Motorcycle Repair: Lack of power, honda 750 four, air filter systems

Question
I just got a 1972 Honda 750 four.  It runs ok, and with no load it it tachs up with no issue.  Under a load however it bogs, and will stall.  It requires nursing the clutch, and racing the rmps to 2500-3000 just to get it to crawl down the road.  once it's moving/cruising it will bog under hard accel, otherwise it's fine with light accel.  When I got this bike the carbs were gummed up, and I cleaned them the best I could.  New plugs, and air filter.  I do know there is some kind of electrical short, since my brand new battery was drained within the week.  someone suggested that it might be the coils.  
Any ideas would be greatly appreciated.

Thank you
Patrick

Answer
Patrick, lots of possibilties here.... is the bike all stock or does it have replacement exhaust or air filter systems? If so, the main jets may need changing to a larger size.

If it is all stock, you may not have the float levels set right or they may need a thorough overhauling.

If the bike isn't charging or discharges while sitting, the rectifier may have shorted out or is someone has been doing some creative wiring for an accessory or something, then the problem may be there. The rectifier is hooked to the battery all the time, so if it fails then there is a direct path to ground for the battery output.

These are battery-operated ignitions, so if the battery is low the coil output is weak and performance is poor.

I suspect that you may not have checked the ignition timing and spark advancer. The mechanical advancer is behind the points plate. You have to remove the small nut on the end of the crankshaft to remove the larger nut, then the plate will slide off the end with the advancer.
Advancer springs should be fairly snug and the point cam able to advance and retard with no effort, when you twist the point cam. Lube the felt pieces with a drop of motor oil or use point cam lube on the point cam when reassembling. Clean the points with a small point file or emery cloth, clean the grit out with contact cleaner or similar. Adjust points to .012-.014" at maximum gap then adjust the point base plates until the points just open at the 1-4 and 2-3 marks on the advancer where they align with the index mark.

For more help go to: http://www.sohc4.net/ and www.electrexusa.com

Bill Silver