# YS624 operating RPM



## 71Dragtruck (Oct 27, 2019)

Does anyone know what the factory spec is for a early to mid 90’s YS624 operating RPM is, mine I think is a bit high, are they also suppose to be run at 3600 like a Honda or are the Yamaha’s a bit higher? Thought I read somewhere they run a bit higher RPM?


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## ST1100A (Feb 7, 2015)

The Yamaha's were pretty much like the Honda engines. You could run them up around 3800 RPM's, but they usually ran around 3600.


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## 71Dragtruck (Oct 27, 2019)

Ok thanks, I’ll have to turn mine down a bit.


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## Coby7 (Nov 6, 2014)

Mine, bought in 2014 runs at 3800 rpm at full throttle.


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## 71Dragtruck (Oct 27, 2019)

That’s close to where my old early to mid 90’s runs, around that 3850, still think I’ll turn it down a bit, go easy on the old girl lol.


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## RC20 (Dec 4, 2019)

Book says 3800, I checked it with a freq meter and it was correct.


I just set the speed to snow conditions, if its real deep max, otherwise someplace below that.


50 RPM over is not an issue.


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## 71Dragtruck (Oct 27, 2019)

Since I started this thread I obtained a copy of the service manual and was actually very surprised on what RPM range it recommends for my 624.


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## RC20 (Dec 4, 2019)

Looks like a bit later option and data, my 98 Manual (owner and Service) does not have that.

I did find that max torque was at 2800 rpm - certainly explains whey it lugs down and keep throwing so good - I did not think that kind of info would be in there. . 2.1 kg*m (I would have to look that up for ft lbs) - Wheel YS is 2.3, no idea why the difference. 


15 ft lbs for 2.1 16.6 ft lbs for 2.3 (never did work with any metric torque though most other units off and on so had to sleuth) 

Also max hp is 4000 despite the RPM max recommended. Also ref to PS at the same speed and its a tad different than HP. Close but not quite the same but at 6 hp its so small as to be meaningless


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## RC20 (Dec 4, 2019)

I was looking up some other specs, Ariens specifically Their killer machine hp to width ratio has a 369 CC engine with 17 ft lbs. Calc wise that is about an 11 hp engine. 



The Yamaha has 15 ft lbs on the track machine and right at 17 for the wheel machine. 



No wonder they are such a beast .


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## Coby7 (Nov 6, 2014)

My manual for proper year (2015) and model ( YT624EJ ) says 3800±50.


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## RC20 (Dec 4, 2019)

Does yours have the torque spec? (and speed?) 



Different era engines, curious how the new ones look, truly amazing to get that out of a non diesel.


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