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Adjusting Techumseh Ssi


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#1 TerryD OFFLINE  

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Posted July 24, 2013 - 12:32 PM

My 1972 MF10 doesn't want to idle right and I've cleaned the carb a number of times with spray cleaner and boiled it with oxyclean. It fires right off with a bit of choke when cold and none when warmed up. It's smooth at 3400 but not so much when idling. Carb is a fairly new Walbro 37 with no play in the throttle shaft.

 

I'm starting to suspect the ignition system. Since it's SSI is there anything to adjust other than the flywheel pin heights at .250 and .187, and the pin air gap on the tall pin at .006 to .010? I need to regap the plug to .028 the next time I get a chance and clean under the flywheel as well as the bottom of the coil. I also plan to test the coil to see if it's breaking down when hot.

 

I have a new head gasket and bellville washers on order for the head.

 

I picked this up a few weeks ago and it had been sitting for a few years. I'm starting to run out of ideas on why it won't idle properly. Any thoughts?

 

As always, thanks.

Terry


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#2 boyscout862 OFFLINE  

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Posted July 24, 2013 - 12:35 PM

Check out Ed Stollers' Web site. He gives a lot of advice and instructions on the Tecumseh Ignition. Good Luck, Rick

http://home.earthlin...ller/index.html

I just noticed that you are fellow lifer. We seem to have alot here.

Edited by boyscout862, July 24, 2013 - 12:36 PM.

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#3 TerryD OFFLINE  

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Posted July 24, 2013 - 12:45 PM

Yes, 26 great years.

 

Thanks for the link, I'll check it out.


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#4 chris m OFFLINE  

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Posted July 24, 2013 - 12:48 PM

Terry did you make sure the flange of the carb isn't warped? And is the choke opening fully?

 

When you check the pins on the flywheel make sure they are straight, I had one recently that the tall pin was bent.

 

Also I see you ordered the head gasket, Have you had the head off yet to see the condition of the valves and to make sure the head is not warped?

 

Other than that just be sure nothing is restricting gas flow to the carb.

 

Good luck!


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#5 MH81 ONLINE  

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Posted July 24, 2013 - 01:11 PM

Terry did you make sure the flange of the carb isn't warped?

 

This was my thought also.

 

part 2 is the small screw on the carb.  try it at 3/4 turn open and see what you get.

 

part 3 is bring the idle stop screw up to where it will just stay running.  I have a couple of them over the years that just will NOT low idle.  I blamed it on Monday or Friday construction practices. :smilewink:


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#6 HowardsMF155 OFFLINE  

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Posted July 24, 2013 - 01:22 PM

You can check the general operation of the SSI with a timing light.  I would suggest hooking up an induction style, get it running, then look at the flywheel and find a screen mounting boss you like, then make a mark where that boss is every time the light flashes.  Then, shut the engine off, fix it so it won't start, then just crank it and see where the mark is.  It should move quite a bit to one side or the other of your original mark.  Then try idling the engine and see if your ignition is jumping back and forth between the normal running mark and the starting mark.


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#7 TerryD OFFLINE  

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Posted July 24, 2013 - 01:41 PM

Head was removed to decarbon (not much there). Valves looked good but I cleaned around them anyway. I didn't check the valve clearance or to see if the head was warped at the time. Head gasket looked okay, but if I take it off again I'll replace it.

 

The carb flange was out .025 to .030 and I've flattened it back down using a piece of glass as a lapping surface and 400 then 800 wet/dry paper (wet). The choke opens fully.

 

I've adjusted the idle screw back and forth a number of times and it doesn't seem to make much difference. I've been leaving it out about 1 turn from closed and the idle stop screw was adjusted as suggested to keep it between 1300 and 1500 rpm.

 

I did notice that the flywheel pins look like they've been dinged up some, especially the tall one. Not so much bent, but a bit rough looking like maybe it had been hit with a wrench. I was thinking of filing the ends flat and punching them back out to the right height.

 

Thanks for all the suggestions. I just wanted to make sure I wasn't overlooking something obvious. Maybe the Tecumseh's just don't idle as well as the Briggs do.



#8 MH81 ONLINE  

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Posted July 24, 2013 - 01:46 PM

at this point, I would try to make the shorter pin a little taller (put it right at the max hgt spec's) and see what you get.  You would be well served to do as advised with the timing light above.


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#9 TerryD OFFLINE  

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Posted July 24, 2013 - 03:48 PM

I will certainly give the timing light a try once I have adjusted the pins, set the plug, and checked the head to make sure it's not warped.

 

Thanks everyone.


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