posted
Rody, I would like to add to the previous post for your opinion. I am quite sure I have read your answers to all of these questions in the past, but was unable to find them in your archive. Sorry for any repetative questions.
1. What is the diameter of the crankpin when the motor is new, and at what diameter do you consider the pin worn out?
2. Would you classify a pin that is 4.72mm in exellent condition?
3. What would cause scapes on the bottom groove inside the case where the rod swings during rotation?
4. Just how much swirl scratches on the backplate do you consider normal wear and at what point to you suspect debris wear?
5. How far should you be able to push the piston up into the sleeve on what should be a motor in exellent condition?
Thank you for you time!
Posts: 4 | From: TX, USA | Registered: Jan 2003
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1) More then 4.71mm, however of the pin is not worn round I suggest to change the crankshaft anyway, even if the minimum size has not been reached yet.
2) The ID cannot be measured correctly once used, this because the hole can wear ovally and so give you the wrong measures.
3) No.
X15T,
1) 4.76mm when new and 4.71 is worn and needs to be replaced.
2) not really.
3) When an engine explodes, the metal parts come between the rod and the crankcase. However if the engine has never been broken, it is probably the conrod then which touches the crankcase, this is not good and a revision is needed.
4) This is normal and can happen that the conrod touches the backplate. However this can also be dirt which goes through the engine and causes the scratches.
5) If you can push the piston flush to the outside of the top of the liner, the idle is very bad and the piston/liner does not hold its compression then you can consider the piston/liner as used.
An engine in excellent condition is always clean, performs well, does not break any glowplugs and has a good and stable idle rpm.
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