Knock or not????

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gas1man

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Good day all,

Here's hoping someone has a modicum of assistance for me please.

Start Boris and the engine has this awesome quite hum and the rev's start to climb as they should on the choke.
Engine is now revving at the top of the carb cam. Blip the throttle and the engine rev's fall and he idles perfectly.
Now all of you are thinking SO? This is where the sound of knocking starts ,only after you blip the throttle.

I find it strange that this only happens after it has got to temp. I am guessing that it means something but this is
a new one on me. I am assuming that it has something to do with the fact that the oil is now warm and thinner and not quite
doing what it does when cold. It has been doing this for a long time now and is not getting louder but it needs sorting.

Engine is 1600 twin port stock AD motor. Oil used is 20w 50 classic from Halfrauds. Engine removed last winter,
work done was remove heads and clean , new valves, clean heat tubes ,carboned up, new rear main oil seal and shaft seal,
this is now leaking even worse hence winter work plan is engine out again. Only thing I did not remove were the heads and split the case.
When replacing the shims at the back and tightened up there was no end play after tightening. I have to say the knocking is not a thud or a
light ting ting. Seems to be somewhere in between.

When listening at the engine I think some times its the alternator then my mind changes :roll: :roll:
Can't quite decide what or where. Engine comes out again this winter so any help greatly appreciated.

J & P
:D :D :D
 
Have you checked the timing recently? And if so did you set it at 3000rpm? What's the advance at idle? (Reason I ask is that I had a distributor that didn't advance properly).

An easy check might be to mark the position of the distributor on the base plate, then once your up and running give it a small rotation. If the knocking goes away then it needs to be reset
 
I’m sure a video would at least give people the opportunity to comment on the noise. Can you take one?


Sent from my iPhone using Tapatalk
 
Will attempt to make one , did think of it , not very tech savy.
Will get my son to help if necessary.

J & P
 
gas1man said:
.....
When replacing the shims at the back and tightened up there was no end play after tightening.
.....

When you tightened up the flywheel, you say there is no end float? There should be. You need to set it correctly to .07mm up to .13mm using a dial guage. Too tight and you will be causing excessive wear.
 
I honestly thought that those figures were the maximum allowed!
Well will have to check when the engine comes out. Thank you for the info.

J & P
:D :D :D
 
Hey bud, do you still have the noise when the motor is good and hot ? when the carb changes on that cam, isn't an exact science temp wise. Plus when did you last change your oil, I try not to go too much past three thousand miles.

ozziedog,,,,,,,plus the big screwdriver / earphone/ careful thing
 
https://youtu.be/TqHY52bzsXo
Length 1 min 47 sec's.

This is a video recording I managed to make this evening. The video was stopped and started a number of times during the take.
The first 20 seconds are with the soothing tones , then around 23 you can hear the sound change.
Hopefully you are all able to decipher something.

Ozzie the oil is less than 1000 miles old and the amount I have to keep replacing every time
we go out it never gets old. :lol: :lol:
(Engine on the cam is quite and when hot and off cam the noise kicks in.)

Sorry it is so long. Thank you for taking the time to listen.

J & P
:D :D :D
 
I'd be checking the valve settings too as it sounds a bit like them .. Or if you suspect the alternator, run it without for a few seconds to prove.

Does sound like it wants further investigation to me tho ..

Hilly
 
This one is a little better and not as long.
All valves were replaced and tappets set and checked every 1000 miles.

https://www.youtube.com/watch?v=LLjDjCK6jKI

Thanks again.

J & P
:D :D :D
 
There is certainly a noise coming from it... You should always check end float, when you refit the flywheel. That 'play' in the crank is to allow for the expansion of the engine when it's hot, if there is no play things get tight and cause wear or worse spins a bearing. Has it got good oil pressure?
 
not quite the same noise but I had the main pulley moving very slightly on the woodruff key, that was similar noise. Does it go away when you rev it? What pulley do you have?
 
Hi Matt,
Seems to disappear when revving I think :lol: :lol:
Not quite sure. Am pulling the engine this winter and will check woodruff key whilst out.
Thanks for the help . Will post results when done.

J & P
:D :D :D
 
Hopefully its not your main bearings.

There Must be end play, it needs some slack. I'd start there, check the big nut that holds the flywheel on, the four cylindrical pegs, the running face of the flywheel, shims, seal etc. Any wear, balling of metal on the surfaces might indicate the source of the noise.

Also check the crank pulley, inner face about 3mm away from where the centre is welded to the sheet metal for a radial crack. I wouldn't worry about a tiny crack, but you'll know if its bad.

I've been through all this. Threw money at the engine shop for an exchange and the noise went away! it was the main bearing.
 
When you get around to setting the slack with the flywheel shim washers, assemble them first without oil as it's easier to measure the movement with no lub on it.
The final setting is just a distinct movement.
A dial gauge is useful and a small magnet to pull shims out without removing the seal.
 
Thanks Hub's I have all the above on order and new seals to replace the old.
Even have a dial gauge and stand on order.
Will report on findings.

J & P
:D :D :D
 
Thanks Hub's I have all the above on order and new seals to replace the old.
Even have a dial gauge and stand on order.
Will report on findings.

J & P
:D :D :D
 

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