Tecumseh Broke Rod

Following up. I proposed to get a used rod and was asking about attaching it to the crankshaft thru the hole the mishap punched into the wall of the crankcase. The rod cap already faces that way.

This was to avoid opening the entire engine because I thought there were a lot of pieces that would fall free and needed to be perfectly aligned when closing. It turns out this fear was unnecessary. Crankshaft, camshaft, and the ball end of the oil pump. How I know this now is quite unfortunate. Read on.

So I got the used connecting rod and got it on the piston pin. Pushed it into the cylinder with a ring compressor. I attached the rod to the crankshaft. Got the cap on with both a socket and open end wrench. Yes, nice and oily. Cylinder head back on.

Made two small holes on either side of the opening. Cut and fit a piece of aluminum (GF's old license plate!), bending it to match. Lots of high temp RTV.

Buttoned it all up. Oil added. Fuel added. Let the RTV cure a couple days.

As you know Tecumseh dumbed things down over time and one adjusts the governed speed on this model by bending the tab the governor spring hooks to. I bent it in the direction of lower speed.

The big day came. Got my strobe ready to set the speed. It didn't want to start on recoil so I removed it and cranked it with a drill. Started right up.

And oversped. Adjusting the gov spring tab had no effect. Within seconds it broke the rod AGAIN. Punched through the patch.

Broken governor.

Choice of giving up or going inside. This is how I now know it's not that terrible. I fully expected the governor gear to be in pieces but it seem fine. It's the spool specific specifically one of the wings that go in between the parts of the governor gear.

I don't know if the damage was there from before or caused by the prior incident.

I do have this incident on video and I fed that to an AI which, from the audio, estimated the RPM at about 4140. Spec is 2950 ± 150, call it 3000. So no surprise it broke.

Not in this very deep. $15 used rod, the ring compressor, some red RTV.

No more $15 rod. Next will be $20.

So here are some questions.

The governor gear shaft has no C clip, just a bulge at the top. It is pressed into the base. Some wrestle it loose with Vice Grips and replace it along with the parts it holds and lightly pound the new one down. Others drill up from the underside and pound something through. A drop of sealant can close the hole. One thing I am looking and is grind away the bulge on the shaft. Seems like there is a groove there. Maybe a C clip or even a tightly twisted loop of small diameter baling wire would work. Leaning to drilling up. But say I did grind off the bulge. Is anything actually needed to retain the gear and spool? The spool has the governor rod pushing down on it with spring pressure.

I guess I should replace the gear as well as the spool.

I'll be replacing the gasket between crankcase and base. Should I put any sealant on it? Doesn't seem like there was any and no leaks.

Yeah it's all crazy but learning all the time.

I cannot believe I am reading some of this stuff.

This has "ethnic engineered" written all over it.

Determined to make it work no matter what?

What's next? A piece of tin, some self-tap and more RTV to cure for a few days?

Any new gasket, or just resealing what's there?

Auto Doc's said:

I cannot believe I am reading some of this stuff.

This has "ethnic engineered" written all over it.

Determined to make it work no matter what?

What's next? A piece of tin, some self-tap and more RTV to cure for a few days?

Any new gasket, or just resealing what's there?

Click to expand...

WTF is "ethnic engineered"?

Gasket where? They don't make gaskets for holes punched in the side of crank cases by broken rods. But now that I have access to both sides I might make the new patch on the inside.

Crankcase and base will get a new gasket. No sign the OEM used any sealant there so I prob won't either.

Is this thread an old episode of RED GREEN that I missed. If so I haven’t seen any mention of duck tape. Can someone please post where I can review this video. OP must have more time and money to even thinking about patching a block with sheet metal. Thank you for brightening my morning each day, good way to start off each day with a good laugh.

Basically the OP trying to bring a dead horse back to life. But the OP can spend all money he wants and still may not ever get the horse alive again. Sometimes there is a time to admit it is not repairable.

Without disassembling the engine there is no way to know the true damage done by either broken rod.

And Rivets you need to see the seat on a Husqvarna rider here it is all duct tape. The guy is even holding the hood on with electrical tape. Too bad my phone died.

Rivets said:

Is this thread an old episode of RED GREEN that I missed. If so I haven’t seen any mention of duck tape. Can someone please post where I can review this video. OP must have more time and money to even thinking about patching a block with sheet metal. Thank you for brightening my morning each day, good way to start off each day with a good laugh.

Click to expand...

I'm glad you are enjoying because I am enjoying it myself. That's the point. If I wasn't I would take it to the curb for the scrappers. I can manage the time and there is very little money involved. Not for this level of fun.

For the record I've replaced the mower so this is just for fun.

But please expand on your objection to the sheet metal patch. This part of the block is not structural, maybe 3 mm thick aluminum. If not for oil flying out I am quite certain the engine will run fine without it. Patch is there just to hold the oil in.

Your mention of Duck / duct tape is intriguing. Everyone knows duct tape is crap and isn't even good for ducts. I don't care if Mythbusters made a boat. That boat would be many times better made of a myriad of better tapes. A patch made from, say, 3 layers of gaffer tape would conform to the curves better with no RTV. But I think it would need more screws to hold without tearing so won't go there. Plus the effect of the hot oil. But thanks for the idea.

Ooh how about aviation speed tape?

StarTech said:

Basically the OP trying to bring a dead horse back to life. But the OP can spend all money he wants and still may not ever get the horse alive again. Sometimes there is a time to admit it is not repairable.

Without disassembling the engine there is no way to know the true damage done by either broken rod.

And Rivets you need to see the seat on a Husqvarna rider here it is all duct tape. The guy is even holding the hood on with electrical tape. Too bad my phone died.

Click to expand...

I have disassembled the engine after all and it seems fine. Aside from the overspeed and self destruct #2 it ran well.

What money? Two rods represent an outlay of $35. The governor spool will be a couple bucks. Plus the piston ring compressor ($9.65 plus tax) and some red RTV.

Remember this is an entertainment project. What do YOU spend on entertainment?

If it works I get a spare mower and can compare Lawn Boy Sense-a-Speed vs Toro (current owner of the patent) Personal Pace. If not it hits the curb bringing joy and ¢¢¢ to the scrapper.

Anyone out there with real Tecumseh experience?

Guy on YT video mangled the gov shaft with Vice Grips, a vice, and hammering so he replaced it, using the vice to press it in. Commenters have suggested drilling from below and pushing it out. But when replacing it he only had the gov gear and washer on it. The spool he pushed on from above getting it passed the raised ridge. If I am only replacing the spool maybe I don't need to take the shaft off all. I had some crazy idea about grinding off the ridge not realizing there was a lower ridge. Gear seems fine. I would gladly replace on principle but if leaving it saves removing the shaft then I'll leave it and just replace the spool.

I’ve probably been working on Tecumseh engines longer than you’ve been around, I might know a little bit about how they run. Your project probably cost you close to $50 when you add up all the incidentals. Are you telling me that 3mm piece of sheet metal can be used to replace a .25” aluminum casting and still be structurally sound. Only time I would stick that kind of money into a “project “ it would be a “hit-n-miss” engine . Red Green and the MythBusters would be proud of you. Trying to justify what you are trying to do has given the experienced techs on this forum something to brighten their mornings. 99% of the DIY guys wouldn’t even attempt this, they know better.

I defer to your experience but you are misunderstanding about the patch. It is not there to add any structural strength but to keep the oil in. Is the block missing that area fatally compromised, I don't know. Maybe it will run for a time then completely break up. You think it will. I have no idea. I guess we will find out.

The photo shows the replacement rod fitted and holes drilled for the patch.

Amazing how negative everyone is. You'd think people would be bemused by the idea of attaching the rod cap from the outside. Or maybe go ahead and open the engine; it's not that big of a deal.

Again, this is mostly for fun.

Phil Swift has several products that might be useable by you on that poor old Tecumseh.

Check out the race car he put back together at about 3:32 of this video at this link.