Modern Vespa

Anyone had any luck with a Gunson Colortune ? Are they effective on a two-stroke ?

I'd never heard of it until you asked.

Having watched their video, I now want one. And a BMW 300 Isetta.

Wow! That is totally cool!

Good for getting your mix sorted at idle.

I guess you could increase throttle to try and get a good balance in other areas of the throttle range.

Just read this on random search results for this topic:

[Corrected] -

I guess you could increase throttle to try and get a good melting of the colotune at other areas throughout the throttle range.

Same thread also suggested they aren't good for 2t cause they don't respond consistent color. They were designed for 4 stroke engines.

What's the thread length? Long reach? Short reach?

Short reach, but they sell adapter kits for long reach plug motors.

I am pretty sure the adapters are for different thread diameters. If you think about it, no adapter is going to allow it to thread any farther into the head and the adapters may even set it higher. The "plug" just provides a spark to ignite the mix and it is really for setting the idle mix and some where just above it. You are not going to run the motor for any length of time on this thing. I don't know if having the spark higher on a long-reach head would make a difference in the reading, but again, most motors it would be used on use a long plug anyway.

I'll add that I have had one of these for years and usually forget that and don't use it. I tried it on the newly rebuilt VBB motor and could get the idle to a bluish yellow but not a clear blue and wondered if the oil mix affected the reading. It may also be that Vespa's stock jetting allows for a slightly rich mix for the sake of the motor. I'll try it on one of the other bikes.

I tried one on m PX once and could never get a steady enough color to tell me much, so went back to just my ears and feel.

Cool idea, but like swiss said above, I'm not sure they're useful on a 2T.