Tecumseh won't run past half throttle

[Arkie]

One example on flea bay at this link.



If you get a float carb on that rig and still no go, let us know and I'll give you a couple of H35 hints that is easily missed in the service manual that will cause such. (before you give up and throw it in the trash with stomach ulcers bleeding and install a HF Predator @ $100)

What are the H35 hints that are easily missed that you mentions in this post:

You can ignore the above. (since it seems you have a intake valve issue)

IMHO:
It appears you have a intake valve issue (because it runs ok for awhile after you have removed the head, cleaned the carbon and oil and lapped the valve) maybe due to a worn valve guide and since that engine has no intake valve stem seal lots of oil is PROBABLY getting into the combustion chamber and as it burns the intake valve seating is getting erratic. I think I seen where you indicated that the valve guide SEEMS worn. (and the momentary puffs of blue smoke indicate possible valve stem seal worn. If you pull the valve up about 1/8-1/4 inch and can wiggle the valve the guide and or stem is worn)
I'm not that familiar with Tecumseh valves, if they ever offered an over size valve stem and reaming the existing guide for such or replacing a guide.[u][u] Probably too costly vs [/u][/u]just re-powering the snow thrower with another engine since the Tecumseh is long time obsolete.
You might check the valve spring and make sure it's not weak which is not likely. (if it's weak either replace or insert a shim to increase tension. (and make sure you did not install the breather oil drain hole upside down) and make sure the valves guide is secure in the block, (not moving up and down slightly with the valve stem. Also make sure the Muffler Exhaust system is not clogged or re-stricted.

It appears to me that engine has lots more hours on it than first suspected when looking at your pictures and was stored out of the weather.

What are you thinking?
(why not re-power with another engine like a 5hp Briggs or Predator if you really want to keep the snow thrower for yourself or if for a customer tell them to get a big manual snow shovel
(gears and parts may be obsolete for the whole machine)

[Roadrunner123]

These never came with valve seals but the new valves do. I'm thinking its the rings because the oil gets dirty pretty fast. I drained it again just to make sure I didn't overfill. The manual says 21 oz and that's what I put back but the oil that came out that was used only a few times was black. I did search for old and new engines and I have never seen a new double shaft one. There was a used one on ebay for short money but the guy won't pack it up. He told me he would rather give it to the junk man than go through all that.
As far as oversize valves are concern they do sell them for approx $32.00 each and I've seen the ream tool for sale also. Reg size valves are $ 6.00 each.
It's a shame to have to trash such a nice looking machine but I can't sell it the way it is unless I just list it for parts only. Crazy thing is the other day when I put it away for the summer and after sitting for a day, I let it warm up for a few mins and it went right to high speed. I put it away on a good note.

[bgsengine]

These never came with valve seals but the new valves do. I'm thinking its the rings because the oil gets dirty pretty fast. I drained it again just to make sure I didn't overfill. The manual says 21 oz and that's what I put back but the oil that came out that was used only a few times was black. I did search for old and new engines and I have never seen a new double shaft one. There was a used one on ebay for short money but the guy won't pack it up. He told me he would rather give it to the junk man than go through all that.
As far as oversize valves are concern they do sell them for approx $32.00 each and I've seen the ream tool for sale also. Reg size valves are $ 6.00 each.
It's a shame to have to trash such a nice looking machine but I can't sell it the way it is unless I just list it for parts only. Crazy thing is the other day when I put it away for the summer and after sitting for a day, I let it warm up for a few mins and it went right to high speed. I put it away on a good note.

You could knock it down and put in a new ring kit , should still be rings available, which might improve things well enough to get it sellable "as-is" , but if your intent is to sell it , then almost always never worth it. And yeah the secondary camshaft drive is a deal killer when it comes to re-powering them.

[Roadrunner123]

If I put rings in it would have to hone the cylinder first. I didn't take this to sell but thought it would be fun to use but I can't afford the space in my shed if it doesn't run.

[Arkie]

I was not aware of the double output shafts.

Like bsengine says you might go ahead and pull the piston and do a close inspection of the piston, rings, etc, BEFORE ordering any parts.
Fixing the valve guide and new set of rings might do if the cylinder not tapered and the piston and ring lands are ok.
I would check the cylinder for wear/scratches and taper, availability of parts. I was surprised to see new Tecumseh H35 intake valves and springs with keepers on flea bay for less than $10 with free shipping BUT did not see any that has the seal.
Being a double shaft (special type engine by code numbers) make sure that correct engine gaskets and shaft seals can be found. I've got into some obsolete same model number Tecumsehs that has different obsolete crankshafts.


If you are going to fool around with engines very much you need to review getting a leak down tester. I use a OTC 5609 engine leak down tester and it's worth it's weight in gold. I mainly use it to see if an engine is suspect of being bad internally, check leak down on engines that I do not have to go to the expense of trying to get it running first, I can tell if the engine has leaking valves or worn rings.
You most likely would not have to bother the exhaust valve area.
Sometimes when I'm looking for parts and have time to wait for something to surface, (not in a big rush) especially hard to find NLA or new old stock or vintage parts I place a SAVED SEARCH on ebay. Use two or 3 saved search descriptions, for example use a Tecumseh part number for the item in question, next do a saved search just doing a description, etc.
Might even put up a saved search for a Tecumseh snow thrower engine.

[bgsengine]

If I put rings in it would have to hone the cylinder first. I didn't take this to sell but thought it would be fun to use but I can't afford the space in my shed if it doesn't run.

I'd have assumed the bore would have been checked at least cursorily when the head was off- If so, and it seemed OK, then you can get away with just putting rings in it - Bore does not necessarily need to be honed, especially if you can see even faint traces of the original cross hatch pattern.. If you can get the right gaskets (and seals!) and a ring set, many engines like that can be suitably revitalized , though not long-term perfectly, with just a set of rings, provided care is taken on disassembly and re-assembly, and cleanliness. New valves may help as well if you can find cheap standard size valves, and like new rings without honing, new valves without "fixing" the guides (or oversize valves) can also sometimes be just enough to tighten up the tolerances to resolve issues over the short term.

But, it all depends on your confidence in your skills to rebuild the engine yourself... Else, as suggested earlier, you might consider doing a saved search on ebay for a good used "short block" or complete engine that meets your specs - But as those accessory shaft engines are relatively rare, you may expect to have to pay a premium (I have seen some that were selling for almost as much as a new short block would have cost, had any even been available!)

In short, your decision is gonna have to consider cost vs benefit but if you can get it running at least you can always sell it "as-is" and just mention you think it needs a carb adjustment (play dumb) to someone who maybe has deeper pockets

And lastly, if you do figure on doing more than a few "restoration" type jobs, and/or regular troubleshooting, a leak down tester would be worth its weight in time savings (and parts you otherwise might buy that it didn't really need)

[38racing]

On some blowers you can flip the gear selector shaft lever and use a single pulley engine and still get the multiple forward

[Roadrunner123]

If I put rings in it would have to hone the cylinder first. I didn't take this to sell but thought it would be fun to use but I can't afford the space in my shed if it doesn't run.

I'd have assumed the bore would have been checked at least cursorily when the head was off- If so, and it seemed OK, then you can get away with just putting rings in it - Bore does not necessarily need to be honed, especially if you can see even faint traces of the original cross hatch pattern..

Thanks bgsengine for the reply. Lets start with the cylinder. Since I only do this for a hobby on my own equipment, I've never done any honing. I've included a link to a picture of my cylinder to gets your thoughts. What are the lines going criss cross on the walls?
https://photos.app.goo.gl/5rCSdt4EFqMXmajz6
Thanks for any input on this.

[Roadrunner123]

On some blowers you can flip the gear selector shaft lever and use a single pulley engine and still get the multiple forward

Can you elaborate a little more on this ? Sounds very interesting. No one has ever suggested this before.
thanks

[Arkie]

What are the lines going criss cross on the walls?

Appears to be honing pattern. Wonder if it's factory honing or if the engine has been re-built?
When you get new rings check the end gap at the top and bottom of the bore with rings in the cylinder before installing them onto the piston. (if you do not gauge the bore with gauges and closely inspect/mic the piston as standard size)
Trying to make sure that a Bubba has not been into the engine and honed the bore too large or taper honed the bore, etc. (not likely but needs to be checked)

Did you notice any oil mist or little bit of smoke coming out the breather tube? (especially after the engine had been warmed up and running for awhile)
Reason I ask is Blowby smoke or oil mist is an indicator of leaking rings.
If the breather tube is connected to the air breather this won't be noticed with the breather in place. (remove the breather tube from the air breather to see such)

Just some general info about additional checks for small engine ring/cylinder wear.
Here is a video to a crankcase pressure test for small engines that rings may be worn or leaking by or a failed crankcase breather. Both are the same video. Keep in mind that a engine with worn valve stem guides and burning oil can still pass this test. (the oil is being sucked into the cylinder above the piston and not upsetting crankcase pressure if rings are sealing good)
You may have little bit of both (rings and intake guide slightly worn) is what we are indicating.
New rings might be just enough to get by. Might just install new rings at first, BUT I would consider trying to find a valve stem seal to use with the worn guide.
The intake rubber seal wiper is usually built into the upper spring keeper. If you cannot find a Tecumseh seal ONLY might even look at the 3.5-5hp briggs type????? I've seen worn valve stem guides and/or bad seals really make a engine look bad when all else was ok.

First one is google nd 2nd is microsoft edge link

https://www.bing.com/videos/search?q=Ho ... &FORM=VIRE

How to Check Crankcase Pressure on a Kohler, Briggs & Stratton, Tecumseh Lawnmower Engine - Bing video