Unaccurate RPMs

[awaffa2003]

Hey guys, new to the MOA and i got few questions, i'm not sure if my tach is too accurate, i have an '83 R65 with a Trail Tech Vapor computer and i have 7500 as my redline cuz i think thats what it was on the old one but it says i hit 14000 in 5th gear and i was only doing 72mph. is this normal? i've never had a functioning tach so i don't know. i think i was at redline or maybe past it but i thought these bikes went faster than that. i only had a short stretch of road tho, maybe if i had more time to gently climb up there it would be different...idk? also thought maybe the heavy vibrations that the R65 is known for might be the cause?

[rocketman]

I've never heard of the trail tech, but I can tell you the bike ain't hitting anywhere near 14K rpms! The stock tach was most likely electronic since around 78 they dropped the mechanical ones on all the airheads I'm familiar with. Might try to find a stock replacement tach.

RM

[wuli959]

Trail Tech Vapor computer and i have 7500 as my redline

It's most likely the Vapor computer. Check and make sure that you have the tach set up correct on it. You only adjust the tach until it hits a good reading . . . any further and you can get wide variation in the read out.

[skiteach]

14k rpm on an Airhead? Lots of schrapnel!!!!

[bikerfish1100]

2 things did NOT happen:
as already stated, you did not attain 14K rpm, as that would have produced a very well grenaded airhead.
and you did not reach the engine's redline; that would be somewhere around low triple digits for speed.

[boxermaf]

Depending on how you setup this electronic tach, I suppose it could give all sorts of readings. At first glance, it is reading at LEAST 2X high as you know, and if the pickup is inductive from a plug lead (I have no idea about this product) it is possible that since the ignition is a wasted spark
that would yield a 2X RPM figure if the computer in the box isn't expecting it. Perhaps if you can find some setup info on the product, or tell us how is is wired into the bike's ignition..

[donbmw]

On my 82 R65 65 mph is about 4500 rpm's

Don

[wuli959]

White connector snaps into mating connector on computer. Black lead is wired to frame ground. Red lead is wrapped around spark plug wire (5 times) or spliced into vehicle coil connector but it just complicates the install without adding value.

Cold shrink wrap tape to the rescue to secure the wrap, this stuff is great.

[Rogslater]

Hello folks
Don't want to sound pedantic but there is no such thing as RPM's. Revs can only be measured based on one minute, not minutes.

Roger

[wuli959]

Hello folks
Don't want to sound pedantic but there is no such thing as RPM's. Revs can only be measured based on one minute, not minutes.

Roger

consider one RPM.
Now consider multiple Revolutions per minute. Not multiple minutes per revolution
Note that RPMs has its plural emphasis on the "revolutions."

:stick