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Discussion Starter · #1 ·

First time poster here, looking for help. This will be long, but I want to give you the whole story. I'm very confused because I am a fairly experienced mechanic but must be missing something. A friend who is not mechanical brought me a 2003 Eiger 400 automatic that didn't run. A quick inspection revealed that the motor was seized. I pulled the top end and found the cylinder and piston rings were rusted together from the machine having been submerged at some point and then left to sit for several years.

I put in a new piston and cylinder and checked the valve lash. Compression test today was 150 psi. Replaced the corroded vacuum petcock with a Yamaha petcock, cleaned the fuel tank out, and replaced all the fuel lines. Replaced the badly corroded carburetor with an Amazon aftermarket model (with good reviews) and it wouldn't start. Found that there was no spark so I substituted an Amazon 4-pin CDI box and found that I now have good spark. It still wouldn't start so I used a little starting fluid and it fired right up for about 3 seconds.

Now, after cleaning and checking out the new carburetor, I have found that when it cranks and fires, the engine actually kicks backwards momentarily and then resumes cranking. It is acting like the spark is way advanced and it is firing before TDC. I know that it is turning backwards momentarily because I still have the recoil off and I can see the starter cup rotating and then literally stopping momentarily when it fires. I've had the flywheel off to check the magnets and the woodruff key. The flywheel does not have the exposed magnets, but the fully enclosed magnets like the replacement RMStator flywheel. The woodruff key was in perfect condition. The pickup coil resistance test was good.

Since it seems like a timing issue, I pulled the cylinder head off again and double-checked the timing. It did appear that the timing marks were off by one tooth, so I corrected that and thought that I had found the problem. Unfortunately, it still does the same thing...It will crank just fine, but won’t start, and kicks backwards when it fires whether I use starting fluid or not.

Since the timing is not adjustable on this machine, I’m wondering if the factory CDI circuitry incorporates any type of variable timing feature that is dependent on RPM? That is about the only thing I can think of.

I've read other threads that discuss this "kickback" symptom and the usual culprits are weak battery or a too lean condition causing preignition. I've installed (and charged) a new battery and triple-checked both carburetors...the original one that I completely cleaned, and the Amazon replacement. Same response with both carbs, which leads me back to questioning the CDI.

Any body else run into this?

Thank in advance for your help.
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