Engine knocking need help identifing

[Jalvarez]

Gerry: The loudest tapping appears to be at cylinder #2 loadest around exhaust valve

Any suggestions on how to check the vacuum advance?

 

[AApple]

Now I'm thinking coil bind on the spring(s)...is it possible that you are adjusting the rockers too tight? I might try loosening them off and see it that changes the noise any...

There are videos with the rockers removed and it still taps.

:blush: DOH! I musta mised those! Thanks! oh2:

 

[dan filipi]

Ok...before any humorous comments begin.....is it possible that the vacuum advance has come apart and is swinging wildly when he accelerates causing it to tap the case? (Now you can laugh at me!) :swoon: :smilie_happy: :cheeky:

It sure sounds like something that taps upon acceleration and it sounds light enough (metal) to not be bearings. But there has to be something light enough to make that tap consistent with piston speed.

Also, is it possible the noise could be transient meaning it is created elsewhere and traveling through the different components?

Hey, wild problems require wild ideas. This could be anything!

 

[mcgovern61]

My Boss listened to the noise and he is a vibration expert. First of all....he can not think of anything in the engine that could cause that kinda of tapping....BUT...he says that it is related to acceleration. The acceleration is exciting a frequency (the tapping sound) in something expotential to the engine RPM. :roll: :shock: (Loose translation he gave to me.......RPM increases....sound frequency changes.....someting is rattling). :cheeky: :Awe:

His question is this....what else could possibly rattle around, in front of or near the left head? Heat shield?? Radiator fins? Are the engine bolts tight on all of the heat shield mounting holes? (located directly on the top of the engine forward of the carbs, behind the radiator. Worth a shot I guess??

 

[Jalvarez]

Looked for rattling around,or near the left head. Nothing is loose the heat shield in tight Radiator is not bolted in at the bottom but it is not making any noise. The sound seems to clearly originate at Piston #2 the loudest exhaust vale.

Do you recommend I put in new springs?

 

[slabghost]

I do. Rattling can be the valve being held too loosely by weak springs. Inner spring is called a damper spring. I suppose because it has the first push from the rocker and last push to the valve in the cycle of operation.

 

[dan filipi]

Jalvarez, if you want to save some money trying to find this I have a complete set of springs I'll send you for just the small flat rate box charge, I think that's $5.50
I replaced mine during a full head rebuild even though the old measured fine.

Putting new in might be better though now that I think about it, if it still made the noise with my springs (being old) we'd still wonder.
Just an idea.

 

[mcgovern61]

Here is some audible help:

https://www.youtube.com/watch?v=JIOdS7Xb ... re=related

 

[mcgovern61]

Bad rod bearing on a Suburu Boxer engine:

https://www.youtube.com/watch?v=S1k7ZKzX ... re=related

 

[dan filipi]

Yeah J's knock is more a tick tick similar to a lifter tap.

 

[Jalvarez]

Dan: Thanks so much for the offer you are very gracious. However I agree at this point I think new will be best even though your offer is very tempting since you would save me about $100 bucks
Thanks again for the offer it was nice of you to make the offer.


Gerry it does sound similar but I don't know anymore................ https://youtu.be/S1k7ZKzXbqM

I am thinking now to give new springs a shot. If it continues my nightmare take the engine out

 

[scdmarx]

If you have the springs off, make sure the valves open, close, and rotate smoothly. I found a burr on the stem of one of the #2 valves causing some hang up. Might not be getting stuck, but causing enough drag to make the valve close a little late, resulting in excessive clearance when running.

Just a thought.

 

[joedrum]

wow i finaly got to listen to it ,,,,it seems top end for sure ....its diffinitly hanging valve on that side ...more than one ...i suspect the guides and valves are not sliding well and at rpm just ....i not sure how thoral the head job was but its not good enough ....either the valves are bad or guides or the y need mated better.....im thinking both these heads you are useing are top end failure heads and parts ....

it seems you have at least two valvs causing the problems ...if it were me id realy go after that head .

you said you had the head milled ....all i know is that the thrickness of the head gaskit if not inbetween the head and block with head on and the oldwing motors will hit the pistons at there highest lift ...so it dosent take much of a hang to get the piston to hit valve knocking right to the cam ...and with the head milled its even closer ....there a guy on another forum who milled 1000 heads to go on a 1200 and i think its cause a stopage on the project ....so to me you got two factors working against you milled head and a couple hanging valves

 

[dan filipi]

Good catch there Joe about milling the head possibly causing this but I think it was making this noise before the head work. J?

 

[esker]

I remember jalvarez saying he had the noise after replacing the belts and syncing the carbs. He then tried to see if the noise went away by repacing the head with a spare one he had. How much space is the between a piston at TDC and a valve that is fully open?

 

[mcgovern61]

I seem to remember him saying that he had the bike running and the problem developed while riding....then changed the head...still had the tapping and even with the valves closed and rockers off...it still taps. Unless all of the valves are in incorrectly and hanging, I cannot see how the tapping (which only sounds like one in the video) can be a valve hanging up. (Not that it can't be that...open to anything at this point)

 

[Jalvarez]

New valves were placed on the current heads and the heads were brushed not milled.

Could the valve guides be the issue?
I suppose I can check the sliding when I replace the springs. Remember knocking continued when rockers were removed. Was no heard with spark plug removed. Mechanic friend believes it must be piston pin coming loose.

 

[slabghost]

I think piston pin is highly unlikely. Almost as unlikely would be valve guides that are not loose enough to cause oil consumption. As speculated previously a valve may catch or bind a bit on the guide remaining partly open temporarily. I believe this possible. The effect would be the same as weak springs. Allowing the valve to be partly open at the moment of combustion which would slam the valve shut. I personally believe this is the source of the sound. Whether it is binding or weak springs or both.

 

[esker]

I am wondering if we are off on a tangent here since there seems to be a consensus that the problem lies with a weak spring or valve binding.
Just a recap on what was done over the past few weeks:
Problem started on a ride returning home.
Timing checked and carbs synced.
Heads was machined (brushed) and new valves installed. This is the second head on the bike with the same problem.
Cylinder walls were inspected an no scratches found on the walls.
Rechecked timing belt alignment .. was spot on.
Checked coils and new spark plugs installed.
Compression checked 150 lbs on all four cylinders.
Ran the engine at low idle .. No knock at low idle
Swapped plug wires.
Checked exhaust for loose baffles.
Removed exh and int rockers from piston #2 Spark plug is in and plug wire is on. knock is still present I take it that valves and springs are not moving.
Same as above except that the plug wire was removed. The knock was reported to be gone but in Post #60 Jalvarez reported that he could hear the knock.
Once again I take it that the valve springs and valves are not moving on piston #2
Rockers back on cylinder #2 and plug . No Rockers on cylinder #4 and no spark plug. No knocking heard
Same as above and spark plug and plug wire back on. Knocking is heard
Swapped cam with old head . knocking is heard
Swapped valve springs between cyl #2 and cylinder #4 . noise could not be heard at idle but can be heard when rpms are increased.

I think I got it all. Let me know if I missed something. But from all that work that Jalvarez did, I somehow do not feel that the problem is related to the left head or its valves or springs. To me it appears that the effect of combustion in cylinder #2 is needed to produce the knocking sound. With the rockers removed from cylinder # 2 and the plug in, there is no valve or spring movement, only that of the piston being forced down by the combustion forces and there was knocking heard. With the cylinder #2 rockers out and the spark plug wire off... there was no knocking even at higher rpms.
Is this all pointing to lower engine problems??

 

[joedrum]

seems so ...but the racthety sound dosnt sound like it though ...it is strange....i cant realy come up with anything myself on what it is ....iwill agree that there sould have been some kind of sign that the piston was hitting the valves...even if lightly it sould have been visable....theres no doutb that this is a noise ive never heard before ...