Might be time to check out a MegaSquirt.
Rick
Japan Meets Britain
So how did we arrive at 250 mains on the cooler day -- well, when we started our runs that day, we had the original 150's in there (pre-big bore etc), so we ran it as is. The top speed we hit under load was about 83mph, and the plugs came out lean. We then went 170, 180, 200, 220, 230, and 250 (replacing the plugs each time with fresh), with each progression resulting in better plug colour and higher top speed (eventually topped out at 105mph). At that point that day we ran out of jet sizes and time. I picked up 260, 270, 280 and 300 jets for our next round of tests. The second day, the temperature was in the low 70s, and we immediately started with the 300 mains. As expected, the bike 'nosed over' at WOT, so we determined that 300 was too big. We kept going down in jet sizes until we had a combination of good plug colour and smooth progressive performance (top speed that day was about 95mph). However, I also found that at about 2/3 throttle the bike stumbled, so John lowered the needle from the top position to the middle position, and that instantly cured that issue. The current position right now is 240 mains with the needle in the middle position, and bike runs beautifully throughout the entire range. As well, we originally had a 29 rear sprocket, and the second day we switched to a 32. We have since gone down to a 30, and we'll run that next week and see. Next week I plan on taking it for a much longer ride (like an hour or so), and will see how the bike does in all-round riding situations.
So as you can see, much of how we're doing it is by plug reading etc by John, and riding perspectives by me. How accurate this ultimately is compared to other methods, I cannot say. But I have faith in John's abilities to tune the engine this way and the bike seems to be responding in a positive direction. I may ultimately double-check things on a dyno at some point, but for now this seems to be working fine. Bear in mind that I put almost 20,000 miles in 6 years on this bike that was basically tuned the same way before all this work was done, and I have no misgivings about that method this time around. Vince
You're a man with just far too much time on his hands to play with motorcycles. :-) Seriously though, I admire your dedication and the way you've channelled yours and John's efforts into developing this bike and getting it just the way you like. Seriously, your approach is right. Providing you take a slightly conservative approach to jetting, your bike will run well and give you more of the excellent service it has shown. The important thing here is to get it running to suit you and your riding habits. Employment has stepped in again to slow the progress of my restorations so my own projects are rather behind now. I envy the fun you're having with your bike but enjoy your posts tremendously. Thanks for sharing your experiences! G '60 C77 '60 C72 '62 C72 Dream '63 CL72
'61 CB72 '64 CB77 '65 CB160 '66 Matchless 350 '67 CL77 '67 S90 '77 CB400F
Yeah but hopefully you guys will spend a lot less money on your respective ventures than I have! Probably could have bought a nice Vincent Black Shadow instead......
Thanks ever so much for the support guys -- this past week, both Jerry in Australia and Jensen in the Netherlands called me on the phone, so I don't know what the heck I'm doing to deserve all this! Deeply appreciate all the encouragement, and hopefully all this craziness will be of benefit to others somehow. I do want it to be over soon though!
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