After my son had so much trouble with plug fouling on my 99 I altered just about everything from oil supply to the head ,halving the pump speed ,adding some electronics to the ignition ,new dissy parts etc etc. had spells of reasonable running but a rich spot just off tickover was annoying and plugs looked like they should not be working at all. Yesterday I re-cut the 3and a bit slide to a 4, reduced the pilot to a 20 and put the needle in slot 2 from top. Nothing like make one alteration at a time!! The bike runs well and the plugs are clean, a very occasional spit off tickover is probably the 20 pilot not supplying enough fuel for the bypass position,I'll try the 25 again, if that does not work I'll get a 31/2 slide and try that. Most importantly the plugs seem happy and the rich spot has gone.I have exactly the opposite problem with the Rudge, Runs weak,hot and plug looks new. Best I keep this saga for the Rudge club!.
HI Lance , I had a similar…
HI Lance , I had a similar problem with 650 pistons and hand filed the inside of the skirts to a knife edge to reduce pumping losses and weight. One thing I would recommend you do is if you have monoblocks is to tighten up the pilot jets after removing the cap nuts,may solve the rich bottom end, good luck.
Hi, Robert.
I've just been having similar problems with my 650SS and have come to almost the same answer as you. I've tried various combinations of settings, replacing the needles (twin Monoblocs) and trying them in different slots, shaving some 10 thou off the float valve housing to reduce the fuel level and changing the pilot jet from a 25 to a 20. I too tried #4 slides in conjunction with the 25 pilot jet and this didn't seem too bad. However it was still too rich at the very bottom end. But when I tried the 20 pilot jet and the #4 slides it didn't like this with the transition from one to the other being just like running out of fuel. I've ended up, subject to any further meddling, with 20 pilot jet, #3.5 slides, 106 needle jets with the needles in the middle slots and 270 main jets. Plug chops at half and full throttle look OK but I might still fiddle with the settings depending on how the bike runs over the next few times. That will be on hold for a short while as I've just stripped the engine down again to identify the cause of much worse vibration since rebuilding following re-sleeving back to standard last year. It turns out the new pistons together weigh some 145 grams more than the old ones so I'm seeing how best to sort that. Just left them this morning with Rod Lee Racing, who sorted the re-sleeving for me, to see if they can reduce their weight so I don't have to resort to stripping the bike right down to get the crank re-balanced. Never thought to check the comparative weights before I put it back together last year!