# Problems with Motor



## cekey (Apr 10, 2016)

Hello,

at first sorry for my english, but in Germany it seems tere isn´t any Forum.

I´ve an MTD Silvertrac with 20HP Tecumseh Motor.

The Engine run´s at Idle and slow drive, but when it have to give more Power it sometimes run on one Piston.
It seems as it´s when the Throttle from the Corbureator is more then a half open.
Now i clean all, withhin i found no dirt, but it futher work´s in same condition.
The Model of it is Tec 640333

Can give me someone information how i have to check.

The Problem is to change all is very expensive, only one of the 640335 Sealing Kit make´s about 30 Dollar Shipping and Tax. Direct in Germany much more. So i had to be sure the Engine works with new Kit.

Greetings, ck


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## RM-MN (Sep 11, 2015)

cekey said:


> Hello,
> 
> at first sorry for my english, but in Germany it seems tere isn´t any Forum.
> 
> ...


If you can hook up a spark gap tester to both spark plug wires, you will probably find that you have one weak coil. It will have enough spark to fire at an idle because the pressure in the cylinder is low and it is easy for the spark to jump the spark plug gap but when the throttle is opened there will be a lot more pressure and it will take a stronger coil to generate the voltage necessary.


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## cekey (Apr 10, 2016)

Hi

because of your Answer i look at the ignition.
I haven´t got an Tester, but a old analouge Multimeter, so i can check both coil´s and they have the same input voltage and output Power.
The Sparkplug´s are new, and flash outside the Motor very well.
Because of the Spark Plug´s works same and only one Cylinder work bad I Think the Ignition ist all right.

But who knows


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## FredM (Nov 18, 2015)

Cekey:

Have you checked the valve clearances ?, I am not familiar with the Tecumseh you may have, but if this is a V twin with a single coil with two high tension leads going to each spark plug, the coil shouldn't be the problem.

There was a post on the tractor forum a few weeks back and after much to and froing with virtually the same problem as you are having, decided the valve clearances should be checked, sure enough, the valves were the problem.

You have 2 of the 3 requirements for an engine to run, spark, fuel supply, but how is the compression ?.

Regards


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## cekey (Apr 10, 2016)

The Compression ist about 8 Bar on one Cylinder and about 7,5 at the other
The Motor was cold, i can test it in warm condition too.

But I think that´s not so bad, and is that important on full load? i thought if there a mechanical Problem like compression it´s most on Idle, not under load.

Should i test it again? warm or cold? what ist the normal range?

Oh sorry, and clearence, how much it has to have.
Can i Adjust it on this Motor?


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## FredM (Nov 18, 2015)

Cekey:

Is the fuel pump OK ?,


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## FredM (Nov 18, 2015)

Cekey:

As yet I haven't been able to find what the reading should be, I did a conversion of your bar readings and this reads
8 Bar = 116 PSI (pounds per square inch)
7.5 Bar = 108.77 PSI

Will the engine rev up when you open the throttle ?, running on one cylinder, the engine should rev up somewhat.


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## FredM (Nov 18, 2015)

I have attached a web address that is both a Tecumseh manual with specifications, 

you will have to read this from the beginning and you will most likely need a bit more info on your model engine, from TEC 640333 I think I read yours to be a TVT model, you will have to make sure though.

Page number 86 has a list of valve clearances for a number of Tecumseh engines, you will find yours most likely towards the bottom of the page with the designation of OHV (over head valve), you will need to work out your model.

Does your model have a single carby or the twin setup, you will find info in the manual for the twin setup.

As yet I haven't been able to find what the cylinder readings should be.

http://www.ccdist.com/_serviceManuals/tecumseh/695933.pdf


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## cekey (Apr 10, 2016)

Thanks for the lot of Information, now i have to read first

my Motor is the Type OV691EP-600903B


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## cekey (Apr 10, 2016)

This seem´s to be the right Manual:
http://www.ccdist.com/_serviceManuals/tecumseh/696325.pdf


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## FredM (Nov 18, 2015)

Cekey:

Page 15 will give you a reference to cylinder readings,
the manual should be of great help for you, personally I would be removing the tappet cover on the cylinder with the lower reading and check the valve clearances, if the clearances are within specifications, then I would suspect that the exhaust valve has been burnt.

Keep us up to date


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## cekey (Apr 10, 2016)

I write again after weekend, then i have take a look


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## cekey (Apr 10, 2016)

So,

i check the valve clearence, and correct it, it was 0,2mm and should be 0,1mm 
now i see that picture show´s another Motor, so i have to make it like it was before.

But i have good New´s, i found the Problem

I looked in the Corbureator´s with dismounted Airfilter, so i can see that one of them bring´s gas on the Tube, the other not. Third time to disassembly.....
Then i take pressure Air, blow into the Tube mounted in his case, and something fly away. But without this Part the Corb.. works, I don´t find it what that was, so i disassembly the second. It was The 632547 O-Ring what is placed after the Main Fuel Jet. So i took two new o-Rings and now it´s fine.
It seem´s the original Sealing´s weren´t really Gas resistant.

now i´m glad that Repair cost´s only some cent´s


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## FredM (Nov 18, 2015)

that is good news Cekey and your repair was of little cost
Cheers


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