Originally Posted by
rajul
Hi glowgeek, Dave, thanks a lot for your inputs! Really appreciate it. I will replumb the fuel tank, and give it a go. Any tell-tale signs, especially at the high and low ends, if the o-rings are not sealing well? Thanks again
With clean parts check the orings for friction when turning the lsn, hsn and intake tube (both ends). There should be some resistance to rotational movement. To check the hsn lift the ratchet spring with thumbnail. Replace orings that feel loosey-goosey.
The thin spraybar oring that fits between the carb housing and hsn ratchet spring is not even needed in most cases due to the super tight fit between the spraybar and carb housing. Would be the last thing I checked with a poor running engine.
As far as identifying which oring is bad based on running characteristics, I have seen too many variations to say. Most of the time the intake pipe oring at the cylinder head is the culprit. If that doesn't fix it I replace the rest because in some cases I've found orings that offered good resistance to rotation but were damaged by the previous owner.
Reasons to suspect a bad oring:
Wandering rpm anywhere from idle to wot, engine runs super rich at midrange rpm but idles ok, difficulty finding the sweet spots for needle settings. These symptoms can be caused by other issues however e.g. bad bearings, valve clearance issues, weak/broken valve spring, sticky valve, leaky valve, carbon fouled ring lands/ring, debris in the fuel system, leaks in the fuel/pressure lines etc
So, I can't answer your question specifically but hopefully this info will help in some way.
Lonnie