Engine rebuild...Yea or Nae???

Here's the status of my Seca as of now:
Compression on all 4 cylinders is around 130psi dry 180psi wet. No smoking or oils loss.
Starts easily and idles almost perfectly (just a tiny intermittent lope).
Runs like a raped ape for a few minutes then starts to miss on #4.

If I apply full choke when it starts to miss she smooths out for a bit. If I Stop and leave her idle for a few minutes she smooths out and is fine until I get on it hard again. If I keep the RPMs down below 4k she runs perfectly for at least 1/2 hour( longest I've ridden lately).

I am going to clean/rebuild the carbs this winter(or sooner if it gets worse).

My questions are of opinion to those who have dug into these engines a little deeper...

Is the compression low enough to warrant pulling the engine for new rings and cylinder honing?

If I do pull the engine, is it worth the effort to crack the cases and replace the crank bearings (main and rod). Mileage is 38k+/-

Time is really the only consideration for me. I have the tools and mechanical ability to do the work but time is at a premium for me.

 

The compression numbers are good. A engine overhaul would be the last thing on my list. I would concentrate on the carbs first, get them in order and do the valves at the same time. After that if it still has the same problems start looking at the ignition system.

 

Sounds like you might not be getting enough fuel to the carbs. Things to look for:

- pinched fuel line
- gas cap vent plugged
- high spot in fuel line holding an air bubble (especially if there's a fuel filter there).
- Plugged screen on the petcock
- Silly little screens on top of the float valves plugged.

 

mlew and MiCarl,

I'm 99% sure that the missing problem is fuel flow related, clogged screen, occluded float valve, bad/clogged petcock, etc...

I'm sure a thorough carb and petcock cleaning/overhaul will fix the problem.

I was under the assumption that 150psi compression was the goal and thought 130 might be approaching the low acceptable limit. I just don't want to spend the time on the carbs only to have another engine related issue next season.

 

another way to look at it is, there's too many motorcycles for sale to worry about 130 psi

 

That, plus finding rings would be a challenge; finding big-end bearings and con rod bearings a near impossibility.