77 Rude 140 High but uneven compression???

[phillnjack2]

Re: 77 Rude 140 High but uneven compression???

that is gonna cost a lot more than the engine is worth to fix it.
I bet the crank is worn as well.

phill

 

[emdsapmgr]

Re: 77 Rude 140 High but uneven compression???

In looking at the first pic, the liquid at the bottom of the cyl looks a little watery. Also, there appears to be a rust line around the right cyl walls. Any chance that you have a water leak at that cyl. Either a head gasket? Or an exhaust leak (which typically affects lower cys.)

 

[Faztbullet]

Re: 77 Rude 140 High but uneven compression???

Incidentally the 150/150 cylinder head has most definately been shaved even with the naked eye which would explain the high comp. So when I change this piston and get a rebore, should I get the head shaved so that even 150 across the board

As posted earlier, shaving heads on a crossflow will not add compression , the way you increase compression is to close the chamber on the head , which squeezes fuel/air charge into smaller area which = higher compression. It (head) may have been trued but due to being warped..... these engines due to reciprocating mass at WOT only have about .020 clearance in top of head due to rod,wristpin, & piston stretch. I dont think that cylinder ran hot but cold due to stuck t-stat or poppet. When cylinders run to cold incomplete combustion occurs causing carbon build up and that would explain compression being low on upper cylinder also due to sticking rings....

 

[urugol]

Re: 77 Rude 140 High but uneven compression???

Thanks for all of the input this is a great forum! I decided to hunt around for another engine and got myself a rather sweet deal on a 2000 Evinrude 115 Ficht engine. I have read many negatives but I couldn't pass it up and it looks like I will be replacing this 35 year old engine I kinda like the thought of fuel injection. I have a fair amount of experience with Ficht/EMM and diagnostics on my jetski as it uses the same system and I love the fuel efficiency and power. So I will be parting this old motor now. Only issue now for me is this new to me engine is an XL shaft so I will need to look at a jack plate option or perhaps there is an easy conversion to long shaft.