Tecumseh OHV Engines

Anyone with questions regarding a problem with their Tecumseh OHV [or even older flathead ones in fact], post a reply here and I'll help you out. I've owned quite a few Teccys for both work and play and have seen their problems and know almost all of their fixes. Most of their problems stem from bad carburetor designs coupled with bad gas. They do have other issues but are not a terribly bad engine line..

Currently, I've got a 2006 MTD YardWorks with a 15.5HP Formula a.k.a. OV490EA, a 491cc single that has pressure lube, a mechanical governor [like most], and provisions for an oil filter under a stamped metal cover on the left side of the crankcase.

My engine:


These engines are particularly common on MTDs assembled between 2000 and 2008.5[when teccy when out of business], and may have been used as base model engines on other makes such as AYP/Husqvarna, Murray, etc...

So leave your questions, comments, suggestions and thoughts below

jack9102 wrote:

Anyone with questions regarding a problem with their Tecumseh OHV [or even older flathead ones in fact], post a reply here and I'll help you out. I've owned quite a few Teccys for both work and play and have seen their problems and know almost all of their fixes. Most of their problems stem from bad carburetor designs coupled with bad gas.

Sooo... Not really any different from the flatheads, then.

I'm a big fan of the older H-series, like my trusty old H60. I've put it thru hell and back repeatedly, keeps coming back for more. To be fair, I wouldn't even say "bad" carb design. They DO seem to be fairly sensitive to old degraded fuel and crap, but I actually quite like the Series 1 carbs. To know them is to love them.

People bash Tec constantly. I think it's a lack of knowledge. I (as a general rule) dont have any more or less problems with Tecs than Briggs. They're respectable engines.

One think I DON'T like- the carb (series 8?) with the plastic emulsion tube/main nozzle with the o-rings. Yecch. Damned O-rings are an odd size and standard ones just don't seem to fit right.

I have a prob with an OHV Tec. It ran good, then backfired and quit. Only backfires now. Adjusted the valves to spec, checked for bent pushrod, checked flywheel key. All good, same thing, just POW! what is going on? It has fuel and spark. I set the coil gap again too and even swapped coils. Same thing. No idea. What is it?

Couple quick points on the spark thing... Is it a good STRONG spark? Possible to have spark, yet too weak to fire. Also- try a known good plug if you haven't already. I've come across the odd one that looks ok out in the open, but refuses to fire under compression conditions.

Plug wire shorting out against the tinwork?

You're quite sure fuel delivery is sufficient?

Check to see if the flywheel slipped?

He DID state that he checked the timing key. Then again, it coulda sheared AFTER being checked, a common problem when the nut's not torqued down.

Doc Sprocket wrote:

He DID state that he checked the timing key. Then again, it coulda sheared AFTER being checked, a common problem when the nut's not torqued down.

Ouch! I need to read, (and remember), better!

I've done all the above. Carb is clean and all new gaskets. Fuel is getting there and she sparks plenty enough to sound like a shotgun going off. Flywheel key is good and I have a new one to try too. Makes no sense. Ran good for around 3 minutes then pow! never again. Compression is good too.

Wow. That's a head-scratcher.

Check the key again, and then remove it. Now put the flywheel on just a tiny bit off-center; which means that the keyways won't line up perfect. Doesn't matter which direction, just try one. Then try to start it. Record results. Then adjust in the other direction. Again try to start it.

Let us know what the results are.

B440 wrote:

Check the key again, and then remove it. Now put the flywheel on just a tiny bit off-center; which means that the keyways won't line up perfect. Doesn't matter which direction, just try one. Then try to start it. Record results. Then adjust in the other direction. Again try to start it.

Let us know what the results are.

Interesting, but- where are you going with this?

my neighbor thought it was acting as if it jumped time too. The keyway is the only way this could happen though. Dunno, you want me to spin it with no keyway in there then. Just nut the flywheel down?

Doc Sprocket wrote:

B440 wrote:

Check the key again, and then remove it. Now put the flywheel on just a tiny bit off-center; which means that the keyways won't line up perfect. Doesn't matter which direction, just try one. Then try to start it. Record results. Then adjust in the other direction. Again try to start it.

Let us know what the results are.

Interesting, but- where are you going with this?

If it is just a little bit out of time, this should tell you that is the case.

dwcopple, you could get the same results by slotting the bolt holes in the coil hold downs, and slide it side to side.

Since the coil is in a fixed position, and the timing key sets timing at spec, I'm a bit lost as to how it could have "jumped". I seem to vaguely remember some older Tecs that had a coil adjustment for ignition timing- now THAT I could understand. But how does fixed timing go out?

no idea. Maybe if the old flywheel key is worn down a hair? makes no sense to me either. Gotta try getting this damn flywheel off again.

I can't see it. 0.006" off the key equates to 1° of timing advance or retard. Engine should still start and run, even if less-than-perfectly.

I can't see it either, but it is something to try, and it would help understand which system is the problem.

Let's see the spark plug.

Maybe try bypassing the carb by using an aerosol to run it.

Could be worth a shot. Seems like all the usual suspects have been addressed already.

got the flywheel off pretty easily, however, the flywheel key is rust welded to the crank. Soaked it good with penetrant and am waiting. hitting it with a screwdriver and hammer is only digging into the key so far. Not good. The plug is new BTW

That aluminum key is probably not long for the planet at this point. Perhaps consider buying another one prior to final reassembly. Although in truth, you don't actually need one.

I have a new one already. I got the old one out by clamping it in a vice grips and tapping the VG with a hammer. Gonna try spinning it with the new keyway today. I hope, wife is pretty pissy this AM already...

dwcopple wrote:

... I hope, wife is pretty pissy this AM already...

lol, Been there.

B440 wrote:

dwcopple wrote:

... I hope, wife is pretty pissy this AM already...

lol, Been there.

You've been there when his wife is pissy???

Does he know?

Well, I guess he does now...

     

got it all back together and gave it a try yesterday, but I only had it clamped down to a pallet with the crank through the board holes. Not good, just spun out of the clamps. I need to figure out some kind of test table for this thing. Ideas?

A junk mower makes a good test stand. Don't need anything but the frame and fuel tank. Maybe some cables, battery etc. if you want to get fancy.

Old picnic table would work too, or any large wooden table.