Another Piston, Again
A little history on the first three pistons: I would rebuild, pressure test and start with a fat jet - like a 172 (original rebuild rode great for months with a 160 main in it) but was never able to tune the spark and then out of the blue and usually within the first 15 minutes it would burn up the rings.
Rebuilt with piston #4 and compression of 140, brought assembled Pilot to the local Honda shop for a dyno run with the A/F sniffer in the tail pipe. While testing on the dyno, started up and was idling well for warm up but A/F ratio was a little high. After a few minutes started dyno pull but was unable to get any change in A/F ratio despite adjustments and then, all of the sudden A/F spiked to over 15. Shut off immediately, removed carb, disassembled and soaked in carb cleaner vat overnight. Reassembled and started back up the next morning and everything fell in line. After fine tuning carb and A/F at 13, left it running with a 165 main jet I knew was too rich but didn’t want to test my luck at this point. It was a little sluggish off the line, plugs were always wet and oil was seeping around exhaust. After a couple of months, I went to a 162 and seemed a lot better but still occasionally fouling plugs and plug still visibly wet when pulled. Went to a 160, warmed her up for a few minutes and 10 minutes into a run - she is dead. Compression is now around 30 . Haven't pulled
motor ((
Internal Combustion Engine ? )) yet and will do a pressure check once removed.
Engine Specs: Paul Turner Pipe, Stock muffler, 39MM Keihin carb, modified airbox (3" intake hole w automotive cold air elbow on original lid), K&N inside airbox treated with oil, K&N on elbow dry with a prefilter on it,
Powerbloc clutch. Oh, and this is the part that is really kicking my A$$ - an 82MM piston which means I now need either another jug that hasn’t been bored out as far or get this one sleeved.
Shouldn’t I have been able to get a nicely browned plug at some point before eating a piston? Is it an intermittent issue with my carb leaning out? Any input is appreciated.
Really would rather have continued to deal with fouled plugs than another piston but too late to look backwards.
Typed this a week ago and was dead set on getting rid of the damn thing. I knew I’d have to get it running again before I sold it and now I’m thinking if its running, maybe I’ll keep it.
Sure is fun when it runs…