tecumseh timing

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  #1  
Old 07-12-04, 07:48 PM
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tecumseh timing

restoring sears lt 10 hp tecumseh engine 143296042. tractor sat outside since 1989. fixed everything working every day for 2wks. mowed yard 3 times kept dying when hot. thought it was carb. would pull carb reinstall and finsh yard. kept getting harder to start, carb was flooding. tear it down again. lap valves and grind exhaust to .oo8. still hard to start. install new pts. and condenser. still flooding and hard to start. ck spark again. no spark at end of plug wire. inspect plug wire. end of wire loses continuity when you wiggle. install new plug wire end. fire in the hole engine starts adjust carb again. next day no spark. pull flywheel again and wiggle coil secondary. meter shows 10000 ohms but shows no continuity when i bend it about 3 in. from coil. take it to small engine shop. he says coil is bad. i buy a new one. wait 3 days. he says timing is set by a special thingamabob. question: can i set the timing by lining up bolts to old scrape marks on magneto assembly without causing problems. how critcal is this. is there room for error. does intermittent spark cause carb flooding. engine has high compression. any feedback appreciated. thank you.
 
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  #2  
Old 07-12-04, 10:01 PM
Azis
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Hopefully the timing thingamabob is your flywheel key, and if it pops when trying to start it sure sounds like a place to check. Here is some info from a previous posting...

.the flywheel key aligns the flywheel with the crankshaft so that the magnet passes the coil at the precise moment needed for the spark plug to ignite the fuel/air mixture in the chamber slightly before at or after top dead center, in other words it is ignition timing. Since the flywheel still spins and passes the coil, it will still produce spark at the plug, however if not aligned (or keyed) it will not spark at the correct time. Alot of the time with a sheared key, the engine will pop or backfire.

As far as the clearance of the magneto to the flywheel, rip a piece of notebook paper, (which is about .005) triple fold a strip, rotate the flywheel so the magnet is at the coil/mag, snug both bolts and one side at a time gap each side letting the magnet do the work and so you can slip the paper gage out with out tearing it but with some resistance. This is not that critical of an adjustment, as long as the flywheel has clearance the closer the better generaly speaking.

Gl and plz let us know how it goes
 
  #3  
Old 07-13-04, 01:55 AM
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Hello l.mitchell!

This one is different from what Azis is thinking. You can't set the armature that way. You were probably told you need a dial indicator to set the timing. You can try to fudge a bit and install the new coil as you mentioned. You might get lucky, but it might also take a few tries to do it. I do agree that you need the new coil.
 
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Old 07-13-04, 10:11 AM
Azis
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Doh...!!! Sorry Mitchel for the miss information

Strike 3 for me....*heads to the corner with the Dunce hat*
 
  #5  
Old 07-13-04, 02:43 PM
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l,
Do you have access to a dial indicator? If so, you should absolutely time the magneto. There are dial indicators whereas you needn't remove the cylinder head to time the engine...can you get to one of these? Post back with these answers and we'll procede further.
 
  #6  
Old 07-15-04, 10:46 PM
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my coil arrives tomorrow. i dont have a dial indicator. the old bolt washer marks that hold armature assembly are clearly visible. will it be ok to bolt to these? or is this measurement so critcal that it requires this special device. i would rather time it myself if possible. i dont have a problem with removing the head. i have done it twice before on this engine. can i time at tdc with both valves closed at their .008 clearance with flywheel key directly at coil. is this proper timing or should flywheel key be rotated back or forward to allow spark just before or after tdc. the guy at the shop said it is like timing a car. any reply would be greatly appreciated. thank you, l.mitchell
 
  #7  
Old 07-16-04, 09:34 PM
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put on new coil today. put on gas shut off. tighten bolts to old washer marks on armature assembly. got real nice blue spark. would not start. when i shutoff gas and squirt starting fluid in carb it will pop thru exhaust or carb but will not start. any suggestions on how to time engine so it will run? thank you, l.mitchell.
 
  #8  
Old 07-17-04, 06:52 AM
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With the "popping" you're getting, you didn't get the timing on the money...you will need to time this properly to get this engine back up and running well. Whichever dial indicator you use, you will need to set the timing at .090" before top dead center (BTDC), on the compression stroke. Using a continuity meter, be sure the points are set at .020" exactly, remove all wires from the point terminal, clamp one meter lead to the point post termianal and the other to the engine block (cooling fin works well), loosen the two bolts that hold the magneto to the block (not too loose - just enough to get the magneto to move), bring your piston to .090" BTDC on the compression stroke, with a light hammer, tap the magneto (at the boss right next to the bolts) so that your continuity meter sounds, at the precise first moment you hear the meter sound tighten the two magneto bolts down. Usually tightening the bolts down will throw the timing off a bit - it will take some getting used to to get it on the money. Always recheck for accuracy after the bolts are tightened.

BTW This engines' Tecumseh #'s are - VM100-157034B
 
  #9  
Old 07-17-04, 10:37 PM
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tecumseh timing

puey: thanks for the reply. as soon as i get the time i will attempt to to retime this engine based on your info. i have an ohmmeter that will tell me when the points break. i will pull the head and measure .09in. from tdc on compression stroke. i will let you know the results. thanks again for your info. l.mitchell.
 
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