Author Topic: Rattle when throttle backed off  (Read 977 times)

Offline redbeeza

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Rattle when throttle backed off
« on: 10.09. 2012 19:10 »
Hi Chaps,

Haven't posted for a while but I do drop in regularly for a read.  Have been riding the SR out here in France (Burgundy) a fair bit and enjoying it.  Haven't come across any other Brit bike riders yet.

Bike has been going well and I finally cured the pinking problem with repeated attempts at getting the timing right.  I have a question about an engine sound (a rattle rather than a knock or a rumble) that is pretty pronounced as I back off the throttle slightly, especially if I've been excelerating fairly hard and then just shut the throttle down a touch.  This being my first Brit bike I don't know how stuff like piston slap sounds.

The engine was rebuilt with new valves, guides, rings, timing side bush etc.  The barrels are on 80thou overbore and the chap who rebuilt the engine checked the bores and said that they should be ok with just a set of new rings.  He also said the little end bearings were ok but did renew the big ends.

I think it is likely to be wear in the bores or the little ends but I don't know.  The engine has good power and doesn't smoke or use oil.  I would just like to know if anyone can say if the bike should be ok to keep riding.  I don't want to cause a major blow-up by riding it around if a I shouldn't be.

Best wishes and thanks,

Terry
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1962 A10 Super Rocket.  First Brit bike, first rebuild.

Offline Flatboy 1950

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Re: Rattle when throttle backed off
« Reply #1 on: 10.09. 2012 20:12 »
Slightly loose primary chain can sometimes cause this rattle when you tap off.

Flatboy.
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Online orabanda

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Re: Rattle when throttle backed off
« Reply #2 on: 11.09. 2012 13:27 »
Petrol tank able to vibrate? (bit loose on the rubbers, top bolt loose)?
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Offline BSA_54A10

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Re: Rattle when throttle backed off
« Reply #3 on: 12.09. 2012 09:54 »
And don't rule out the dynamo chain.
Did you pack the cavity with liquid grease ?
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Trevor