counterweight knocking? 31H777-0210-E1

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oldntired55

Well-Known Member
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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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.
 
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.
???????????????
 
Last edited:
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
 
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.
 
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