is my p220g in my 520 knocking?

[enticer 340 1]

ive noticed a weird noise on my toro, it sounds like a knock. but i read on the forums it might be a valve noise. would anybody know which one it is? ( im reving the engine, its not surging )

Edited November 27, 2025 by enticer 340

[Ed Kennell 44,085]

to the All I can hear is a badly surging engine.       Remove one spark plug at a time to determine if there is a problem in one of the cylinders.

[oliver2-44 11,137]

[lynnmor 8,384]

 

If you throttle up you should be able to keep the engine running on one cylinder.  See if the sound changes when you do that.  Next step would be a compression test, it might show which cylinder is the problem but it may not prove that there is a valve seat issue.  Surging is usually caused by an intake air leak or a dirty carburetor.

[ri702bill 10,960]

2 hours ago, lynnmor said:

Surging is usually caused by an intake air leak or a dirty carburetor.

Welcome!

I do not own one, but I have read enough posts describing both.

How many hours on the engine?? I ask because the dreaded loose valve seat issue seems to show up mostly in machines with a lot of hours...

[Handy Don 15,605]

3 hours ago, ri702bill said:

I ask because the dreaded loose valve seat issue seems to show up mostly in machines with a lot of hours...

and with poor cooling airflow--especially on the rear cylinder. 

[parsonsponyz 272]

[enticer 340 1]

On 11/25/2025 at 4:51 PM, Ed Kennell said:

to the All I can hear is a badly surging engine.       Remove one spark plug at a time to determine if there is a problem in one of the cylinders.

i was just reving the engine to see if it would make the noise. it doesnt surge when i leave the throttle alone

Edited November 27, 2025 by enticer 340

[enticer 340 1]

On 11/25/2025 at 7:51 PM, ri702bill said:

Welcome!

I do not own one, but I have read enough posts describing both.

How many hours on the engine?? I ask because the dreaded loose valve seat issue seems to show up mostly in machines with a lot of hours...

the engine has more then 2000 hours on it, the hour meter stoped working since the fuse blew up

Edited November 27, 2025 by enticer 340

[RED-Z06 2,700]

I hear a bit of something, either rod or piston slap.  That said...some onans make noise, ive got a B43G that rough at higher rpms but silent idle, a p218g that has a prounounced idle rattle but hums off idle..1100 and 250hrs respectively.

[kpinnc 16,514]

If you go to the trouble of sealing the manifold and cleaning the carb- it's a good time to clean the carbon on the heads and adjust your valves. If everything else is good, it might help with the noise. 

 

Onan engines that I've had always had alot of carbon on top of the pistons and clickety valves. Very few people do the 500 hours head cleaning.

 

The valve rattle is always more prevalent when increasing speed or when the governor pulls in under load. 

[Retired Wrencher 6,262]

 Enjoy the site as you can see lots of help here already.

[enticer 340 1]

On 11/27/2025 at 7:06 PM, kpinnc said:

If you go to the trouble of sealing the manifold and cleaning the carb- it's a good time to clean the carbon on the heads and adjust your valves. If everything else is good, it might help with the noise. 

 

Onan engines that I've had always had alot of carbon on top of the pistons and clickety valves. Very few people do the 500 hours head cleaning.

 

The valve rattle is always more prevalent when increasing speed or when the governor pulls in under load. 

yea i did start noticing the noise when i was pulling a snowmobile with it. i took the engine out so i will check the valves.