engine knocking

[scubadog]

I have twin 200's 1987. My port engine has recently started knocking quite a bit. I have not notice any preformace effects yet. The engine has never been without oil to my knowledge. Is there anything I can do, add to oil to see if I can correct knocking? Do not want to rebuild at this time. Look forward to your help. Thanks.

[axolotl98]

NO.
Address the knocking immediately, or else you will get a big hole in one of your pistons and a bigger in your pocket.
I would suggest to dismantle, thoroughly clean and rebuild your carbs to Yam specs. Also replace the fuel pump or its membranes.
Try also to check engine operating temps, just in case you have a partially stuck thermostat or a blockage of water flow, which could lead to increased temps
The whole issue should be fuel or temp related and this cleaning an replacing act should rectify it.

[scubadog]

You do not think this could be oil related?

[99yam40]

Lack of oil usually gets the bearings, crank, and wrist pins first.
Lean fuel air mix usually get a piston first.

Anyway you look at it you should not be running a motor with a problem, as it will just get worse. Find out what is wrong with it

[scubadog]

My mechanic is telling me it is one of the cylinders based on the compression readings he took at the beginning of the season and the way it sounds. Tells me the only way to fix is to replace power head, not worth just reworking the damaged cylinder. His fall back is always your engines are old and you need new ones. If the cylinder is bad what more damage can running the engine until it fails completely do? I rather limp through the season and look at the repair in the winter months.

[Tucker]

Get another opinion or do a comression check yourself.

[shallowmindedguy]

Compression is everything

If you have low compression in a cylinder that is where I would start.
You can purchase a compression tester for less than $30 and will take about 20 minutes.

Most importantly compression should be equal in all cylinder +-/ 5 lbs.

If you have a low cylinder something caused it. Typically a carb problem.

Only solution is a rebuild and I would look for a quality repair shop.

I have had great performance and reliability out of a good rebuild over decades.