Black Sooty Plugs - Ignition Timing or Carb issue?

[Brucie64]

After reading numerous posts of late regarding ignition timing I thought I better check mine as my bike has a slight tendency to shudder a little when opening the throttle more than half way and the plugs seem to be very black and sooty when I check them.

I checked the ignition timing yesterday and it seems that my timing is 27.5 deg BTDC (i.e. a little less than the 5/16" or 32 deg mostly stipulated as being aroundabout correct for an A10).

Does this mean that my bike's igntion is a little more retarded than should be, and is this 5.5 deg error in timing be something that I should be correcting immediatey for fear of doing untold damage to my beloved motor?

On the fuel side....my carb is an Amal Monobloc 389/37 with a 270 main jet, some books say it should actually be a 240 main jet but I have no air filter fitted so is this extra size in jet compensation for having no air filter YES/NO?  .  The needle was also on position 3 and I have now dropped it down to position 4 to try and lean up the fuel/air mixture....This seems to have helped a bit in the running but still the plugs are sooty!

Anyone know if my issues are ignition or fuel related (or indeed all in my head!)

[Josh Cox]

Hi Brucie, in my opinion,

You need to retard your timing further, presently your spark enters the engine at 27.5 BTDC, it needs to be there at 32 BTDC.

Flame burns at a certain speed, depending on temperature and octance rating ( go to Wikipedia, it has lots of answers ),  the flame ignites the fuel BTDC so when the piston is at TDC the pressure will start to build at the correct time and product thermal expansion/push.

With the spark going in late, you will not get full power from your engine, but the fuel will still burn, usually in the exhaust pipe, or shortly thereafter ( BSA after burner ), often leaving quite a mess of carbon in your head and pipes.

[Triton Thrasher]

Hi Brucie, in my opinion,

You need to retard your timing further, presently your spark enters the engine at 27.5 BTDC, it needs to be there at 32 BTDC.

That would be advancing the timing.

[a101960]

A visit to the SRM site and a click on the TECHNICAL tab will reveal the following information.


BSA A7/A10
    
A7.  Alloy Head: 35 degrees (5/16th) (btdc)    
A10, Iron Head: 33 degrees (9/32) (btdc)
A10, Alloy Head: 35 degrees (5/16th) (btdc)

5/16th is no where near 33 degrees and this amount of advance relates to alloy head bikes. Iron heads should be set to 9/32.

[Josh Cox]

Oooops.

[royboy]

Brucie a bit basic but have you checked the choke sounds as thouge you are running rich. Just a thought.
cheers

[beezalex]

I agree.  A few degrees of timing isn't going to make you run rich.

[Brucie64]

Thanks again for all your coments, I looked at choke mechanism yesterday and it seems to be ok so decided to re-check the ignition timing again. Sure enough it still seems to be around 27-29 deg BTDC. I then bit the bullet and attempted to change it to the preferred 5/16" (32-35 deg) BTDC, off came the timing cover and this is where I hit a snag. I managed to remove the nut from the magneto gear wheel but couldn't work out how to get the actual gear off. Is there an approved foolproof method of extracting this gear in order to reset the ignition timing?

I then put everything back together again yesterday and decided to take the bike on a longer run (30 miles). Starting the bike isn't an issue as it normally starts on the first kick (without choke or retarding the ignition). The bike seemed fine on the run and I now think the pinking really doesn't feel all that bad and it's probably all in my head, however the plugs and exhausts were very sooty again when I checked them later on. I then turned my attention back to the fuel and the carb itself, does anyone think it maybe a good idea to drop the man jet down a size of two from 270 to say 260 or even 250 to try and stop the sooty plugs issue or is there anything else I could be checking on the carb?

[a101960]

Brucie,

Two things: To remove the A/R unit undo the bolt, it will then go slack after a few turns. continue to undo and it will then tighten up again continue to undo and it will release. Note it will be a sudden 'pop' when it does so. The release is not a gradual release more a definite and sudden affair. Now for the timing. 35 degrees = 5/16th advance BTDC 33 degrees will be retarded in other words it is not 35 to 33m it is 35. The 35 degree figure applies if you have an Alloy head and 32 degrees is the figure for iron heads. I recently reset my ignition timing an retarded it a bit to far and it did richen the mixture considerably. I shall be playing with it again later on today and we can compare notes as to how it all went. I have purchased a magneto timing light from Independent Ignition Supplies to ensure accurate points opening setting this time around. Do not omit to wedge the bob weights fully open otherwise your timing will be way out. Just to cheer you up it will probally take several attempts to get it spot on (the A/R unit has a tendency to creep round on the shaft as you tighten it up). good luck.
 John.

[a10sausage]

hi...what plugs are you running-i use a ngk b6hs...they are perfect for me...i did try a b7hs and they sooted and oiled up all the time....def worth a try,also make sure your air slide is not stuck and have a big fat spark!

[Brucie64]

Hi Thanks for the reply, Errrrr I am a little confused now as I don't have an "AR" unit, my magneto is a manual K2FC unit and hence I don't think I have any bob weights etc. The photos show all I have as  took the timing cover off.

[Brucie64]

Hi Thanks a10sausage for your post. I originally has BP6ES plugs in and then have recently changed to B7ES plugs.....both soot up.

[flashblack]

Hi Brucie,
 try this previous thread
http://www.a7a10.net/forum/index.php?topic=497.0


regards R

[G/F DAVE]

Hi, You need to undo the magneto retaining nut then use a proper extractor to remove pinion.The extractor required will also fit BSA singles cylinder bikes as well, dont be tempted to tap the magneto shaft as you are bound to damage something. As for your bike running rich (sooty plugs) definately a carb problem Try lowering the needle in the slide then take bike for a run if  improved you need a smaller main jet. If the problem is at pilot jet stage then start engine  and hold throttle just above tickover and adjust pilot jet screw if it is runnuing lumpy it could be the pilot jet itself not seated properly.I have seen people with bikes that screw jet into cover nut first then insert jet so it cant seal against its taper.If none of the above helps then I would totally strip carb and examine & rebuild with all standard jets/settings then work from there.

[BSA_54A10]

Sooty plugs can also be a by product of the crap that we get sold now days masquerading as petrol.
Old style plugs just can not handle it and will soot up at the slightest provication.
There are a lot of heavy fractions that simply do not burn in our engines.
I tune my engines with a colour tune so that I know every where from idle to the needle is correct but I still get sooty plugs.
the solution is to put in platiniums.

The other thing that will make the plugs soot up a lot is if the ignition is not up to scratch and is not igniting the mixture, ie missing