Carb tuning

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madcow

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What do I aim for when tuning the air/fuel mixture? I know with 2-strokes you should have a bit of oil smoke on hard acceleration, but I have no idea what 4-strokes need. Please don't send me to another site or forum that I have to register for, I'm on dialup and it takes forever to get anything done. :(
 
i believe you are looking for a good tan color on the spark plug, white is too lean, and black is too rich.
 
Yea I figured. I think the guy I bought my warrior from just stuck the biggest main jet he had in the jet kit and left it like that. Right now it's a 150, should I switch to a 147.5? Also, the pilot jet is a 50 if that matters.

I also read at Bluetraxx that you can adjust the air/fuel mixture with an e-clip on the main needle. Is that the proper way to do it? Turning the screw on the bottom seems to do almost nothing.
 
Well I moved the e-clip on the main needle up one notch and that seemed to clean up the top end, but now the bottom end sputters like mad. Below mid-throttle it barely makes any power.

Also, my accelerator pump doesn't work anymore. The pump moves with the throttle, but it doesn't squirt any gas through the needle.

I just don't get it, this carb is too confusing. :(

Could somebody enlighten me on how to properly tune this carb?
 
Yeah it's really simple once you get the hang of it and understand what circuits do what...
0 to 1/4 throttle Pilot circuit. Fuel screw, pilot jet, air jet.
1/4 to 3/4 throttle jet needle, needle jet also main jet.
3/4 to full. Main.
Now to adjust them. First start with the idle. Pilot circuit. Turn idle up to a fast idle maybe 2000 rpm. Adjust the fuel screw. OUT for richer, IN for leaner. Start lean and work your way out at 1/2 a turn at a time. Bike should be warm. You hear poping out the carb LEAN when cold. You hear missing through the exhaust RICH. Once the engine gets warm it will miss out the exhaust lean or rich but when you start engine braking and have the throttle totally off then it will backfire through the exhaust if lean. Back the fuel screw out a 1/2. So adjust the idle up, and find the point where the engine gets to top rpm.. stop there. Your close to perfect mixture. You may have to richen the screw up a 1/4 turn.
More then 3 1/2 turns out bigger on the pilot jet or smaller air jet.
Less then 1/4 turn in smaller pilot jet or bigger air jet.
Main circuit is next. Start rich and work lean. At full throttle WOT and high rpm the bike should stutter at high rpm. If it doesn't bigger main. If is does then one size smaller main until this miss goes away and your perfect stop there.
I've found stock setting on the needle works perfect and I wouldn't mess with it as the main is now effecting the needle.
 
middle.
Click to expand...

There is no middle notch. Think about it, 1-2-3-4-5-6, which number is in the middle?

I read that thread, I even have a copy saved on my desktop. :) Everything seems fine with the pump, it works perfectly when I test it with the carb off. But it seems like it gets stuck when I start the motor. About that article, which way would be "up" for the e-clip on the needle jet? Towards the blunt end or sharp end?
 
[quote:fc54y9gr]middle.
Click to expand...

There is no middle notch. Think about it, 1-2-3-4-5-6, which number is in the middle?

I read that thread, I even have a copy saved on my desktop. :) Everything seems fine with the pump, it works perfectly when I test it with the carb off. But it seems like it gets stuck when I start the motor. About that article, which way would be "up" for the e-clip on the needle jet? Towards the blunt end or sharp end?[/quote:fc54y9gr]

yeah, there is only 5 spots on the stock needle. So you would put the clip on the 3rd, "stock" setting.
it would move the needle down into the jet so lean the mixture out.
 
Ahh, I knew I was missing something. I can't seem to think straight today. For some reason I thought that moving the clip towards the sharp end made the needle move further into the jet. It all makes sense now. :D

Thanks for all the explanations, you just saved me a ton of time.
 
I just read up on my jet kit on dynojet's website, turns out my main jet is most likely too big, I should be using something around 148. I know I shouldn't follow their instructions word-for-word, but that size seems right because it's been running really rich. Since I don't have any extra jets I moved the e-clip up one notch on the needle. Hopefully that'll be good enough until I get a new jet.
 
I just read up on my jet kit on dynojet's website, turns out my main jet is most likely too big, I should be using something around 148. I know I shouldn't follow their instructions word-for-word, but that size seems right because it's been running really rich. Since I don't have any extra jets I moved the e-clip up one notch on the needle. Hopefully that'll be good enough until I get a new jet.
Click to expand...

It will lean it out in the middle throttle postions but still be rich at 3/4 and above. I'm not really sure what dyno jet goes by as they use different numbers then stock which in my opinion is retard. I think 147.5 is what you want. I'm not sure with all your mods though.
 
i think that the 50 pilot is your problem, stock is 42.5 , you shouldnt need anything bigger than a 45 pilot.
 
I don't know what I was thinking when I wrote 50, it's actually 42.5. Hopefully one of the local stores stocks jets, or can order them at least. I was thinking 147.5 too. And what do you mean by "all my mods"? All I have is the usual filter+exhaust.

A UNI filter with no airbox flows just a bit better than a K&N with an airbox, but the exhaust heats it up and I seem to lose a bit of power because of that. I don't think I should change the jetting because of that.
 
I don't know what I was thinking when I wrote 50, it's actually 42.5. Hopefully one of the local stores stocks jets, or can order them at least. I was thinking 147.5 too. And what do you mean by "all my mods"? All I have is the usual filter+exhaust.

A UNI filter with no airbox flows just a bit better than a K&N with an airbox, but the exhaust heats it up and I seem to lose a bit of power because of that. I don't think I should change the jetting because of that.
Click to expand...

I have the same style of setup as far as air filter goes... I don't feel a difference when the bike gets hot. I think it's your jetting. As when the bike is cold it likes to be richer and then as it warms up the bike wants to be leaner.
I was just wondering what you have for mods.
You may have to go 1 or 2 sizes bigger on the pilot. The stock air box is really restrictive.
Also just a reminder and I'm sure you already know this is don't over oil the air filter.
 
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