I'm new to trials and recently bought a 2014 GasGas TXT 250 Pro.  I had a plugged pilot jet so I tore the carb apart and cleaned it up.  I set the idle by ear but being the analytic type, I was curious what the idle speed was.  I have a cheap trail tech tach/hour meter (see the link).  You just wrap a wire around the spark plug wire and it picks up the ignition firing inductively.  I've used this on my 4 stroke KTM successfully.

 

I put it on my GasGas  just temporarily to see where my idle was set.   I set up the tach so that it would expect one ignition event per revolution (i.e. two stroke).  The tach picks up a signal but the RPM is off.  It hovers around 3840 and then drops to 2400ish when I rev it which seems quite odd.  I'm not sure if there is something odd about the GasGas that's preventing the tach from working correctly.  I'm curious if anyone has sucessfully used one of these cheap tachs to read the RPM of your GasGas.

 

 

http://www.amazon.com/Trail-Tech-723-A00-Digital-Tachometer/dp/B0068EQZ06/ref=sr_1_2?ie=UTF8&qid=1456786206&sr=8-2&keywords=tto+tachometer

Those meters are useless as tachometers. Don't worry about it.

WHY?

 

As I explained in the original post, I tore my carb down to clean it.  When I put it back on, I just wanted to put the tach on temporarily to set the idle.  Yes, I can set it ear but it would be nice knowing it was set close to what the factory specifies.

The factory has nothing to do with your riding preferences. Some like a high Idle so they don`t stall, some like it to just barely keep running. The only bikes that really need to care about idle speed are the one`s with fuel injection.

If its a 2014 itll have a kehein they need a fiddle every trial. Better to get used to setting it.....

A four stroke (can) fire each rotation of the crank, but only combusts ones per two rotations. But different setups are possible.

 

A two stroke, and so your gas gas, should fire every revolution, so every spark should be counted as a rev. Is the tachometer programmable for this? Otherwise it might be caused by radio waves and a non-resistor type spark plug?

 

But like above mentioned I would not bother to much, just look what you like. I have it little bit higher than enough to keep it running. Makes stalling nearly impossible (especially when tired) and is easier with balancing and hopping and stuff imo.

Edited March 1, 201610 yr by crazybond700

I keep my idle high. If i stall in a section I turn it up as a general rule. Eventually i might turn it back down based on that day but in the end it is an on demand thing. When i rode with you last i felt that the temperature was causing my idle to be low so i set it a bit higher. Since then i have set my idle lower and tomorrow i would expect it to be different. 

 

--Biff

 

PS welcome back.

Thanks for the input. Yeah it's not a big deal and I'm sure I got it into the realm of reasonability just setting it by ear.

Biff - thanks, I'd like to say it's good to be back but sitting on the beaches in Hawaii drinking lots of rum sure beats all the snow shoveling I've done this week! The temps are looking awesome for next week. Any plans to get out and ride?

Have you tried cutting back on the number of turns of wire around the spark plug lead. Too many may cause too great an inductive pickup and amplify the revs. This is the advice from another brand of tacho that uses the same approach. Try 2 tuns only - what do you get? But heck, how many turns is going to be determined by what looks to be correct - so maybe the ear is the best truth.

There was one of  those aftermarket tach/hour meters on my 2013 Txt Pro when I bought it, and I've come to really appreciate it.

Works perfectly - and since most maintenance activities on these bikes is run time based, nice and convenient way of keeping track. Mine also has a little feature that shows number of starts - is actually kind of funny because it really shows when a ride has been technical, and/or physically tiring, as the starts/hr go up dramatically.

If its a 2014 itll have a kehein they need a fiddle every trial. Better to get used to setting it.....

 

Same for the 2015?

I noticed something funny when using a timing strobe light triggered by the HT lead. On one bike I was checking the timing (a DT175 with electronic ignition) and found it had a pulse in the HT lead at a few other positions (as well as the usual one that fires the spark plug) strong enough to trigger the strobe

That could be why your tacho is being tricked

Just out of curiosity if you pinch the conductor coil wires you wrapped around the spark plug with your fingers, what happens to the RPM?

Can it be Hidria twin spark ignition?