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I have a Tecumseh 10.5hp 358cc HMSK105

Anybody know what the max RPM is? I have been reading values anywhere between 3500-3900 on various websites, but I can't seem to find anything official from Tecumseh,

I have a digital tach to set it with, I want to make sure I'm not over revving it/setting it too high
 

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Tecumseh 3,600

Chinese much higher
 

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Without an exact recommendation from a manual, I think that 3,600 is pretty common as the max for most standard horizontal gas engines.

.
 

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I have the smaller 318cc version of it. It was set to 3500 rpm (safe rpm) when I got it. I just recently raised it up to 3600-3670 rpm. That is the max rpm of those Tecumseh engines. They are flat head engines, so they might lost HP at that rpm already. However, the faster impeller spinning give you a small boost in performance.

It is best to keep it at 3500 rpm, but if you want more performance like me, raise it to 3600 rpm. It is not much of a different and not worth it in most cases. I have double belts auger, large diameter impeller and extended to close the gap, and high output pulley ratio so it helps when I raise it up to 3600 rpm.

To be honest with you. It is scary for me to run it at 3670 rpm. That is why I'm planing to add a few drops of 2 cycle engines in the fuel to help lubricate and cool it down. Maybe enlarge the fuel jet by a little. Old Tecumseh engines don't lubricate themselves very well. They splash oil up to lubricate their internal parts, instead of using oil pressure systems like modern engines. They are good engines, but you got to take care of them and don't abuse them.

I don't think it is going to blow up at 3700-3800 rpm. Some members on here have ran it at that speed, but really, they were testing the limits. The reasons why they blow up are: running on low oil, running at high rpm with no loads (not blowing snow), not warming the engine up and cold start at high rpm, stuck throttle linkage and butterfly valve (this happens a lot so I'm going to lubricate them). Why they blow up more than Briggs & Stratton and others? Because, they were on most snowblowers. Not that they are bad engines. They are just a little old school.
 

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However, the faster impeller spinning give you a small boost in performance.
if you were just looking to up the impeller speed could always put a larger pulley on the engine or a smaller pulley on the impeller. also the impeller mod gives you a pretty good performance boost as long as you machine has the power throw the snow without bogging too much. i am not sure if running at a higher RPM would prevent a bog under load.

could also run motor kote in the engine to help keep things lubricated better at high rpm's. my snowblower doesn't have any in it yet but i do got some for it. just waiting till i change the oil on it.
 

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if you were just looking to up the impeller speed could always put a larger pulley on the engine or a smaller pulley on the impeller. also the impeller mod gives you a pretty good performance boost as long as you machine has the power throw the snow without bogging too much. i am not sure if running at a higher RPM would prevent a bog under load.

could also run motor kote in the engine to help keep things lubricated better at high rpm's. my snowblower doesn't have any in it yet but i do got some for it. just waiting till i change the oil on it.
I only want to up the speed a little. I have a double belts system, so there are no pulleys out there that are exact fit. I would have to modify/metal welding them. Plus, I already achieved what I want (similar to the output of the Ariens SHO) by closing the impeller gap to 3/16" and raise the engine rpm to 3600. I didn't use rubber to close the impeller gap. I metal welded it.

I never heard of motor kote so I'm a little skeptical with it. I will do more research on it.
 

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thanks for all the replies.

i think i am going to play it safe and set it around 3500-3600, i want this engine to last me a long time,

not because i can't afford another one, i just like taking care of things like this properly, and getting the most life possible out of them,

i don't think setting it 100-200 higher is worth the risk, for a very minimal performance gain, if any at all
 

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doing the impeller mod should make a huge difference to how it throws snow with no extra stress put on the engine. got a 8/24 that i would have likely parted out or sold if it wasn't for the impeller mod making a pretty significant difference to how far it threw the snow. it would only throw snow about 6-8 which is almost useless to me. need at least 10ft or i am moving it twice. impeller mod had the snow moving at least 14 ft and moves almost anything including the slush.
I didn't use rubber to close the impeller gap. I metal welded it.
I never heard of motor kote so I'm a little skeptical with it. I will do more research on it.
with rubber you get a bit better seal all the way around. 3/16" gap is definitely better than the 1/2" or so gap that most machines have factory but at least rubber is a bit more forgiving.

project farm did a video on it. if it wasn't for his video i would have likely never bought the stuff. he is one of few people that seem to really test things and is not paid to do so and not advertising for 1 company or another like most other channels are nowaday. i think it would likely help a engine last better at higher rpm or at least it should help it stay lubricated if that is the issue they have at higher rpm's
 

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thanks for all the replies.

i think i am going to play it safe and set it around 3500-3600, i want this engine to last me a long time,

not because i can't afford another one, i just like taking care of things like this properly, and getting the most life possible out of them,

i don't think setting it 100-200 higher is worth the risk, for a very minimal performance gain, if any at all
Yes, you don't want to run it at low rpm either, because it doesn't has enough torque and low performance. Most snowblowers run at 3500 rpm. Raising it up by a little is not going to hurt anything, but not helping either.
 

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doing the impeller mod should make a huge difference to how it throws snow with no extra stress put on the engine. got a 8/24 that i would have likely parted out or sold if it wasn't for the impeller mod making a pretty significant difference to how far it threw the snow. it would only throw snow about 6-8 which is almost useless to me. need at least 10ft or i am moving it twice. impeller mod had the snow moving at least 14 ft and moves almost anything including the slush.

with rubber you get a bit better seal all the way around. 3/16" gap is definitely better than the 1/2" or so gap that most machines have factory but at least rubber is a bit more forgiving.

project farm did a video on it. if it wasn't for his video i would have likely never bought the stuff. he is one of few people that seem to really test things and is not paid to do so and not advertising for 1 company or another like most other channels are nowaday. i think it would likely help a engine last better at higher rpm or at least it should help it stay lubricated if that is the issue they have at higher rpm's
The thing is that I have cup shape impeller blades. It is hard to put the rubber on and it would take spaces (making the tip of the blades narrower). Also, I did not want the impeller to rust out.
Someone on Youtube welded his impeller as well and his gap was only 1/16" as he claimed. Even at 3/16" gap, it was very hard for me to fit the impeller in its housing. His snowblower throws snow like crazy, but he had other mods on it.

I watched projectfarm before and really liked his channel.
 

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i guess it would be a bit trickier bit likely not impossible. you almost need to be able to bolt the rubber on with the impeller in place. with the machine like Jerry and i have it is a pretty simple thing to do with the shoot off. here is a picture i took the other day when i did the impeller mod on the machine i was assembling for my nephew. installing the impeller mod on it is easy as long as the stupid carriage bolts come out without rounding the holes. .
 

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Here is my impeller before I grind it down to fit. I grind it a little too much. I wish the gap is only 1/8". You see why it would be hard to put the rubber on? Also, I wanted to keep the tip of the blades as wide as possible. I have another snowblower with the impeller mod.

 

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it would be a bit trickier to bolt a piece of rubber to but not that bad. on something like that you would almost only need to bolt it in the middle and it would likely stay in place. but 2 would obviously be better.
 

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About motorkote, you might want to avoid using it. I know it was impressive on project farm test, but you don't know its long term reliability and if it would make the oil too thick to flow in the winter. People compared it to slick 50 and other similar products. They had PTFE and chlorinated. Chlorinated is corrosive to some metals. Teflon PTFE is not good for the engine either (i don't know the reason for that).
Think of it as snake oil. They know how to market things. If it works so great, then why don't they have that in engine oils already? Oil companies could easily figure out whats are in it. They just don't tell you whats are in it, because they want to sell you some of that.
 
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