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counterweight knocking? 31H777-0210-E1

#1

O

oldntired55

i have this 18hp intek, model listed above... there is some (not measured yet) play in the counterweight links to crank journals... could this play have caused a low speed knock? similar to the sound a bad rod would have made? was noticeable more at idle to low rpms, than under full power.... any ideas where i can find measurement limits?

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#2

Tiger Small Engine

Tiger Small Engine

oldntired55 said:
i have this 18hp intek, model listed above... there is some (not measured yet) play in the counterweight links to crank journals... could this play have caused a low speed knock? similar to the sound a bad rod would have made? was noticeable more at idle to low rpms, than under full power.... any ideas where i can find measurement limits?
Click to expand...
First check engine mounting bolts to be sure they are tight.


#3

O

oldntired55

Tiger Small Engine said:
First check engine mounting bolts to be sure they are tight.
Click to expand...
that was not the problem... they were tight, i have the engine on my bench torn apart... my question was, where can i find measurement specs for these links?


#4

StarTech

StarTech

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#5

O

oldntired55

StarTech said:
View attachment 69343
Click to expand...
thank you, now i can find out if this is where my knock was coming from


#6

F

Forest#2

Keep us posted. I've had same issue with couple of those single cylinder Inteks. Low speed knock that sounds like a rod.
I pulled the counterbalance from another donor engine and same symptoms. The donor engine had a bad crankshaft or I would have swapped the complete assembly.
I set the engine aside in storage for external parts. Maybe it's the crank eccentrics instead of the counter balance. (I did not mic them)
I could see some aluminum wear on the sump portion that guides the counterbalance but did not look bad. I checked the crank end play and it was at max spec of .030 and I shimmed the crank end play to .005 and still has same knock. (seemed to reduce the knock sound little bit
Engine runs really good except for the low speed knock.
It came to me as a new to me engine on a craftsman riding mower.
Do not know any previous history of the engine, but appeared to be not neglected. (clean air filter, clean oil and outside surface of engine clean, tractor and deck clean, good tires)
Bought whole rig non running for $35. Previous owner said it has a knock.
???????????????


#7

O

oldntired55

Forest#2 said:
Keep us posted. I've had same issue with couple of those single cylinder Inteks. Low speed knock that sounds like a rod.
I pulled the counterbalance from another donor engine and same symptoms. The donor engine had a bad crankshaft or I would have swapped the complete assembly.
I set the engine aside in storage for external parts. Maybe it's the crank eccentrics instead of the counter balance. (I did not mic them)
I could see some aluminum wear on the sump portion that guides the counterbalance but did not look bad. I checked the crank end play and it was at max spec of .030 and I shimmed the crank end play to .005 and still has same knock. (seemed to reduce the knock sound little bit
Engine runs really good except for the low speed knock.
It came to me as a new to me engine on a craftsman riding mower.
Do not know any previous history of the engine, but appeared to be not neglected. (clean air filter, clean oil and outside surface of engine clean, tractor and deck clean, good tires)
Bought whole rig non running for $35. Previous owner said it has a knock.
???????????????
Click to expand...
Mine is at high limit on crank eccentrics... i didnt find ANY wear on rod or journal... interesting, i may put it back together and run it. i ran this mower at high throttle for 3 mowings ( about an acre each time) never skipped a beat, ..just that annoying low speed knock.when i saw the counterweight assembly, i wondered if that was the knocking, maybe its characteristic of these engines?my block did not seem to be worn excessively, i never found discard specs on that


#8

StarTech

StarTech

They are in the service manual.
1722624058707.png


#9

F

Forest#2

oldntired55 said:
Mine is at high limit on crank eccentrics... i didnt find ANY wear on rod or journal... interesting, i may put it back together and run it. i ran this mower at high throttle for 3 mowings ( about an acre each time) never skipped a beat, ..just that annoying low speed knock.when i saw the counterweight assembly, i wondered if that was the knocking, maybe its characteristic of these engines?my block did not seem to be worn excessively, i never found discard specs on that
Click to expand...

maybe its characteristic of these engines?

No, it's not typical for these engines.
I did not do any precise measurements with mics on the one I mentioned above. I could see some wear on the sump end of the block where the counterbalance has the guide groove boss. I'm thinking I'll eventually go back into this one as a winter project. I seen some counter balance wear on the aluminum where the counter balance moves up down on the aluminum guide boss at the sump end of this vertical shaft engine and thought maybe taking the crank end play to minimum might fix but knock was still bad at low rpm. I shimmed the crankshaft by installing a .025 shim at the lower sump end of the crank. I should have shimmed at the flywheel end of the crank so as to also reduce the counterbalance clearance at the sump end but I did not want to pull the crankshaft for such. (shimming the crankshaft at the sump end increased the counterbalance mating slack at the sump end whereas shimming at the flywheel end would have reduced the counterbalance end play where I was seeing the aluminum groove wear)
I would also like to think it's a typical BRIGGs but it's not, even though I'm not a Briggs fan. I just can't operate a knocking engine, even a Briggs.


#10

O

oldntired55

StarTech said:
They are in the service manual.
View attachment 69379
Click to expand...
thank you very much!! ive been looking for a manual that covers this 31H777 intek...


#11

O

oldntired55

so, does anyone know the measurement specs on counterweight groove, and the rib it rides on??? i have .005 clearance... when i move it side to side it 'knocks'


#12

F

Forest#2

oldntired55 said:
so, does anyone know the measurement specs on counterweight groove, and the rib it rides on??? i have .005 clearance... when i move it side to side it 'knocks'
Click to expand...
I do not have any specs. I seen the same thing on my knocking briggs. (counterbalance raised groove surface weat at the sump end)
What you mention is what I also seen on my engine that I mention in post #6 and 9. I could see some wear on the counterweight raised groove on the sump. I installed a counterweight from another engine that had bad crank My engine had .030 crankshaft end play using the sump gasket. I shimmed the crankshaft at the sump end to reduce the end play to .005. It slightly changed the tone of the knock.
I'm thinking I should have shimmed the flywheel end of the crankshaft so as to reduce the counterweight clearance at the sump end at the raised groove.
I just set the engine back for maybe sometime later. I thought about just removing the counterbalance and trying the engine at low idle and see if it still knocked or maybe another sump from a salvage engine. I could also see where the counterbalance has been banging on the raised aluminum groove. I just recently had a donor engine come to me non-running so I now maybe have some donor parts to try and take two and make one or have parts to sub.
It will be few months or cooler weather before I get back into this one.
Keep us informed as the what you try?


#13

O

oldntired55

Forest#2 said:
I do not have any specs. I seen the same thing on my knocking briggs. (counterbalance raised groove surface weat at the sump end)
What you mention is what I also seen on my engine that I mention in post #6 and 9. I could see some wear on the counterweight raised groove on the sump. I installed a counterweight from another engine that had bad crank My engine had .030 crankshaft end play using the sump gasket. I shimmed the crankshaft at the sump end to reduce the end play to .005. It slightly changed the tone of the knock.
I'm thinking I should have shimmed the flywheel end of the crankshaft so as to reduce the counterweight clearance at the sump end at the raised groove.
I just set the engine back for maybe sometime later. I thought about just removing the counterbalance and trying the engine at low idle and see if it still knocked or maybe another sump from a salvage engine. I could also see where the counterbalance has been banging on the raised aluminum groove. I just recently had a donor engine come to me non-running so I now maybe have some donor parts to try and take two and make one or have parts to sub.
It will be few months or cooler weather before I get back into this one.
Keep us informed as the what you try?
Click to expand...
yesterday i was between jobs in my shop, i remembered quite a few times using a centerpunch to raise metal for a closer fit.so i put several marks on the edges of the sump. where the weight rides... the counterweight fits alot more snug on the sump. i know it will not be a permanent solution, was just trying to make it tighter. i may do the same inside the counterweight links, as they are at their size limit... so i really cant be sure where the 'knock" was... but im thinking it was the weight rattling... it was quite noticeable.. more later


#14

O

oldntired55

oldntired55 said:
yesterday i was between jobs in my shop, i remembered quite a few times using a centerpunch to raise metal for a closer fit.so i put several marks on the edges of the sump. where the weight rides... the counterweight fits alot more snug on the sump. i know it will not be a permanent solution, was just trying to make it tighter. i may do the same inside the counterweight links, as they are at their size limit... so i really cant be sure where the 'knock" was... but im thinking it was the weight rattling... it was quite noticeable.. more later
Click to expand...
another thought, i wonder, with all the yrs Briggs has been using plastic internal parts... couldn't they have designed a replaceable nylon sleeve for the counterweight??


#15

StarTech

StarTech

The unworn sump guide is .248-.250". Don't have the counter weight currently available to measure the groove.


#16

O

oldntired55

StarTech said:
The unworn sump guide is .248-.250". Don't have the counter weight currently available to measure the groove.
Click to expand...
i need to go measure the sump guide again..im thinking it was on the .248 side..


#17

A

Auto Doc's

I have seen worn electric PTO clutches produce a knock at low RPM.... if this has an electric PTO


#18

O

oldntired55

Auto Doc's said:
I have seen worn electric PTO clutches produce a knock at low RPM.... if this has an electric PTO
Click to expand...
no it does not...but tks


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