Exhaust Valve Sticking?

[ih782dmike]

I run a lead additive in my model 70 and under heavy loads like plow day or mowing, I have never lost power or had issues with a sticking exhaust valve. I tend to see that problem more on the larger HP Kohlers over the smaller 7 and 8 horse models. These old Kohlers dont seem to like this new gas we have. Once I treat it with the lead additive, I notice it run smoother and seem to do its work easier under a load. Some guys run MMO, I never have. Clean up the head and seating surface, you will find the warpage if any will be mainly on the head and not the block. But check both. Keep the piston at the top of the bore when doing your work, keeps the crud out of the bore. A putty knife will clean the top of the piston, as well a wire brush on a cordless drill. Also double check your points with your feeler gauge, make sure they are set to spec, might as well get a new set and a new condenser while your in there. Give the old girl a fresh ignition turn up.

[RPalmer]

Originally Posted by jfinney

Ok, here comes a novice question...how do you lap the valves? Thanks for your input Rpalmer.
Jason

You have to remove the keepers. They are what "keep" the valve spring compressed. You put a little grinding compound on ...enough to thinly coat the surface of the valve, and then you use a twisting motion like you see starting a fire with a stick with a tool about 15 bucks or you can use a kids suction cup dart from his dart gun. What you want to accomplish is to get the two surfaces mated. They need to both seat without pitting or restriction. Just like your head surface. They will then have a positive seal and once again last for many hours without being an issue. That is not to say though that they will never need their adjustment checked/adjusted.

This might sound like a lot but it isn't. Actually pulling the head is the most work. And you have that done. Take your time, don't rush and when you are finished you will not only be rightfuly proud, you will have a great running engine. ... I promise.

[jfinney]

Thanks again for the encouragement and helpful advice. I'll be diving in head first tomorrow morning. I checked the head with a straight edge and all seemed well. Should I still use the glass and sandpaper? Jason

[Merk]

Page 1.5 in a Kohler service manual recomends to use clean, fresh unleaded fuel. The lead additive leaves deposits on the piston and valves.

Here is s link to a kohler Service Manual:
http://www.onlycubcadets.net/forum/showthread.php?t=38

My old Kohlers don't have any problems on todays gas....as long as it is fresh. I haven't had any fuel related problems since I went to a 30 day gas rule. It is an easy rule to follow. I try to buy enough gas for all ( 2 and 4 cycle) my small motors to last only a month. I will add a fuel stablizer to my gas before I fill my gas container(s) up. Two good fuel stablizers are the one made for Briggs and Stratton and Sta-Bil. I use Sta-Bil because it is cheaper in my area. Any gas (2 and 4 cycle) that is over 30 days old is dump into one of my autos...usually my Suburban or my Monte Carlo.

How you store your fuel containers is important too. The container(s) should be sealed. Watch closely the next time you fill you gas on your Cub. You should see vapors coming out of fuel tank when you fill it. The vapors is the additive package that the gas company puts in the gas. You need all the additive package so your Cub will run at it's best performace. I store my fuel containers in a cool dry place in my shop. All my fuel containers sit on a board. I feel that storing fuel containers on a cool garage/shop floor-ground can attract moisture easier-quicker than placing a fuel container on a piece of wood.

This works on straight gas and ethanol blended gas. The ethanol in the ethanol blended gas will help clean deposits in the combustion chamber (top of piston-valves). I haven't had any problems with ethanol. The key to ethanol blends fuel is how you store it.

Kohler has a FAQ section:
http://review.engines2008.kohler.com...ance/faqs.htm#
There is a question and answer about fuel additives.

Can I use any oil or fuel additive in my KOHLER engine?

Kohler's answer
Kohler does not recommend using additives or cleaners in the oil or fuel system. Air-cooled engines operate at higher temperatures than liquid-cooled automotive engines, and additives developed for automotive use may not perform properly at higher temperatures. Oil additives can prematurely break down, altering the properties of the oil and leading to extensive internal damage or failure. Fuel system cleaning additives have a tendency to separate and turn acidic, causing damage to fuel system components. However, a fuel stabilizer is recommended in the fuel during periods of non-use (one month or more) to retard fuel deterioration.

[RPalmer]

Originally Posted by jfinney

Thanks again for the encouragement and helpful advice. I'll be diving in head first tomorrow morning. I checked the head with a straight edge and all seemed well. Should I still use the glass and sandpaper? Jason

If you are happy with it, fly it. :biggrin2.gif:

[Yosemite Sam]

I would go ahead and use the glass and sandpaper, even if just enough to clean the head mating surface. It's hard to check a head with a straight edge, a couple minutes work and you KNOW it's good.

[ih782dmike]

Dale, I dont think unleaded fuel was avaible when the 70 or the 73 for that matter was new was it?? I think that manual is updated for more current times, I bet a vintage maunal from 1964, the vintage of a model 70 doesnt say that.

[jfinney]

The job is over and done with!!!!! Well, the worst part of it was figuring out how to get the keepers out. Having never seen them before, and the service manual having a poor picture, I didn't know what I was looking for. I poked around and pulled on the Retainer (don't know what it's really called, but it sits over the keepers) for about 45 minutes before I realized the keepers were under the retainer thingy. Then, the next valve came out in about 1 minute. I lapped the valves, checked the clearances, replaced the weird filter thingy, cleaned up the cylinder head surface and put all new gaskets back on. Put everything back together and...turned the key. Success!!!! My worst nightmare was that it wouldn't start and I would have screwed something up. I drove the tractor around for a few minutes and, it could have just been my imagination, but it seemed much more peppy. I started out pretty easily in third gear on a flat surface with it running just slightly over idle. It also went up hill in third better and with less laboring than previously. I then did a dry compression check and got just around 120 psi, give or take a few psi. The true test will be when I have to cut the grass, as that was when I was really noticing difficulties. I will run it a bit longer and then retoque the head bolts. Sorry for the really long post, but I just wanted to thank everyone for their help, it motivated me to try something I had never done before. To everyone who's been putting this off, or any other repairs you've never tried before, give it a shot, you'll be really happy you did. Did it take me WAY longer to do this than someone with experience...absolutely...but, I learned a lot, had fun, and feel a great deal of satisfaction in taking on a new task and giving my old tractor some new life. Again, thanks to all for their advice, helpful tips, and inspiration/motivation.
Jason

[papaglide]

Congrats!! Awesome story.

[TEET]

Way to go Jason!

Jeff (teet)