gauging rpm

[mike75925]

do you guys just go to the dyno, or are you all using michron setups? what is the easiest tach? in getting more power i threw a 1/4" plate across the vehicles seat in case of fragging. as i don't have access to a dyno could anyone ball park my ponies? stock bottom end, GX160 head, gov yanked, carb tweaked, straight pipe 1", super thin head gasket, flat bottomed valves, longer rockers, dished piston, paper element ripped out of filter, and ram aired (not quite sealed yet but should help to inflate 'er lungs)? thanks in advance ps 50 racing oil, 89 octane

 

[modelengineer]

You can work it out from your gearing, wheel size and max speed. Why do you need to know while your driving? You should know what it sounds like at max RPM, so you can gauge how much you've got left, I would have thought.

But to answer your question I use an Autometer Adjustable Shift Lite Tacho

 

[BAMBY]

the tach i have is this one...

http://www.tinytach.com/tinytach/commercial.php

i like it a lot. tells rpms, total run time, run time for a job, two service timers. its awesome.
BAMBY

 

[freakboy]

how did you attach that tach?

 

[Kaptain Krunch]

65 bucks and it only lasts 5 years

 

[jr dragster T]

You'l spend more in gas in 5 years then you did for the tach. I do agree it is a bit pricey and thats why I dont have a tach on my kart. You just wrap the lead wire around the sparkplug wire. I'm sure if you REALY wanted to replace the battery you could carefully disect it and replace it.

 

[mike75925]

thanks, for the info. and to model engineer, i'm used to engines the rev to 14k (crotch rockets) getting used to the smaller output type motors though

 

[Kenny_McCormic]

You can use a cheapo digital bicycle speedo as a tach, simply mount the pickup on your flywheel shroud(might need to cut a hole, the pickup needs to "see" the magnet) set it to display mph and input 268mm for the wheel size.

http://www.instructables.com/id/S9RSH6XFD80WTNY/

 

[mike75925]

ok grabbed a schwinn 12 function, had to make a jack of sorts for the mag. about 1/8" away and picks up when hand spinning the wheel. jb'd the jack into my manco wheel. figured since it has no tach function, i could take the speed and input it into the speed calculator. installed on non-drive wheel.

 

[anderkart]

ps 50 racing oil

From all I've heard, you might be better off using a thinner oil (like 30 or10-30 wt.) in a high reving motors like yours.

 

[EagleTalons]

Here is a cheapie one. I bought two, one for MPH and the other for RPM.

 

[oscaryu1]

Here is a cheapie one. I bought two, one for MPH and the other for RPM.

Where is here ?

 

[freakboy]

Where is here ?

its over there.

 

[EagleTalons]

Oh sorry.

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&ssPageName=STRK:MEWNX:IT&item=160305540501

 

[mike75925]

if my revs are low enough i may change weights. i have yet to remove fan fins or use an offset key.

 

[brendonv]

but a bike computer only reads to like 100km/h so it wouldnt gauge the rpm.

 

[freakboy]

if my revs are low enough i may change weights. i have yet to remove fan fins or use an offset key.

do not remove fly wheel fans, bad things happen to lightend flywheels man. just cause they wont go stock at 5k that dont mean if you drill or mess with them they wont go at that speed.

 

[oscaryu1]

Fins help cool the engine also. Remove them, and not give it enough cooling, you'll fry some parts.

 

[mike75925]

i have some edf's (electric ducted fans) the faster they spin the less efficient they become. on a six blade setup, remove three and you will see high end gains. granted some of the motors spin to 100k rpm, but if the pitch is not matched to the motors capability, it would be like running a 5hp carb on an 8hp engine

 

[EagleTalons]

but a bike computer only reads to like 100km/h so it wouldnt gauge the rpm.

It reads in 100 rpms, read the link Kenny gave us.