Tecumseh LH195 versus the HS50/HSSK50

cfh

Well-Known Member
#1
I have a *ton* of Tecumseh powered mini bikes. Way too many. But they all share one thing, the Tecumseh HS50 family (though a few have HS40 engines.) By family I mean HSSK50 and HS50 (which are pretty equivalent), rated at 5 horse power. The only real change happened in the 1990s when Tecumseh decreased the bore size .020" and switched to thin piston rings and a smaller exhaust valve. But to be frank, that's a pretty small change, and one you would be hard pressed to tell when installed on any given mini bike.

But in the late 1990s, Tecumseh came out with a new motor, the LH195. It is basically an HSSK50 engine. It has the exact same bore and stroke as a mid 1990s HS50/HSSK50 engine (the thin ring piston and small exhaust valve). So what is different? I mean why a new motor? And WHY is the LH195 rated at 5.5 horse power (instead of 5hp like the HSSK50) at 3750 rpm????

I have not come across many LH195 engines. In fact, I only have one. Bought a snowblower and harvested the LH195 motor, and converted it to mini bike format. Put it on a Fox Thunderbolt 170, and rode it a bit. The engine worked fine, no issues. Did it seem like it was more powerful? (Seeing how it's advertised as 5.5 hp.) I would have to say no. It was running a 16mm slide carb and an open exhaust (through a torque converter). It seems pretty much like all the other HS50/HSSK50 engines...

But here's where things get off the rails... Lately I've been going back through the Tecumseh motors, and cleaning up some prior work. For example, on the LH195 it's running a 16mm slide carb. But i never removed the governor. It was just sort of hanging there. It looked unprofessional like that, so i thought it would be a good idea to split the case and remove the governor properly.



Upon splitting the case, the first thing I found was the mechanical compression release on the cam had come apart! I had *no* idea this happened... the parts were in the bottom of the case! It didn't do any damage... everything was cool... the bore was really nice on this engine too. But it made me think that *any* sort of compression release (be it mechanical or bump style) is a bad thing, and I shouldn't be running it. I mean come on, i know to pull the starter cord until i get to the compression stroke *before* i do a full pull! duh!!

Since I had the case apart and the cam out, I thought it would be a good idea to check the cam. I had a hunch that the reason Tecumseh gave the LH195 a 5.5hp rating was that the cam is different. In fact, the cam is different, it is a different part number than the HS50/HSS50/HS40 cam. There's probably a reason for that, and sure enough, it's a damn good reason!

Bottom line... the LH195 comes with a Dynocam 245 with a mechanical compression release! I kid you not on this... I have a Dynocam 245 sitting right here, and did the measurements... The dynocam 245 and the LH195 cam are nearly identical. Heck it's like a christmas gift inside a late model Tecumseh engine! But that said, there are some caveats... That is, at some point, Tecumseh neutered the LH195 and switched to a plastic cam (and light duty cam springs)! Obviously you don't want that variety of LH195. But any who, below are some pictures that compare a Tecumseh HS50 cam, Dynocam245, and LH195 cam and the lobe sizes.

Note I will check the lifters and see if they are different than an HS50. I will also measure the actual valve lift (and how it compares to a Dynocam245.) Perhaps they did something different there. But my hunch is, that's not the case...

Comments appreciated...





 
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#2
that's first I have ever herd of one of them newer compression release broke/sort of? no wait... someone spun that motor in reverse and broke the cam lever off. yes never spin them backwards or your done and yes the 195 I have seen the steel cam with compression release in them before. that was standard on the ohh-motors. make a story short some ohh's had plastic and others steel.
cfh that would be a real good hot rod motor. just buy the new plastic cam kit on ebay and use the new spring/swing arm/thin washer on your steel cam. install hot coil,mikuni carb,header,good springs and retainers and it will pull real good up to 4700+ rpm's
if i remember right the base circle/cam is little different size then the old stlye bump cams are(hs-motors).
also in the pass i help a friend install the 195 cam in a black widow motor. i remember too i had to grind the lifters down some to get the correct clearance. (it was to much material to grind the tip of the valve) so make a story short. those lifters in that motor go with that cam. I believe markus was looking for that part number(lifters) can you post the ID tag. that will give the correct info to buy those lifters to use with that cam in a older flathead. so a guy wouldn't have to grind the lifters down. it's not to bad to do when I have the correct tooling to do it. but if a guy doesn't have the tooling, makes it little harder to do.
big thing when installing this cam in a older motor you have to weld a very small part on the inside side cover where the cam rides or the cam arm will push on the thin thrust washer into a small gap and damage the arm or more...parts
ohh-cover comes filled in with just a small gap for oil. older covers are wide open and need to be welded up



if you go back and look at my hs-build I machine a compression release in my 245 cam. works pretty slick on a motor that has the timing advance a lot.
for the most part I let that motor idle over 2000 rpm's. I can get it to idle very low and also here the release unit pop the valve open at low rpm's..around 500 or so rpm's

https://www.oldminibikes.com/forum/index.php?threads/hs-40-build.161335/
 

cfh

Well-Known Member
#3
since the compression release on this cam is already trash, i'll just be leaving it off completely. Heck i've been using the motor with the MCR broken anyway! it wasn't any different to start than my other HS motors. there's just no need for compression releases in my opinion. It's habit for me to just light pull until i feel the power stroke, then give it a good tug to start.
 
#4
yep, I agree. it's not hard to pull these little guys over. when you know how to find the sweet spot...easy for me. but when you install a hot coil(advances timing) and forgot to pull it right. it's hell on your arm and your going to pay for it....lol. the overhead valve engines seem to be worst,if you don't pull it right.
 

cfh

Well-Known Member
#5
Del, please tell us more about this hot CDI coil. I’ve heard you talk about it before but I’m not sure what it actually does. Is a hotter spark really needed? How can it advance timing? Are the coil plates in a different location? Thanks
 
#6
hot coil was developed for the motorsports racing engines. direct replacement coil for the stock coil. stock timing is set right about 20 degrees. the hot coil puts it closer to 30 degrees. to me it's a day and night difference. when running this coil on my ohh-motors i have no problems spinning the ignition 7000-8000+ rpm's and even my ohh build with my 356 cam was turning 9000 rpm's.
 

cfh

Well-Known Member
#7
Do you have a part number for the hot coil? I’ve never seen one for sale, except maybe you had one for sale?
 
#8
yep,your not going to find them anymore. I do have one I would sell you if interested. I can't give it away.
if interested just pm me. I could get it out tomorrow....off to work now.
 

cfh

Well-Known Member
#10
On the Tecumseh LH195 here's the numbers... LH195sp - 67526d DOM 05222cd0788
On the valve lifters, you were correct, they are slightly different...
LH195 valve lifter length = 1.445"
HS50 valve lifter length= 1.480"
So the LH195 valve lifters has a shorter length of about .035"



 

cfh

Well-Known Member
#11
I measured the lift right at the valves and it’s .280” for both exhaust and the intake valves. If it was a Dynocam it should be .300 inches. Stock hs50 is .245” lift at valve. So it is more than a stock motor but not as much as a dynocam
 
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#12
I measured the lift right at the valves and it’s .280” for both exhaust and the intake valves. If it was a Dynocam it should be .300 inches. Stock hs50 is .245” lift at valve. So it is more than a stock motor but not as much as a dynocam
i'm little loss on your measurements cfh. for example base on my hs-40 cam and a ohh/195 cam I have.
i got totall length from the tip of the cam to the base/bottom .980 and the base circle side to side .783 minus from .980=.197 lift for the hs-40 cam
ohh/195 cam is 1.048-.853=.195 lift so both are about the same lift.
last year i fab up set of 1.3 rocker arms on a ohh motor giving it about .253+ lift. with all the tricks i did also with that motor i could get it to pull easy 6000+ rpm's. keep telling my friends it has a stock cam in it...lol .....
 

cfh

Well-Known Member
#13
I am measuring the lift like this. below is a picture of a stock HS40/HS50 cam and actual lift is .245". If you put in a Dynocam245 that measurement will be .300". With the LH195, it's between the two at .280" actual valve lift.

 
#14
I don't have a 245 cam in front of me,but it almost looks you could grind a 195/ohh cam to a 245 spec's without rewelding the cam? maybe little welding on the tip only? then of course you would run the old style lifters.
 
#15
hot coil was developed for the motorsports racing engines. direct replacement coil for the stock coil. stock timing is set right about 20 degrees. the hot coil puts it closer to 30 degrees. to me it's a day and night difference. when running this coil on my ohh-motors i have no problems spinning the ignition 7000-8000+ rpm's and even my ohh build with my 356 cam was turning 9000 rpm's.
just wanted to add something what i was say about the hot coil for some of you guys that may want to run a coil like this or modify a older points system and advance it. advancing the motor on a tecumseh is really only any good when doing alot of mod's and doing them right. so for example if you are still running the stock intake,carb and a snowblower muffler your wasting your time. heavy mod's are going to make a big difference and that means also to the bike,gearing and a high stall in the clutch,for example 3000 stall is a good start. if you cut corners on any of this it will affect the out come of the performance of the bike and yes if you weigh alot it might be a dead end...lol
:scooter:
 

cfh

Well-Known Member
#16
Actually the lh195 cam is pretty much a dead nuts copy of a Dynocam 245. But when it’s installed in the lh195 motor with those different lifters, it doesn’t give you the same valve lift. Now if you transplanted the LH195 cam into a HS50, that’s a whole different story. You would get the same result as a Dynocam 245 in that hs50.

As to your point about advancing the timing ... You are very correct if you put in a hot cam and a slide carb but are running a stock exhaust, you don’t see much effect. The system is only as good as its weakest link. You need all the elements together ... slide carb, open exhaust, modified cam.
 

cfh

Well-Known Member
#17
For giggles I put in the Dynocam 245 cam in the LH195 motor. It has good valve lift but the valve lash is like .025” with the lh195 stock lifters!

then I installed the dynocam 245 with Hs50 valve lifters. That works except you would have to grind either the valve lifter ends or the valves ends because there is no (negative) valve lash. Not a huge deal but you would have to do something to make it work to get the .006” valve lash

So I guess you’re right in fact the LH 195 valve is not a direct copy of the Dynocam 245. It’s close but no cigar

To exemplify this point further, I put the LH195 cam into an HS50 engine. It does show that the lh195 cam is damn close to a dynocam245; the lift is nearly identical at .300” for each valve. But the problem is there’s zero or negative valve lash. So you would have to modify either the ends of the valves or the length of the valve lifters, to make the LH195 cam work in a HS50 engine

But frankly that’s not much overhead or work for getting basically a free Dynocam 245 !!

To Dell’s point, I bet that Dynocam was using stock LH195 cams as a base for grinding the dynocam 245. Because if you look at a 245 cam, there’s no evidence that it was ever welded. So they will probably just bought LH195 cams and reground them ever so slightly to be a Dynocam245
 
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