Excessive engine noise

timmyC · Jun 10, 2018

I purchased the 750 Commando about 2 years ago and have not been able to ride it because of an oil leak. I have solved my oil leak but the engine seams to make a great deal of noise at idle. When I started it today and let it idle it sounds very different than what I am use too (Honda CB350, Kawasaki 4 cylinder). At first I thought the valve clearance was out of spec, I checked it and adjusted one exhaust valve but the noise persisted. Can anyone suggest/recommend a repair shop in the Metro Detroit area that can evaluate my problem? Your thoughts and suggestions are appreciated.

rvich · Jun 11, 2018

Is the timing chain properly adjusted? These bikes have a fairly noisy valve train.

But to answer the question, I can't recommend a shop in your area. There may be a forum member in the area that can listen to it. Or you could try recording a video on your phone and posting it here.

rivera · Jun 11, 2018

Open the primary drive case and look for loose nuts on the alternator rotor and clutch. I am about to restore a 68 fastback which sounded horrible when started.
I also firts changed the timing chains- a little better. Then we decided to have the engine overhauled. Upon tearing the engine out of the frame I noticed these two nuts were only handtight ! the clutch and rotor had an awful lot of play. The engine itself was in good shape.

SteveA · Jun 11, 2018

This motor and transmission is going to deafen you with new noises after overhead cam and 4 cylinder motors. You need to hear some more Nortons running before you judge if it is at all excessive.

baz · Jun 11, 2018

You really need to give us a bit more info
Is it knocking/ rattling/ squeaking?
Worse when you start it?
Worse up hills?
Etc etc

timmyC · Jun 11, 2018

Thanks for all the replies! I know it's very difficult to diagnose sound without well.... without sound. So I am working on getting a short video uploaded to YouTube so you can hear it run. I should be able to get that up tonight. I really love this forum, great people, great advise!

Thanks again!

peter12 · Jun 11, 2018

I will second SteveA. A different beast all together, there is a possibility it is normal so should be listened to by a current owner or specialist. Otherwise all the above can cause noises.

drones76 · Jun 11, 2018

Go on YouTube and search for Norton's. You should see plenty running and compare the sound to yours.

timmyC · Jun 11, 2018

I went to YouTube and listened to a few videos and it did make me feel better about the sounds it makes. Below is a link to the video I posted on YouTube of the engine at idle (1100 rpms ish). The bike is a 72 750 Combat with 4100 miles. Anyone willing please take a listen and let me know your thoughts. Thx!

eskasteve · Jun 11, 2018

Not sure what that is but it sure doesn't sound very good. I am listening to it on my laptop with speakers about the size of a Canadian dime so it's impossible to tell. I second rvich's idea about getting a local Norton guy to have a listen. Maybe contact your state INOA club or the Ohio folks if they're closer
Michigan Norton Owners

Dan Clark
8076 S. Seymour Rd.
Gaines, MI 48436
810-635-4969
dmjlc@hotmail.com

Northern Ohio Norton Owners

Skip Brolund
11418 Girdled Road
Concord Twp, OH, 44077
216-644-4671
sbrolund@yahoo.com

timmyC · Jun 11, 2018

Eskasteve,
Thanks for the feed back. I thought it was just to loud to be right. I will start with the Michigan group and see if there is anyone close by that I can talk with. Thx!

batrider · Jun 11, 2018

You can't really tell with amateur videos like this. I thought it sounded like mine.

rvich · Jun 11, 2018

Sounds just like mine!

RoadScholar · Jun 11, 2018

I agree with batrider about the limitations of your video, but I didn't hear anything that would cause me alarm. It sounds like mine also. I would encourage you, however, to follow your gut and get a second opinion from someone knowledgeable who can listen to it up close.

As a sidebar: I bought my first new English bike in 1970, it was delivered to my residence in late January, in New England. By early February the itch was so bad I registered it and started riding. After 15 minutes I headed to the dealership, it was making a lot of mechanical noise. The head mechanic came out, listened to the engine and said, "Come back when it stops making noise".

I hope your noise is a normal noise.

timmyC · Jun 11, 2018

I love your story! I hope it's just paranoia and FEAR (False Events Appearing Real) of the unknown not a serious problem. I am dying to put some miles on the bike. I emailed Dan at the Michigan Norton Owners group and he already responded. He suggested a shop not to far from me and a 72 Combat owner that has emailed me his contact info. When I have a diagnosis I will update the post. Thank you all for your input and help!

Bodger · Jun 11, 2018

timmyC said:
I love your story! I hope it's just paranoia and FEAR (False Events Appearing Real) of the unknown not a serious problem. I am dying to put some miles on the bike. I emailed Dan at the Michigan Norton Owners group and he already responded. He suggested a shop not to far from me and a 72 Combat owner that has emailed me his contact info. When I have a diagnosis I will update the post. Thank you all for your input and help!

My bet is your engine is fine. The tappets sound noisy, but that's probably just the way the mic on your phone picks up the sound. Have you run it long enough for it to warm up?

Steves · Jun 12, 2018

Nortons make a racket from the top end, the clicking type noise, sounds normal, it's the music made by pushrods, rockers, tappets and valves in an air cooled cylinder head. The other noise sounds like induction and mechanical. I think you are idling at about 1200 rpm, should be able to get it stable at 900.

timmyC · Jun 12, 2018

It ran for 5 mins or so at 1100 ish rpm.

oldmikew · Jun 12, 2018

sounds a bit noisy but its only tappets . Do check the clearences... 8thou inlet !0 thou exhaust on a combat . Amazed at the low mileage . btw.. extended idling
is not a good idea..

cash · Jun 12, 2018

I've heard worse.
The valve stem hard face usually dents a little over time, the feeler blade will bridge it leaving you with a larger gap than anticipated.
You can check it using a DTI or work out the number of turns of the adjuster using its TPI or pitch to set the gap.

Cash

Excessive engine noise

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