Tin can full of nails!

My Mk5 750 was rebuilt by the previous owner (a kiwi) with "the knowledge". It has 7000 miles since rebuilt and if you put your hands over the pipes, its quieter than a sewing machine. Barely a tick to be heard. If you have noise, you have a problem.

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From someone who has a quiet example I guess you would be worried if you heard something louder and more rattly. The valve tips are most likely, well they always are in my case. Here is mine after new exh valves and adjusters, PW3 cam with 011" clearances. Tappets can be heard loudest at 12-20 secs but its not a great vid.
http://www.youtube.com/watch?feature=pl ... HqU3SIqdHM

I have noticed that the Commando heads are very acoustic. They work very well to amplify the noises in the valve train. I adjusted my Combat to spec when I built it. Got it running and during the warm up period and re torquing, noticed an increase in the noise. Re-checked clearances, they had opened up as everything bedded in, so they were re-set to specs, and the noise went away. Now it's fairly quiet except for the power pulsed from the peashooters. I don't think it is possible to get rid of all the noises, there are too many parts whirling and clashing around in there.

There are two significant ways to improve your experience of Commando engine noise.....

Open exhausts!

Ear Plugs! someone already mentioned using them, don't use them at your peril, I wear hearing aids for a reason....which includes open exhausts....

I have the experience of riding the same Commando before and after fitting just a small handlebar fairing, it amplifies the valve train noise brilliantly! even better than the head alone, it becaomes clear enough that there is no doubt what it is.....

If everything is bolted up tight, you have good compression, you are not using oil, sound big ends (knock) and mains (rumble), well adjusted cam chain, primary chain (if used) and well adjusted tappets, it is just noise after all.

If you are not sure of the condition of these parts, mileage is unfortunatly not a good guide for an original engine, but a better one for an engine built by a competent individual less than 10 years ago! (having owned an air cooled 1200 4 cylinder bike with 160K miles on it, never having had the head off, I find the mileages quoted for Commandos quite depressing)

Unless there is a new noise, one that tends to increase in amplitude....and you don't want to fit open exhausts!....get some decent earplugs....

I have the experience of riding the same Commando before and after fitting just a small handlebar fairing, it amplifies the valve train noise brilliantly! even better than the head alone, it becaomes clear enough that there is no doubt what it is....

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Only have the half fairing and like you say it don't half amplify the noises!! One trick I tried a few years ago was wedging hard rubber bars about 5/16" dia between all the fins. I copied it from somewhere and it reduced the fin ringing until they got too hot, collapsed and fell or got blown out. Not tried it since but with the right material who knows. I think some Japanese aircooleds have them as std?

A friend of mine tore his engine apart looking for the catastrophic noise on his Italian steed. Put it back together after finding nothing obviously wrong and ran it again. Noise still there. After a little more investigative listening he did determine the culprit. His front fender stay was cracked.....

Hi,the early 750 engines vibrated and rattled a bit in a Featherbed Frame from memory, but were very quiet in a Matchless Brazed Lug frame. Different periodic frequencies. The Combat engines were thrown together ( I used to know a fitter who built them ) and with poor assembly the rocker gear wears very fast due to the pushrods are the wrong length, and the cams are soft. Sometimes the Stellite tips on the cam follers fall off, very noisy, and metal in the oil. The rocker spindles can revolve and shut off the oil as well. Drop the sump plug and check for metal in the oil. If in doubt, strip the motor and Blueprint it. Peace of mind. Use straight 50 oil, Not Synthetic. A good engine should sound like a slightl noisy sewing machine! Have you got FAG 306E-M1-c3 main bearings in it? If not put them in, a wise precaution. I hope you sort it out OK, as these bikes are for riding, you are dead longer than you think.

Like the Egyptians , i will be taking the bikes with me to ride forever in the after life, if Mummy will let me! :lol:

jagracer47 said:

Hi,the early 750 engines vibrated and rattled a bit in a Featherbed Frame from memory, but were very quiet in a Matchless Brazed Lug frame. Different periodic frequencies. The Combat engines were thrown together ( I used to know a fitter who built them ) and with poor assembly the rocker gear wears very fast due to the pushrods are the wrong length, and the cams are soft. Sometimes the Stellite tips on the cam follers fall off, very noisy, and metal in the oil. The rocker spindles can revolve and shut off the oil as well. Drop the sump plug and check for metal in the oil. If in doubt, strip the motor and Blueprint it. Peace of mind. Use straight 50 oil, Not Synthetic. A good engine should sound like a slightl noisy sewing machine! Have you got FAG 306E-M1-c3 main bearings in it? If not put them in, a wise precaution. I hope you sort it out OK, as these bikes are for riding, you are dead longer than you think.

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Now that's deep wisdom to take to heart

I hope you sort it out OK, as these bikes are for riding, you are dead longer than you think. jagracer47

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A bunch of us go though cycles of subjects that flash us back to our late resident experts that have died off after leaving some the best oil threads and flying leaps testing handling innovations.

Gerry and Mrs Bristow had done 80,000+ miles on his Mk3 Commando, original engine. And swore by Mobil 15W/50 (synthetic), and Duckhams before that.

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