I was experiencing some issues with just off idle stumble and jerkiness which I thought was a fuel delivery problem. I had done a plug chop, but admittedly, only to the outside cylinders as they are the easy ones to get to. They looked a bit lean if anything so that's what led me to think fuel starvation caused by the miserable Kreem job in the tank (the most obvious looking culprit). How miserable was the Kreem flaking?
This was just what was recovered with a BBQ tongs through the gas cap. Pretty cruddy, but actually not that bad as most of it came out in large sheets. On the bottom 3 inches of the tank (with a very defined line), the liner is actually still adhered very well and not worth scraping off. I drained the rest of the tank and removed, cleaned, and rebuilt the petcock, finding really not much more than a few flakes in the screen.
I thought maybe the tank vent was clogged, so I drilled a small 1/8" hole in the cap. The flow out of both spigots was clear and quick, so checked that issue off the list as a potential issue.
The drive chain was a bit loose, so I tightened that to spec as I though maybe it was whipping a bit under load. A good idea to adjust, but not the culprit.
I decided at this point that maybe I should consider the possibility that when the PO said, "I just adjusted the timing, cam chain, and valve clearances", he may have meant "adjusted poorly".
I popped off the tappet covers and dug in. The valves were ALL outta whack. Some very loose, some very tight. I adjusted all to spec with my fancy new tappet adjuster and closed the tappet covers. I did discover that I had cracked one cover when removing it, but I Bogarted one from my donor motor. Now the valve train sounds like a smooth sewing machine. I don't know why I hadn't thought about the lack of valve sound before, but it was definitely running too quietly. A recipe to burn up valves...
I was still experiencing my jerkiness so I tried chopping plugs when it happened (all four plugs
), easiest to reproduce in 2nd gear at about 2k rpm. Looked like my 1 and 4 cylinders were perfect and tan, and 2 and 3 were VERY sooty and rich. Hmmm, air bleed screws are set the same, carbs are fresh and clean inside, AHA, timing!
I opened the points plate and got out my test light. I gapped the points to .014 and noticed the 2/3 point was drastically over spec. I don't have a strobe, but then successfully static timed both sets with slightly advanced timing. Closed it all up and hit the start button and she purred to life as expected. To my great amazement, that tiny adjustment to the point contact solved the richness issue in the 2/3 cylinders. I guess at low rpms the 2/3 were greatly retarded, causing incomplete combustion and a struggle in the crank shaft. Now the bike pulls predictably through the low rpms and screams up to the high end with no issues.
I now have a great respect for the process of the full 3000 mile tune up. When performed in order it really eliminates any mysteries or potential issues methodically and systematically. When you might think it's something big like a flaking tank liner, logic will lead to you to a mis adjustment of just one hundredth of an inch!
I also learned to really take a PO's statements with a grain of salt. Really, how likely is it that someone that can't clean a set of carbs knows how to set timing and valve clearances?
I also stripped the paint off the tank as it was brutally flaking, cracking, fuel stained. I had some rattle can and threw that on until I have a chance to get the tank stripped by a radiator shop. Advanced Radiator in Escondido quoted me $50 to burn off all paint and old liner, degas, and Redkote the interior. That's definitely next on the list!
