How to: Hp Carb Tuning. Thanks to someone - Pocket Bike Forum - Mini Bikes
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How to: Hp Carb Tuning. Thanks to someone

Mixture: Mixture refers to how much of each. example): How much sugar added to your coffee. How much oil added to your gas. In this case how much fuel being added to the air passing through the carb. This is the fuel / air mixture.

Rich: Rich means a lot or in this case more than perfect. (example): If your coffee is too sweet, it is to rich with sugar. If your engine is running rich, it is getting to much fuel added in with the air that the engine is bringing it.

"The mixture is rich".
Lean: Lean means little or less than perfect. (example): If your coffee is not sweet enough then it is to lean, there isn't enough sugar. If the engine is running lean, there is not enough fuel being added to the air the engine is bringing in.

" The mixture is lean".
Bog: This is the sound you hear due to a lean mixture. When you open the throttle by squeezing the trigger to the bars, you are letting the engine draw in all of the air it can. If there is not enough fuel added to that air, the engine will not accelerate, it will bog and usually die.

Chutter: This is the sound an engine makes when it is getting a lot of fuel. You may hear this sound at any throttle position including at wide open. Go-Peds® run better with a little "Chutter" at low to mid throttle settings



The H.P. Carb includes 3 adjustment screws. These are the idle adjustment screw, low throttle adjustment screw & high throttle adjustment screw. Some people call them the Low speed & High speed screws, but they actually operate based on throttle opening not engine speed.

Idle Screw: The idle screw keeps the throttle slightly open allowing enough air to pass for the engine to idle. Turning this screw in or clockwise allows more air to pass. Turing it out or counter-clockwise decreases airflow.

Clockwise = more air = faster idle.
Counter-Clockwise = less air = slower idle.

Low Throttle Screw: This screw adjusts the amount of fuel added to the air passing through the carb at partial throttle, or up to 1/3 throttle openings.

High Throttle Screw: This "T" Screw adjusts the amount of fuel added to the air passing through the carb from 1/3 throttle to full open.

NOTE: The fuel added by the Low Throttle Screw is still being added at 1/3 to full open. Adding more fuel with the Low Throttle Screw will affect the High Throttle mixture slightly



In order to begin tuning your carb you must first get the engine started so you can listen for Rich or Lean mixture. We recommend these initial settings to start with:

Idle Screw - All the way clockwise
Low Screw - 1 1/4 turns out (counter-clockwise from closed)
High "T" Screw - 2 turns out (counter-clockwise from closed)





Step 1: If you just installed your H.P. Carb Kit. Push the primer until fuel can be seen returning to the tank in yellow return line. (Primer Note: The primer brings fuel from the tank to the carb. Priming the carb not the engine. Raw fuel is not actually being pumped into the engine. Pumping will not help start a cold engine).

Step 2: If the engine is being started for the 1st time with an H.P. Carb, we recommend you pull off the filter and place your finger over the carb opening so no air can pass. Now pull the pull start. After each pull check to see if your finger is wet with fuel. Once your finger is wet, the engine is ready to fire. Hold the throttle 1/2 to wide open* and pull start. Once the engine starts keep it running at the lowest possible RPM. (* without holding your finger on the carb)

Step 3: Warm the engine up all the way. When you are sure it is warm let off the throttle to see if it will idle. If the engine idles slow, chutters & dies then turn the Low Throttle adjuster in 1/4 turn and try again until it idles steady.

Step 4: Once the engine idles steady, use the low throttle screw to get a slow chuttering idle. If the engine slowly chutters and dies, then it is to rich and the low throttle screw must be turned in, to lean the mixture a bit (1/8 to 1/4 turn). If the idle speed gets too fast with the leaner low throttle setting use the Idle screw to get a slower idle speed. The ideal low setting is as rich as possible without loading up (Chuttering & Dying). Once the low throttle mixture and idle speed are set, you are now ready to move on to the High Throttle Adjustment.

Step 5: The object of High Speed adjustment is to obtain the highest possible RPM under load with the richest possible setting. The richer you can keep the mixture while still getting peek RPM the better. The engine will accelerate, it will live longer, run cooler and respond better. Just adjusting the high throttle screw for max RPM on the kick stand would leave the engine very lean and when the engine is under load it probably won't accelerate well at all and could seize.

Instead, start rich and lean the mixture out in small increments (1/8 of a turn). Testing each new setting under a load. Once the acceleration starts to suffer, you have gone to far. (Go back 1/8 of a turn). It is better to depend on cylinder porting to get peak

RPM than on ultra lean mixture settings. Optimum settings for typical stock engines is about 1 1/8 to 1 3/4 turns out.



Problem: Engine Chutters at full throttle and doesn't rev high.
Solution: The "T" screw is to far open. Close 1/8 turn and test under load until acceleration suffers and then open 1/8 turn. NOTE: Engines with stock porting tend to chutter at high RPM.


Problem: Engine bogs from low speed.
Solution: The "T" Screw is to far closed. Open it 2 or more turns and tune for chutter. NOTE: Worn parts, tall gear ratio with heavy porting, high intake duration, restricted exhaust and low cylinder compression can cause low speed bog.


Problem: Engine idles but slowly dies.
Solution: The low speed screw is to far open. Turn in 1/8 turn at a time until idle cleans up. If idle speed is to fast after adjustment slow the idle down using the idle screw.


Problem: Engine idles smooth but runs poor under load unless throttle is full open.
Solution: The low speed screw is to far in. Turn idle screw all the way clockwise and set a low idle using the low throttle screw.


Problem: Engine idles fast and stalls when you try to slow idle speed down.
Solution: These are the symptoms of an intake leak. Go-Peds
®
usually leak at the manifold to cylinder gasket. Make sure the carb mount screws arent' going to far through the manifold and causing an air leak. Screw marks or cuts in the gasket are a tell-tell sign of screw interference. You can check for leaks with the ped running. Spray WD-40 around the manifold, if the idle speed changes you have a leak.
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post #2 of 58 (permalink) Old 08-25-2004
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very good tips... when i was having idle problems I couldn't find a thread this informative
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post #3 of 58 (permalink) Old 08-25-2004
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this belongs in the FAQ's
great job!!!
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post #4 of 58 (permalink) Old 08-25-2004
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Quote:
Originally Posted by joelanza
this belongs in the FAQ's
great job!!!
thats what i said
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post #5 of 58 (permalink) Old 08-25-2004
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New guy here. Just signed up to ask how to tune an HP carb and here it is . Thanks bmarley5780.
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post #6 of 58 (permalink) Old 08-25-2004 Thread Starter
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wORd ....LOL
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post #7 of 58 (permalink) Old 08-25-2004
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Quote:
Originally Posted by joelanza
this belongs in the FAQ's
great job!!!
Done....
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post #8 of 58 (permalink) Old 08-25-2004
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Administrator, please make this a sticky!!!
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post #9 of 58 (permalink) Old 08-25-2004
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Arent you suppose to be on vacation zee...Coudlnt resist the call of PBP huh =)
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I have a quick question?
My bike idles fines but when i give it full throttle it dies.
I have checked the intake manifold and the gasket seems to be ok (no rips or cuts). I made sure the carb is fitted tighly and nothing is loose. I have an intake and v-stack, no choke and stock carb. But before i got the intakei ran the bike a few times without an air filter. Could this have caused my problem?

Last edited by keitho; 08-25-2004 at 10:00 PM.
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doesn't sound like that's the problem
i play around with your 2 screews. (stock carb that is)
make it idle high and see if it runs.. let us know
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most people with a pocket bike have the common combination of pipe, carb, filter/vstack. What is a good starting place with the H and L screws on the WT-603 carb with these parts? Anyone know? thank you in advance.
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Quote:
Originally Posted by keitho
I have a quick question?
My bike idles fines but when i give it full throttle it dies.
I have checked the intake manifold and the gasket seems to be ok (no rips or cuts). I made sure the carb is fitted tighly and nothing is loose. I have an intake and v-stack, no choke and stock carb. But before i got the intakei ran the bike a few times without an air filter. Could this have caused my problem?
it sounds like your bogging out ytry tuning air fuel screw for more gas 1/8-1/4 turns at a time only!
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**** i needed this thread about a week ago. but i figured it out with the help of Kirk from proline. i called and he gave me some instructions. i also had to change the spark plug, it had been fouled by the previous owner who mixed way too much oil on a cateyes i bought. great thread though
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Sumthing Wrong?

what's happening if you're not even at throttle and your bike is already on the move? What does that mean? And my bike always back-fire! I need help!
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Quote:
Originally Posted by Moto_Mike
what's happening if you're not even at throttle and your bike is already on the move? What does that mean? And my bike always back-fire! I need help!
that means your idle is too high (idle screw is too far in )back you idle screw out some, your letting too much air into your carb, just like when you throttle. thats why it wants too go while your not even on the throttle.
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well can you tell me where the idel screw is at? I just got my bike last week and do not no nothin about it but i love it. And how do i drain the motor? I accidently put in 10x the amount of synthetic oil in the mixture and it's also choking alot. Man i need help, seriously!
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Quote:
Originally Posted by Moto_Mike
well can you tell me where the idel screw is at? I just got my bike last week and do not no nothin about it but i love it. And how do i drain the motor? I accidently put in 10x the amount of synthetic oil in the mixture and it's also choking alot. Man i need help, seriously!
the idle screw is the philips head screw at the top of the carb, the air fuel mixture is the flat head screw on the side of the carb. also just pull the hoses off the carb, the black one, and the clear one, and let them drain into something. and then pump the primer bubble on the carb to get out the little bit of gas thats in that, and slide the hoses back on fairly simple.
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Thanks Bro!!! I'll have to try it later.
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i have to idle my cateyes way to high to keep it running(it sometimes moves by itself)
and if i turn it down it dies how do i fix this?? mess with the jets?? or something ele HELPPP??!??
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