Yamaha KT100s Carbu settings

Most folks are smart enough to let off the throttle when the motor revs up real high LOL
To get a good test on the stand you can use the brake as a speed control and do full throttle pulls for 2 or 3 seconds... definitely not more than 4 seconds.
Steve O'Hara
 
Throughout this conversation it appears it has been assumed that everything is right with the engine. Perhaps it is, but perhaps it isn't!

Has the engine been pressure checked for air leaks? Do we know how many CC's in the combustion chamber? Do we know what the compression pressure is? Do we know what the timing is? Do we know that the ignition module is well grounded? Are we sure the OP even understands what we are saying? Often I see different words used for the same thing. Just one example; scavenging cone and diverging cone. A newbie may not understand that they are the same thing. Diverging cone is the proper terminology, while the term scavenging is the Colloquial usage. As an avid designer and builder of kart expansion chamber's, I never used the word, "scavenging" in my description of any pipe.

In general, there are four parts to an expansion chamber; the diverging cone, the center section, the converging cone and a Stinger. There are other parts to a kart exhaust system, but these are the proper terms for the expansion chamber by itself.

From the desk of Al Nunley
Comments compliments criticisms and questions always welcome.
If the data does not support the theory, get a new theory.
(Al Nunley)
 
Steve O'Hara said:
Most folks are smart enough to let off the throttle when the motor revs up real high LOL
To get a good test on the stand you can use the brake as a speed control and do full throttle pulls for 2 or 3 seconds... definitely not more than 4 seconds.
Steve O'Hara
Click to expand...

Agree, but wouldn´t recommend that to someone new to this. Everyone knows they always start karts on stands before big international races using brake/throttle control.
 
Brake throttle control. Will this minimize the top end rev and avoiding the engine to run too quick? Or what happends?
 
First never run the engine wide open on the stand,period. Here it is the easy way run the stock yamaha settings on you carb,period. You will have to have someone set up or teach you to set up the carb to run Steves settings. You will also need a rebuild kit and a pop off gage for steves settings, to set the carb up. You really need to find someone local to you to show you how to rebuild the carb. Its not easy to explaine to someone that has no idea of what the part look like and how the carb functions, without being able to show them.
 
Ohh. Do you realy need rebuild kit and a pop of gauge for Steves rebuild? I thought it was enough with a screwdriver to set high and low to his settings.
 
Arc, your correct about the demand diaphragm being pulled down by vacuum "or" when a low pressure area is created under the diaphragm the high pressure area over the top pushes it down, whichever way you want to look at it, it overcomes the spring tension to open the needle for fuel to flow, that's how the carb functions, but Paul's description of pop-off pressure is exactly correct, perhaps he should have said pressure instead of fuel pressure, unless like EC used to recommend, you put some fuel in your pop-off gauge line before pumping some pressure to it. The pop-off pressure is simply the amount of pressure it takes to lift the needle off it's seat just like Paul said, with carb vacuum and diaphragm function not a part of the equation. Al, I'm sure we all appreciate the lesson in correct terminology, I highly doubt that Pota will need to be building a chamber anytime soon though, do you really think how many CC's he has in his combustion chamber or what the ignition timing is matter's at this point. Pota, get you a clutch of some kind so you can start the motor yourself, get in and go play. For direct drive you will always need a very athletic entourage. Jon
 
Jon Brogden said:
Al, I'm sure we all appreciate the lesson in correct terminology, I highly doubt that Pota will need to be building a chamber anytime soon though, do you really think how many CC's he has in his combustion chamber or what the ignition timing is matter's at this point. Pota, get you a clutch of some kind so you can start the motor yourself, get in and go play. For direct drive you will always need a very athletic entourage. Jon
Click to expand...
perhaps the problem is only that you "doubt", while I have two years of experience with a direct drive rotary engine.

Well I admit that having some help on starting is nice, during practice most people are busy with their own stuff. Many times I have push started my own kart, with no help. Having an engine that starts on the first try is a godsend, thus the attention to detail. And even if you do have help, that help appreciates an engine that fires right up. I believe that meticulous attention to every detail that I mentioned, "is very important".

From the desk of Al Nunley
Comments compliments criticisms and questions always welcome.
If the data does not support the theory, get a new theory.
(Al Nunley)
 
Just so you know, I could try to run with it, im acutaly an elite class sprinter 100m :)
But I agree with Jon, maybe keep things simple for me, im pretty new :) I know where the high and low needle is... But in details what they do etc, i dont have a clue ^^
 
As I tried to explain to you in my previous post USE THE KISS THEORY, and reread my post. Yes you will need the tools unless your carb has been set up at 18psi pop off and a much higher fulcrum arm height then you will need to reset the whole carb to run those jet settings. Most Yamaha guys run around 10psi pop off and .045 fulcrum height, which is what I would guess is what yours is set at. With your total lack of experience with walbro carbs its going to be almost impossible to explain how to do al this. You open the jets by screwing the out counter clock wise the desired number of turns. Stock settings are 7/8-1 on low and 5/8-3/4 on high. Before setting the jets to these settings You must bottom the jets out by turning them clockwise gently until they bottom out then turn them clock wise the correct amount. Take Jons advice and get a clutch and get rid of the direct drive. There are a lot of clutches here on Bobs for sale at a good price just make sure it for a Yamaha kt100 crankshaft taper Do you have a kart shop close by if so go there and get some help directly in person to get started.We can explain till were blue in the face and your still not gonna get it.
 
Also you need to know that these settings are just for getting it started and out on the track, then they will usually need to be adjusted while out there, then while coming in off the track, at least the low end should be turned back down, or you will be fouling a lot of plugs. IMHO, the easiest and best way to go is with what Steve suggested, I would do exactly that if I were running gasoline, but I run mine on alky and that's a whole other ball game. I also have kill switch on mine, so it won't load up while idling, or you can just put your thumb over the carb. vent hole over the diaphragm cover.
'
 
okay i understand Jack. But to quickly clear things up. I could go for Steves setup and be happy with that?
 
Report :)
Today I started the Gokart. I ran with it and let it go. Worked great. But i noticed it smoked alot of white smoke at higher revs.
Tried to reduce the H from 0.5 to 0.2 turns. I also reduced the L abit.
Any tips?
 
Pota said:
Report :)
Today I started the Gokart. I ran with it and let it go. Worked great. But i noticed it smoked alot of white smoke at higher revs.
Tried to reduce the H from 0.5 to 0.2 turns. I also reduced the L abit.
Any tips?
Click to expand...

Pete Muller has run the Yamaha a lot with the direct drive, maybe you could PM him and find out what carb settings he used.

I gave you some things to check but apparently you disregarded them. Hard to help someone who wants to ignore the basics.
 
" Worked Great", is what you're looking for, now you need seat time. what oil are you using and how much per gallon? They are supposed to smoke, more when you let off the throttle.
 
Alvin, I dont know how I could check all that, i dont have the equipment.
Jack you are right, it get pretty smokey when i rev hard and then let off the throttle.
I use 4% Castrol racing oil full synthetic.
 
I know this is about carb settings but I need some help? I have prd 100 tag motor and it has a walbro wb42 carb on it. Will those same base setting that is in a early thread work also would the needles from a kt 100 carb set up work I don't have enough adjustment with what I have. I mean I can only turn the high speed 1/2 open and the low speed sticks out to far. Thanks
 
Pota said:
I use 4% Castrol racing oil full synthetic.
Click to expand...
if you're going to get serious about this stuff, you should have the equipment.

How did you come up with that number for the oil.

From the desk of Al Nunley
Comments compliments criticisms and questions always welcome.
If the data does not support the theory, get a new theory.
(Al Nunley)
 
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