Some information regarding common carburetor tuning problems

[benckie]

Here is some helpful information regarding common carburetor tuning problems:

If your engine stutters at full throttle and cannot reach full RPMs:
The high jet is too far open. Close the jet by turning it clockwise slightly, and then ride-test. If no improvement, repeat until desired results are achieved. Once you have found a workable setting, open the jet approx 1/16 of a turn to ensure sufficient fuel/air mix.

If your engine bogs out when transitioning from low speed:
The high jet is too far closed. Open the jet by turning it counterclockwise until you are at least 1 1/2 turns open, and then gradually close the jet until performance is as desired. Poor engine compression, blocked exhausts, and very heavy engine loading can all also cause bogging.

If your engine idles very fast and kills if you attempt to slow the idle:
You may have an air leak in your intake. An easy way to check for leaks is to spray the intake manifold and area surrounding it with WD-40. If the idle changes after you spray the WD-40, there is an air leak. Common areas for leaks are between the manifold and the cylinder, and between the carb and the intake manifold. Inspect the manifold, carb gasket, and intake gasket for cracks or other signs of damage, and replace if necessary.

If your engine idles but then slowly kills:
Your low jet is too far open. Close the low jet by turning it clockwise until a stable idle is achieved.

 

[bajamaniac69]

hey guys...


I have a esp 30.5 fully ported and machined in my 5t....still only has a tank thru her.....bogs alot on take off but once on throttle goes great...needlesat 1.25 on low 2 on high.....run for about 3 or 4 passes...bring it in ..plug still pretty dark.... so...do i need to lean out hsn or richen lsn???


Thanks


j

 

[Super654]

Nice informitive write up benckie....

 

[benckie]

hey guys...


I have a esp 30.5 fully ported and machined in my 5t....still only has a tank thru her.....bogs alot on take off but once on throttle goes great...needlesat 1.25 on low 2 on high.....run for about 3 or 4 passes...bring it in ..plug still pretty dark.... so...do i need to lean out hsn or richen lsn???


Thanks


j

esp have there own tunning guide for there motors heres the new one

New carb tuning instructions, ESP

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With more people coming into the RC engine, so does the amount of lean seizures. I rewrote my old instructions to what I think is easier to understand. There are other methods people use, but knowing how fast a lean RC engine can seize at higher RPM, I can't think of a safer, in the field, way of tuning the H jet for that day.

Do the new instructions make sense to you? (hard to tell sometimes, when your the guy who wrote it.)



CARB TUNING FOR GAS RC ENGINES

Thank you for buying A ESP engine. This is a guide only. ESP will not be responsible for failures unless it is the fault of ESP workmanship.
Keep in mind that the low speed carb jet screw flows fuel from zero to about 1/3rd throttle opening. The high speed jets starts flowing from about 1/3rd throttle open to full throttle. Both jets flow fuel above 1/3rd throttle.
Set the high speed jet at 2 turns out from bottom to start. Set the low speed jet at about 1&½ turns out and set the idle up for easier first time starting. Warm the engine on the stand for a few min, rev the engine on the stand a bit while rough setting the low speed jet and idle, for idle to rev throttle response. Close the low speed too far, and the idle goes up and starts vibrating from a lean condition. Open the low to far and the engine will run rich and die. Stay on the rich side, but make sure throttle response from idle is good. Typically, you will end up with a L jet at 1&1/8th to 1&1/2 out. Continue to rev the engine for a few minutes above half throttle, but not holding it in any one position, to run the engine with the high speed jet flowing. Shut it down, and check the plug color. The plug should be a dark color like a dark brown or black. The rich settings we start with could possibly foul a spark plug, so you might want to have a new plug or two on hand for tuning. This dark plug color is good for now, it means we are getting plenty of fuel--at least on the stand.

The H speed jet is critical, and a RC engine can seize in seconds if the fuel/air mixture is lean at high rpm. Because of this, we creep up on high rpm one run at a time, checking the plug for each higher RPM run.

1. With the H speed screw out 2 full turns, run the buggy 30 seconds at a time at about 8,000 to 9,000 rpm (or where your clutch is just engaged). Keep running the buggy at the low RPM until the plug starts building up some dark color. We will need deposit built up on the plug to burn off for “reading the plug”, when we start leaning out the carb H jet later.
2. The plug should stay dark for the rest of this test, until we start adjusting the H screw more lean after we get to full throttle tests. We are now going to raise RPM approx 1000 rpm for 30 seconds for each run, and check the plug after each run to make sure it is still dark. You should have about 10 increments of 1000 rpm from clutch engagement, to full throttle, but the more increments you use, (less RPM rise for each run), the safer you will be. If, while your doing the runs, and getting higher in the rpm, you start seeing the deposit burning off the plug to a brown or lighter color, you have a problem with your fuel system (bad carb, fuel filters, fuel lines) or a possible air leak that you have to fix before you can continue. You may have just saved your engine from a lean seizure.
3. When you get to 30 sec full throttle runs with a dark plug, now it is time to start leaning out the H jet. After a full throttle run, check the plug, and it should still be dark with the H screw 2 full turns out. Turn in the screw 1/16th at a time, and continue doing full throttle runs, plug checks, and H screw carb adjustments, until the plug is a brown paper bag color. Do one or two full throttle runs to make sure the plug does not get any lighter. Then fine tune the low speed jet for the best hole shot, and your done. It is a good idea to write down the amount of turns you are at when done, for a reference.

Note, many carb bolts are too long. If your long carb bolts (that hold on the filter, and go through the carb, into the intake manifold), reach all the way through your intake manifold, you will have to shorten the bolts, or risk a damaged cylinder and air leak, possibly seizing the engine.

To help insure you don’t seize your engine due to a carb failure or clogged fuel filters, etc (something other than your set screws), it is a good idea to do a few increments and plug checks every time you take out the machine. Jet richer on cold days, and always re jet for any modification you may make. There is no such thing as “stock settings”, jet it yourself from scratch, or risk seizing the engine.

Doug @ ESP
(616) 458-8103 (Eastern standard time zone) [email protected]

 

[tongham runfold]

great informative thread..... one other cause of erratic idling and stalling can be a blocked pipe, especially if you have been running a tad rich
had this happen to me and spent a couple of hours trying to re-tune carb
even at base settings i couldn't cure it. Put another pipe on and it worked fine
poured paint stripper in pipe, gave it a good shake, left it for 20 mins and cleaned out all the goop. now it works fine

 

[benckie]

i clean the inside of my pipes regulary with old 2 stroke mixed fuel

 

[Bigger the Better]

hey guys...


I have a esp 30.5 fully ported and machined in my 5t....still only has a tank thru her.....bogs alot on take off but once on throttle goes great...needlesat 1.25 on low 2 on high.....run for about 3 or 4 passes...bring it in ..plug still pretty dark.... so...do i need to lean out hsn or richen lsn???


Thanks


j

What exhaust are you using?

 

[bajamaniac69]

dom rear pipe.................

 

[bajamaniac69]

v1............

 

[Bigger the Better]

If you richen the low, and find its worse then lean it by 1/16ths. You will probably be at 1.25 on the low when your done but keep an eye on your plug no matter what. It should not bog on take off with that set up.

 

[bajamaniac69]

Should i lean out the hsn????...the lsn is at 1.25-1.35 or so ...hsn is on 2.....after car starts to go ..if feels good on throttle.....wheels almost most come off ground...plug is still black...

Since motor only has almost 2 tanks thru her ...don't want to lean here out too much...........thanks for the help ....

 

[slawhammer]

Yup start to turn the High needle in by 1/16 turn at a time....make some high speed runs
then check you plug...you want a coco brown look...Slawhammer

 

[Passamal]

Yoooo!!!

It seems to me that the gas carb is is very much like the nitro carb!!!

3 needle, hi low and idle.

is this correct!?

It looks like its as complicated as nitro engines to tune it...

The spark plug in gas engines have a good run time or they fail easy??

At least with my nitro engines i had long run time with the glow plug...

 

[Bigger the Better]

Yoooo!!!

It seems to me that the gas carb is is very much like the nitro carb!!!

3 needle, hi low and idle.

is this correct!?

Yes, high low and idle.

It looks like its as complicated as nitro engines to tune it...

Absolutly not, in reality once its set its set and you have no need to readjust except if its winter.

The spark plug in gas engines have a good run time or they fail easy?? At least with my nitro engines i had long run time with the glow plug..

They will only fail if rattled real hard in a bad crash and crack internally or you break them off with a direct hit. They will not burn out like on nitro. Think of your cars plugs.

 

[Passamal]

yea heheuhauha

same thing hehehehe

thanks!

 

[Bigger the Better]

yea heheuhauha

same thing hehehehe

thanks!

Ya, takes a while to get out of nitrothough. :laugh:

 

[pipeous]

and a cy engine is different from say a solo. I was tuning my cy for the first time after all the playing with my solo and the needles were not adjusting right. then I realized the needles locations are backwards between these 2 engines. so be sure you are adjusting the proper needle!!

and I just traded my clone fg for a hot bodies 1/7 nitro. can't believe I got another nitro though LOl

 

[Passamal]

and a cy engine is different from say a solo. I was tuning my cy for the first time after all the playing with my solo and the needles were not adjusting right. then I realized the needles locations are backwards between these 2 engines. so be sure you are adjusting the proper needle!!

and I just traded my clone fg for a hot bodies 1/7 nitro. can't believe I got another nitro though LOl

hehehe

I think nitro engiines are a lot of fun...

they drink a lot of fuel... but they are fun!!

I had a onroad 1:10 MUGEN mtx4-r and i have a REVO 3.3 (mod it to platinum).

One thing i believe ill miss is the 1:10 agility... you put your finger in the trotle and the car goes like loney toones road runner...

1/5 i see that have a "slow" start comparing to 1:10 on-road pro 12