Re: IHC LA Engine Trouble HELP!!!!

Posted by KEB on July 06, 2007 at 08:03:33 from (72.19.170.5):

In Reply to: IHC LA Engine Trouble HELP!!!! posted by H fanatic on July 05, 2007 at 21:26:46:

An LA is throttle governed, not a hit & miss. I have one I'm working on, but its not running yet, mostly due to a lack of time.

Here's a couple things to check:

First, is the impulse on the magneto working? As you turn the engine over you should be able to hear it click. Take the end cap off the magneto and watch the shaft as you turn the engine. The shaft will stop turning as the piston comes up on compression, then snap through part of a rotation as it opens the points. If the shaft just turns, the impluse is stuck & needs to be cleaned. Weak, thin spark is a possible result of the impulse not working.

You can check ignition timing just like any other four stroke engine. Take out the spark plug, put your finger over the hole, turn the engine over until you feel pressure against your finger. Pressure indicates that the piston is coming up on compression. Watch the top of the piston through the spark plug hole (it's easy to see with a small flashlight on an LA) so you can tell when it reaches TDC. The impulse on the magneto should trip just after the piston is at top dead center. If it trips too soon, the engine can kick back.

I don't have the official timing procedure, but a quick check will tell you if its close enough for the engine to run. If your friend's engine is actually sparking a quarter turn before TDC, theres no way it would run. The spark would be happening with the piston at the bottom of the intake stroke. Are you determining this based on timing marks or on actually watching to top dead center? Timing marks have been known to be off.

If you don't get compression, then valve timing is off which means the camshaft is not synchronized to the crank. A quick check for valve timing is to watch the intake & exhaust valves open & close. You should be able to see the exhaust valve close and the intake valve start to open (sort of a rocking motion between the two valves) as the piston reaches top dead center on the exhaust stroke.

Hope this helps,

Keith

Replies:

• Re: IHC LA Engine Trouble HELP!!!! H fanatic 09:12:00 07/06/07 (2)
  • Re: IHC LA Engine Trouble HELP!!!! KEB 20:31:20 07/06/07 (1)
    • Re: IHC LA Engine Trouble HELP!!!! KEB 20:36:21 07/06/07 (0)

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