Hey everyone,
I've got a question regarding my 1982 Honda Magna. It's regarding my fuel pump. When I turn the key, the fuel pump does pressurize, but when the engine is running, the pump does not pump. I've spent countless time searching for any useful information on what the "fuel pump cutoff relay" actually does. I have yet to find a schematic that shows me the internals of it. If I put my ear to the "main" relay, while it's running, I can clearly hear the relay rapidly clicking.
So hear's my question....Does anyone have any idea how this particular fuel pump cutoff relay actually works?
One somewhat related question. When I got my bike, it'd been sitting outside for some time. I rebuilt the carbs and I have an occasional problem. If I bypass the fuel cutoff relay to force the fuel pump to pump, I'll get fuel coming out of one of the black crossover tubes that connect the carbs together. (and you can see it in the airbox). I suspected that because of my rebuild, one of the needle valves wasn't seating, so I pulled the carbs out and checked and then reinstalled. I still have the problem. Does anyone have any ideas on what might be causing this to happen?
Mark
I can't really shed much light on the relay. But, the 2nd question about the fuel coming out the vent line I might be helpful. I would replace the needle valves. The springs get weak and just because you did everything correctly does not mean the spring has sufficient tension to full close when pressure is applied.
DG,
The needle valves are brand new. They came with the carb rebuild kit that I purchased. Since we are on the topic of needle valves though, the needle valve is suspended by a very thin wire device. Does it have a "right" way to go on there. In other words, you can turn them one way or the other. Initially I thought that might be the issue, but they are all turned the same way now and no luck.
My next step is to try to isolate what carb is leaking (or at least which pair). I plan on clamping the fuel hose off to one pair of carbs and then charging the line. If the fuel continues to seep up, I'll clamp the other pair. I believe that the carb setup is a pair of pairs. So not all four carbs are connected via the crossover tubes. If I can isolate the pair that leaks, hopefully I can disassemble the bowl while it's on the bike and figure out which is leaking. I truly hate removing the carbs. They are an enormous pain.
I'm still open to anyone else's thoughts on the issue.
Well, that rules that out. I don't know about the wire but don't see why it would matter which way it is turned.
There are 3 fuel tubes, the first supplies 2 carbs then one passes to the next. I don't know how you would block them off effectively.
You checked the float height also? I have some pics of my carbs off the bike with the fuel and vent lines lableled but they are on my office computer and I won't have them till Monday to post again.
DG,
My carbs actually only have two tubes. Trust me, this was a point of much confusion on my part. I disassembled the carbs to overhaul them and I had a parts diagram. I thought the parts diagram would show me how to put it all together, but as you mentioned, some carbs have three tubes, some have two. Mine had two, but the drawing showed three. I spent three days ripping my garage apart and accusing everyone in the house of losing a critical part of my carburetors. When I finally calmed down and started looking at the carbs, I only saw a place for two tubes. I confirmed with other forum members that my carbs should only have two tubes. (they both look like a T, but the vertical part is extremely short and the horizontal part is long)
As far as isolating the pairs of carbs, it was actually very easy. The fuel line goes from the pump to the carbs. There is a T in the line that connects the left pair to line and then the line continues to the right pair. All I had to do was take a small pair of vice grips and clamp the fuel line to the left pair off. I energized the fuel pump and had no leaks. I then switch the vice grips and clamped the rubber fuel line that feeds the right pair. Once again, no leaks.
So in summary. I didn't actually do ANYTHING other than selectively clamp the fuel lines and my crossover tubes have stopped putting fuel into my airbox. I don't have high hopes that this will remain this way. It stopped doing it once before and came back, but for the time being, it's stopped.
Regarding my original fuel pump problem, I've located and purchased the fuel cutoff relay and it's on it's way. Hopefully that will correct my fuel pump issues. If not, I'm prepared to start "engineering" a solution. I'll keep everyone posted on the status.
Mark
Well, I figured I'd give everyone an update. I was able to find/purchase a fuel pump cutoff relay for my specific model. I paid $25 shipped from a salvager. I installed the relay and started the bike. The good news is that it did fix the fuel delivery problem. The bad news is that after I got the bike running, I couldn't synchronize the carbs. Carb #3 would not adjust. In looking down the throat, I noticed that the vaccuum slide was not functioning. If I manually retracted it with a screwdriver, it stuck open. Clearly, the carbs are going to have to come back off for another round of cleaning.
It's ok though. I don't mind investing the time/effort in cleaning the carbs if I know that the fuel delivery is working.
One minor hiccup this weekend though. Because the bike isn't really roadworthy yet, I've just been jumping the bike off and was planning on just purchasing a new battery when I get the engine running. (Battery is 10 years old and completely dead). Well, I wasn't as diligent as I should have been and crossed the cables at the car side. As soon as I connected them to the bike, I heard a faint pop and realized my mistake. Fearing the worst, I tried to start the bike and it would not start. (In fact, nothing even turned on.)
Luckily, the bike has a fusible link right by the battery and I'd smoked it. The spare was still in place, so I installed it and voila, the bike cranked right up. If that spare ever smokes though, I may have to do some "engineering" and install a 30amp fuse. The fusible link looks very unique and I'm not sure you can purchase them anymore. (Even if you can, it's probably not as cheap as a 30 amp fuse)
I'll keep you posted on the carb rebuild/road test.
You can still get them from Honda and other places
http://www.hdlparts.com/fiche_section_detail.asp
Part number 98200-53000 $2.50 each
Charles,
Thanks for the link. In removing the carbs last night for a rebuild, I noticed an ugly problem has resurfaced. The first time I removed the carbs (almost a year ago), I found the black caps on the choke assy's had broken on three of the four carbs. Basically, the threads had sheared off from the caps. I hoped that some industrial adhesive would save them (and me $160). I glued and clamped them back together and they worked great....for a while. When I removed the carbs last night, three of the four are broken again.
Rather than cat/mousing this again, I'm going to try and procure some from Ebay and reinstall. I also noticed that one of the choke plungers had snapped at the top. (Really wierd considering they are made of brass) Anyway, buying new ones should correct that problem. But as I'm sure everyone can attest, it adds to my cost of getting this seemingly free bike running. Who said motorcycling is cheap?
On the next episode of "As the Magna Turns"....will Mark get the carbs clean and synched? What will the next roadblock to windshield time be? Stay tuned to find out.....
Mark, if I were you I would check Ebay under Honda Magna parts or even consider looking for a "parts bike". I did the same thing you did - breaking the head off the choke piston. Bought a used set of carbs off of Ebay for 35.00 that were dirty, but the choke pistons were good. As a bonus all the diaphrams were in good shape. You don't want to have to pay through the nose for new parts, if there even available.
Quote from: mark_gober on April 07, 2010, 11:36:20 AM
But as I'm sure everyone can attest, it adds to my cost of getting this seemingly free bike running. Who said motorcycling is cheap?
I see that you're a relatively new member...
After owning my 85 Magna for 5 years now...its never been cheap.
And I didn't get it for free...
3k for the bike, another 2k repairing it (never buying from a dealer again!)...it was a LEMON.
30,000 miles, 5 years later, my bike runs, and the internals are excellent....i've done everything from fork seals, carbs, valves, electrical...
but i still have some negatives... no speedometer (i deal with it)
dent from letting neighbor ride my bike ( i deal with it)
Many forum members bicker that I hate my Magna...that's not true...I like riding it and wrenching.
I do hate the hard earned bills $$$ that I've used to keep it in shape when I hear about people getting bikes for much less and sometimes free ;)
Good luck...you're way ahead of the game!