Author Topic: carbon deposits - seems excessive after 1200 miles  (Read 833 times)

Offline Slide

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Folks
I guess we all like pictures, and especially pictures of the insides of engines - see attached.

Anyone like to comment on the amount of carbon in my A7SS after only about 1200 miles from a rebuild. OK so I guess it is running too rich but I was surprised to see the gritty chunks of carbon? Same appearance on both cylinders. No sign of any wet oil so I'm assuming it is from richness of the mixture rather than from leaky guides or rings. Interested in comments as to what 'normal' looks like, or comments on what the the difference would be between carbon from a rich mixture versus carbon from oil geting into the cyclinder...

Wondering if a few tweaks of the carb such as main jet or needle position will rectify it..

cheers

Lambretta LD150 1956 ~6 hp
A7 SS 1958 ~30 hp
Ducati 996 2001 ~ 128 hp

Online Triton Thrasher

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Re: carbon deposits - seems excessive after 1200 miles
« Reply #1 on: 02.02. 2014 17:59 »
Why did you take the head off?

Offline Slide

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Re: carbon deposits - seems excessive after 1200 miles
« Reply #2 on: 02.02. 2014 18:15 »
I took the head off as the top end has been a bit rattly when hot and I was suspecting a loose valve guide, also a while back the nipple had fallen off of the air cable in the carb and gone into the engine, so it was a chance to check for any damage. But all looks ok after a quick assessment, aside from the blackness..
Lambretta LD150 1956 ~6 hp
A7 SS 1958 ~30 hp
Ducati 996 2001 ~ 128 hp

Online bsa-bill

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Re: carbon deposits - seems excessive after 1200 miles
« Reply #3 on: 02.02. 2014 18:22 »
Well dry black would not concern me so much it is after all a combustion process so soot is to be produced, if it's wet oily black that's a different matter and point's to oil being present
All the best - Bill
1961 Flash - stock, reliable, steady, fantastic for shopping
1959 Rocket Gold Flash - blinged and tarted up  would have seizure if taken to  Tesco

Online Triton Thrasher

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Re: carbon deposits - seems excessive after 1200 miles
« Reply #4 on: 02.02. 2014 19:16 »
That scene in the combustion chamber might suggest richness, but how the bike was running is more important.

Is it safe to assume you have not followed the Amal tuning procedure?

Offline terryg

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Re: carbon deposits - seems excessive after 1200 miles
« Reply #5 on: 03.02. 2014 08:11 »
What fuel were you running on?  I've noticed much cleaner, less sooty running on 'super unleaded' (around 97-98 RON) with one of mine.
Terry
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Online muskrat

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Re: carbon deposits - seems excessive after 1200 miles
« Reply #6 on: 03.02. 2014 08:25 »
Looks to me like your adding a valve saver type additive. Also see evidence of pinging.
Cheers
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, 88 FXST .
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Offline Slide

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Re: carbon deposits - seems excessive after 1200 miles
« Reply #7 on: 03.02. 2014 21:58 »
thanks for all the comments - yes I have been adding castrol valvemaster or whatever it is called. It has original valve seats so I thought it might be a good move, perhaps not! The super unleaded I guess is a good idea. Regarding the carb set-up I did go through the Amal procedure, although lost patience a bit after several changes and not being totally sure if it was getting better or worse. Installed a new throttle slide as well although needed quite a bit of rubbing down to get it to fit which could mean the carb body is a bit out of shape. The other thing is it has boyer electronic ignition and without any timing marks to go by for a strobe gun, I did the timing by feel as it were. With so many variables I guess it could easily be off somewhere. Having said all that it was running quite well. I guess not too much to worry about except perhaps some tweaks when I clean it up and get it back together. I guess checking the colour of the plugs might help, come to think of it I have a colour tune gizzmo in the shed somewhere which could be worth a try. Again thanks for the comments, seems to be some concensus that it is sootier than it should be.
Lambretta LD150 1956 ~6 hp
A7 SS 1958 ~30 hp
Ducati 996 2001 ~ 128 hp