MUlti carb mixture setting

[Anonymous]

OK -- setting the mixture on a single carb is pretty simple, but how about on the 4 carb setup? Assuming you start with all 4 mixture screws set the same and make the same adjustment, at the same time, to all 4, if you have 1 carb that isn't working right, how can you tell which one it is?

Dan

[kz]

One way of checking is to mount mew sparks, drive a test ride (not with chocke or at idle speed).

After the test drive you can inspect the carbs for different colours.

light brown is good.

black is to rich, and so on...

[Anonymous]

Check the spark plugs. If it's a mixture thing, one of them will look different from the rest.


Tim

[kz]

Sorry, should be:

dismantle the sparks and check for different coluors....

[Anonymous]

KZ, looks like great minds think alike. :twisted:

[kz]

Jepp tbarnby, I think our messages must have arriwed exactly at the same time.

Well I mixed carbs and sparks, but apart from that I hope that our common suggeston helped wayback

I used to drive rally car a couple of years back and had to adjust the mixture on two SU carbs mounted on an 4-cyl engine.

At that time we used special spark plugs with a glass window so you could se the flame inside the cylinder during running and you where able to adjust the mixture according to the flame color (adjustment and colour like a gas welder).

Have you came across something like this for a bike engine?

A more modern way is probably to meassure the CO value on each exhaust pipe (if possible to mount the sensor)

[Anonymous]

Kz

HEY KZ THAT TOOL IS CALLED COLOURTUNE, YOU CAN ORDER IT FROM WWW.MOSSMOTORS.COM , BOUT 50 BUCKS.

[kz]

Thanks Rick,

I accually still have two of them somewhere in the garage, probably with the wrong thread for bikes.

My question is if anybody has used glass-sparks succesfully in connection of balancing carbs on a bike engine.

[earlfor]

Well, after reading the various replies to this question, I guess I'm the only one nutty enough check how the carbs are by putting his hands on the exhaust pipes. :-) (NO, not right at the header :-) )
Anyway, I can pretty much tell what kind of mixture I have going at any rpm setting by the heat in the pipes. You can also tell very accurately how your choke/enrichener is working on each cylinder.
I find my hands are very sensitive to a change of a few degrees in a pipe's temp.

Earl

[kz]

Hi Earlfor,

I aggree that is one way of checkning, and it works up to certain limit

[TheNose]

Earl,

Where do you get your hands calibrated? Explain the temp differences for me please. I might try one of those infrared heat sensors on the pipes.

Thanks,

Terry

[kz]

Hi Terry,

It is possible to see if the mixture is correct by meassuring the temperature in the exhaustpipe.

This is done in aeroplanes (at least Cessna with pistonengine) by mounted NiCrNi sensors in the headders and the adjustment is done from the cockpit by turning a knob.

The reason for adjusting mixture during flying is that the air is getting thinner as higher you get and you need to adjust the mixture to get a correct lambda value.

[TheNose]

Thanks Karl. I assume that you want to achieve the maximum temperature? I'm not very technical when it comes to engines. I don't know what you mean by the lambda value either.

Terry

[kz]

Hi Terry,

With the risk of getting to theoretical at this forum.....

The lambda value of an engine is the gas/air relation of the mixture that is feeded through by carbs in the engine and has the value 1.0 if you have the reation air/gas realtion 14,7 to 1.

This is the theoretcal optimal relation of air/gas to have a complete combustion.

The value 1.0 is also needed if a catalytic converter should works properly and is regulated if the bike has a catalytic converter.

To get higher engine power you decreese lambda value to approx. 0,85 - 0,95, meaning less air.

All this is done by the carbs mixture setting at a GS -engine.

So for the temperature...

The temperature in the cylinders are related to the lambda-value, i.e mixture setting in the carbs.

If you for exampel have a higher lambdavalue meaning to much air the temperature in the cylinders the temperature will rise and it is even possible that you burn the pistons in the engine.

To adjust the mixture, one way is to measure the temperatur directlely in the exhaust pipes beacuse the temperature is changing according to the mixturesettings.

This is that is done in for exampel in a cessna plane beacuse the pilot must adjust this setting during flying, the reason is that the air is thinner higher up and the lambda value will change.

For a bike engine its the same, so if you know the temperature at your GS exhaustpipes and can feel a difference as Earl dicribed it is possible to make some conclutions related to mixturesettings.

[earlfor]

Very funny Terry. eh eh eh. The truth is though that I do have
"hand calibration" :-) I read the colors of my plugs. Usually, at least one will be burning at the mixtures I want. I remember how each cylinder's plug is burning. I warm up the bike and get it off of choke as soon as possible, then run the rpm range (jet) I want to
check for. I compare how quickly the pipe on the correct cylinder comes up to temp and what that temp is to how the other pipes come to temp in the same time span and what their temp is. I also compare exhaust pulses and temps at the mufflers. I then let the bike cool down and repeat the process at the next rpm range.
I also have a mercury manometer for balancing carbs, but frankly,
I have a much better feel for what is going on using my own method. As for the heat range to adjust to, I dont want maximum possible heat as that would indicate a lean condition. The normally lean fuel air mixtures for GS's give best economy, but a richer mixture gives better power. For my GS750
it appears that optimum economy without excessive heat yields about 50 miles per gallon. I prefer a little cooler running engine, and a little more power, so when I have the mixtures right for me, I get about 46 or 47 miles per gallon. (just another way of double checking what is going on)

Earl

Earl,

Where do you get your hands calibrated? Explain the temp differences for me please. I might try one of those infrared heat sensors on the pipes.

Thanks,

Terry