[img]i/expressions/face-icon-small-confused.gif[/img]I have a 1998 425 magnum 4x4 that I purchased from a neighbour recently. I purchased it not running he tells me it quit on him after he swamped it.
My neighbour had it at a dealer and the dealer told him it was a bent valve, My neighbour decided he didn't want to fix it. I purchased it from him and took it to a friend who is a very good mechanic. He has so far from what he tells me has changed cam,lifters,stator,rings and tells me the valves are not bent and that compression is where it should be at 75 psi. The only thing he tells me that it does is back fire through the carb and once in a while through the exhaust. any help with this problem would greatly be appreciated.

 

have you took the carb apart and cleaned everything also check all vent lines make sure they're clean

 

75 psi compression is on the bottom side of running.Needs to be closer to 90-100 psi.

 

I looked at the tech manual earlier and it is within spec actually. If I remember correctly it said it needs to be between 55 and 90. It also said that the reading can change according to cranking speed I would run a cylinder leakage test on it. A leakage test is a better test to determine engine condition. Especially ones like the 425 that have automatic compression release mechanisms built into the camshafts. I would do the carb also. Make sure it's in good shape. Make sure the carb is adjusted correctly(air/fuel) and make sure the ETC switch is adjusted.

 

[img]i/expressions/face-icon-small-smile.gif[/img]

 

[img]i/expressions/face-icon-small-smile.gif[/img]My mechanic phoned me about two hours after posting my plea for help and told me that he had got it running.Turns out that on the flywheel there is some kind of trigger and that he was looking at the wrong timing mark,he tells me that it is now running fine. thank-you for all your reply's