The Problem
Alright folks, after what seemed like a never ending search to find the elusive hammering noise that suddenly appeared in my newly built 107 motor at about the 2154 mile mark, I believe I've found the problem. Let me say that I hated to have to tear into my motor again this soon, especially given the amount of money that I spent to build it, but I couldn't stand the noise any longer and was determined to figure out what was going on. I recently tore down the top end and found that the Pistons and cylinders were badly scored. I showed my friend (who has been a certified HD mechanic for over twenty years), pics of the carnage and he immediately told me that the Pistons were trashed and needed to be replaced. He also said that he was certain this was the cause of the hammering noise that I had been experiencing. I asked what could have caused this so quickly and he told me that it could have been caused by the Pistons being too tight cylinder bores, or it was the result of a dry start; meaning during the initial startup following the build, the oil hadn't fully circulated and reached the piston oil jets and the heat and friction caused damage to the Pistons and cylinders at that time. The problem then became progressively worse over time. Now, I did use generous amounts of assembly lube in all of the critical places during the build, but just not in the cylinder bores (I only rubbed them down with oil before installing the Pistons). After talking a little more with my friend, he shared with me that a method he uses to alleviate a dry start, is to pour a quart of oil in the bottom end, fill the oil tank, connect a battery charger to the battery and prime the motor by pressing the starter button for 15 seconds, fifteen times in a row (with the spark plugs out and the ignition coil disconnected), to get oil up to the top end.
The Solution
To make sure the new Pistons fit the cylinders properly this time, I will take them to my friend's cylinder boring specialist and have them checked and honed to the new Pistons. I will then make sure to prime the motor very well before startup this time around. As for the pics of the carnage, well here they are:
Alright folks, after what seemed like a never ending search to find the elusive hammering noise that suddenly appeared in my newly built 107 motor at about the 2154 mile mark, I believe I've found the problem. Let me say that I hated to have to tear into my motor again this soon, especially given the amount of money that I spent to build it, but I couldn't stand the noise any longer and was determined to figure out what was going on. I recently tore down the top end and found that the Pistons and cylinders were badly scored. I showed my friend (who has been a certified HD mechanic for over twenty years), pics of the carnage and he immediately told me that the Pistons were trashed and needed to be replaced. He also said that he was certain this was the cause of the hammering noise that I had been experiencing. I asked what could have caused this so quickly and he told me that it could have been caused by the Pistons being too tight cylinder bores, or it was the result of a dry start; meaning during the initial startup following the build, the oil hadn't fully circulated and reached the piston oil jets and the heat and friction caused damage to the Pistons and cylinders at that time. The problem then became progressively worse over time. Now, I did use generous amounts of assembly lube in all of the critical places during the build, but just not in the cylinder bores (I only rubbed them down with oil before installing the Pistons). After talking a little more with my friend, he shared with me that a method he uses to alleviate a dry start, is to pour a quart of oil in the bottom end, fill the oil tank, connect a battery charger to the battery and prime the motor by pressing the starter button for 15 seconds, fifteen times in a row (with the spark plugs out and the ignition coil disconnected), to get oil up to the top end.
The Solution
To make sure the new Pistons fit the cylinders properly this time, I will take them to my friend's cylinder boring specialist and have them checked and honed to the new Pistons. I will then make sure to prime the motor very well before startup this time around. As for the pics of the carnage, well here they are:
Attachments
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