Need Help! 84 Honda Magna 500

6

6mtsedan

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Inherited this bike from my dad...

Problems are i cant set the idle for the life of me, its been to 2 shops without luck. The bike will hold an idle but after riding for a bit the bike stalls, bogs and dies.

Carbs cleaned and synced. Everything is functional.

New fuel filter, new oil/filter,

Can anyone help me with this issue :( I wanna ride!
 
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my uneducated guess is that something in the fuel system is opening up when it gets warmed up... it's an old bike, what are the rubber bits/gaskets/carb boots like?

I had a problem with a cracked fuel filter, bike would idle and then you give it gas it would die... maybe something is clogging up the fuel delivery when your bike is warmed up.
 
Hmm. are you sure the choke is working properly? Sounds like you're running too rich
 
More than likely...another thing, it will shoot blue smoke. Whatever you guys recommend i am going to try as I am completely lost now. I've had several bikers check it out and no one can help me.
 
Blue smoke means oils burning. I think you'll need to do an engine rebuild
 
Forget the smoke issue. If you are having idle issues, you have a) too much gas b) too much air. In most cases it is too much air and usually as a result of air infiltration around the carb. As CruisrnGrrl mentioned. Intake boots or intake boot o-rings are leaking. Some bikes like suzuki GS series are very touchy if the airbox is not airtight too.

Rubber parts on these old bikes wear out and if there are o-rings in your carbs (very likely) they should be changed as they too will leak air.

I'd start by pulling the carbs and removing the intake boots from the head. You will likely find big o-rings that may have shrunk or split and that is the most likely spot for air infiltration. change them. Go through the carbs again and change the o=rings. Make sure the airbox is tight and it fits securely.

Its also been my experience that despite paying to have the carbs cleaned they are not usually done correctly and you could still have some plugged jets or passages. I would strongly recommend you do them yourself. Carbs need to be stripped (all rubber bits out) and dipped in carb cleaner for a minimum 24 hours. a quick spritz with carb spray is not going to do it. Carbs are not hard to do it just takes organization. Tutorials are available and if you look up the GS Resources you will find a great one. Maybe not your exact carbs but close enough for you to get the idea.

Deal with this first then worry about the oily smoke.

Good luck.
Spyug
 
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I had an '84 interceptor and it would randomly die on me. The vacuum hose was cracked since it was so old and some times would stop the flow of fuel. I also had the main fuse break but it would be touching and running fine and then suddenly act funny and stop. Other then those two things, no clue, just going by my experience
 
RE: Airbox....
I ordered a new (used one) as the one that was on the bike was shot (mouse ate through the intakes). In addition, i replaced the seal inbetween the two sections with window lining as there is a 1.5 or so mm clearance and the old lining was deteriated. I could not figure out the bottom lining that connects the airbox to the carb.

I will check these seals but unfortunately, this information i am passing on to a friend that knows bikes. I don't know where this stuff is on a bike :)

Thanks for all your help guys. Cant wait to be able to ride to a meet!
 
Once you get the airbox back on, if you're still having the problem, start the bike and spray some ether (starting fluid) or acetyline (for expienced mechanic) around the individual carbs and vacuum hoses. You will hear the idle raise as the vacuum leak sucks in the flammable spray. Could be just a cracked vacuum hose opening up more as the engine warms it. Spybug has good recommendations if this method doesn't pan out.

Just curious, the bike has been sitting a very long time with no fuel stabilizer. The gas will be solidified like oil. I hope you drained the old fuel after changing the fuel filter or the new filter will be instantly plugged. You'll get an idle, throttle on, bog, bog, sputter, stall. This is likely your blue smoke as solidified gas will present the same as an oil burner. Change the gas!

Run your finger around the insides of the tailpipe(s). If it's slick, black stain, you may in fact have seized oil rings, and an engine rebuild may be necessary.Start with the very basics I've given you first and work to worst case scenarios.

6mtsedan said:
RE: Airbox....I ordered a new (used one) as the one that was on the bike was shot (mouse ate through the intakes). In addition, i replaced the seal inbetween the two sections with window lining as there is a 1.5 or so mm clearance and the old lining was deteriated. I could not figure out the bottom lining that connects the airbox to the carb.I will check these seals but unfortunately, this information i am passing on to a friend that knows bikes. I don't know where this stuff is on a bike :)Thanks for all your help guys. Cant wait to be able to ride to a meet!
Click to expand...
 
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Spyug said:
Forget the smoke issue. If you are having idle issues, you have a) too much gas b) too much air. In most cases it is too much air and usually as a result of air infiltration around the carb. As CruisrnGrrl mentioned. Intake boots or intake boot o-rings are leaking. Some bikes like suzuki GS series are very touchy if the airbox is not airtight too.

Rubber parts on these old bikes wear out and if there are o-rings in your carbs (very likely) they should be changed as they too will leak air.

I'd start by pulling the carbs and removing the intake boots from the head. You will likely find big o-rings that may have shrunk or split and that is the most likely spot for air infiltration. change them. Go through the carbs again and change the o=rings. Make sure the airbox is tight and it fits securely.

Its also been my experience that despite paying to have the carbs cleaned they are not usually done correctly and you could still have some plugged jets or passages. I would strongly recommend you do them yourself. Carbs need to be stripped (all rubber bits out) and dipped in carb cleaner for a minimum 24 hours. a quick spritz with carb spray is not going to do it. Carbs are not hard to do it just takes organization. Tutorials are available and if you look up the GS Resources you will find a great one. Maybe not your exact carbs but close enough for you to get the idea.

Deal with this first then worry about the oily smoke.

Good luck.
Spyug
Click to expand...

Im looking through the clymers and i can't find any reference to "intake boots" or "intake boot o rings". I assume you are talking about the airbox and the chambers which dont have any o rings which i can think of.

I will take apart the Carb and try again to do it. Where can I get carb cleaner thats not in an aerosol can?

On a positive note, I did get to ride 2 days ago from scarborough to newmarket. When i arrived to newmarket, the bike stalled out on me. The 40km ride back was very stressful having to keep the bike idled at a minimum of 2000rpm. Trying to pull out of first was a nightmare as the bike was bogged down so id have to throttle hard and it would cause the bike to fly. Not fun for a newbie rider!
 
I am not 100% familiar with your engine and couldn't find a fiche for it but on most bikes of this vintage the carbs are connected to the head by rubber tubes referred to as "boots" but more properly as "intake manifolds". Some of these tubes connect to the head using spring steel clamps, some are bolted to the head directly. The bolted type generally have a flat steel base molded into them and on this base is a circular groove to hold a large o-ring that forms a tight seal. If the "boots" or o-rings have nicks or cuts in them or if they don't fit tightly on the carbs air can get in.

On the other side of the carb as you mention there are boots that connect them to the airbox. The same comments apply. If the seal is not tight and or the boots are nicked or cut, extra air will get in, throwing off the mixture in the carbs and causing the racing idle. So its important both sides of the carbs are free of air infiltration.

You can get carb dip in 4 litre containers at Napa, Carquest or even some Crappy Tire stores ( around $25 I believe). Carb rebuild kits should be available from Honda dealers or good independent bike repair shops (that can buy through Parts Canada). The secret to doing carb cleaning is to be organized and thorough. You need a clean, well lit area and some containers to store disassembled parts and some tubs or buckets to soak the carb bodies and parts. I use plastic ice cream and or margarine tubs. You need to immerse the complete body of the carb and the jets in the fluid for a minimum of 24 hours or so. You will also need some small brushes, thin wire, q-tips, dental picks, paper towels etc etc for cleaning any buildup of gunk on the body of the carb or inside the float bowls and such. The fluid is reusable so pour it back in the container (through a coffee filter) after use.Look at the filter and see how much gunk was in the carb.

You may find that some of the screws holding the connector rails, float bowls and carb tops are hard to move so you should add an impact wrench to your stable of tools. A good wack with one of those will loosen things up. Once all the screws and rails are off store them in one container. You should also have a container for each individual carb. Keep the carb parts seperate and make sure you don't lose any....some are quite small. Obviously, what came out of the carb goes back in.

While these are not the same carbs as yours this tutorial from the GS Resources website is one of the most explicit and easiest to follow and will give you the basic idea http://www.thegsresources.com/gs_carbrebuild.htm.

The first time you do it it may seem a daunting task but it really isn't. Just take your time and don't rush.

I hope this helps a bit.
Good luck with it.

Cheers,
spyug
 
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6mtsedan said:
Im looking through the clymers and i can't find any reference to "intake boots" or "intake boot o rings". I assume you are talking about the airbox and the chambers which dont have any o rings which i can think of.

I will take apart the Carb and try again to do it. Where can I get carb cleaner thats not in an aerosol can?

On a positive note, I did get to ride 2 days ago from scarborough to newmarket. When i arrived to newmarket, the bike stalled out on me. The 40km ride back was very stressful having to keep the bike idled at a minimum of 2000rpm. Trying to pull out of first was a nightmare as the bike was bogged down so id have to throttle hard and it would cause the bike to fly. Not fun for a newbie rider!
Click to expand...

The intake boots connect the carbs to the heads. You would need to loosen the band clamps on the boots to remove the carbs. If the boots are original, they'll be hard and brittle. Your carbs come out as an assembly, the front and back are mounted at an angle to the head. All this leads to making it very easy to get air leaks at the boots.

You don't want to just willy nilly splash carb cleaner around in the carbs. Carb cleaner will attack the rubber in the O-rings and diaphrams. Remove the diaphrams before you get carb cleaner near the carbs.

It sounds like you might need a proper carb rebuild.
 
Update:
Worked on the bike last night. Found that 2/4 were completely fouled with fuel and or detonation.

Checked the spark plugs and the spark was very weak on all 4 spark plugs. Replaced all 4 spark plugs with new ones and no success.

Checked the ignitor coils (ohms) and they should be at 2.8ohms and they were showing 3.7 which could be causing the problem.

Checked the spark plug wires and there was no continuity in any of the wires. Bingo! That could be a problem. Ordered a set of universal and express shipping.
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