[aaron33_dg@f]

i am running a 170 in my kitaco 124 it cuts on and off like arev limiter if i put in 150 runs the same i need help whats up

 

[dood]

i am running a 170 in my kitaco 124 it cuts on and off like arev limiter if i put in 150 runs the same i need help whats up

Go leaner. I remember running as small as a 130 in a 124SE engine.

 

[boonacka]

what carb?

 

[boonacka]

the whole jetting efficiency thing has still got me boggled.



I was thinking about when i turbocharged my first car and was running 390cc injectors. but with 12lbs of boost i had to increase the fuel pressure to compensate for the lack of 450cc injectors.



anyways, i still cant get away from the idea that if i had to increase the amount of fuel going into the combustion chamber, it would be dependent on the amount of air that was going in. therefore, logically i would be making more power because of the increase in air & fuel being ignited.



common guys. school this new old fart.

 

[RLucky82]

I don't get what your saying that you think doesn't make sense?

 

[RLucky82]

the difference between fuel injectors and carburation is that injectors inject x amount of fuel pressure through specified diameter hole, where as a jet doesn't inject fuel as much as it allows a certain amount of fuel to be sucked out of the float bowls which is dependent on negative atmospheric pressure in the carb. A better flowing pipeline (ported, matched) is going to allow more pressure to be created and consequently suck more fuel through a 105main jet then a bolt on setup.

 

[boonacka]

that explanation there has made the most sense to me for some reason. i now understand it. i feel kinda dumb that i didnt get it the first time around. thanks lucky

 

[OLDSCHOOL]

Another thing to add into the mix as an FYI.



The Keihin and the OKO jets have different numbering schemes.



And although the Mikuni vm26-606 vm26-7020 and the vm26-takegawa versions all take the same main jets, they all use different emulsion tubes and needle jets causing differences in the main jetting.



I have a thread on here about bolting up 3 different carbs to the exact same motor and taking it out for some passes. I have the VM26-606, the TM28 Flatslide, and the TM24 Flatslide. The main jets all come out differently as does the final speeds.



One other note that I have personally experienced...the VM26-606 and 7020 come out DRASTICALLY different in terms of main jets. ON one application the 606 cam out with a 220 and the 7020 came out with a 155. Nothing else different, just the carbs (and jetting).



Personally, I will keep increasing the main jet size until the bike no longer revs out cleanly and then back off 1/2 size. So, if I go 190, 200, 210, 220 and at 230 it starts breaking up, I'll probably end up with a 215. Then I'll do some chops at 215, 220, 225.



I'd worry about jetting your bike based on plug reading and revving out more so than what it is "supposed" to be.

Excellent information....!



I have 4 new MOLKT Carbs and all 4 run different on the Same motor and 1 of the 4 the Air screw works backwards from the other 2 and 1 slide barrel is slightly bigger than the others. pilots are different sizes and Mains not drastic but not the same of any two set-ups....:33:



also not one of them appears to have the same size Needle jet they seem to slighly very just a bit.



Ive also noticed a difference between a VM26mm from BBR and a VM 26 bought from 2 bros (Takegawa) I believe not positive needles were deffinetly different.





Ive got a Buddys Bike thats running a Basic TB 146 Kit with a BV Head fresh rebuild. Bikes running a Mikuni Vm26 (606) #75 Needle came with a 22.5 Pilot and (155,165,175 & 195) mains



this bike would not idle and rev off the bottom until a #30 Pilot was installed and will not run or rev out with any of the mains it came with and even down to a 130 main and still a sooty black plug



Jets on Order but Im guessing a 110-120 Main and possibly down to a #25 Pilot



not even close to MillBillys bike with a 160cc KLX his Vm26 has a 22.5 Pilot and a 175 main and has run flawless all season long but needs a slight tweek with the cold weather on the pilot



low 40's -30's Temp (sea level)



Jettings been hit or miss lately...:fingersx:

 

[boonacka]

ok how about we add fuel type into the mix.



higher octane would usually require upping or lowering the jetting from pump gas settings?

 

[HACKMUNCH]

neither. octane is a scale the describes how fast a fuel burns. now if it's oxygenated your jetting is gonna have to change.

 

[burch753]

Abesolutely, The higher the octane the slower the burn of the fuel due to the length and conjugation of the octane molecules in the mixture... This is why higher compression motors will require higher octane fuel to reduce predetonation and knocking, again also reliant on motor set up/timing, etc...



so, hackmunch... you gonna help me with my piece on Sat. or what?

 

[boonacka]

yeah, sorry i meant to say race fuel. I know higher octane burns slower.

 

[burch753]

good call, race fuel has different specific gravities and, as hackmuch said, some are oxygenated and leaded. SHHH... don't tell the EPA about lead!! lol.



Specific gravities will interfear with jetting very minimally, I would think mostly with pilot jetting. A slightly higher specific gravity/density would produce a slightly higher drag to be pulled by vaccum through the carb. I should say this could be resolved by turning air/fuel srew 1/8 turn.



Oxygenated fuels hold oxygen in them, meaning awesome power!!! and a hotter engine Lead is used as lubricant.



This would really mess with jetting setup in a parabolic curve relationship, because more gas also equals more fuel in a higher dose than regular fuel. In this case I'm baffled as to which way to go on jetting...



I can't afford race fuel.. shell loves my buisness. haha

 

[HACKMUNCH]

pm sent about your turd.

 

[dood]

good call, race fuel has different specific gravities and, as hackmuch said, some are oxygenated and leaded. SHHH... don't tell the EPA about lead!! lol.



Specific gravities will interfear with jetting very minimally, I would think mostly with pilot jetting. A slightly higher specific gravity/density would produce a slightly higher drag to be pulled by vaccum through the carb. I should say this could be resolved by turning air/fuel srew 1/8 turn.



Oxygenated fuels hold oxygen in them, meaning awesome power!!! and a hotter engine Lead is used as lubricant.



This would really mess with jetting setup in a parabolic curve relationship, because more gas also equals more fuel in a higher dose than regular fuel. In this case I'm baffled as to which way to go on jetting...



I can't afford race fuel.. shell loves my buisness. haha

You know and understand stuff. I like it.



Most standard race fuels like C12 or Rocket fuels 110 stuff will need to be richer because of there slighty increase in oxygen. Most also have a lower specific gravity to try and cure the reasoning to run a richer mixture.



Oxygenated fuels like Rtech OUTLAW or VP U4.2 need tuning because of the increase in oxygen molicules in the fuel.

Think of it this way. A regular welding torch can make a strong flame. Turn up the oxygen and now you have a cutting torch. Now imagine that kind of power and heat in your combustion chamber.

Unless you buy real race fuel like VP MR9 or MR11 or Rtech PRO V1. Most gases are not gonna give you any benefits of making more power. They will just give you more octane which you know as well as I do, doesn't make more power.

There are fuels out there that cost me over $80 a gallon and Yoshimura's fuel is just over $200 a gallon.

All these special chemicals cost money and the time to blend it but they make HUGE gains in power and are legal in most racing organizations.



If your bike runs better on std race fuel, then your jetting was off to begin with.

 

[burch753]

You know and understand stuff. I like it.



Most standard race fuels like C12 or Rocket fuels 110 stuff will need to be richer because of there slighty increase in oxygen. Most also have a lower specific gravity to try and cure the reasoning to run a richer mixture.



Oxygenated fuels like Rtech OUTLAW or VP U4.2 need tuning because of the increase in oxygen molicules in the fuel.

Think of it this way. A regular welding torch can make a strong flame. Turn up the oxygen and now you have a cutting torch. Now imagine that kind of power and heat in your combustion chamber.

Unless you buy real race fuel like VP MR9 or MR11 or Rtech PRO V1. Most gases are not gonna give you any benefits of making more power. They will just give you more octane which you know as well as I do, doesn't make more power.

There are fuels out there that cost me over $80 a gallon and Yoshimura's fuel is just over $200 a gallon.

All these special chemicals cost money and the time to blend it but they make HUGE gains in power and are legal in most racing organizations.



If your bike runs better on std race fuel, then your jetting was off to begin with.

MOLECULES.. goof ball, LOL!



I see, richer begins to make more sense because no matter how much oxygenation is possible in any given fuel, there is not as high of concentration of oxygen as in normal atmospheric ambient temp. air. around 20% oxygen.



is there a cost effective race fuel for a researcher attending graduate school on a budget?

 

[dood]

MOLECULES.. goof ball, LOL!



I see, richer begins to make more sense because no matter how much oxygenation is possible in any given fuel, there is not as high of concentration of oxygen as in normal atmospheric ambient temp. air. around 20% oxygen.



is there a cost effective race fuel for a researcher attending graduate school on a budget?

I like Molicules.



Shell fuels...



Stuff like MR9 or PRO V1 is close to $25 a gallon.

Look at it this way.

My race bikes go through a 13 gallon drum between practice and my racing.

Pitbikes might go though a gallon of fuel riding all day.



It's not that expensive to race or ride a pitbike. Trust me, if you use GOOD fuel, as soon as you twist the throttle, it will justify the price.

 

[burch753]

fair enough... lol.



Where and how is the best way about getting these fuels?? here in B.F.E. Ohio. I dont know of distributors



what type of racing do you do?

 

[boonacka]

i like technical discussions. i feel smarter after reading things like this. alot of forums these days are filled with mumbo jumbo when your really in it for research.



well i use shell 93. it still surprises me how much higher my jetting is compared to similar setups. you think my cam would be the differentiating factor between a 98main and a 115main?

 

[burch753]

hehe... here we go again...



assuming that is is the exact same engine... NO.



same air fuell mixture is going in.. regardles of cam... just more of it!



is everything on your motor matched?