No start Yardman trimmer YM400 31cc

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  #1  
Old 06-07-08, 07:36 PM
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No start Yardman trimmer YM400 31cc

Hi all, new guy here.
Got my brother in laws string trimmer kickin my butt here.
It had broken the easy start spring (not the recoil spring, the other spring that runs the star-shaped driver). Had to order the whole recoil assembly, got that and installed it so the motor will crank now, but can't get it to start.
I tryed a new plug for grins. The plug does seem to get wet. The old plug actually seemed to foul out because I'd get a drop of fuel between the electrode and ground. With a dry plug, and grounding plug on metal, I do get spark.
I swapped out the fuel, although the old fuel would flash if I dipped a screwdriver in it and lit it with a lighter.
After I fixed the easy start spring, it did pop off once after a few pulls, but that was it. A couple more pulls did result in a bit of exhaust smoke but now the engine seems dead. Primer bulb seems to act normally, fills with fuel etc, although I was trying to tell, where does the fuel actually get introduced into the carb?
The only thing I haven't tried (because I just fouind out about it) is the screen in the muffler.
Unit is about 2 years old per brother in law, and also the "born on" date stamped on the head in ink (2006).
It is a Yardman YM400, serial 1B276DH1273 and also the number 41ADY40G901
Gilly
 
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  #2  
Old 06-08-08, 04:40 AM
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Just checked muffler screen, and also removed muffler and checked the port, all is nice and clean. This thing looks like new! But no start........
Gilly
 
  #3  
Old 06-08-08, 08:32 PM
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If the plug is actually getting that much fuel on it, the engine is getting waaay too much fuel. Start by removing the plug and pull the rope several times to clear the cylinder, retry, repeat if the plug gets wet again. There may be too much fuel in the crankcase as well. The carb probably needs cleaning if it's flooding that badly.
 
  #4  
Old 06-09-08, 05:09 PM
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This is a 2 stroke, so I don't think fuel in the crankcase is a problem. Well, it could be, but anyways, I am on to the answer but may need a little help yet.
As I mentioned, I had to replace the "Advanced Starting System" spring. It goes between the recoil pulley and the star drive that engages into the flywheel.
I started thinking, what the heck am I missing? Then I remembered; someone on one of the forums I was reading mentioned [I]timing[I].
So I checked it out. The flywheel has 2 magnets fairly close to each other embedded into the side which I know triggers the spark. Well sure as heck, the magnets were opposed to the coil pickup at TDC! I figure when the piece of spring let go in the flywheel area (the spring I replaced), it must have thrown the timing off. The bolt that hold the flywheel on just rotates, so I can adjust the tming that way, I don't know if it is keyed into place or not but I just might mess with it and find out.
Does anyone know how I line up those 2 magnets to the pickup on the coil to get the timing set? At least right now it is coughing and smoking, which is more than it HAS been doing! I have it set with the magnets on either side of the pickup right now.
Gilly
 
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Old 06-09-08, 09:28 PM
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It's supposed to be keyed so that it can only fit one way. If the key is made as part of the flywheel, it has sheared off and you'll need a new flywheel.
 
  #6  
Old 06-10-08, 02:22 AM
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Thanks, that is the case here. I did get it running for now by eyeballing. It would smoke when pulling, then once it stopped and I rechecked timing and was way off again. I eyeballed it again (where the "tab" was that imitates a half-moon key and the slot in the crank) and tightened it "tighter than tight" and now runs but hard starting, which I assume is the timing being slightly off by my eyeballing.
Will see how it starts cold later today.
Also got the trimmer line on. It's dual line and was the first time I wound double line, found owners manual online so I think the line is on OK.
Gilly
 
  #7  
Old 06-11-08, 11:18 AM
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Well gang, I was a bit disappointed by the whole thing. I mean it was only BUILT a little over 2 years ago and I think bro in law said it was used 1 year. This Advanced Starting thing is BS and I don't mean Briggs and Stratton!
To get the flywheel would be about $35 with shipping and tax. maybe I could get it lower online somewhere, but that's not the point. The point is I already have about $21 into it for the pulley I had to buy (OH but just needed the stupid spring) and even if I could get it down to $25, that's still over halfway to what a new version of this hunk-a-junk (can buy this thing new at Farm and Fleet for about $70).
So since there is a woodruff key slot in the crank end, I thought I'd try a repair and damned if it didn't fix it! Found a 1/8" woodruff key to be the closest, although a tiny bit to wide. The flywheel is aluminum so I thought maybe a 1/8 wide file. Closest I could get it a chainsaw blade sharpening file, which was about $4-5 at Ace. It is round though, I really wanted a square profile for obvious reasons but had to work with what I could get and make it affordable. So I filed my slot into where the "fake" key used to be, so the location I know is at least very close if not perfect. I made a groove through the hole crank hole so I know I was good on location and straight, then made it a little deeper on the engine side of the flywheel hole. Test fitted it and the flywheel wobbled a bit and also it seemed to stop through about 1/2 of the rotation (only had about 180 degrees of spinning in other words. Took it apart and saw the key was dragging on the dust seal where the crank exits the block, and also the wobbling was because the slot needed to be a bit deeper. So with a normal file I took some of the tip off the woodruff key and made sure i would have that blunter end facing the engine, then I made the slot a bit deeper on the engine side of the flywheel. Went back together just fine, tightened the nut and the wobbling was gone and engine turns through now fine.
Put the cover (with the starter pulley) back on and the thing started up lke in 3 or 4 pulls and runs just fine now.
In your face, MTD!
Gilly
 
  #8  
Old 06-11-08, 07:57 PM
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There ya go! The only thing now is that the key you used isn't going to shear if whatever hapened to make it shear before happens again. Personally, I'd use it anyway.

A lot of folks would never have even thought of doing that, let alone attempted it. Kudos for using your noggin'.
 
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