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Author Topic: Knocking, now what?  (Read 1196 times)

Hugh Conway

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Knocking, now what?
« on: February 12, 2024, 10:45:02 PM »
So, at the conclusion of the previous thread (Spun the rod bearing) I replied to keith71 with my repair update.
Without going into detail again, after about 8 hours of run-in over a few days, a loud knock suddenly appeared.
My first thought was "check the keys" They seemed OK, I spent a lot of time fitting new ones and they fit pretty well.
Pulled keys out and did a fitting check with a sharpie, nice contact along the tops of both keys.
One flywheel has a wider keyway, about .012" wider than the Gib, although the Gib fits nicely into the crank keyway. I shimmed the side of the wheel keyway on installation of the key, good fit, as far as I can tell.
I then pulled the bottom end to check the rod bearing again. Clearance was less than .003",  re torqued. Everything rotated smoothly and felt good.
Restart ..........no joy. Same loud knocking sound. If fuel is cut, the knock disappears. I would think that the problem is an improperly fitted key, but maybe not, as I have fitted them as well as I am able, and I'm sure the fitting is better than I did 12 years ago.
Maybe timing? I don't know if this would cause the problem.  The flywheel timing mark shows the correct position relative to the "creak" I did not change anything there from before the original sand damage.
Any ideas? I am out.
Assume I know nothing........that's how I am feeling this afternoon!
Cheers
Hugh
JKSON6/1  (Utterpower PMG ) Off-grid
Lister 6/1 Start-O-Matic engine......running with PMG
1963 BMW R-27 project

EdDee

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Re: Knocking, now what?
« Reply #1 on: February 12, 2024, 11:21:10 PM »
Hi Hugh,

I had similar on one occasion and it took a lot of searching which showed up in an unlikely place...

A large mud wasp nest in the mouth of the air intake was restricting airflow into the inlet manifold...

As to why it causes the knocking, I have no clue... But I could replicate it by restricting the intake by hand...

I presume your piston slap etc is within reasonable tolerances...

Enough said...

Cheers
Ed

Ps... You haven't accidentally filled up the tank with some petrol contaminated juice...?
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Hugh Conway

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Re: Knocking, now what?
« Reply #2 on: February 13, 2024, 12:17:09 AM »
Hello Ed
Have not seen you around these parts in quite a while!
Oh, I wish it was mud wasps! Same fuel as before. It sounded & ran fine for about 8 hours.
I am fairly convinced it IS a key that does not fit  but I don't seem to be able to make any difference.
The felt tipped pen looking for high spots and filing them down until I get a pretty good contact along the whole length of the top of the key.
On the suspect flywheel, the key goes in nearly all the way. One can see the end of the Gib just peeking out of the inside end of the keyway.
On the other flywheel, the key head is about 3/4" from the flywheel boss. Both keys require a light tap on a brass drift to run them in, then they quickly take up as they near the end of their travel. Both keys are take a bit of effort to draw them back about 3/8", then they come right out.
Here's  youtube link that illustrates the sound. This is from a member (carbon rod) back in 2012)
https://www.youtube.com/watch?v=mgWt2sxhUTA
Same kind of problem here. I don't have the ability (skill or equipment) to weld up and machine for a solution as he did, but I have resolved this kind of problem previously with shimming. this time, I am having no success after several tries at it.
I'm done for today, tomorrow, back at it.
Fortunately there are a few sunny days ahead, so my solar panels are filling up the batteries, and the generator is thankfully not required. I had better get it fixed before the clouds/rain start again!
Cheers
Hugh
JKSON6/1  (Utterpower PMG ) Off-grid
Lister 6/1 Start-O-Matic engine......running with PMG
1963 BMW R-27 project

dax021

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Re: Knocking, now what?
« Reply #3 on: February 13, 2024, 07:22:01 AM »
Jeepers, welcome back Ed.  Where the hell have you been?

Powdermonkey

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Re: Knocking, now what?
« Reply #4 on: February 13, 2024, 12:23:09 PM »
It could very likely be the wrist pin/piston or wrist pin/conn rod....Run that cylinder to TDC with the exhaust valve bypassed.  Rock the flywheel back and forth around TDC, and determine if you can feel/hear slack in that wrist pin.  "MIGHT" take a gentle feel....ahem. 

COULD also be fuel pump timing, versus the burn rate of your particular diesel fuel.  IIRC, cetane SLOWS the burn rate of diesel fuel.  If I'm correct, you could add some cetane to the fuel, and determine if the pump might be too far advanced....of course you could also mechanically check your timing too. 

A simple way to retard your fuel pump timing is to slacken up both anchor bolts on the pump, and add in equal amounts of "body shims" (automotive panel shims) between the fuel pump base and fuel pump.  Then...retighten those bolts.  Try about a 1/16" set of shims first. 

38ac

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Re: Knocking, now what?
« Reply #5 on: February 13, 2024, 12:39:41 PM »
Pull both gibb keys and then push them back in by hand as far as you can make them go. Then push on one flywheel rim while pulling on the other and reverse that motion. If there is any more than the slightest movent back and forth on the keys it is likely the problem, especially the one that goes in a long way before it tightens. You need some shim stock about .010" place a strip under vthe key that goes all the way in before tightening. Then tighten the key and start the engine. This usually isnt a permanent fix but will tell you if that's is the problem
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Hugh Conway

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Re: Knocking, now what?
« Reply #6 on: February 13, 2024, 10:43:48 PM »
38AC to the rescue!!!
I suspected that it was at least one key, and the same one as you thought. Yesterday, I was out of energy and ideas though.
This morning, I tried your method, and it worked! As you said, I withdrew the keys, pushed them in as far as possible and rocked the wheels in opposite directions. I did this with one key at a time. The culprit was the side opposite the injector pump. The other key was OK.
I had some some metal roof flashing in the shop, .012" thick to make a shim for the crankshaft keyway bed. Reinstalled the key with the shim and started the engine. The knock was not eliminated, but very much reduced.......on the right track!
That is the same flywheel with an over-width keyway. On the old damaged crankshaft the shaft keyway was also over-width.  I had corrected that 12 years ago with shims made of steel from a broken tape measure blade cut to the taper of the Gib key, then installed along the side of the  keyways. That worked.

This new crankshaft actually has proper width keyways on both ends, the Gibs are a very nice fit into the keyways. That left the one flywheel with a .017+" wider keyway. When I installed the suggested shim under the key in question, I also carefully cut two  shims tapered to the profile of the upper half of the key. With the crank and wheel positioned with keyways to the side, I was able to work the shims into the .017" between the upper half of the side of the key and the side of the wheel keyway. Tapped the key home and started the engine.
OH Joy! The knock is gone!!! Ran under load for an hour, and will do so again this afternoon. So far all is good.

I am now thinking that I will get a new set of keys and as a more permanent solution, try carbon-rod's solution of weld build-up at the side of a key, then machine for a proper fit. ( https://listerengine.com/smf/index.php?topic=6547.msg75154#msg75154 ) I will have to arrange a bit of work with a shop to mill this for me, but at this point, I have some time...........as long as the temporary side shimming works.
I am sure open to any other more permanent solutions.

I thought of maybe spraying the whole flywheel and shaft end with salt water and let it corrode into a solid mass...................well, maybe not.

So, at the very least, the source of the knock has been located and temporarily repaired. The previously mentioned shim repair (of 12 years ago held up nicely for all that time..
 
Thank you again Butch for keeping me on track. This is not the first time your seemingly small tips (gathered by long experience) have made a huge difference in keeping my off-grid power system operating. As well, your balancing method was easy and very effective. Wish I had known and done it 12 years ago!

Cheers
Hugh
JKSON6/1  (Utterpower PMG ) Off-grid
Lister 6/1 Start-O-Matic engine......running with PMG
1963 BMW R-27 project

38ac

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Re: Knocking, now what?
« Reply #7 on: February 14, 2024, 11:39:02 PM »
Glad it worked for you,
As for corroding the flywheel to the shaft if you can let the engine sit a while you could try relieving your bladder withbit directed in the area of the shaft, flywheel junction???😅😅
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Hugh Conway

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Re: Knocking, now what?
« Reply #8 on: February 15, 2024, 12:28:15 AM »
Ahhh Butch,

You are, as always, a fountain of valuable information!
Have you tried this method yourself?
 
Thanks again!

Cheers
Hugh
JKSON6/1  (Utterpower PMG ) Off-grid
Lister 6/1 Start-O-Matic engine......running with PMG
1963 BMW R-27 project

38ac

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Re: Knocking, now what?
« Reply #9 on: February 15, 2024, 01:44:41 AM »
Ahhh Butch,

You are, as always, a fountain of valuable information!
Have you tried this method yourself?
 
Thanks again

Cheers
Hugh

Strictly Hearsay,,,,
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ajaffa1

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Re: Knocking, now what?
« Reply #10 on: February 15, 2024, 08:05:50 AM »
No wonder these flywheels are so difficult to remove if Butch is recommending urine rather than Loctite. well done guys, Hugh is back in business!

Bob

38ac

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Re: Knocking, now what?
« Reply #11 on: February 15, 2024, 11:43:54 AM »
Bob, at one of the Amish sawmills I work part time everyone goes to one back corner to relieve themselves. The mill is sided with tin and it is rotted off about 3 foot high from people pissing there, LOL
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keith71

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Re: Knocking, now what?
« Reply #12 on: February 15, 2024, 08:21:41 PM »
Glad to hear you are up and running again.. You should be good for another 12+ years.. I know 38ac will still be around to help us out of our troubles..
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BruceM

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Re: Knocking, now what?
« Reply #13 on: February 17, 2024, 03:36:58 AM »
I just got caught up on this thread.  Wow, 38AC sure nailed it.  Bravo on your troubleshooting and persistence, Hugh. So glad it worked out.  I hope you can find a small machine shop nearby who can help with your custom key project.

For Christmas I got myself a cheap TIG torch, filled my former nitrogen bottle with argon and taught myself some beginner level scratch start TIG.  Added a new tap so I could use just 2 batteries plus the sheet metal resistor of my direct battery DC stick welding  TIG likes the lower voltage better.  Tried some silicon bronze brazing with it too- easy and quite fun.  That's what I'd use to build up the top edges of your keys, I think. 

Best Wishes,
Bruce

cujet

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Re: Knocking, now what?
« Reply #14 on: February 17, 2024, 01:24:12 PM »
I'd love to see a video of it up and running again.

These engines really are special. With basic skills, they can be kept running nearly forever. Good job on the repair!!!!
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