# Tecumseh BTDC timing dimension.



## dcinma (Dec 13, 2017)

Have a circa 1978 Tecumseh HSK70 Snow King that's been in the family since new.
Replacing the points, condensor, and coil.

My old circa 1980 Tecumseh engine repair manual says to set the piston at .050" btdc.
The 1996 Tecumseh L head manual (linked on the site) says to set it at .080" btdc.

Last time I changed the points I only had the older manual to refer to and used the 050 btdc setting and it seemed to run well. While on the discussion is a larger btdc setting more advanced or retarded timing . I want to say advanced.


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## scrappy (Dec 7, 2014)

My 2 old books (mid 80's) show .080 BTDC advanced.


My oldest book (1973) shows .090 to .100 for all medium frame engines.


Or you can read this.


http://www.smallenginesuppliers.com...cumseh_L-Head_Engines_Service_Information.pdf


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## paulm12 (May 22, 2015)

are you sure is a Snow King, I thought those were all solid state ignition. Anyways, do you have the full engine model number off of the main shroud? The L-head engine handbook has 0.080 and 0.090 for various 7 and 8hp points ignition engines. 

tx


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## dcinma (Dec 13, 2017)

Definitely a Snow King, still have the original Tec. owners manual.
H70-130210D Serial No. 8195.


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## dcinma (Dec 13, 2017)

scrappy said:


> My 2 old books (mid 80's) show .080 BTDC advanced.
> 
> 
> My oldest book (1973) shows .090 to .100 for all medium frame engines.
> ...


I think mine is a small frame.


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## paulm12 (May 22, 2015)

the Snow King engines start with "HSK -xxx". The H70 engines show 0.080" and 0.09" BTDC, dependent on bore size. this info from the Tecumseh Technicians Handbook for 3 to 11hp 4 cycle L-Head engines. The timing specs are on p95 and p96 for the H70.

also:

V - Vertical Shaft
LAV - Lightweight Aluminum Vertical
VM - Vertical Medium Frame
TVM - Tecumseh Vertical (Medium Frame)
VH - Vertical Heavy Duty (Cast Iron)
TVS - Tecumseh Vertical Styled
TNT - Toro N’ Tecumseh
ECV - Exclusive Craftsman Vertical
TVXL - Tecumseh Vertical Extra Life
LEV - Low Emissions Vertical
H - Horizontal Shaft
HS - Horizontal Small Frame
HM - Horizontal Medium Frame
HHM - Horizontal Heavy Duty (Cast Iron) Medium Frame
HH - Horizontal Heavy Duty (Cast Iron)
ECH - Exclusive Craftsman Horizontal
HSK - Horizontal Snow King


.


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## classiccat (Mar 1, 2014)

I set both my H70 (1980) and H50 (1970) to 0.080" and both start and run beautifully (per L-head service manual).


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## ST1100A (Feb 7, 2015)

If it were me, I would throw the points and condenser in the garbage and put the solid state ignition module in the place of the points and condensor unless you are trying to keep it original.
You can get the ignition module kits for less money than the points cost. They are very easy to install, just disconnect the wire from the points and hook it to the wire to the module and hook up a ground wire to the module, then mount the module, and its done.
You can leave the old points in the engine, they do not have to be removed. Once the module is hooked up you no longer have to worry about adjusting and replacing points and condensers again, which have to be serviced fairly frequently. 
A good module kit will last a long time and comes with the necessary wiring adapters and wiring plugs. They are available from companies like Sten's and can be found on EBay for a good price.
And one of the nice things with the module kit is you do not have to worry about trying to set the timing with it like you do with the point set-up.
With points, you have to get the timing set to break the point gap or to make it set to fire when the coil reaches its maximum saturation point so it can produce a strong enough spark, the module does that automatically, and no more worries about point gap being out of adjustment, or burned, pitted, bad points and bad condenser.


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## 2.137269 (Nov 15, 2019)

agree with st, change the coil loose the points and never worry again,


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## ST1100A (Feb 7, 2015)

If you use the module kit, you just use the original coil and don't have to change it. The kit works with Tecumseh, Briggs and Kohler point type ignition, but you can also change the coil over to the solid state type coil, then you don't need the module kit.
Certain Briggs engines, you had to change the flywheel to use the solid state pointless ignition coils, that was on the cast iron engines, but you could just use the module kit and wire it to the point wire from the coil and leave the flywheel alone and use the original coil.
Other engines you could get the new style coil and just change it. The module kit cost less money and was easy to install.


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## scrappy (Dec 7, 2014)

dcinma said:


> I think mine is a small frame.


 H6, H7, H8 horsepower engines are all medium frame. There are also H4 and H5 medium frame, and then there are small frame known as HS5, HS4 engines. Then there are small frame H3.5, H3.0, down to 2.5 HP. A little confusing...


I would not install electronic ignition on a Tec for 2 reasons. 1, no way to set actual timing, 2 they are chinese junk. The 2 small engine places near here both advised me of this many years ago. My dads 1967 H5 is points/condenser, fires up on 1 or 2 pulls, never mises a beat.


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## dcinma (Dec 13, 2017)

Lot's of good information guys thanks .
For I'll just put in the new points and condenser because I need to finish this a have it ready for the next snow storm.
I might just order an electronic module and keep it on hand.
I had the same thought as the last poster, if you don't have to set the timing with an electronic module, then how does it know when to fire at the optimal time?
Yes the engine block sizes seem confusing.
My engine says H70 not HS or HM, so a plain H is the same as an HM?
.


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## ELaw (Feb 4, 2015)

I'm sure others will disagree but here's my $0.02...

These engines are not F1 racing engines that are super-finicky and where getting the last 0.1% horsepower could make the difference between winning and losing a race.

If I were doing that job, I'd set the point gap at 0.020" (thickness of a matchbook cover), set the new coil in about the same position as the old one and call it done.


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## ST1100A (Feb 7, 2015)

The timing automatically sets itself. The spark occurs when the armature senses where the magnets are in the flywheel by it producing its peak voltage at a certain point in its rotation around the armature or ignition coil to make it fire. 
Instead of mechanically timing it by setting the air gap, it does it electronically by sensing the peak voltage before it drops after the magnet passes a leg on the armature coil. When you set the point gap, you are trying to set the timing point when the points "break" or open compared to the position of the magnet on the flywheel. It senses when the magnetic poles switch from N to S and at that split second it is at its peak to fire.
With the electronic ignition you get a stronger spark at the spark plug, plus no mechanical parts that wear out like the points,condenser and related parts like the lifting plunger.


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## scrappy (Dec 7, 2014)

ST1100A said:


> The timing automatically sets itself. The spark occurs when the armature senses where the magnets are in the flywheel by it producing its peak voltage at a certain point in its rotation around the armature or ignition coil to make it fire.
> Instead of mechanically timing it by setting the air gap, it does it electronically by sensing the peak voltage before it drops after the magnet passes a leg on the armature coil. When you set the point gap, you are trying to set the timing point when the points "break" or open compared to the position of the magnet on the flywheel. It senses when the magnetic poles switch from N to S and at that split second it is at its peak to fire.
> With the electronic ignition you get a stronger spark at the spark plug, plus no mechanical parts that wear out like the points,condenser and related parts like the lifting plunger.


 True, but there is no way to tell if the spark occurs at the proper advance. Is it .100 or .010 BTDC? The factory installed solid state coils usually fire at 20 degrees BTDC. Tec has a "hot" coil that fires at 30 degrees, and makes a big difference in power. My point being that timing effects power, and with some chineesium after thought it's anyone's guess. Unless you set up a timing light and degree the flywheel. I'll stick with points/condenser.


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## classiccat (Mar 1, 2014)

ST1100A said:


> The timing automatically sets itself. The spark occurs when the armature senses where the magnets are in the flywheel by it producing its peak voltage at a certain point in its rotation around the armature or ignition coil to make it fire.
> Instead of mechanically timing it by setting the air gap, it does it electronically by sensing the peak voltage before it drops after the magnet passes a leg on the armature coil. When you set the point gap, you are trying to set the timing point when the points "break" or open compared to the position of the magnet on the flywheel. It senses when the magnetic poles switch from N to S and at that split second it is at its peak to fire.
> With the electronic ignition you get a stronger spark at the spark plug, plus no mechanical parts that wear out like the points,condenser and related parts like the lifting plunger.


The magneto (coil assembly) rotates on an old Tecumseh therefore you still have to set the spark advance even with the electronic ignition (Nova) module.


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## ST1100A (Feb 7, 2015)

They are set to go off at factory specifications, whatever the factory wanted the spark to fire at is when the module will fire, that is all done by the placements of the magnet in the flywheel.
On some of those "Hot coils" the timing is changed a bit by the way the coil is manufactured by where it sits/placement on the mounting lugs.
The amount of timing change with the point gap setting is usually not enough to notice a big difference in power with an engine that doesn't spin/run that fast like a racing engine would at very high rpm's and it doesn't have to accelerate quickly because they are set to run at a fixed speed.
Also by setting the armature/ignition coil air gap to the flywheel can change the ignition timing a little bit.
You can always use a timing light to check the timing on the engine if you have a degree wheel set up on it.
Some of the cheaper module kits are made in china, some of the better more expensive kits are made here in the USA.
Some of the Nova kits have problems, the kits by Sten's seem to be a lot better.
The nice thing with the module kit is you don't have to constantly adjust or replace the points and you have a lot better more consistent hotter stronger spark that doesn't change all the time like the point type does, so for maintenance and longevity the module kit is better that the engine is producing better power with less down time for repairs of the ignition system and spark plug replacement.
Now if you are building race engines, they are a whole different story. All of the high compression high revving engines I know of are using the electronic ignition due to reliability and customization of advance curves if needed for the application, but the race kits are different than a standard commercial or consumer use kit.
What is nice with the module kits are is that they are simple to install and they work on a simple principle, not like the breaker points do which can be very complicated for the average person to set up and understand, because anything that is out of adjustment like the point gap or a failing condenser will change the timing, even point bounce. The module always stays the same unless the magnet in the flywheel moves, which is very unlikely. If that happened, the engine wouldn't run, like a sheared keyway or a flywheel that blew apart.
I have engines that have been running the module kits in them for the past twenty years now, and still with the same module, it didn't fail yet. I could imagine how many point and condenser sets I would have replaced by now if I didn't have the module kit installed.
But you have to watch where you get the kits at, the cheap chinese kits were junk in the beginning, but they are starting to get better now. I would rather use something made in the USA.


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## paulm12 (May 22, 2015)

I have yet to see an internal magneto system (points) replaced with a CDI system. In that case there is no way (that I have seen) to set the timing. Please correct me if I am wrong and it is do-able. 

Thanks


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## 2.137269 (Nov 15, 2019)

dcinma said:


> Lot's of good information guys thanks .
> For I'll just put in the new points and condenser because I need to finish this a have it ready for the next snow storm.
> I might just order an electronic module and keep it on hand.
> I had the same thought as the last poster, if you don't have to set the timing with an electronic module, then how does it know when to fire at the optimal time?
> ...


ECH - Exclusive Craftsman Horizontal
ECV - Exclusive Craftsman Vertical
H - Horizontal Shaft
HH - Horizontal Heavy Duty (Cast Iron)
HHM - Horizontal Heavy Duty (Cast Iron) Medium Frame
HM - Horizontal Medium Frame
HS - Horizontal Small Frame
HSK - Horizontal Snow King
HMSK - Horizontal Medium Frame Snow King
AV - Lightweight Aluminum Vertical
LEV - Low Emissions Vertical
TNT - Toro N'Tecumseh
TVM - Tecumseh Vertical (Medium Frame)
TVS - Tecumseh Vertical Styled
TVXL - Tecumseh Vertical Extra Life
V - Vertical Shaft
VH - Vertical Heavy Duty (Cast Iron)
VM - Vertical Medium Frame
VSK - Vertical Snow King

Using model LEV115-57010B, serial 8105C as an example, interpretation is as follows:

LEV115-57010B is the model and specification number
LEV Low Emissions Vertical
115 Indicates a 11.5 cubic inch displacement
57010B is the specification number used for properly identifying the parts of the engine
8105C is the serial number or D.O.M. (Date of Manufacture)
8 first digit is the year of manufacture
105 indicates calendar day of that year (105th day or April 15, 1998)
C represents the line and shift on which the engine was built at the factory.
Engine Family: Engine Tracking Information


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## classiccat (Mar 1, 2014)

paulm12 said:


> I have yet to see an internal magneto system (points) replaced with a CDI system. In that case there is no way (that I have seen) to set the timing. Please correct me if I am wrong and it is do-able.
> 
> Thanks


the magneto rotates. I mark them for advancing and retarding the timing. 



















It's super easy esp w/ the head off...I had to fab up a little contraption for doing it through the plug hole.


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## ST1100A (Feb 7, 2015)

paulm12 said:


> I have yet to see an internal magneto system (points) replaced with a CDI system. In that case there is no way (that I have seen) to set the timing. Please correct me if I am wrong and it is do-able.
> 
> Thanks


The module is basically the CDI that just takes the place of the points, that's about all it is.
On the expensive racing systems they are adjustable, some have a dial on them and others it is done by hooking them up to a computer and adjusting them that way.
The simple average user system it just takes the place of the points to make the engine less maintenance involved and more reliable running by not having to adjust and replace the points all the time.
They were designed for a lot of the engines built back in the 70's with points and before they started coming out with the newer style electronic ignition coils that did away with the points.
They can be used on the engines with the points mounted under/behind the flywheel.
There are some websites that explain how they work, you might want to check on them, it could explain them better and to see if it would work for your engine application.
When I first started using them, I was not sure if they would work for me, but they worked out very well.


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## ST1100A (Feb 7, 2015)

classiccat said:


> the magneto rotates. I mark them for advancing and retarding the timing.
> 
> 
> 
> ...


The magneto is stationary, the flywheel rotates around it. The module system would work on that set-up. Just attach it to the wire that went to the points. You can mount the module on the outside of the engine where you can get to it easily. The module is small, about 1 inch square.
Just disconnect the condenser and hook the wire from the coil to the points to the module instead of the points.
The module works with magneto ignition, not the battery type ignition.


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## classiccat (Mar 1, 2014)

ST1100A said:


> The magneto is stationary, the flywheel rotates around it. The module system would work on that set-up. Just attach it to the wire that went to the points. You can mount the module on the outside of the engine where you can get to it easily. The module is small, about 1 inch square.
> Just disconnect the condenser and hook the wire from the coil to the points to the module instead of the points.
> The module works with magneto ignition, not the battery type ignition.


the magneto is stationary* once it's secured to the block* however the magneto assembly is slotted so that it can be rotated CW or CCW for advancing or retarding the timing.

the flywheel magnets in relation to the crank/piston/cam position is of course not adjustable...unless of course you re-glue the flywheel magnet, shear a flywheel key or screw-up the cam / crank installation.


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## classiccat (Mar 1, 2014)

here's a good video to explain tecumseh ignitions.


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## SimplicitySolid22 (Nov 18, 2018)

Your H70's birthday is July 14,1978.


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## ST1100A (Feb 7, 2015)

Set timing like you normally would with points then just disconnect the wire to the points and connect it to the module. Disconnect the condenser and you are good to run the engine again without having to adjust or replace the points again.


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## Mike C. (Jan 28, 2016)

Two years ago I changed the points and condenser in my Allis/Simplicity 828(Tecumseh HM80).That's the only time they've been touched in the 20 years I've owned that machine.They really don't need adjusting/cleaning/replacing "all the time".Someone correct me if I'm wrong,but I also believe that engines with extra magnets on the flywheel(alternator) won't work with the solid-state modules.


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## paulm12 (May 22, 2015)

ST1100A: do you have a pic showing an internal points system that has the module replaced, and the coil still under the flywheel? And yes, I had to rig up a dial indicator for setting the timing, I am still on the lookout for a (cheap) Tecumseh timing tool that threads into the spark plug hole. 

tx


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## ST1100A (Feb 7, 2015)

Paulm12,
Trying to find that tool will be hard since they are an old tool. I knew people that made their own using a dial indicator and had the piece machined for the head,spark plug hole adaptor.
Sorry I don't have any pictures of the module kit installed in those engines. When I did them I just did the necessary wiring and installed the module to the blower housing to mount it. I did a lot of them on Briggs engines but never photographed them, they were very simple to do.
The only thing the module kit does is it takes the place of the points and condenser.
On the newer solid state systems, the module is built into the coil armature so you wouldn't even know its there.
Briggs, Kohler and Tecumseh ignition systems look a little bit different in appearance but the module kit is the same for them as long as it is a magneto ignition and installs the same way.
Tecumseh had a couple of different systems, external and internal coil armature, they had solid state and point type that were all magneto type, and they also used a battery type that used a whole different ignition coil almost like an automobile, and the module kit will not work for that particular set-up.
The newer electronic ignition systems are much more technical. They will automatically advance the timing at certain rpm's, and they will allow engine start with very little timing advance to help prevent "Kick-Back" when starting the engine, and some have a "Rev-Limiter" that retards the timing if it senses an over-speed situation. That is all built-in to the coil.
Then you have your different types, CDI,TPI, DTPI and so on.
The original Tecumseh system was a bit complicated because of having to set the timing advance and the point gap, where Briggs and others was just the point gap. The Tecumseh was good for more of a performance engine where speed mattered like on a mini-bike or Go-kart. Most people just set the armature coil right around the middle of its adjustment because they did not have the tools to set it exactly right, and it worked o.k. for them. Eventually Tecumseh realized it was a bit too complicated and changed it to a more user friendly set-up, then eventually they came with the solid state or electronic ingition to do away with all the hassles of the point system.


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## ST1100A (Feb 7, 2015)

Mike C. said:


> Two years ago I changed the points and condenser in my Allis/Simplicity 828(Tecumseh HM80).That's the only time they've been touched in the 20 years I've owned that machine.They really don't need adjusting/cleaning/replacing "all the time".Someone correct me if I'm wrong,but I also believe that engines with extra magnets on the flywheel(alternator) won't work with the solid-state modules.


Mike, it might not work. Sometimes that set-up is a solid state already.


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## ST1100A (Feb 7, 2015)

Classiccat,
That's a good video to help people. It may also confuse or scare them from the system but it does help explain how to set the timing correctly, thank you for posting it.


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## ST1100A (Feb 7, 2015)

I remember the first time I installed a module kit, I didn't trust them at first, I was used to the points. After I used them a couple of times and they seemed to work pretty well and didn't experience any troubles with it, I felt more relaxed with them.
I was surprised at how simple they were to install and did not think they would work, but they did and was less work to do during the annual tune-up time, being I didn't have to remove flywheels to check points or remove covers if they were external mounted, it saved a bit of time there and they lasted longer than the points did in most of our applications. They basically simplified everything.
If you remember when automobiles used point type ignitions, then when they switched over to "Pointless" it took a short time to perfect it but it worked better than the point type did.


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## dcinma (Dec 13, 2017)

SimplicitySolid22 said:


> Your H70's birthday is July 14,1978.


Thanks
I'm thinking this machine was purchased in 79 or 80?
Serial no. on tractor is 092, on bucket is 09902.


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## dcinma (Dec 13, 2017)

Well it's done. Did what I said I was going to do and success!
Funny thing is the RPM was around 3900, had to make an adustment to bring it back to about 3600. I wonder if this is because I set the BTDC clearance to .080 unlike the last time @ .050?

After retuning the carb it appears to be running fine. I let it run for about an hour and it never died like before.

The only issue I had was I installed the points but left the leads off so I could hook up my continuity tester for the "make, break" part of the set-up. The problem is that after you attach the leads to the points stud, tightening the nut changes the gap!!!
So what I did is re-do all the adjustments and then because the stud was long enough I put the leads over the already tightened stud and used another nut with lock tight for the electrical connections. The gap did not change after this.
I have a big blue spark and the engine sounds strong. Not really hoping for snow but can't wait to try it out.
To make the .080 clearance I ground down and polished a large washer to .080 and used a machinest rule across the deck.


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## paulm12 (May 22, 2015)

Glad you got it all figured out, and working again. Looking forward to hear how it does in the snow again.


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## scrappy (Dec 7, 2014)

Glad it's running strong. See, those Tecumseh engineers knew what they were doing when they made the timing adjustable.


Ya wont see this on a Briggs. Or with the aftermarket electronic conversion unless you set up timing marks and use a timing light.



Amazing that .030 added that many rpm's.


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## classiccat (Mar 1, 2014)

dcinma said:


> Well it's done. Did what I said I was going to do and success!
> Funny thing is the RPM was around 3900, had to make an adustment to bring it back to about 3600. I wonder if this is because I set the BTDC clearance to .080 unlike the last time @ .050?
> 
> After retuning the carb it appears to be running fine. I let it run for about an hour and it never died like before.
> ...


Kudo; sounds like you did a proper job getting that ignition dialed in!! Many would've thrown-in the towel. 

Yeah, you have to set the gap and timing with that nut tightened down (I believe it's briefly mentioned in that looong tecumseh video I attached earlier).


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