Motorcycle Repair: 1986 450 rebel, float bowls, valve diaphragms

Question
I have an old 450 rebel that has been in storage for 11 years. Got it running for my wife and it does so intermitently. hard to start sometimes and backfires for a few minutes then clears up. Have cleaned the carbs and bypassed the kill switch because it would sometimes still run with it off. Didn't want it to die on my wife. It has done just that, I am very mechanically inclined and wonder if the coil,igniton switch,module,or stator could act like this? Can you help direct me and since I dont have a repair manual, should I get a Clymers or stick with an original Honda service book? I wish to give my wife some trouble free time on the road without having to recue her especially from any kind of a cell phone dead zone where she would have to walk or heaven forbid hitch a ride to call me. Sincerely appreciate any help you might be able to give me buddy. Thanks Michael

Answer
Micheal, when you pull a bike out of deep storage, you have to go through it from top to bottom.

You mention "cleaned the carbs" which could mean a full overhaul or just cleaning out the float bowls and main/idle jets. They should be thoroughly cleaned and both air cut valve diaphragms checked carefully for damage.

http://www.cmsnl.com/honda-cmx450c-rebel-450-1986-usa_model1055/partslist/E++18.

The fuel tank has a filter screen up inside the fuel supply which should be checked and replaced. The petcock diaphragm is also subject to failures and should be renewed with a repair kit. Any rust or corrosion/contamination in the fuel tank must be removed and cleaned.

There were some issues with earlier 450T models where the needles are tapered too thick, so the bikes ran very lean. You might want to either put a very thin shim under the needle to raise it up in the slide or perhaps bump the main jet size to #115. This helps to offset the alcohol based fuel issues, which were not present when the bike was built. Some #38 idle jets might make starting and idling easier. You do have to check the manifolds for any signs of cracking and insure that they are sealing properly to the cylinder head (o-ring).

Backfiring through the intake is usually a sign of lean running. You probably will need to run it with full choke for a minute or so with OEM jetting. I'll assume that you put in new spark plugs. Check the spark plug caps for 5k ohm resistance values. Both should read out the same.

The OEM Honda book is probably best to use as a reference resource.

The CDI systems are pretty much pass-fail. There were a lot of issues with pulse generators in the early 400T motors, but seem to be fixed by the end of production in the mid-80s. The KILL switch and ignition switch put ground on the ignition to shut it off.  The CDI ignition is self-powered so doesn't need a battery and the only way to stop it is to ground out the input with KILL/IGN switches. On other battery operated ignitions, the switches open the circuit, not ground it. If your KILL switch wasn't stopping the engine, then there is an open circuit to ground in the switch or the wiring.

Check all the electrical connections and grounds for clean and tight fitment.

I hope you have reviewed all the other systems in the bike and renewed the tires, drive chain, and lubed the suspension. Be watchful for fork seal leaks, brake system corrosion and leaks at the master cylinder, etc. Lube and adjust all the cables. As you say, you want it to be 100% reliable for your wife.

Bill Silver