HS 49cc Red Line RPM??

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fredgold52

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Dec 3, 2009
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Illinois
I'm betting some of you four strokers have been messing around with tachometers. I'm curious about what RPM would a person expect to be the Red Line RPM on a stock HS running unloaded?
 

The_Aleman

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Jul 31, 2008
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el People's Republik de Kalifornistan
Redline's about 8000, although they can take more than that for short bursts. The GXH50 can take it for a little longer than the HS can, due to tighter engine construction and a better connecting rod. Extended high RPM can cause the oil slinger to break off either engine, and even more extended may cause the connecting rod to break.
 

BE-tech

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Sep 14, 2011
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Bozeman
Redline's about 8000, although they can take more than that for short bursts. The GXH50 can take it for a little longer than the HS can, due to tighter engine construction and a better connecting rod. Extended high RPM can cause the oil slinger to break off either engine, and even more extended may cause the connecting rod to break.
This is exactly correct. They can only take it for short periods due to the lack of lubrication to the big end con rod. The con rod welds itself to the rod journal, often breaking or bending the con-rod in the process. You can modify the rod for a bit more oil flow, but this has to be done carefully. After that, I'm guessing the limiting factor would be the con-rod itself, oil slinger, or valve springs.
 

fredgold52

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Dec 3, 2009
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Illinois
The reason I asked for unloaded red line rpm is because from that I can figure roughly what it should be under load, and from that about what mine should be running hauling my big butt around. Best I can tell, mine runs at about 5K under load. And that's just fine. It's also not where I run it very much.

I run the bike up to a comfortable speed, then back off the throttle and let it freewheel. RPM drops to idle during freewheeling times. At this rate, my HS 49cc will last 3,000 years I'm guessing. Well, maybe not.