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Help! Noise in my engine

#1

B

Bange

I recently bought a used Murray 18.5 (B&S 31P777), and I believe it's hitting connecting rod or clearance in the crankshaft housing... i have can check without opening?
Tks.


#2

M

mechanic mark

Engine cold remove rocker covers & check valve clearance. Post complete model xxxxxx, type xxxx, trim xx, & code xxxxxx.

Results

www.briggsandstratton.com www.briggsandstratton.com

Results

www.briggsandstratton.com www.briggsandstratton.com


#3

B

Bange

The machine was stopped, with the starter burned ... I have already recovered and it is operational ... certainly there is a slight malfunction in the valves, but I am still not sure of the right checking / adjustment moments. There are videos showing TDC verification and another 1/4 inch further on the exhaust. what is the right moment?
Model 31P777
Type 0602B1
Code 100209ZD


#4

B

Bange

Well, I found this video excellent, well prepared and referenced to the Briggs manual ... now I have no doubt.
In my case, before the adjustment, it was:
Input + - 0.13 mm (+ - 0.0005 inches)
Output + - 0.20 mm (+ - 0.0008 inches)
After adjustment:
Input 0.010 mm (0.0004 inches)
Output 0.015 mm (0.0006 inches)
Note: I don't have an inch gauge

The head part was a little quieter, but the initial noise continues ... is it just opening and measuring or is there another method of evaluation?


#5

Scrubcadet10

Scrubcadet10

go to the part store and buy some feeler gauges.


#6

B

Bange

I have, but only in millimeters ...


#7

S

slomo

Lot of people set the wrong valve ON the wrong valve. They mistake intake for exhaust. Confirm what valve you are on. The video seems proper.

His video description is alarming. He said at 0.004" it was tight but okay. To me tight is not in spec for clearance.

Lastly with the feeler gauge, all you need is a SLIGHT DRAG. Like pulling a sheet of paper out of a closed book.

slomo


#8

S

slomo

Back to your original problem, post up a video of your engine running.

slomo


#9

B

Bange

slomo said:
Lot of people set the wrong valve ON the wrong valve. They mistake intake for exhaust. Confirm what valve you are on. The video seems proper.

His video description is alarming. He said at 0.004" it was tight but okay. To me tight is not in spec for clearance.

Lastly with the feeler gauge, all you need is a SLIGHT DRAG. Like pulling a sheet of paper out of a closed book.

slomo
Click to expand...

I'm not sure what he said, because I don't speak and hardly understand English (I use the Google translator), but it is possible that with a gap he refers to the lower or tight value ... I always prefer a central point, because it corrects previous positioning errors. I have a good knowledge of 4-stroke automotive engines, but this single cylinder is the first one I got and without precise technical information, unfortunately ... Please, if you don't understand something, ask me ok? ... Google is not exact ...


#10

B

Bange

My engine...
Where I pointed out is that the noise occurs


#11

R

Ranamow

Bange said:
My engine...
Where I pointed out is that the noise occurs
Click to expand...
Make sure the engine mounting bolts are tight. I had a guy come by thinking his engine was about to blow up. It ended up being loose engine bolts.


#12

Scrubcadet10

Scrubcadet10

really sounds like the valves clattering, to me.
I've always adjusted valves with this method:
Exhaust valve OPEN (exhaust rocker down) ADJUST the INTAKE.
Intake valve open (intake rocker down)adjust EXHAUST valve.'


#13

B

Bange

Ranamow​

Screws that close the engine or those that secure the engine to the chassis?

Scrubcadet10
Allow me to disagree ... I don't see how a subtle mismatch in valves can cause noise in the crankshaft or connecting rod ... the same happens in cars ... When I speak of subtle noise, it is because it will always occur ... less when the adjustment is correct and a lot when out of tolerance. Valve noise is a frequent tic tic tic and on crankshaft or connecting rod, it is a heavy tuc tuc tuc less frequently ... do you understand what I mean? It's an analogy I make to ordinary cars, I could be wrong ...
The method you describe is correct, but generic ... there are design specifications that must be observed for the best performance, such as the difference of 1/4 inch in the exhaust.


#14

Scrubcadet10

Scrubcadet10

I believe ranamow is referring to the bolts that hold the engine to the frame.
if it is in fact the connecting rod knocking due to excess clearance , not much you can do.
On occasion i have seen the counterweight make a knocking noise. since he link arms are attached to the crank. however it appears there aren't any bearings used on the crank journal for the counterweight.


#15

B

Bange

I understood...
In fact, I didn't see any bearings with balls, cylinders or bronzine, and if there is excessive play, both parts are exchanged.
I saw a guy (video) assembling one of these and an axial clearance appeared, I will see if it is my case ... in any case, to resolve it has to open and this is my problem, because here there are not thousands of units and dozens of stores like in USA, so the price is high ... there is no mystery to do. My question is whether there would be any procedure that could help in an evaluation ... Well, I'm going to see the screws that hold the machine and shoot something I noticed, but I don't know if it helps ... I'll be back soon ...


#16

B

Bellcrank

Think'n a rod knock would change with engine rpm increase / decrease.


#17

B

Bange

Well, in practice this happens, but when recording with increased RPM, the noise of the discharge increases (mufler), suppresses the TUC TUC TUC ... and it is not very clear.
In the video I forced a low RPM in order to make the TUC TUC TUC clearer ... did you notice?


#18

B

Bange

Here I removed the spark plug and moved the flywheel ... turn up the sound to hear ....


Before anyone asks, the tape on the grid marks the TDC.
I never had contact with an similar engine in order to compare this noise...

As for the screws that hold the engine, they are like rock.
As for the axial clearance in the crankshaft, there is a little bit ... but it is not the cause of the problem


#19

Scrubcadet10

Scrubcadet10

Now what i would do is,
With the everything just like it is in the video, stick a pencil or wood dowel/screwdriver in the plug hole, see if there is any delay in movement of the piston relative to the movement of the crank.


#20

B

Bange

I agree with the idea, but a millimeter gap that in practice results in a noise, I don't think it's noticed ... but I'll try ...
The ideal would be to hold the piston by the head and pull and push (impossible ...), even so I do not know if very small clearances would be perceived.
Wait for me...


#21

B

Bellcrank

Bange said:
Well, in practice this happens, but when recording with increased RPM, the noise of the discharge increases (mufler), suppresses the TUC TUC TUC ... and it is not very clear.
In the video I forced a low RPM in order to make the TUC TUC TUC clearer ... did you notice?
Click to expand...
Thanks , I did hear.Go to the source with a long dowel or ready rod etc. between the engine case and your ear to check noise/engine rpm relationship.


#22

B

Bange

It is my friend, impossible to notice any difference ... by this procedure I would not condemn the gap between the crankshaft and the connecting rod foot (crankpin journal).
But the slack can come from the two other points (mag journal or PTO journal).


#23

B

Bange

Bellcrank said:
Thanks , I did hear.Go to the source with a long dowel or ready rod etc. between the engine case and your ear to check noise/engine rpm relationship.
Click to expand...
Let me see if I understand ... do you mean by a big screwdriver with the cable in the ear and the crack in the motor housing (like a stethoscope)? We do this procedure here to detect bearing snoring on car wheels, bearing alternators, air conditioning compressor ... is that it?
1617230343941.png


#24

S

slomo

You can use a piece of rebar, long socket extension, piece of copper pipe and so on.

slomo


#25

B

Bange

That's what I imagined ... here we always use a long screwdriver ... I'll do it tomorrow morning and post my impressions, but because I don't know a perfect machine, I don't know if it will help.


#26

B

Bellcrank

Here is an idea. Check oil before using mower and use these.

Attachments





#27

B

Bange

:ROFLMAO::ROFLMAO::ROFLMAO:... good idea...


#28

B

Bange

Well, I did the test of auscultating the engine ... not conclusive in the sense of defining the clearance point, regardless of where I place the screwdriver.
One thing that I clearly noticed is that the "tuc tuc tuc" does not increase in intensity with the increase in RPM, on the contrary, it even decreases.
I measured the idle RPM and it is + -1700 (is this normal?) The options are running out and before I open my engine, I still have to hear another one in good condition for a comparison.


#29

B

Bellcrank

Bange said:
Well, I did the test of auscultating the engine ... not conclusive in the sense of defining the clearance point, regardless of where I place the screwdriver.
One thing that I clearly noticed is that the "tuc tuc tuc" does not increase in intensity with the increase in RPM, on the contrary, it even decreases.
I measured the idle RPM and it is + -1700 (is this normal?) The options are running out and before I open my engine, I still have to hear another one in good condition for a comparison.
Click to expand...


#30

S

slomo

Bange said:
Well, I did the test of auscultating the engine ... not conclusive in the sense of defining the clearance point, regardless of where I place the screwdriver.
One thing that I clearly noticed is that the "tuc tuc tuc" does not increase in intensity with the increase in RPM, on the contrary, it even decreases.
I measured the idle RPM and it is + -1700 (is this normal?) The options are running out and before I open my engine, I still have to hear another one in good condition for a comparison.
Click to expand...
I've read around 1850rpm is low idle speed.

Not good to idle these air cooled engines like a Harley Davidson at 400rpm. You want a full 3200 to 3600 revs for normal ops. Somthing about lack of lube at low revs. Check your manual for proper rev settings.

slomo


#31

B

Bellcrank

When we suspect internal damage we would inspect the oil and oil filter for flakes of worn parts. Looks like metal flake paint . I have used a briggs 18.5 model number 31h-777-0202-e1 for five years. Sounded like a rod knock when I bought it. Use it a lot and pull regular maintenance . Still run's and sounds like a rod knocking. Use regular 30w oil and briggs oil filters for warm weather work. I suspect the knock has something to do with the briggs counter balance set up , but have no proof of that.
We all must sit at the banquet table and fest on the consequences of our decisions. Jim Caldwell, ex-Detroit Lion head coach.


#32

B

Bange

slomo
I found the information in the Engine Repair Manual, it speaks at 1750 RPM ... it's not far from mine ... I'm going to make an adjustment starting from scratch.

Bellcrank
It is a good idea to observe the presence of flakes ... in my car I see it in the magnetic crankcase screw ... In my B&S, the existing filter is not a Briggs, it is a filter for some French car and to be analyzed it must be destroyed / opened. I have had this engine for just over 2 months and it has not even been used, that is, I have no history ... the filter and oil (which is clear), may have been changed 4 or 5 months ago.


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