Forum

[zonggong]

Hi everyone ... I'm wondering if you have any advice or comments on my problem. My bike is 2 months old and has done about 1000 km (600 miles). It is a Bullet 500 with EFI and has been running on 95 octane fuel. After a few hundred kilometres , and before the first service, I pulled the spark plug because the exhaust smelled quite rich. The plug (original Bosch WR7 DDC4 with two earth points) was heavily fouled with carbon. I cleaned it up and ran for another few hundred kilometres then took it to service where the dealer adjusted the large brass screw on the throttle body. As far as I know from the service book this screw is only for the idle speed and has nothing to do with air/fuel ratio. It ran OK for another couple of hundred kilometres until I got misfiring at over 80 km/hr (50 mph). The plug was fouled and I cleaned it again and took it back to service. The dealer again altered the brass screw on the top of the throttle body on advice from the importer. Afterwards it ran OK. About the same time, after reading some advice on internet forums, I changed the plug to an NGK BPR6EIX iridium. It idled and ran well for a couple of hundred kilometres and then I decided to pull the plug to see if there was any difference. The plug was again fouled with carbon but less so in the vicinity of the electrode tip. The carbon fouling is more than I have seen on any spark plugs in the past 40 years or so .... even on 2 strokes. The carbon seems to be relatively soft and brushes off easily.

Is it possible that one of the engine sensors could be providing inaccurate data to the ECU to cause this. The malfunction indicator light goes out on startup.

It seems to me I have about 4 options.

1. Put up with it
2. Try and have the dealer do more than just adjusting the idling speed screw. It is difficult to get the dealer to understand the problem unless I have the bike limping in there with a fouled spark plug.
3. Fit a Power Commander
4. Do away with the EFI and fit a Hitchcock's retrofit carburettor. Actually this is a less expensive option than the Power Commander

I guess I should try and persevere with the dealer for the time being but in the longer term I'm tending to favour the carburettor option.

Any thoughts would be appreciated.

Thanks for your help

[Gwilly]

What about trying a couple of tankfuls of higher octane fuel, Shell Vpower for example.

Also stop puttering around at 35mph and give the motor some hills to work on..

Don't mean prolonged motor way at steady throttle but up and down A roads with gear changes, keep the motor spinning and don't lug it..

Try this before technical changes and come back at 1500 miles and tell us..

Also check your nuts for tightness..

[Rattlebattle]

Hi Zonggong. Welcome to the club. The symptoms you have described apply to my 2015 C5 exactly. Forget the iridium plug; it won't help and will foul even more quickly. NGK BPR 6ES is the one, but that won't solve the problem you have. Neither will an O2 sensor eliminator. The big brass screw only sets idle speed and the throttle stop screw should not be meddled with; it is factory set. I don't believe that a PCV is the answer either. If I were you I'd fit the carb kit now that it uses the standard generator and is cheaper than the PCV. Hopefully mine will arrive today. Maybe then I won't be paying to keep NGK employees in lives of luxury.....
You could try checking that the air filter has an air tight seal. Contrary to what many believe an air leak on the inlet side causes richness on an EFI bike because the ECU compensates by chucking in more fuel. I think the problem is the open loop idle control is too crude and causes rich running. The electrodes on my plugs are ok ish but the plug bodies get really sooty. Bin the EFI and fit a carb I say.

[Wayne]

Check that your cold start cable has some free play in it - you should be able to feel a little when the lever is closed - if you dont - it may be too short and holding the air way open a little to the cold start circuit. This will give you a rich mixture.

[jefrs]

I also had problems with the stock plug and the iridium. Imo the stock Bosch-India is poor quality and the iridium is like Marmite. Plug fouling and sooting up can be down to the work you ask from the motor and the plug's self cleaning temperature; if you race an engine you want a cold plug ('cos the motor gets hot enough to clean it), if you potter around you need a hotter one. The 'heat' of a plug it actually down to how much heat its electrode can conduct away, how hot it will burns. I resorted to using a BPR5ES which is like half a step hotter than the 6 to burn carbon off. Same EFI motor.



The idle does run rich so don't let the bike sit idling for too long.



The brass screw is the idle and the throttle body can be rotated for access; 1050rpm or thereabouts.



Having sooted up, I ran a good double dose of RedEx through the tank twice which cleared away the soft fluffy soot nicely.

[Thack]

Wayne writes: "Check that your cold start cable has some free play in it - you should be able to feel a little when the lever is closed - if you dont - it may be too short and holding the air way open a little to the cold start circuit. This will give you a rich mixture."



Wayne, that isn't correct. This has been discussed extensively in the forum, as you will find if you search around.



The lever-operated cold start circuit, as you call it (the bi-starter as RE call it) does NOT cause any enrichment. It simply raises the idle speed. Fuel injection systems don't need the rider to tell them when to enrich the mixture because they've got a temperature sensor to tell them exactly how much enrichment is needed. You will find yours on the back of the barrel.

[Thack]

Rattlebattle writes: " I think the problem is the open loop idle control is too crude and causes rich running."



The idle on our Bullets is CLOSED loop. It deliberately aims for a rich mixture, though, by setting the O2 sensor set point to around 0.94V.



In fact the OPEN loop idle - which you can force by disconnecting the O2 sensor - is excellent. No gradual hunting up and down (a side effect of the closed loop control), no stopping at traffic lights. I'm probably going to switch mine to open loop running whenever it's idling.

[Thack]

zonggong: It is essential that you persevere with the standard setup until you warranty has run out. Fitting a PC-V or a carb conversion kit will make conversations with your dealer re. warranty claims MUCH more difficult.



A few hundred miles after purchase my Bullet had a "fit" of misfiring and bad running. Despite having studied the FI system at length I didn't have enough time to chase down the fault properly. Fitting a new BPR6ES (the only plug you should consider using) I got a temporary cure. Strangely, after a few tens of miles the fault disappeared and it has run perfectly ever since.



So, fit an NGK BPR6ES now, and keep riding it. Forget about looking at its colour (this is NOT a reliable indication of mixture, it's a reliable indication of plug temperature, and running-in type driving often leaves the plug rather cool, and thus black). Forget about sniffing the exhaust. Just ride and ride and ride it.



The brass screw you refer to has no effect on the mixture - it is solely an idle speed control. If you think the bike is idling too slowly you can unscrew it a bit.



Something weird happens with our bikes, and countless owners have reported it. As you exceed a thousand miles or so the bike starts to run very much better, and I'm convinced you will find the same. Nobody knows why (although that won't stop a few people telling you anyway!)



I repeat: do not mess with the bike until it is thoroughly run in, because the way it's running now is NOT how it will run in another 600 miles. Only think about PC-Vs and carburettors AFTER the bike is run in, if you are still unhappy with it.

[jefrs]

The Lambda O2 provides closed loop except during warm up for about 90 seconds and most probably down the 0% and 2% throttle (idle) columns where it is obliged to run in open loop. Running open loop at idle is fairly normal due to low air flow producing 'false' data from the narrow-band O2 sensor. By using my PCV and the add-on Autotune AT-200 Bosch wide-band O2 sensor I can see the air:fuel ratio in real time and the AFR at idle is all over the place as the ECU hunts in open loop but generally on the rich side to keep the engine running. I can by using the far more sensitive Bosch O2 sensor control the idle mix at idle and have found by back-calculation that the stock ECU is attempting to set an AFR of about 12.9 where 14.7 would be considered the stoichiometric value.



As far as I can work out the Bi Starter acts as a form of secondary throttle increasing air flow into the inlet but by bypassing the MAP encourages the ECU to direct the injector to enrich the fuel slightly.



After working on the bike running whilst stationary with the laptop for about 10 minutes the engine will start to overheat, and the mix goes all over the place.



A hotter plug will burn hotter and thus self-clean at a lower engine temperature than a cold plug. The CGT EFI-535 which has a very similar engine uses a slightly hotter plug as stock than the EFI-500. The Bosch-India WR7DDC4 is not a Bosch plug but originally from a company Bosch-India bought out.

[Thack]

jefrs writes: "The Lambda O2 provides closed loop except during warm up for about 90 seconds..."



Correct.



"...and most probably down the 0% and 2% throttle (idle) columns where it is obliged to run in open loop."



Actually, no, it runs closed loop at idle.



"Running open loop at idle is fairly normal..."



Yes. Interestingly, our Bullet is not normal in this regard.



"...due to low air flow producing 'false' data from the narrow-band O2 sensor."



Not really. It's because many bike engines need to run too rich for closed loop control using a narrow band sensor. Most, if not all, cars run closed loop at idle, because they can (due to tamer valve timing) and because they have to comply with a higher standard for emission control.



"I can see the air:fuel ratio in real time and the AFR at idle is all over the place as the ECU hunts in open loop but generally on the rich side to keep the engine running.



Actually, the hunting you describe is typical of a CLOSED loop system with substantial phase delay in the loop. This delay arises from the slow response time of the O2 sensor. ALL vehicles that run closed loop "hunt". Open loop systems maintain a steady AFR because there is nothing to cause it to change.



Our Bullet seems slightly unusual in that it uses closed loop control of the mixture even at idle, but instead of the set point for the loop being 0.45V (for a stoichiometric mixture) it is at around 0.92 - 0.95V, making the mixture richer. It still hunts, but it hunts around that higher voltage (richer mixture)



One point where we agree is that the end result is poor.