Dynojet kit messes with choke?

[XS1100_OEM4ME]

Cat

Thanks for the detailed description Clint! The fact that we can't see the actual flow of air and fuel while running seems to make these carbs a bit mysterious sometimes. The more times I take them apart, the more I slowly begin to learn how the physics actualy functions inside them.



Yes. Once the engine is warm, which does not take an unusually long time, and I push the choke lever in, everything runs perfectly.

I had not messed wth the float levels since I got the bike, since I never seemed to need to. Plug color was always really good, and sync and colortune (at idle) always worked great. However, when I pulled the choke lever, the RPMs would always slowly climb over 4K. I'd push he lever in the 1/2 choke, and the RPMs would drop, then slowly climb to 4K again.

Now, after the Dynojet kit was installed, I noticed my plug color was super WHITE! That, along with the strange change to the way the engine responds to the choke made me start wondering what was going on. So, I decided that I should check the float levels. They were set REALLY lean, based on the manual for the '80 carbs (I have an '81, so generally fuel, not foat, levels are measured with the carbs ON the bike). I richened the float levels, and set them to the exact setting that the manual calls for on the 'SG. Of course, this didn't affect the choke response (I'm learning while I'm doing this).

I just read this in another thread:



After instaling the Dynojet kit, this describes exactly what is happening. I guess my main concern is that, since I ride all winter, in temps below freezing, I am worried that the "new" choke respose will affect my ability to start on cold mornings. However, if the new choke response is "normal" then I can simply ignore it and wait for the winter temps. As mentioned earlier, everything else is running perfectly. Should I just smile and be thankful that the Dynojet kit put my choke response back to were it is "supposed" to be?

Cat, my "gues" is that your new rich mix will help your winter start ups and your choke working like is should now will continue to do the same in very cold weather, how be it, you will want to leve it at full and half a little longer, you may even want to start your cold weather rides on half for the first few min. If your bike run's like I said the new ones ran, then your mix, even with mods is giving the motor what she needs, please let me (AND all the other's who think I don't know what I am talking about) know if she doesn't run just like I said this winter Good luck with your bike

[Joab]

You people break my brain on a daily basis. Keep up the good work.

[79XS11F]

It this factory manual layout of the pilot circuit it appears that no air is being added. Just additional fuel. All air still appears to enter through the carbs mouth as it would under normal use conditions.



In any case, I can in deed get my bike to fast idle correctly by holding the chock at different positions then the rod detains are set up for.
Rob

[natemoen]

See that little arrow on the top of the choke plunger in the diagram. The is open to the cavity under the diaphragm but above the slides. That area is open to the airbox through another hole. So in theory it could easily be sucking in extra air through that opening. Jat

[79XS11F]

On my carbs there is no hole or blind plug at that location. The fuel also appears to be being added on the engine side of the butterfly which is never fully closed. I don't have a side view of the set up but yes, there may be a small hole to the underside of the diaphragm. I will check it out when I am in the garage later today.
Rob

[natemoen]

On my carbs there is no hole or blind plug at that location. The fuel also appears to be being added on the engine side of the butterfly which is never fully closed. I don't have a side view of the set up but yes, there may be a small hole to the underside of the diaphragm. I will check it out when I am in the garage later today.
Rob

Maybe the later carbs are different but my 78 carbs have a rather large hole there, maybe 1/8 to 3/16 of an inch across.

[79XS11F]

My carbs are 78 / 79 ?
rob

[79XS11F]

On my carbs there is no hole or blind plug at that location. The fuel also appears to be being added on the engine side of the butterfly which is never fully closed. I don't have a side view of the set up but yes, there may be a small hole to the underside of the diaphragm. I will check it out when I am in the garage later today.
Rob

Yes there is a small hole from the underside of the diaphragm and into that fuel circuit so air is also being delivered when the chock is activated.
Rob

[clcorbin]

The air IS getting added in there Rob. That is just one of the facts of life in internal combustion engines: Friction is a function of engine speed. To increase engine speed, power MUST be increased to overcome the higher friction. To increase power, larger volumes of fuel AND air MUST be introduced into the engine.

The diagram makes it look like the extra fuel is completely blocked off when you push the "choke" into the half "choke" position. I doubt that for some reason. The people that draw these diagrams are not usually the engineers that designed the carb. Often, the diagram only has a vague relation to the actual operation of the part in question.