OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Engines Questions On Tecumseh / Kirby Engines Are Kirby-Lauson positive or negative ground?

I posted a question in this thread before realizing I was in the Briggs & Stratton section. https://www.outdoorking-forum.com.au/forum/ubbthreads.php/topics/90584.html#Post90584

My question is about Tecumseh engines so I decided to re-post the question here.

I purchased an ignition conversion module recently for a Kirby-Lauson VK-30. I have not been able to get it to work. Every now and then the engine fires, but it appears to be mis-firing. I have double-checked the timing and the armature is where it should be.

The module comes with a very basic diagram, showing positions for positive and negative ground.



How do I find out if my engine is positive or negative ground?

I assumed these engines would all have to be negative ground, however I notice the "live" wire from the coil is covered in blue plastic, suggesting they must be positive earth. Also the wire to the stop switch is white with a red terminal, which also suggests positive earth.

So can anybody please tell me if these 1960s Kirby-Lauson engines were positive or negative earth? It is a very basic question but I can't find the answer in any of the manuals.

I have good spark on test, but could the timing be reversed if I've got the positive or negative the wrong way around? I am tempted to try it the other way, but thought I should ask first in case I damage the module. Perhaps I have already been using it the wrong way around??? I do not appear to have harmed the unit, as it is still firing, but I wonder if this is what's causing the firing sequence to be reversed?

Don't hurt to ask as someone may have already found out which it is.

Yes the ignition timing would off as it would fire on the trailing edge of the flywheel magnets instead of the leading edge. It shouldn't hurt the igniter if connected wrong on magneto system but will lead to having spark just at the wrong time and a non-start condition. And as you might think negative ground is the rule but wasn't back in the 60's or earlier. I have seen engines with points both ways. Now old cast iron Briggs are a good example of positive grounded systems.

I even have old trucks were they are positive ground and an inexperience tech it can lead to some serious damage to the electrical system.

I tried it the other way around this morning. There was no spark at all. So I had it right the first time. I put it back the way it was before and tried again. It ran but the timing was a bit off. Then disaster struck!

I got the engine to run for about 5 seconds, then it gave a small backfire and stopped dead with a suspicious "crunch" sound. I went to pull the flywheel, only to find it had shattered in about 4 pieces. I found the key was stuck to the magnets inside in two pieces, which is possibly what caused the failure. And when the flywheel broke it took out the coil armature and most of the ignition, and also broke a chunk out of the key slot on the shaft. What a mess! Now I remember why I dislike Lauson and Tecumseh so much.

Yuck...Never had the pleasure or displeasure to work on Lauson engines but I do remember a tech behind my home when I was a teenager that hated them.

My day was a little frustrating too, I have been working a Chinese ATV since late December. One problem right after another. hat is what you get when someone that no idea of what they are doing screw everything up. I got it finally to hit several weeks ago to only find out the head gasket was blown. Not fun to tear down and reassembly without even an IPL to go by. Well got the engine on and tried starting it. Didn't won't to go at first then she fired up and ran fairly good after carburetor adjustment. So I put the foot rest back on then it would start. I from lost spark again even with a new CDI system module and coil. I definitely was hoping it wasn't the trigger module.

The only thing I did different during shut down was to use the handle bar kill switch. Well it had to be the part that I couldn't get back in January. So I disassemble it to find the kill switch reading shorted even in center run position. Since I use to take these switches apart when I worked on office equipment I proceed down that path to see why it was shorted. It turned out a brass path between the contacts form wear, once removed the short was gone. Reassemble with dielectric grease (none found in the switch which explains the wear) and on the first try engine fire back to life. Just lucked out that was it.

So glad to finally have this nightmare repair ready to leave the shop as the distributor and the parts supplier were of no help providing any diagrams; just the parts that I guess at being the right ones. I am so frustrated that I think I might not even try working any more these clunkers but It should be good training while learning to work on ATVs.

Sounds like it must have been "one of those days" for both of us.

I had a bloke come around today and he insisted I look at his chain saw and Ryobi bent shaft line trimmer. He had had then at another mower repair bloke that I know for over 3 monts and he said the other bloke didn;t have time to look at them. I told him the same I didn't have time and I was not interested in them but he insisted he wanted me to look at them. The Chain saw is Chinese so I have figured the best way to get rid of this bloke is just tell him the Ryobi is going to cost $150 to fix and $300 for the chain saw. That should get him out of my hair, 98% of this Chinese stuff is not worth wasting time on even though the ATV's cost quite a bit of money, most people are not prepared to pay for the countless hours you have to spend on repairing them.They buy cheap things and so expect it will be cheap to repair them but it is exactly the opposite.

Especially ATVs. Some are royal in the backside just to even remove a carburetor or any engine work. Today's automobiles are just as bad due the tight engine compartments. The one I just finished I have spent over 6 hrs on and billing for only 3 hrs. This don't even include the time I spent hunting the parts. Some of this I can chalk to the learning curve as I am teaching myself these repairs.

Customers do expect cheap repairs even on the $7000 - $10,000 ATVs just because I work out of a shop at my home. Most times my costs are even higher due to being a small shop.

Now when it comes to the Chinese stuff it is extra difficult due lack information as you got to figure what they cloned plus where and if you can get the parts. Plus when it comes to handhelds equipment they tightly packed, making even more difficult to repair. I recently had the displeasure of working on an Echo CS330T chainsaw. It took over two hours just to get the engine out the case so I could disassemble it. Not too bad though as it was the first time for one. Now that I know how they come apart it would not take as long next time.

Those curve shafts are so cheap around here they not even worth fixing as replacement cost are less. At Walmart I seen as low as $68 and my starting labor is $43.80/hr plus parts. Does not take long to exceed replacement cost.

So far I haven't seen any Chinese chainsaws but there will be the day that I will. I already hearing about them here.

I got it to run. So I can now say with absolute certainty that the Kirby-Lauson VK-30 engines are negative earth. This is despite them having a blue wire running from the coil to condenser as the "live wire".