Motorcycle Repair: 1998 Honda Shadow ACE bogging under a load, honda shadow ace, honda shadow ace 750

Question
My friend has a 98 Honda shadow ace 750... in neutral the bike will free rev fine (All the way to the rev limiter...) about 8 months ago we removed the baffles from the exhaust and the bike has been running fine since... all of the sudden we were on a ride and his bike started bogging... (Almost sounds like hitting the rev limiter but low in the rpm range...) we took the bike to where he bought it (He has a warranty) and they looked it over and told him the carobs were out of sync. the re-synched the carobs and it ran ok for a little bit but started messing up again (Bogging under a load) we took the bike back and now they said it needs to be re-jetted...  I don't have a lot of bike experience but it sounds like a coil dropping out under a load but not sure ( the bike has 2 coils... ) Does one coil run on the low end and the other cone in in the high rpm? Or do you think it could be jetting... (I don;t trust the shop we took it to because of the mis-diag from the first time... ) Any help would be appreciated... (I have a sync gauge and will check that tomorrow...) Thanks again in advance...

Answer
Robert,

Try usual tune up stuff first, plugs,
air filter, fuel filter.
If it was running okay up until now
I would not change any jets.

-the trick is to figure out if it is the fuel
or ignition causing the problem.

-Sometimes the spark plug color and condition
can be a clue. If they are very black
or sooty, it could be an air box
or filter blockage.

-The air cutoff diaphagms on carbs could
have pinholes. They richen the fuel
on deceleration to prevent backfire.

-are the enricheners (choke) okay?
-does partial choke help the problem?
-is the bike running on both cylinders?
check the pipes for equal warming.

-try a timing light, see if the spark cuts out.
-The plug caps should be under 5000 ohms.
-Check coil towers for corrosion. Check coil ground.
-Check the ignition control module connector
for corrosion or loose wires.
-Tighten the battery cables.

-The ignition coils are not for high end and low
end. They work through all rpm ranges.

-it is possible the pulse generator coil
is faulty. Resistance is usually
around 400-480 ohms.
The connectors are usually under the right side cover.

-Coils primary are around 2-3 ohms,
Secondary is 20000-30000 ohms depending
if caps are on or not.

-Make sure fuel is clean and carb jets
have been checked physically with
small piece of guitar string or fish line.
The fuel these days can plug up jets
in less than a month of sitting.
Use some fuel stabilizer.
Check the petcock for any problems
with blockage.