Tecumseh engine repair

I have a bike with an auto-decompressor (650CC single cyl), the valve lash is set at TDC on the compression stroke with no special steps required, except that you must be sure to turn the engine over only forwards as the decomp feature is also used as an anti-kickback feature.

It is quite possible the exhaust valve has sunk into the head just enough to eliminate the previously set lash.

If you can see the cam and there is no 'widget' on it, it's a cam imperfection that is opening the valve because there's no lash, the decomp mechanisms are either centrifugal or activated by a cable or cam or such when the starter is applied (pull rope, E-start, kick- start, etc).

Dave

I have an old manual (1981) that refers to a compression release on the VM80 and VM100 engines. These are both rated at 8 hp with 3.125"x 2.53 (bore x stroke) and 3.187" x 2.53". So there is a resonable chance it has a compression release. It was really unclear exactly how it worked.

Hi, John. Can't help with your question, but want to make you aware that the Tecumseh factory closed it's doors Dec. 31, 2008.

I got a new Northern Tool catalog about the same time the engine on the little Troy tiller blew up. Northern lists a replacement, but is factory shipped. The motor has a 1/2 speed PTO shaft used for reverse. When I was ready to order on their web site, the engine is no longer available. A Google search revealed the factory is closed.

So, be careful on your engine work. There are no more new units being made.

Paul

I've got three Kohler K301S engines to maintain on my Gravely fleet. I overhaul one of them every other year for the last 20 years now. I'm due to do one shortly. never knew they had a compression release option. I used to buy short blocks, can't anymore. I'm in real trouble when I go past 0.030 over on all my blocks. I'll be there in a couple years.

Karl

Compression release is a little tab under the lifter hooked to a pair of fling arms (like in a distributor)mounted on the cam gear.

I've got the whole parts manual/ service parts/ pricing/ suppliers/ aftermarket thing pretty much figured out. The trouble is, my block will clean at .003", the aftermarket pistons are stock and .010". So I pay the Kohler rate or I pay my engine guy to take it out to .010" over. But the .003" over is for a 1964 vintage engine that has been in continuous use since new. Not bad!

Currently running a K241 until I get the K301 back in service.

Did the first mow>> On the other hand, I can give you an up close and personal report on the

Hunting around, I came across the Tecumseh manuals, about halfway down the page:

Here's the manual you probably should take a look at:

I have a shredder with an 8 HP Tecumseh horizontal shaft engine. It's

Thanks, guys. I ended up calling the Tecumseh service number - new company now - and after many minutes on hold got to talk to a live tech rep. He confirmed that the slight lifting of the exhaust valve at the beginning of the compression stroke is indeed the compression release, and that valve clearance should be set at TDC on the compression stroke.

Ground the valve stems to the correct clearance and put everything back together.

One thing did surprise me. I adjusted the carburetor with the air cleaner off, as it was a lot easier to get my hand in there that way. With the air cleaner on, the engine wouldn't run. Tried putting it on with the engine already running, and it died right away. Have to turn the needle in quite a bit further to accommodate for the air cleaner. The element looks pretty good, and I would never have guessed it would make that much difference. I'll try a brand new one.

Thanks again,

John Martin

It's not necessarily just the amount of restriction, sometimes the effect the housing has on airflow is important.

Just the wrong pressure wave at the right time, or vice-versa.

Dave