LiteTouch
04-09-2008, 05:41 AM
Well, it all started out when I decided to move my Raptor from one side of the workshop to the other. The next thing I know all the bearings have been cleaned and relubed, a new set of blades has been balanced and a couple of servos have been replaced.
Well I just could not leave well enough alone & since the engine was out anyway I decided to take a peek inside the case.
After pulling the head and backplate off & placing the piston at TDC, I can move the piston up & down a few thousandths.
Can anyone provide me with the maximum permissable clearance between the crankpin and lower conrod bearing, and the same for the wrist pin and upper conrod bearing.
In other words, I am going to pull the piston & con rod out of the engine. I measure the size of the crank pin, measure the inside of the lower con rod bearing, do a little subtraction and come up with the clearance between the two.
At that point all I need to know is how much is too much!
.... and I would prefer to learn this before the engine lets me know in a sudden and terminal manner! (although that would be a whole lot more exciting)
this particular engine has had about four gallons of fuel run through it, so it is not a high time engine. A little mineral spirits was used to clean up the engine inside and out - when I give the crank a nice spin, there is a noticable "click" with every revolution, which is definately coming from the con rod.
The liner and piston look great, no scuffing, no scoring & a nice warm brown color - so it does not look like it has ever been run too lean. The crank ball bearing feel smooth and tight, so if there is too much clearance on the con rod bearings I asm wondering how it might have happened... and no, it has not had a case of overspeed (yet).
With the right information, I may find out that there is no problem at all.... so how much is.... too much?
Well I just could not leave well enough alone & since the engine was out anyway I decided to take a peek inside the case.
After pulling the head and backplate off & placing the piston at TDC, I can move the piston up & down a few thousandths.
Can anyone provide me with the maximum permissable clearance between the crankpin and lower conrod bearing, and the same for the wrist pin and upper conrod bearing.
In other words, I am going to pull the piston & con rod out of the engine. I measure the size of the crank pin, measure the inside of the lower con rod bearing, do a little subtraction and come up with the clearance between the two.
At that point all I need to know is how much is too much!
.... and I would prefer to learn this before the engine lets me know in a sudden and terminal manner! (although that would be a whole lot more exciting)
this particular engine has had about four gallons of fuel run through it, so it is not a high time engine. A little mineral spirits was used to clean up the engine inside and out - when I give the crank a nice spin, there is a noticable "click" with every revolution, which is definately coming from the con rod.
The liner and piston look great, no scuffing, no scoring & a nice warm brown color - so it does not look like it has ever been run too lean. The crank ball bearing feel smooth and tight, so if there is too much clearance on the con rod bearings I asm wondering how it might have happened... and no, it has not had a case of overspeed (yet).
With the right information, I may find out that there is no problem at all.... so how much is.... too much?