I took the day off work today and completely put my top-end back together. The bike ran fine for 15 minutes or so, then went back to the same old problem - the top cylinder does not seem to be firing at full strength. It begins with misfiring at low rpm, and soon becomes intolerable. My next effort will have to be aimed at ignition (even though I have already replaced one of the CDI units). Any ideas? There still seems to be a spark in the top cylinder, but it is pink, not blue. _________________ '87 MC16
Have you checked all the connectors for corrosion and that the loom earth points are clean and tight? _________________ MC21SP Plaything
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Yeah I've checked the only earth I know of on the top of the frame, the connections look fine. I guess I need to find someone around here with a '16 that wouldn't mind swapping parts around. _________________ '87 MC16
Silly question (sorry, it's been stretched out over threads and time, so I forget!) but have you swapped CDI packs top to bottom to see if the problem switches barrels?
How about switching coils? Same problem? Top cylinder still?
New plugs, new battery? Have you tested the charging circuit - especially with the bike running?
It very much sounds like something electrical breaking down if you say it initially ran OK. A pink spark really would indicate something in the system breaking down. _________________ Andy.
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Andy - I will try different combinations of coils and CDIs to try to find if there is a weak component somewhere. Maybe the other CDI is going ! I think the rebuild helped on the performance side as I had a great time before things started to act up again. Last time I checked the battery was fine and had the correct voltage when charging. I put a pair of new plugs in before starting it up after the rebuild. Hopefully I can find the bad component soon as someone is selling bits cheap on a local auction site _________________ '87 MC16
First thing I would do is put the battery on a slow charge for a few hours, and try it again without changing anything. If it's fine for a short time again, then starts to fail again, it's most likely the regulator/rectifier or the battery itself. (Or the wiring in between.)
Don't forget Electrex have kindly let us publish their superb fault-finding guide in the Workshop. _________________ Andy.
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I noticed something just now, when I increase the throttle the tachometer doesn't rise until both cylinders fire. From what I read in the workshop manual, the tachometer is linked to the ignition system on the top (rear) cylinder somehow. I assume I can concentrate on this cylinder now - does anyone know how the tachometer gauges rpm?
Coincidentally, the rear cylinder doesn't fire until the RC valves move to their first position at 2000 rpm.... _________________ '87 MC16
Adjusted the RC valves again, problem still exists. Also seems to be independent of the CDI units as I swapped them round and problem still occurs on top cylinder. _________________ '87 MC16
I rechecked the carbs today - the jets that are in there differ from the stock settings. My main jets are #115, slow jets #35. The stock settings are #110 and #38 respectively. Would this make much difference, and are my settings richer or leaner than the original settings? Also my needles are thickest in the middle rather than at the top (not sure if this is wear or if they are always shaped like this). _________________ '87 MC16
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I think the rebuild helped on the performance side as I had a great time before things started to act up again. Last time I checked the battery was fine and had the correct voltage when charging. I put a pair of new plugs in before starting it up after the rebuild. Hopefully I can find the bad component soon as someone is selling bits cheap on a local auction site 