'83 Honda Magna engine problems

M

magnalex

New member
Greetings fellow riders,

I'm relatively new to the riding scene and I've been enjoying my old '83 Magna V45 for two months now and two days ago while riding to work, I noticed that the bike was just suddenly lacking power and started to sputter a little bit. One thing very noticeable was that my tachometer started to have erratic readings and the needle was jumpy.

I did some investigation and below is the summary of it:

1. There's fuel and it is clean since I've been going to the same station and always use the same grade.
2. There's spark on all four cylinders. It's a V4 engine and when I checked the spark plugs, the two upright cylinders close to the fuel tank showed black oily plugs. The other plugs seemed fine. I put a fresh set of plugs and it showed the same after running it around the block.
3. It has two ignition coils and I suspected a bad one but I swapped the coils and still ended up with black/oily plugs in the same set of plugs.
4. It runs fine when idling, but once I ride off, the power isn't there and like I mentioned there's sputtering and hesitation.
5. The engine has 4 carburetors and I just sprayed some carb cleaner and revved it a little but did not help.
6. These engines are known for pre-mature cam wear and I just hope that it's not the cams!

Looking forward to any replies from the technical Gurus in this site!

Just when the weather is getting better then I get this! Arghhh!

Thanks,

Magnalex
 
Magnalex,

This doesn't sound like a cam problem. The cam issue makes itself known by the gnashing and hammering noise in the cam covers.

It more probably has something to do with the carbs. The carburetors on these bikes are mounted 2 facing forward, 2 facing rearward. This makes for some rather complicated linkages for the fuel feed, throttle and starter valves. I would start by looking at the starter valves on the front 2 carbs. They might be stuck open.

Try to avoid spraying carb cleaner into the carbs. The slide diaphragms can be harmed by the cleaner.
 
Black oily plugs indicates that extra oil is getting into the combustion chamber, either from leaky valves or worn piston rings. Depending on how much oil is actually getting in won't necessarily be the cause of your problems. In extreme cases, it will foul the plugs. Unless you notice that's there's lots of blue smoke when it's running, it's unlikely that it's causing your problems here.

As for the cams - are the valves really noisy? If not, then I wouldn't worry about the cams, time has weeded out many of those with problems.

If it idles fine, but bogs down under power it might be getting starved for gas... possibly a clogged fuel filter or even a clogged petcock. Is there an inline fuel filter or is it the original one that's over the petcock within the fuel tank? Try switching your petcock over to 'Reserve' and see if it runs any better... if so, then there's some debris (likely with the age of your bike) blocking the intake tube on the petcock. If it still bogs when running on reserve then you should remove the petcock to check the fuel filter (if it's still there). The Magnas have filters that go over the petcock intake. If that all checks out, then move on to the ignition system.

There are a ton of possibilities in the ignition system... check the wires and spark plug boots for any cracks...

Start with those and let us know.
 
Wow! Thanks guys for all your great suggestions...I think the bike fixed itself just by your replies! I will definitely work on the old bike this rainy weekend. Thanks for keeping my hopes up Ed and VFR.CBR. This is my first bike and can't afford an engine rebuild right now. I will definitely keep you guys updated. Thanks for your guidance!

Magnalex
 
To VFR.CBR and ED,

The old bike is running fine again! I did several things like change the fuel filter, soak the carb linkages with WD40 and wiggled and jiggled the wiring inside the headlight bucket since the tach won't run properly. It's either one of the steps or all them fixed the problem. I checked the plugs after riding around the block and all plugs showed a grayish/brownish tip...no more oily soot on two cylinders. I honestly think it was just some corroded connectors because of the bike's age.

Back on two wheels again thanks to you guys....woohoo!!!!

Magnalex
 
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