Compression readings are 120psi for Cyl 1, 3, and 4. No 2 reads 90. Specification is 130-160 per the Clymer manual directives. A wet compression test on No 2 brings it up to 160. Here's the question... When I assembled the 1st set of rings and piston of the kit I had a bear of a time getting the top and second rings down over the piston and into their grooves. I had to pry slightly, carefully between the ring and piston with a small, slotted screw driver, because I didn't have the ring expander. I feared this might mar the ring groove so I checked the ring-to-landing clearance on the next piston before assembly to find no gap and a very snug fit. The specification per Clymer is a clearance of no more than .0071in between the top ring and its landing, .0065 for the second, and .0045 for the oil ring. I installed the rings on all of the pistons and they were very difficult to rotate to the 120deg offset positions; hence they were not very free in their grooves. Would this cause low compression, poor sealing, and oil to rise into the combustion chamber?
Background: I picked up most of my parts from a certain retailer and I’ve had to replace a few of them for manufacturing defects. I got two "sour" batches of aluminum valvespring retainers which are sold with the valvespring upgrade kit. I've had to disassemble twice since the original assembly of this F motor, and I'm still having trouble. If interested please read on... Many details follow that might narrow the responses or address certain questions.
Assembly (F motor replaces blown K motor). Disassembly, machining, cleaning, and assembly are performed by myself while aiding in an engine rebuilding class I've taken two times previously. I machined the head and cylinder surfaces to level out measured warpage of up to .006in and I generated a surface Ra of less than 6.0 microinches to as low as 1.9 microinches; plenty smooth and I have pictures. I slotted the cam gear to compensate for reduction of distance between cam center line and crank center line. I did a valve job using our machines and tested it by pulling no less than 25mmHg vacuum at each port. I reused the stock cam but installed aftermarket valves, valvesprings and aluminum retainers. The heads and cutting tools were too big to bore and hone the cylinder block and I was looking to save money so I bottlebrush honed the cylinders and reused pistons and rings (I would have replaced the rings at least, but I couldn't find standard-sized replacements at the time).
1st disassembly involved replacing the first set of aluminum retainers with a second set of aluminum retainers. The first set showed grinding wear on the upper face where they had risen up along the keepers and contacted the rocker arms. As they spun around the rocker scraped the whole upper face until it finally dug in and created a grove. NO GOOD. The valve was ultimately held open and compression was lost taking power along with it. It was a very palpable feeling much like the K behaved right before I blew it up due to oil starvation. *At this disassembly and rebuild I had the cylinder block professionally over-bored and honed to match the $200 .25mm over piston kit purchased from said retailer.* New gaskets all around and an APE studs upgrade to boot.
2nd disassembly occurred because the second set of valvespring retainers showed the characteristic wear described above after a month of service. When I removed the caps to adjust the valves I found this wear and immediately knew disassembly had to happen. I sourced stock, stamped steel retainers and a cam from Curt Jordan of Jordan Engineering in Oceanside, CA. I went no further than removing the head to disassemble it and replace the retainers (the cam was replaced upon assembly). *I reused the head gasket this time.*
I synchronized the carbs and tried to dial in the mixture. No 2 was really dark and I suspected it was causing the fouling and loss of power I had been experiencing. I thin the mixture in No 2 only and repeatedly to no avail; still black as soot. I get stranded on the freeway as the bike bogs to a stop recurringly but runs again after a while sitting. This is something that had occurred between my 1st and 2nd disassemblies as well where I had a new head gasket. This leads me to conclude no issue reusing the old one at the 2nd assembly. I attributed this problem originally to the valvespring retainers. However, those have been replaced. And now I know it's not a rich fouling as I've leaned the pilot jet screw almost entirely out. I now suspect oil fouling. I set the pilot jet to 1 3/4 turns out per Clymer as a preliminary setting. I heated up the engine to operating temperature then pulled the plugs to see No 2 black as can be. And attempt to reseat the rings has failed, and I have also been experiencing bogging and smoke billowing from the exhaust; I'm not really experienced with the color reads on smoke, but it's mostly white with tinges of blue (I know blue indicates oil being burned while white means water/coolant.; but our engines are air cooled so that's moot)...
That's it... Refer to compression figures and question above. I’ll add pictures and any other details that may be requested.
