VMAX Powerhead rebuild

[m21mca]

I have just had my powerhead (Vmax 175tlry) rebuilt due to a failure in #2 cylinder. The failure was at the crank and rod bearing, the rod cup was pitted, the crank was pitted at same area and there was cylinder head scarring due to the metal from the crank & rod connection. I had this cylinder bored .020 over and all parts replaced with exception of 5 rods and 5 pistons. THe question I have is why this would happen, the "bad metal" response I have heard does not seem feasible. Is there anything I should check prior to too much operation. The new rebuit is running fine with about 1.5 hours of double oiled break in operation per manual. Could this be an ethanol related problem? I am now running stabil. Any info is greatly appreciated.

 

[m21mca]

Re: VMAX Powerhead rebuild

I appreciate any help that could be provided, I can't afford to do this again due to some small unknown. Thanks again

 

[rodbolt]

Re: VMAX Powerhead rebuild

pitting, not blueing, is typically caused by rust,rust is typically caused by water.
excessive sitting without fogging can create this as well.
if this is a V150 its carbed and oil is injected behind the carbs, if the crank is blued only on 1 journal carefully inspect the #2 oil line check valve.
yes ethanol fuels can bring in enough moisture to destroy a power head in a month or so of non use.
filtration wont help as you simply cannot filter it with the avalible filters and filter media.
there is a cure though,fog the engine for storage OR unclip the oil link from the throttle and allow the oil pump to go wide open and let the engine idle about 10 min then shut it down and reclip the link if storage is anticipated.

 

[m21mca]

Re: VMAX Powerhead rebuild

How do I inspect the #2 oil line check valve? Should there be oil coming out of this line above the check valve if I turn the motor over a few times without cranking? Sounds to me like it would be worthwhile just to replace the oil line check valve on this cylinder (top passenger side). I will use stabil and fog the engine and/or let the oil pump go wide open. I thank you for your help in this matter!!

 

[rodbolt]

Re: VMAX Powerhead rebuild

you check them with a vacumpressure guage and the service manual.