Tecumseh VLV126 too hot

[mk378]

You could probably check this at home by taking the side cover off to confirm there is a gap between the end of the valve stem and the tappet when the valve is closed. I say probably because it isn't clear in the video if that area can be reached with the valve spring and keeper in place. If it needs to be adjusted though that's a fairly major disassembly.

If the blade is not directly attached to the bottom end of the crankshaft then it's unlikely the flywheel key has broken. They're designed to break away to reduce damage when the blade is directly attached and it hits an obstacle.

 

[ripcord]

Always fix the known issues in a poorly running system first. You should not receive a shock when touching the engine. You have a broken wire, bad insulation, or similar in either your ignition system or the charging system. This mostly likely why it is running badly.

 

[Cosmopolit]

If it needs to be adjusted though that's a fairly major disassembly.

Yes, this is what it looks like.

If the blade is not directly attached to the bottom end of the crankshaft then it's unlikely the flywheel key has broken. They're designed to break away to reduce damage when the blade is directly attached and it hits an obstacle.

You are right. The mower has V-belts that power the blades, that means there should be no direct impact to the crankshaft if the blade hits an object.

 

[Cosmopolit]

Always fix the known issues in a poorly running system first. You should not receive a shock when touching the engine. You have a broken wire, bad insulation, or similar in either your ignition system or the charging system. This mostly likely why it is running badly.

Yes, to check this I don't have to take apart all the engine... Well, this mower is a longtime project. But I still love it, it is much smaller that all the other riding mowers, it looks like a toy. The difference between men and boys is the price of the toys.

 

[Cosmopolit]

As the seat wears, the valve lash gets tighter not looser. So you will be taking a very small amount off the stem to meet specs.

Well, after taking opening the head and the small box where the valves are, I found something strange: at any first dead point, the valves sit tight. Then, as I turn the crankwheel one full turn until the next dead point, both the valves are so loose, that I can turn them with my finger (seems to me at least 0.5 millimeter?). Then, as I turn the crankwhell another turn, they sit again right.

That means, that the valves may be of the right lenght.

The problem seems to me is inside of the engine, this mechanism that pushes the tappets from inside of the engine, that in their turn push the stems of the valves. Sorry, I don't have the right vocabulary for all those technical terms. It seems to me that a general overhaul of the engine is due, probably not worth anymore... very sad.

 

[Kamele0N]

Worn out camshaft?

Find its P/N here..... And typ it on a Ebay.de make fun&learning project out of that expirience

PartsTree - Home of OEM Parts for Outdoor Power Equipment

Parts lookup and repair parts diagrams for outdoor equipment like Toro mowers, Cub Cadet tractors, Husqvarna chainsaws, Echo trimmers, Briggs engines, etc.

www.partstree.com

 

[Cujet]

Well, after taking opening the head and the small box where the valves are, I found something strange: at any first dead point, the valves sit tight. Then, as I turn the crankwheel one full turn until the next dead point, both the valves are so loose, that I can turn them with my finger (seems to me at least 0.5 millimeter?). Then, as I turn the crankwhell another turn, they sit again right.

That means, that the valves may be of the right lenght.

The problem seems to me is inside of the engine, this mechanism that pushes the tappets from inside of the engine, that in their turn push the stems of the valves. Sorry, I don't have the right vocabulary for all those technical terms. It seems to me that a general overhaul of the engine is due, probably not worth anymore... very sad.

The valve springs are not very strong on these engines. You should be able to rotate the valves easily when they are "up". If the valve guide has a lot of play, the valves will move from side to side.

 

[Cosmopolit]

The valve springs are not very strong on these engines. You should be able to rotate the valves easily when they are "up".

That's right, I can turn them quite easily when they are open or "up".

If the valve guide has a lot of play, the valves will move from side to side.

No, they don't have any side play. What I don't understand: does this fact, that they don't close on the second turn as I explained before, have something to do with the four cycles of the engine? Should it be like that, that on one Top Dead Center the are closed, and on the next TDC they are a little open (not full, but only 0.6 mm)?

 

[Propflux01]

No, it is purposely built in the cam to release a slight amount of compression for easier starting.

 

[Cosmopolit]

No, it is purposely built in the cam to release a slight amount of compression for easier starting.

Ah, OK, that sound reasonable. Thank you. Well, I will continue then to look for another "troublemaker". The flywheel key is OK, just checked it.

 

[Propflux01]

I would look real hard at the ignition coil And plug.

 

[Cujet]

Carb jets are clear? And muffler is not clogged? Ignition timing remains OK over time? (just thinking aloud here, but sometimes ignition timing gets delayed as the coil gets hot) , Carb primer bulb is not cracked?

 

[Cosmopolit]

I would look real hard at the ignition coil And plug.

Ignition coil is either good or bad, isn't it? There is a spark, so it is good... If it were bad, then there would be no spark. There is no half spark, am I right?

The plug, yes, I changed it already once. It did not show any signs of either too fat or too lean.

 

[Cosmopolit]

Carb jets are clear? And muffler is not clogged? Ignition timing remains OK over time? (just thinking aloud here, but sometimes ignition timing gets delayed as the coil gets hot) , Carb primer bulb is not cracked?

The carburettor is new, but I will clean it again. Muffler.. how to check if clogged? Should I try to fire the engine without the muffler in place? Then, the possibility of ignition timing remains, but I have checked the flywheel key already, and don't know how to continue...

 

[super20dan]

I know know how you service Tecumseh valves and they are NOT ADJUSTABLE!!! I don't consider. removing a valve and grinding away the stem an adjustment

 

[Cosmopolit]

they are NOT ADJUSTABLE!!!

Right, it's a pity, otherwise I would have tried it long time ago. But, as someone here wrote, if faulty, they are always too long, never too short. Anyway, in my case, I am not sure they are faulty, because sometimes they sit tight.

 

[Propflux01]

Ignition coil is either good or bad, isn't it? There is a spark, so it is good... If it were bad, then there would be no spark. There is no half spark, am I right?

The plug, yes, I changed it already once. It did not show any signs of either too fat or too lean.

No! Coils can and do go bad yet will still run. They get weak from intermal insulation breakdown, and many time when they get hot they simply quit. Since your getting shocked touching the engine, that’s telling me a bad ground or short in the coil. JMHO.

 

[Cosmopolit]

No! Coils can and do go bad yet will still run. They get weak from intermal insulation breakdown, and many time when they get hot they simply quit. Since your getting shocked touching the engine, that’s telling me a bad ground or short in the coil. JMHO.

Yes, you are right. I did not relate the shock that I sometimes get to the malfunction of the engine. I shall check the coil and if I find a spare one, replace.
In one of the videos I saw a guy cleaning (filing) the place where the coil is attached to the chassis/ground with the two screws, he wrote that bad electrical connection to the ground is sometimes a cause for malfunctioning. I shall check that, too.

 

[Kamele0N]

Eppur si muove

 

[Cujet]

The coil is $11 online.