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Hi,

I have an '83 Yamaha Maxim 650 with 22,000 kms on it. I was given it by my father and it has not been started (except for maybe about 5 times) over the past 3 years. The bike is in excellent condition except for the following problem:

The problem with it is that it starts, but once I give it gas it stalls. it will also stall after about 20 seconds of idling. After starting it for a few times, gas will start to leak out of both the exhaust joins near the foot rests.

Here is what I have tried so far:

1. If I remove the spark plug wire from either of the outside plugs, it stalls.
2. If I remove the spark plug wire from either of the 2 inner plugs, it has no effect on the engine - so I assume they are not firing.
3. All 4 plugs have sparks (turned the engine over with the plug only connected to the spark plug wire and not in the engine and I see a spark).
4. I noticed after an hour of trying different hings, the spark inner 2 plugs were wet. Could have happened sooner, but that was when I tried to test the spark plug to see if they had a spark.

I can only believe that this is a carb issue (clogged jets, stuck floater, something along these lines), but not having much experience with this, I thought I would get some feedback before diving deeper in and taking the carbs apart.

I would like to learn how to fix my own problems on this bike and not have to try and find a mechanic that would look at something this old

If you have any need for more info that I didn't mention, please let me know

Any and all help for ideas would be greatly appreciated.

Thanks!

where are you at?
i have the same prob with an '82 XJ650 maxim... after a few days of trying mine, it would try, but then would die very quickly. with mine i only had it leaking from the exhaust and the overflow hose when i had it on prime for a while..i dont know what to do either
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honda750 wrote:where are you at?
i have the same prob with an '82 XJ650 maxim... after a few days of trying mine, it would try, but then would die very quickly. with mine i only had it leaking from the exhaust and the overflow hose when i had it on prime for a while..i dont know what to do either

I am in Ottawa, Ontario, Canada. If I have mine on Prime, it will start to leak gas sooner than if it is on Run. It only leaks after a few minutes of running (at 20 seconds a time that is - so about 6 or 7 times of starting it and letting it stall) when it is on Run.

I'm only guessing here, but it sounds like you both have one or more carb floats sticking. One of the problems with an old bike is that after sitting, the inside of the tank will rust, and the rust particals will make their way to the carbs and needle valves. One of the first thing you must do is install an inline filter between the petcock and the carbs . After that you will want to drop a couple of the float bowls and take a peek inside to see if it is full of junk like I suspect. It may be posible to clean the float bowls while the carbs are on the bike, but I'm afraid you might be into cleaning the carbs on the bench. If the carbs are full of rust and junk, you should address that issue first and flush the tank and install an inline filter. The filters are not expensive and can be purchased at any Yamaha shop. The petcocks prime position is only there to fill the carbs after they have been drained for storeage or rebuild. The run position is vaccum activated and will only turn the gas on when the engine is fired. I don't know if that's any help to you guys. As a side note, if the gas is running out the exhaust pipes, my guess that the raw gas has contaminated your oil, and the crankcase may be over full. Also, too much raw gas in the cylinders will wipe off the much needed oil for the piston and rings, don't lunch out the pistons while you are trying to get the bikes started. XS

that's what i was thinking, when i get time this week im taking them off and cleaning them out with GUMOUT carb/choke cleaner. i put new gas in the tank and swirled it and cleaned it, but looking at the inside, there isnt much rust and i thnk it might just be the resin from the gas. either way, i'll find out this week! thanks for the suggestions. BTW, does anyone recommend a safe/efficient way of cleaning the carbs other than just attacking them with an old tootbrush and some gumout?
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Most likely a stuck needle and float. I'd definately clean the carbs and shoot some compressed air through all the passages and jets. I'd also change the oil and filter and put in fresh plugs before start up with the cleaned carbs.

I like to use spray carb and choke cleaner, and like Fordthunderz said, use plenty of compressed air thru the jets and passages. After you clean them with carb cleaner, get an old plastic tub and clean them in Dawn dishwater soap and hot water, rinse with hot water, then blow them out good. I sometimes use spray brake cleaner instead of carb cleaner, but you have to be careful with the brake cleaner, it's pretty hot and might melt any rubber gaskets and seals. But it gets them clean. Be careful with these cleaners, they also melt your prized paint job. XS

Excellent - thanks everyone. I'm going to give it a try this weekend - provided I have enough time with Canada Day on Saturday!

Thanks again!

I had this same problem on an 81 yamaha xj550 seca. Turned out to be sticky floats, and clogged jets. I had to tear the carbs apart, and completely clean them, but now it runs pretty good.

carbs are clean as a whistle...after 3 hrs of complete disassembly....and she's running like a champ! windy roads ahead!
thanks for getting me back on the road!
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