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Old 12-13-2010, 01:35 PM   #1 (permalink)
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Hard starting Yamaha 340 - after sitting for a while

This is my first post and I got on here looking for help with fixing this problem.

It's a low mileage 1987 Yamaha Excel III 340. Most years, it is only run maybe 50 miles or so.

Each year when we start it for the first time, we have to pull the spark plugs and pour a little fuel into each cylinder to get it to fire. We have to do that about half a dozen times until it will stay running. Then it runs perfectly, for the rest of the day. It also starts first pull after shutting it off. A few days later, if we let it sit again, we then need to put a little gas into the cylinders again. Of course the battery died years ago, so we pull start it.

Any ideas for the cure on the hard starting after not running for a while? Fuel pump? Fuel lines? Or??

Thanks for your help!
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Old 12-13-2010, 01:50 PM   #2 (permalink)
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Clean the carb.
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Old 12-13-2010, 02:32 PM   #3 (permalink)
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Would a carburetor in need of cleaning do that? If so, what part of the carburetor pulls the fuel through from the tank?

It acts like there's not enough suction or pumping to move the fuel from the tank to the carburetor. Once it's "primed" it runs perfectly with no hesitation or any performance problems.
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Old 12-13-2010, 02:41 PM   #4 (permalink)
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I agree with RJ. Normally, you have a little gas coming into your engine from the main jet and a little air coming in from your pilot air jet. If either one of those has the slightest bit of blockage, you can pull all day and get nowhere.

If you have fuel in the fuel line all the way to the carb, it should start fine with a carb cleaning. If not, try taking off the gas cap and blowing into the tank for a few seconds (keep your mouth sealed to the tank so no air escapes) until the gas enters the carb.
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Old 12-13-2010, 04:16 PM   #5 (permalink)
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Clean the carbs is a good idea. My excel is hard starting if you pull, because I get maybe a foot of pull before the end of the cord. I'd put a battery in it, it's make it a little easier to start. Also if your enricher circuit is jammed, not working, or has a broken cable to the plunger, it'l take forever to start.
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Last edited by Yamaha440; 12-13-2010 at 04:17 PM. Reason: spelling
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Old 12-13-2010, 05:41 PM   #6 (permalink)
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check the line in the tank. it usually has a check valve which keeps the fuel from bleeding back into the tank and having to keep pulling until it priomes itself again. i would also clean the carb and replace the lines and rebuild the fuel pump. you might have a small vacuum leak, so your sucking air instead of fuel.
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Old 12-13-2010, 11:01 PM   #7 (permalink)
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Thanks everyone for the ideas.

Can anyone tell me what the idle speed should be on this machine? It idles at about 3000 rpm now once warmed up. That seems a little high to me, but on the other hand it doesn't sound like it's revving.
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Old 12-14-2010, 09:44 AM   #8 (permalink)
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It says in the upper left hand corner of the hood as well as plug gap etc. It is 1750 RPM.
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