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Boring only one cylider

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canam1

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"I recently blew one piston on

"I recently blew one piston on my 94 johnson 140 looper. I talked to a guy at the machine shop and he said that he could bore just the one cylinder and put an oversized piston in and get the motor running cheap. My question is by doing this aren't you throwing the motor out of ballance? should I replace the rings on the other pistons while I have it apart, to keep compresion within the 10% range. right now all pistons are +.020, so how much of a difference would having one of those at +.030 make? Thanks for any help."
 
"i personally,dont do it,and d

"i personally,dont do it,and dont like it....it is,however,....a common practice at many shops...
my thoughts on it are,if u r gonna overhaul it,..do it right,..do it once."
 
"I blew a single piston on a 9

"I blew a single piston on a 98 johnson 225 in nov-I decided after much consideration to have the single piston replaced; they also replaced the rings for the other 5, bearings, gaskets and after the break-in period, did a decarb and replaced the plugs-things seem to be running very good....best of luck."
 
"Mark,
I would agree that a

"Mark,
I would agree that a .030 over with the rest being at .020 over should not cause a problem. But I don't believe OMC offered pistons at .020 over which means that you probably have after markets installed. Sierra, Wiseco, who knows. If so, I would suggest that you stick with the brand installed. That will most likely come closest to matching the weight. There may very well be quite a disparity in weight between the different manufacturers at the same diameter."
 
It doesn't matter if there

It doesn't matter if there are differnet pistons sizes. but it is reommend to have all the same size. But if $$ is the question then just do what is needed at the moment. I personaly have have a 115 with 3 .020 and 1 with .030 and it runs just fine.
 
"Thanks for the help. they ar

"Thanks for the help. they are wisco pistons so I will ask them if they all weigh the same. Bill, did you replace the rings on the other pistons and are the compression readings close if you didn't? Jus tbefore mine blew the compression an all four was at 100. does that sound close to what the new piston and rings will give me if I just do the one?"
 
"I put all new rings in, now I

"I put all new rings in, now I'm getting 130 psi on all four now. before I couldn't tell you because I bought the motor blowen and rebuilt it. I went with 0.20 on three cly. because that is all it needed and .030 on the other to get the groove out where the rist pin worn in. By going with 0.20 it leaves room for a future rebuilt before having to put a sleeve in. Just prolongs the life of the block and saves $ in the future if you plan on keeping her for several years."
 
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