'86 350X engine work

[dyrtryder]

Well, since I won't be trusting Mr. Twisted with anything of mine, I plan on rebuilding my 350X engine myself.
I hadn't had it running in about 5-6 years or so, and the last time I ran it, I did not have any reason to suspect that the intergrity of the engine was questionable. Late this winter I went through the carb, cleaned the gas tank, air filter and box (mouse nest,) and changed the spark plug. It started on the second kick. I let it warm up for 5 - 10 minutes to warm up the oil, and it seemed to run o.k. Shut it down, drained the oil (I don't know how much was in there) changed the oil filter and put fresh oil in. Started right up, but now it smokes bad. Checked compression and only getting about 90 lbs. If I put some oil down the cylider, the compression comes up a bit. Definitely going to do a top end rebuild on it, but at what point should a guy be concerned with the bottom end. Since the engine is out and mostly apart anyhow, should I be worried about doing any seals or bearings? Why would it have started smoking only after the oil change? Maybe because it was low on oil when I first started it, and then once I changed the oil and brought the level up to where it was supposed to be, it started smoking??
Thanks...

[trike savior]

compression sounds a little low, so it could be blow by. and sitting for some time can cause the valve stem seals to dry out.

definitely should change the valve stem seals and while in there lap the valves with some lapping compound.

as long as you have no scoring of the cylinder or piston, you should measure the piston and then the cylinder. as long as piston to cylinder clearance is within spec, i would just hone the cylinder, replace the rings and put it back together. everyone always wants to go straight to boring over the next size when that is not always necessary as long as there is no damage and measurements are within spec. Piston rings are a wear item.

[dyrtryder]

So you don't think there is a need to get into the bottem end at this point then?

[NeverLift]

As long as there was no metal shaving in the oil, it shifts good, no loud noises (knocking). I would leave the bottom end together. With my experience Hondas only need to be rebuilt if they NEED! to be rebuilt.

[dyrtryder]

Thanks for the info. guys.

[atc007]

When you get in there,check your rod for up and down play. There should be none. Side to side yes. but None up and down. But the bottom will probably last longer than you with clean air and filter going through it. You can do the top end in the frame,but it is easier working on the bench.

[86125m]

Its fumny how some honda engines lkke the one on my 86 125m had been sitting for at leat 8 to 10 years and all I had to do was clean thecarb and she runs like new.

[86125m]

But others when they sit need a overhaul.