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Re: Diagnosing a lovely knocking noise

Posted: Mon Nov 15, 2021 8:45 am
by donnybach
Nice one. 👍

Re: Diagnosing a lovely knocking noise

Posted: Tue Nov 16, 2021 9:13 am
by motorang
So you did not find any loose parts or wear, and apart from gaskets the only thing you changed was the camshaft including decompression mechanism?
Piston etc still the same?

Andy

Re: Diagnosing a lovely knocking noise

Posted: Tue Nov 16, 2021 1:01 pm
by dan3
motorang wrote: Tue Nov 16, 2021 9:13 am So you did not find any loose parts or wear, and apart from gaskets the only thing you changed was the camshaft including decompression mechanism?
Piston etc still the same?

Andy
I didn't change the camshaft in the end as they all disappeared from the Internet once I started looking for one. I only changed the gaskets and set the valve clearances.
Maybe the timing was out ever so slightly? Is that possible?

Re: Diagnosing a lovely knocking noise

Posted: Tue Nov 16, 2021 2:36 pm
by motorang
Did not sound like it, really. No loose engine frame bolt?

Andy

Re: Diagnosing a lovely knocking noise

Posted: Tue Nov 16, 2021 5:36 pm
by scottieh
dan3 wrote: Tue Nov 16, 2021 1:01 pm
motorang wrote: Tue Nov 16, 2021 9:13 am So you did not find any loose parts or wear, and apart from gaskets the only thing you changed was the camshaft including decompression mechanism?
Piston etc still the same?

Andy
I didn't change the camshaft in the end as they all disappeared from the Internet once I started looking for one. I only changed the gaskets and set the valve clearances.
Maybe the timing was out ever so slightly? Is that possible?
On a number of different xt’s I have accidentally made the valve clearances be way way off when resetting them. I would rotate the engine to tdc, set the clearance, and then rotate the engine a few times only to find that my clearances were off by a mile. Somehow the original tdc wasn’t properly setting the rockers or the valves or something got off and i had to do the valves a second time to make sure the clearances were right. If not double checked before closing up the engine and running it, that gap between the rockers and valves would make the kind of knock in your video. Obviously too late to know now if that was the case since everything got taken apart and put back together but that has been my experience in the past.

Glad it’s all running smoothly for you!

Re: Diagnosing a lovely knocking noise

Posted: Tue Nov 16, 2021 6:31 pm
by donnybach
It definitely sounds like the valve to me. I’d be interested to know if that newer decompression system you had can stick open too. Just glad your sorted. Lovely motors when they’re on.
Just need a good synthetic fuel supply in the future to keep em going.

Surely the energy in space dust sherbet in the ‘70s could be harnessed? :stir:

Re: Diagnosing a lovely knocking noise

Posted: Wed Nov 17, 2021 1:03 pm
by dan3
motorang wrote: Tue Nov 16, 2021 2:36 pm Did not sound like it, really. No loose engine frame bolt?

Andy
Nope

Re: Diagnosing a lovely knocking noise

Posted: Wed Nov 17, 2021 1:04 pm
by dan3
scottieh wrote: Tue Nov 16, 2021 5:36 pm
dan3 wrote: Tue Nov 16, 2021 1:01 pm
motorang wrote: Tue Nov 16, 2021 9:13 am So you did not find any loose parts or wear, and apart from gaskets the only thing you changed was the camshaft including decompression mechanism?
Piston etc still the same?

Andy
I didn't change the camshaft in the end as they all disappeared from the Internet once I started looking for one. I only changed the gaskets and set the valve clearances.
Maybe the timing was out ever so slightly? Is that possible?
On a number of different xt’s I have accidentally made the valve clearances be way way off when resetting them. I would rotate the engine to tdc, set the clearance, and then rotate the engine a few times only to find that my clearances were off by a mile. Somehow the original tdc wasn’t properly setting the rockers or the valves or something got off and i had to do the valves a second time to make sure the clearances were right. If not double checked before closing up the engine and running it, that gap between the rockers and valves would make the kind of knock in your video. Obviously too late to know now if that was the case since everything got taken apart and put back together but that has been my experience in the past.

Glad it’s all running smoothly for you!
Cheers scottieh, I'll bear that in mind if it happens again.

Re: Diagnosing a lovely knocking noise

Posted: Wed Nov 17, 2021 1:08 pm
by dan3
donnybach wrote: Tue Nov 16, 2021 6:31 pm It definitely sounds like the valve to me. I’d be interested to know if that newer decompression system you had can stick open too. Just glad your sorted. Lovely motors when they’re on.
Just need a good synthetic fuel supply in the future to keep em going.

Surely the energy in space dust sherbet in the ‘70s could be harnessed? :stir:
I'll be drilling for my own oil if need be! Not ready to go electric yet