What is max safe RPM?

[dgray56]

Max RPM's

Most 2 stroke engines will let you know when you hit its natural rev limit. The unmistakable sputter is a clear indication ;-) I built an 80cc 2 stroke mountain bike that I have tried several different rear sprockets on. With a 44 tooth rear sprocket the engine was absolutely screaming to do 30 mph. With a 36 tooth rear sprocket, things get much better. Bike ran up to 42 mph smooth as silk, but the engine was still screaming at the top end. With a 32 tooth sprocket, acceleration suffers a bit, but the top of the power band where the motor runs smooth and isn't being taxed produces a constant 45 mph. I have over 300 miles now on this bike with no problems. BTW, I've had this particular model over 50 mph many times but I wouldn't recommend pushing 6k+ rpms for an extended period of time. Pre-denotation can occur at the top of the power band that can destroy your motor.

 

[Skyliner70cc]

Max rpm is easily to calculate:

While under load, increase throttle setting until engine failure occurs, then back off 500 rpm for good measure.

 

[duivendyk]

I assume failure means misfiring&stumbling ?,not destruction

 

[stude13]

kablooee

 

[zetti_the_man]

i want a tachometer now.. what's it plug into??

 

[andyinchville1]

Hi Zetti,

Most tachs use induction to calculate RPM's....A simple wire wrapped around the spark plug wire is all it takes....Tachs are battery powered (small internal button type battery).

Hope this helps you.

Andrew

 

[teamgorillaracingTGR]

Most 2 stroke engines will let you know when you hit its natural rev limit. The unmistakable sputter is a clear indication ;-) I built an 80cc 2 stroke mountain bike that I have tried several different rear sprockets on. With a 44 tooth rear sprocket the engine was absolutely screaming to do 30 mph. With a 36 tooth rear sprocket, things get much better. Bike ran up to 42 mph smooth as silk, but the engine was still screaming at the top end. With a 32 tooth sprocket, acceleration suffers a bit, but the top of the power band where the motor runs smooth and isn't being taxed produces a constant 45 mph. I have over 300 miles now on this bike with no problems. BTW, I've had this particular model over 50 mph many times but I wouldn't recommend pushing 6k+ rpms for an extended period of time. Pre-denotation can occur at the top of the power band that can destroy your motor.

is any one that has these engines intrested in gettin over 9g in rpms? i think that these cranks in the motors are to weak for a heavy piston and high rpm also if you get pre detonation its cause your fuel has not enough octane or your head doesnt cool off enough

 

[Skyliner70cc]

I assume failure means misfiring&stumbling ?,not destruction

WordNet - Cite This Source - Share This engine failure

noun
engine does not run

WordNet® 3.0, © 2006 by Princeton University.

 

[B.K. Hosken]

That's a really nice little hour and tachometer. Another toy!!