Fresh rebuild...Uneven compression?

[redjmp]

So I've put about 3 hours on my 86 115 rebuild (everything 30 over) and pulled the plugs and checked compression and dry I'm getting 125 to 140.
#1-125 #2-135 #3-135 #4-140 #5-135 #6-125.
With a shot of wd40 in each hole everything climbs by 10lbs.
I'm running double the oil so the plugs are fouled, but it seems to run ok especially when I hammer down after it gets on plane. Spools up to 5600 very quickly.
Do I need to keep breaking it in some more and see if the compression climbs on the 2 weak cylinders or should I tear it down and check for broken rings?

 

[Windykid]

Re: Fresh rebuild...Uneven compression?

After break in, the valves might need readjusting. Then check compression.

 

[Chris1956]

Re: Fresh rebuild...Uneven compression?

Red, I think you are OK. That much deviation is acceptable. You might like to avoid WOT for a couple more hours. Also, you can check it again in a couple of hours. You should use double oil for at least 6 gallons of fuel.

 

[Texasmark]

Re: Fresh rebuild...Uneven compression?

What valves? This sucker is a 2 cycle and has a reed valve assembly that lets fuel in.

I'd finish breaking it in before I got worried. Breakin has to include loading the engine to seat the rings but you have to do it intermittently to keep from overheating things with the initial increased friction.

So varying amounts of idle, up to plane, WOT for a few minutes, back off to cruise (4000 rpm) run it for 5 or so min, back to WOT for a couple, cut it. idle for a few minutes, back up to WOT etc......after 10 hrs of that, new comp test and new plugs and be on your way.

Mark