanks again.

Ian

[Rattlebattle]

There is another option: fit a carb conversion kit. That’s what I did on my C5 when I faced a similar problem. It now runs much better, looks better and sounds better because the air filter is where it should be. I took a chance on the warranty - as it happens I had no further issues and the bike is now out-of-warranty. IIRC the cost saving of the carb kit over the PCV for a CGT is less advantageous. Like I said, just another option to consider.

[ric]

Assuming you don’t have an air leak or the cold starter plunger is being held off it’s seat which would result in rich running you could just unscrew the sensor in the down pipe and clean it with carb/ brake cleaner or even the correct stuff (but not any people have that to hand in their garage) and see if that improves things.

[ric]

Also....how high is the idle?

Assuming two bikes are the same apart from their idle speed, the bike with the higher tick over will have a darker tailpipe than the one with the lower tick over. Chances are the one with the darker tailpipe will also hit the Rev limiter quicker because it will be running richer at WOT.

[Dan H]

I believe the cold/bi starter should not have any effect on the mixture when in use or if the plunger is not seating fully. All that should happen is the idle will increase slightly due to the extra air being passed through the passageways.The ECU should compensate the correct amount of fuel to match this extra air using the MAP sensor as its reference and should not cause any excessively rich running.


The Power Commanders are ideal to pair to the bike after changing the silencer to give an optimum setup but should not be a necessity. The symptoms the OP has listed sound excessive for only changing to a goldstar silencer whilst retaining the standard fuel injection setup. Has anything else been changed on the bike that could may be having an effect? Perhaps its worth looking over the bike in case there is an issue lying elsewhere?

[Rattlebattle]

I’m inclined to agree; it shouldn’t make that much difference. I doubt that it’s much to do with the O2 sensor. It could be the TPS has been knocked and the adjustment upset. That happened to mine with the original sensor and the engine got more and more choked until it wouldn’t start at all. A simple fix. The O2 sensor on these bikes is narrow band and only affects the mixture over a limited rev range. One way of fooling the ECU is to install a resistor into the sensor wiring and remove the O2 sensor (which I believe you do anyway if you fit a PCV). Another possibility is a leak in the air filter. On an EFI bike this causes rich running as the ECU compensates for more air. I’d do a bit of checking before needlessly splashing the cash.

[beamish]

I am not technically minded (as you may have guessed from previous contributions!) but I fitted Mr. H's free flow exhaust pipe and silencer to my 2009 EFI and it has run in a delightfully spritely manner since then. I understand that it is the additional fitting of the modified air filter which is the final straw, making a revised ECU necessary. I have not taken that step because the bike performs perfectly for my limited ambitions.

[ric]

Agree it shouldn't but that is the result for me when I rotate my tickover screw.
I have no Bi-starter (or decomp) as my bullet will start without touching the throttle and happily tickover at around 0*C. It occurred to me that I'm unlikely to ever want to go out for a ride at temperatures lower than freezing so decided to completely junk the Bi-starter. The extra clearance through the nacelle without the cable makes for a much much easier clutch pull.
However this IS what happens on mine, perhaps it's because my TPS value is set at 0.8V who knows!
When I run a slow tickover by turning the screw about 1.25 turns clockwise from the factory setting (I'm talking a 350rpm tickover), I lose the WOT performance and sometimes fail to even reach the rev limiter unless I can use a very long downhill stretch, but easily obtain over 100mpg. I raise the tick over to around 1200rpm and the bike will then happily bounce off the rev limiter on the flat, I lose mpg and end up with a very sooty exhaust whereas before it would be light grey. So something is definitely making it richer and the only thing that is being altered is the amount of air bleed passed the tick over screw. I can only deduce that the air screw affects idle and WOT settings and the ECU/lambda sensor takes care of all the bits in between.
I've had miss firing problems in the past caused by a dirty lambda sensor, cleaning it immediately solved the issue.
I'm only making suggestions from my own Personal Experience (not guesses) as to what may assist in solving the OPs problem He's free to follow or dismiss them like anyone else.