Looking for information about 'redline' and tachometer advice

[ionia23]

Hello all,

The motor on my bicycle is an 80cc two stroke of the Umoto/Insight brand. So far, it's been a pretty sturdy little engine.

I had two questions for ya'll today I haven't had much success in getting answered on my own.

1. Is a tachometer for an engine like this actually feasable? Do they even exist?

2. What would the typical 'redline' be for a motor of this size? No, I'm not planning on running up to/against it. it would just be good for reference during normal operation if I happen to be 'pushing it'. The idea of an engine disintegrating while flying down the road (much less having it throw a rod in between my poor legs) is a little unsettling.

I've been fortunate in that I've never seen the carnage of what happens when one of these little motors decides to blow up.

Thanks in advance.

 

[MotorBicycleRacing]

TTO makes the nicest digital tachs for 2 stroke and small 4 stroke motors.
Wrap a wire about 4/5 times around the spark plug wire is the simple hook up.
They also have an hour meter function.

http://www.trailtech.net/digital-gauges/tto/surface-mount/tach-hour

 

[zippinaround]

You can get real cheap ones on ebay I got one for €5.09
http://www.ebay.ie/itm/322178540579?_trksid=p2057872.m2749.l2649&ssPageName=STRK:MEBIDX:IT
Could just be trash but says is accurate to 10rpm , will see when it arrives!

 

[Deleted member 12676]

usually manufacturers decide on what RPM the redline is dependent on piston stress due to piston speed. So usually on a small engine the redline can easily be 12,000 since the stroke is so short the engine has to rev really fast to reach that maximum piston speed limit.
But on these engines the maximum stress on the crank bearings is reached first due to crappy balance. Once you get the crank balanced then there will be no worries about redline.
see http://www.dragonfly75.com/motorbike/vibes.html