If you wanna avoid hard learned lessons, let me offr you one little point of wisdom.. Be VERY careful in the sand trap.. those rakes are Murder..

I don't believe the Dial a Jet works all that well on a CV (Constant Velocity) carb.

The concept looks valid to me.

However, I don't like the way they display a lack of understanding about mixture and temperature. It makes me wonder a bit about who wrote the description.  Surely the inventor knows about the relationship between mixture and temperature.  

"Motorcyclists often discard their standard air filter and install a high flow air filter. This will upset the air to fuel ratio making the engine run even leaner and hotter. Custom exhaust systems are usually lower restriction which also causes the engine to run leaner and hotter. The combination of the high flow air filter and the low restriction exhaust system substantially alters fuel flow requirements, leaning the engine and raising the operating temperature."

Leaning or richening the mixture lowers the combustion temp on either side of peak temp.  

That said, I am still intrigued by the idea.

I wonder how hard it would be to take it one step further and hook it up to an oxygen sensor or something to automatically adjust the mixture,.. sort of like what a fuel injection system does.

tarkm812 wrote on 10/10/12 at 11:11:46:



No.  This is a common old wives' tale.  Optimal mixtures create the most energy, and, therefore, the most heat.  Mixtures leaner or richer than optimal create less energy and therefore less heat.

Gyrobob wrote on 10/10/12 at 11:13:23:

This certainly is the case for a/c engines, but I wonder if it directly translates to m/c engines.  You've told us how the engine loading is different, and I don't know whether the engines are muffled or not.

I do know that under stock conditions on our bikes the pipe will turn purple, change the jet for a larger one and it'll only go gold.  As our mixture goes lean, the mixtures fails to burn in the cylinder.  This left over gas collects in the pipe and will burn later, some times very noticeably.  

This burning creates heat that may not exist in a/c engines as with the higher altitudes the back pressure is lower and the less oxygen is induced up the pipe.

Come on Gyro, both of us in that old discussion were getting our data from air cooled aircraft engines because the data existed (they adjust their mix ratios on the fly and they have head and plug and oil temp gages already set up).   And by golly they have DATA for all that sorta stuff !!!!

..... and we can't have a good discussion without data, now can we?

Same sources said later on that running lean under heavy loads could cause a holed piston and require an emergency landing (you do remember me pointing that out, don't you?)

Quite a bit of difference between running at steady state (aircraft engines run steady rpms and steady loads at cruising speeds) while your are cabin fiddling with your optimum mix ratios ....

..... and a motorcycle engine that never ever has a steady load or a steady rpm at any time on the particular road that you are on.

Motorcycles live in the world of trade offs, and I think one trade off that we do is to run mebbe a little leaner lower down (cruising range) and nominal to rich on the WFO throttle setting to make sure we don't damage our engines under heavy loads.

Well that may change what I have always thought about engines being lean/rich.  I thought that when an engine ran too lean and was burning exhaust valves, spark plug insulators and piston crowns....that it was running with the most heat of combustion.  And that when you richened the mixture up a bit the engine ran a little cooler and nothing burned.

It may be that when the engine is too lean the left over air/oxygen can burn the hot metal away.......as there is no fuel left to burn.