# Low Compression Tecumseh H70 130003



## gr0leau (Feb 12, 2015)

Good Afternoon,

I am trying to bring back an old snow blower. Its an Ariens snow blower with a Tecumseh H70 130003 engine. I have replaced the Carb, head, exhaust and intake gaskets, cleaned the valves; lashed and lapped them. Before i lashed and relapped the valves i got 88 PSI compression, however now i get about 60 PSI and the engine wont stay running at all. Before i got it running but at high speeds it would sputter and backfire, thats when i lashed the valves based on someones recomendations(exhaust to .012 and intake to ~.010) However now it wont run and my compression greatly decreased. Any help would be awesome.

Thanks, 
Tim


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## classiccat (Mar 1, 2014)

Welcome to SBF Tim!!!

is that 60psi using the recoil? if so, that's not-terrible / not-great...on a starter, you could do better. 

Did you coat the new metal head gasket? I've been using the Permatex Copper head gasket maker...2 coats is plenty. Also, make sure you torque to 200 inch-lbs and in the proper order...then re-torque after a few heating/cooling cycles. 

For the bad running, have you had the flywheel off to make sure you don't have a sheared flywheel key...throws off the timing? It could also be that the carb just isn't set properly...I understand that it's tough to set it properly if it won't run long enough...I would try leaning-out the mixture a bit to see if it performs better. Idle-jet is in play when you're not under load & the governor is set properly; high-speed / no-load throttle position should be barely off of the idle throttle position. That throttle is probably bouncing around like crazy...again making it tough to tune.


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## motorhead64 (Dec 15, 2013)

Hi gr
Welcome to the Forum. Make certain that your cylinder head bolts are properly torqued to 200 inch lbs( 16.5 foot lbs.). Also, recheck yor valve clearances. You lapped your valves. Did you check your clearances at top dead center with both valves closed? You are leaking somewhere. You need to retrace your steps. MH


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## gr0leau (Feb 12, 2015)

That 60 PSI is with the starter, was 90 with the starter. I had the fly wheel off when i rebuilt the magneto, and the key looked good. It was also stuck in there, couldn't pull it out with my fingers but didn't try with any tools because i didn't really need it out.


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## gr0leau (Feb 12, 2015)

motorhead64 said:


> Hi gr
> Welcome to the Forum. Make certain that your cylinder head bolts are properly torqued to 200 inch lbs( 16.5 foot lbs.). Also, recheck yor valve clearances. You lapped your valves. Did you check your clearances at top dead center with both valves closed? You are leaking somewhere. You need to retrace your steps. MH


I did lash the valves and lap the valves at TDC


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## gr0leau (Feb 12, 2015)

motorhead64 said:


> Hi gr
> Welcome to the Forum. Make certain that your cylinder head bolts are properly torqued to 200 inch lbs( 16.5 foot lbs.). Also, recheck yor valve clearances. You lapped your valves. Did you check your clearances at top dead center with both valves closed? You are leaking somewhere. You need to retrace your steps. MH


I didn't torque the bolts just did hand snug, but i was going to go get a new crank case gasket in case that was in, maybe i will get a new head gasket, (Ive opened it up like 4 times now) and try to torque them down.


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## motorhead64 (Dec 15, 2013)

Like I said, you will need to backtrack. Everything you did should have improved compression...or at least left it the same. You erred somewhere....most likely on your valves. Did you end up grinding your valve stems to get the proper clearances? MH


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## gr0leau (Feb 12, 2015)

Yeah I ground down the valve stems. The exhaust was at about .004 and the intake had no clearance.


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## CarlB (Jan 2, 2011)

thats a little strange that the intake valve had less lash then the exhaust to start with. I think .010 is a little big for the intake. You probably have a leaking head gasket. Replace the head gasket and torque to correct inch pounds and in the correct sequence.


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## motorhead64 (Dec 15, 2013)

http://www.asos1.com/tecumseh4hp/Tecumseh.pdf

Change out the head gasket and torque in proper order to specs. MH


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## scrappy (Dec 7, 2014)

Any way you can do a leak down test before its apart? You will need compressed air and a regulator. this is the best way to tell where the leak is.

If you don't have the tool in the vid, simply putting 50 psi in will show a leak.


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## gr0leau (Feb 12, 2015)

So I did the leak down test and I think it's at tdc and it goes down to like 30% and when I turn up the psi I can hear the air coming from the oil tube. What would be the best way to fix this?


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## gr0leau (Feb 12, 2015)

Sorry, a little less than 70% cylinder leak


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## Grunt (Nov 11, 2013)

gr0leau said:


> That 60 PSI is with the starter, was 90 with the starter.


As stated by classiccat, 60psi is not a bad compression reading and if spark and fuel delivery are correct, your engine should start and run. The drop in compression from before to now is probably related to the carbon removal during the valve work? Air coming from the oil dip stick would indicate leakage past the piston rings and some blow by is normal. Have you tried squirting a little oil in the cylinder and see how much compression increases? It may be the cylinder needs honing. I also agree with the other gentlemen, you will have to torque the head down to get a better idea where your starting problem is.


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## gr0leau (Feb 12, 2015)

When honing would I need to get a larger piston? Or would I home and just replace the rings?


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## Motor City (Jan 6, 2014)

gr0leau said:


> When honing would I need to get a larger piston? Or would I home and just replace the rings?


If you hone it, just a set of standard rings. You would only need an oversize piston, if you have it bored out by a machine shop.


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## scrappy (Dec 7, 2014)

If this is a 'cool bore' honing is not a good thing to do. Easy way to check is stick a magnet on the inside bore, no stick it's alloy. 

when you leaked checked did you notice any thing from the valve ports.. if you hold your hand over the port do you feel pressure? When you had the head off , was the bore scored?

This should run with 60 psi compression. Make sure you have spark, and the keyway did not shear.


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## gr0leau (Feb 12, 2015)

It looked like I had very light vertical scoring. I'm not sure about the material but it's a h70 130003 Tecumseh engine. I can check the fly wheel key tomorrow


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## WestminsterFJR (Dec 30, 2013)

60# seems quite low. My motors are in the 85-90 range. Assuming that the head is re-torqued, I'm curious as to why the big drop in compression after the valve job.


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## motorhead64 (Dec 15, 2013)

If you had 88 psi before you worked on this engine, your rings and cylinder should be well within the normal limits...you made a mistake in your repair procedure somewhere. Is it possible you have a valve spring hanging up or that you over-ground your valve stem ends or your head is not sealing adequately? MH


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## gr0leau (Feb 12, 2015)

motorhead64 said:


> If you had 88 psi before you worked on this engine, your rings and cylinder should be well within the normal limits...you made a mistake in your repair procedure somewhere. Is it possible you have a valve spring hanging up or that you over-ground your valve stem ends or your head is not sealing adequately? MH


OK I'm going to try some things this weekend and will let you guyes know what i find out. I feel like at this point the only thing ive got left it to hone and replace rings so i may just do that to save myself from having to open it back up again.


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## Grunt (Nov 11, 2013)

gr0leau said:


> I didn't torque the bolts just did hand snug, but i was going to go get a new crank case gasket in case that was in, maybe i will get a new head gasket, (Ive opened it up like 4 times now) and try to torque them down.


Before you go through the time and expense of honing and replacing the rings, try torqueing the head bolts to spec and take another compression or leak down test.


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## gr0leau (Feb 12, 2015)

Grunt said:


> Before you go through the time and expense of honing and replacing the rings, try torqueing the head bolts to spec and take another compression or leak down test.


Ok I will do that, also some of the head bolts at getting stripped, i think they are 2 12 in 5/16 bolts but would 2 inch work. the only reason is because on the 2 1/2 bolts the threads don't go long enough and i cant seat them down far enough, would the 2 inch bolts be OK?


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## classiccat (Mar 1, 2014)

gr0leau said:


> Ok I will do that, also some of the head bolts at getting stripped, i think they are 2 12 in 5/16 bolts but would 2 inch work. the only reason is because on the 2 1/2 bolts the threads don't go long enough and i cant seat them down far enough, would the 2 inch bolts be OK?


 if they are all the same length, then you might be missing spacers (i.e. for the fuel tank ).


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## motorhead64 (Dec 15, 2013)

Head bolts are hardened and heat treated and should not be replaced by ordinary steel bolts. It's always a good idea to number the heads of bolts so that they can be reinstalled in the same locations. MH


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## WestminsterFJR (Dec 30, 2013)

Good suggestion on keeping track of which head bolt goes where, MH.


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## scrappy (Dec 7, 2014)

Beware honing a alloy bore. poke around on the web, it's not good. 

This should run run with 60 psi, and don't forget the compression release will lower cranking PSI.


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## gr0leau (Feb 12, 2015)

So i looked all over for the ring set i needed this weekend but no one had then in stock (not surprised) but i did tell a local tech what was going on and the tests i performed, he said it sounded like i was looking pressure through my rings, so i dismantled the engine for what felt like the 100th time and this time i removed the piston. It appears i am missing a ring all together. The lower ring looks like it is missing its inner coil. I didn't see any remnants of it in the crank case so I'm not sure what happened to it. I also used a magnet on the sidewall and it stuck so I'm assuming its a steel sidewall and would be safe to lightly hone? 

I got new valves, crank case gasket, head gasket, and I'm ordering new rings, a new shaft key, and some oil seals and gaskets. Does anyone have any advice or tips before i put this back together? The engine is a h70 130003 Tecumseh.

Thanks for any help,

Tim


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## Shryp (Jan 1, 2011)

This guy has some good videos on an HM 80 if you want to watch. It was like 6 parts and titled "Refurbishing a Tecumseh Snow King".

https://www.youtube.com/user/MultiKhaz

I would replace the fuel lines as well. 1/4" ID fuel line from any auto parts store.


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## gr0leau (Feb 12, 2015)

Shryp said:


> This guy has some good videos on an HM 80 if you want to watch. It was like 6 parts and titled "Refurbishing a Tecumseh Snow King".
> 
> https://www.youtube.com/user/MultiKhaz
> 
> I would replace the fuel lines as well. 1/4" ID fuel line from any auto parts store.



Yeah I replaced the fuel line as part of my initial repairs. the Carb i bought had the choke handle going in the wrong direction so i bent it down so it would work, but I'm not sure if that means I got one that doesnt go to this machine. I figured as long as it fit then the adjustments are what would make it hum.


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## DANMAN (Feb 15, 2015)

Yes get the new head gasket 6 bucks on the ebay .


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## gr0leau (Feb 12, 2015)

So after getting new piston rings I realized that the shroud I had with the model number was for an h70 but what I ended up actually having is an h50 motor. So, now I have the correct parts, however yesterday I went to put in the new valves and the gap is .015 which is way off of the .004-.008 it's suppose to be. So my question is, am I suppose to have the valve sockets cut down so the valves fit?

Tim


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## classiccat (Mar 1, 2014)

gr0leau said:


> So after getting new piston rings* I realized that the shroud I had with the model number was for an h70 but what I ended up actually having is an h50 motor*. So, now I have the correct parts, however yesterday I went to put in the new valves and the gap is .015 which is way off of the .004-.008 it's suppose to be. So my question is, am I suppose to have the valve sockets cut down so the valves fit?
> 
> Tim


Man...that stinks! 

I may have missed it...what's the reasoning for replacing the valves? Are the old ones broken? if not, I'd adjust the clearance on the old valves, lap/reseat them, then recheck the clearance since lapping usually reduces the clearances a bit (0.001-0.003").


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## gr0leau (Feb 12, 2015)

My exhaust valve I ground down too far. It's at ~ .014 and the intake is at ~.009... So I'm in a tight spot


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## classiccat (Mar 1, 2014)

gr0leau said:


> My exhaust valve I ground down too far. It's at ~ .014 and the intake is at ~.009... So I'm in a tight spot


I don't think that you're that far out-of-spec...which I believe are 0.008" to 0.012" (see page 95).

Intake is g2g...I bet you can get exhaust in spec by lapping.


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## CarlB (Jan 2, 2011)

You should be fine at .014 and .009 on those valves. Just give them a good lapping, you might even loose a thousand or so.


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## Dave C (Jan 26, 2015)

gr0leau said:


> So after getting new piston rings I realized that the shroud I had with the model number was for an h70 but what I ended up actually having is an h50 motor. So, now I have the correct parts, however yesterday I went to put in the new valves and the gap is .015 which is way off of the .004-.008 it's suppose to be. So my question is, am I suppose to have the valve sockets cut down so the valves fit?
> 
> Tim


Your .004-.008 spec came from the Tecumseh manuals, right? I used that data when I replaced / lapped the exhaust valve on an HSSK50 recently. I put it right at .006 which should be in the center of that range. Compression came up to 90 PSI from the 45 that it was prior. Then I noticed the spec in my Craftsman owner's manual and it said .010" for both valves. I revisited the exhaust lash and compression came up to 150 PSI!

If you do some more lapping you can drill it down a couple thou. I wouldn't touch the .009 one tho.


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