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Old 21st February 2011, 14:53   #1
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Default Advice sought : Black smoke and rear brake pedal problems on Classic 500

Hi All,

This is my first post on T-BHP. Being a "little" more biased towards 2 wheels than 4, I felt it is more appropriate that I seek advice on 2-wheels and then move on to 4-wheels!!!

I own a Classic 500, which I acquired 4 months back. The bike was running like a dream, until I got the first service done.

Now I notice black-smoke spewing from the exhaust, with the bike occassionally missing a few beats and some oleum blasts here and there (just like the ones from old autorickshaws).

I read similar complaints from Classic 500 owners on various forums and none had a conclusive answer. Upon enquiry at the service station, they too were not aware of the exact root-cause. Some of the explanations they provided were as below:
1. maintain more than 6 litres of petrol in the fuel tank always (sounded pretty impossible on long rides)
2. fill up only premium fuel from the Shell petrol pumps (sounds feasible only when riding within major cities, they did not even know the recommended octane number, so I am assuming that this is a guess)
3. This is common phenomenon only in Winter

They also indicated that they are getting they are getting down some engineers from Keihin to figure out if this is a problem with the ECU.

From my side I thought that the ECU was set-up to run a little richer, so I figured if there was more air let in (which I accomplished by fitting in a K&N stock replacement filter) the problem would be corrected.

But in spite of filling in 10 litres (point 1) of Shell premium unleaded fuel (point 2) and riding during hot afternoons (point 3) and with a little tweak of my own (K&N filter), the problem still persists.

Also please note that this is my 5th bull (started with an A350, moved between all versions of Thunderbird) so I assume no problems with riding style!!!

I am wondering if any of you out there have faced similar issues and have found a remedy to it.

My heart stops every time the UCE misses a beat. (considering I waited for more than 6 months and shelled out a small fortune to buy this).

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Old 21st February 2011, 17:18   #2
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Default Re: Advice sought : Black smoke and rear brake pedal problems on Classic 500


This is a problem faced by quite a few C5s in India. The lack of an O2 sensor and the presence of a lame ECU is touted as the popular reason for this.
On the advice front, I doubt the qty of fuel makes any difference. Pratikjammy, a member here, is facing a very similar problem.

This thread is a good place to look for C5 related advice.

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Old 21st February 2011, 18:47   #3
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Default Re: Advice sought : Black smoke and rear brake pedal problems on Classic 500

Improper combustion is definitely the reason for such scenario. Wondering if this could be related to fuel injectors? There are fuel injector cleaners available that can clean the fuel injectors.

And O2 sensors are usually the culprit for bad combustion.
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