Topic: Miss/Backfire Problems

[Mosier]

Hello, I am having some issues with my 1971 CB 750.  Bike was running fine until one day mid June when the battery began to drain.  I kick started the bike and rode it for the duration of the day.  The next day I kick started and rode to work, upon my return trip the bike kick started fine and rode fine until about a mile or so away from home when it back fired a few times and power dropped past 2500 rpm or so.  So being close to home and living in the city I nursed it home on back roads in 2nd gear.  Upon inspection I immediately thought of points/timing.  So i opened the cover to the points to discover that the previous owner had converted to an electronic ignition.  Therefor this is ruled out, correct? or not?  Then I checked the coils which were good.  Upon testing and starting it up in vain the backfiring increased and now sounds as though it is missfiring as well.  This got progressively worse and now blows the fuse every now and then.  I took all the plugs out and checked for spark, all OK.

When I first got the bike it blew a the fuse in the middle of no where at night, for no reason, as i was just going a steady 55 through country roads.  Never blew it again.  Also sometimes when turning the key from off to on, and then past on it will try to engage the starter for just a second.  I also noticed while checking the plugs that when either switching the key from on to off, or the kill switch from on to off the plugs will arc a yellow/oj arc.  Is this normal?

So i believe there is probably short somewhere, but whether it is in connection to my current missfire/backfiring problem or a whole separate issue I do not know.  Could a short or faulty wiring be the culprit of the miss/backfire?

I looked in my Honda shop manual and Haynes manual and both do not have any information on checking the timing chain.  Could this even be the issue at hand?  If so how does one go about checking this?

A final note about the bike: it has been bored to 836cc and has an aftermarket camshaft which may make timing issues hopless to check/read.

Any advice or suggestions would be warmely welcomed.

Thank you!

[flybox1]

Welcome to the forum!

the majority of your running issues can be remedied by performing (YOU) the 3000 mi scheduled maintenance.
Its detailed in the shop manual in the Maintenance section.  the manual can be downloaded here.
Set your valves.
clean carbs, and when i say clean.  i mean CLEAN - no shortcuts.  do it right the first time. 
note jet sizes and needle clip positions, mixture screw settings, check/set float height
fresh, gapped NGK D8EA or Denso X24ES-U plugs, new plug caps if yours meter out incorrectly 
tell us the intake and exhaust configuration.   new air filter unless you are rnning poods.
Tested, Good working Battery
Clean tank - no debris, or it will ucfk up your carb cleaning and you'll waste more time taking them off/apart again.

your electrical issues are most likely caused by bad or corroded connections on 40+ year old electricals.  go through your wiring harness and clean/treat all the bullet connectors and block connectors.

[Vinhead1957]

Use the trouble shooting guide in the FAQ section for your charging system. It could be a bad connection to any electrical component of your charging system. A good multimeter and that guide will do the job

[Vinhead1957]

You do have an electrical issue that is over draining your system. It might also help to use the bulb method in place of the fuse to isolate the intermittent short.   Inspect every inch of that wiring harness to find possible chaffing

[Mosier]

I replaced sparkplugs when initially trouble shooting.  The battery is fine and has been recharged.  It is 4 into 1 kerker with freshly cleaned pods.

I'm going to go through and clean all electrical contaces and check entire harness, I've quickly checked it the visible sections but should probably thoroughly go through it.

So from reading the FAQ and googling the best way to clean the connections is with steel wool and then applying dialectic grease? or should I skip the grease?