crackling noise from engine
- Thread starter gwallen
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gwallen said:
For those intent on using "numbers from the book" to tune the engine, remember the timing scale is a stamped aluminum sheet metal bit attached to the outer primary cover, two bolt joints away from the engine case. MASS PRODUCED. Variation happens.
After re-assembling my engine, I put the timing on the mark to start & test ride, but pokey throttle response and dull thudding exhaust note (as noticed by a seasoned veteran).
I suggest that when obvious signs of improper timing exist, you should follow them.
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pierodn said:
I think terminology is getting a bit screwed up here. Think of ignition timing as advancing the point of ignition into the rising piston of the compression stroke.
For a conventional Commando points ignition and Automatic Advance Unit (AAU), crankshaft ignition is specified and set fully advanced. I recall the AAU is fully advanced at around 3,000 rpm so that is where you strobe to set and observe the 28 degrees BTDC. At idle the ignition is probably around 2 degrees BTDC.
A Boyer a employs an electronic determined advance curve which is asymptotic which means that it continues to advance towards infinite RPM but from a practical sense it is more or less fully advanced at 5000 rpm. Opinions and results vary as to the ideal ignition timing for a Boyer but for this discussion we will use the Boyer recommendation of 31 degrees BTDC.
Dyno Dave does an excellent job of illustrating example curves in the following link:
http://atlanticgreen.com/boyerexposed.htm
Keep in mind that he is working is distributor degrees and distributor RPM. One needs to double both values to convert to crankshaft indicated degrees and RPM.
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your timing is correct at 31 degrees following your Boyer instructions fully advanced strobed at 5000rpm, so leave it for now
this is assuming you are using an old Boyer, not a newer digital one, which one are you using?
you don't say what year Commando you have but on a standard 8.5/1 compression non Combat motor you do not need to use "high test" gasoline, so don't
but take those plugs out and put in correct ones, like NGK BP7ES - why would you have put those hot plugs in there anyway, who told you to do that?
this is assuming you are using an old Boyer, not a newer digital one, which one are you using?
you don't say what year Commando you have but on a standard 8.5/1 compression non Combat motor you do not need to use "high test" gasoline, so don't
but take those plugs out and put in correct ones, like NGK BP7ES - why would you have put those hot plugs in there anyway, who told you to do that?
Am using an old boyer. Purchused 2 years ago. My commando is a 1971. I have installed a new set of NGKBP7ES as was advised earlier on this site. The reason I started using the Autolite 63's is because they were listed as a crossover from the champion N7Y. Has been raining here in new york so maybe tommorow will have a chance to take a spin. Thanks for the advice everyone.
ashman
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Not all cross overs from diffrent brand of plugs with the same rating as the N7Ys are the same heat range, many years ago I changed diffrent plugs when Champion plugs had a few problems back in the late 70s and using cross reference from plug book, but found my Norton for some unknown reason ran better with the Champion N7Ys, lucky it was a bad batch of plugs at the time to this day I still run the N7Ys and get very long life out of them without any problems and now after running a Joe Hunt maggie my plugs seem to last forever, after 7 years with the J/H maggie with new plugs at the time the same plugs are still in it with 30,000 miles on them.
Ashley
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