The Secret of Engine Tuning

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Xrc-2

cyclops1970 said:
copy'd from DDM's tech page
How should I adjust the jets on a Walbro Carburetor (WA-167 / WT-603 / WT-668 / WT-257 / WT-813, etc)?
These carburetors require regular adjustment to ensure peak performance, and also to avoid an unsafe lean condition, which can prematurely damage your engine. If you find your top-end RPM's have fallen off a bit, or if you experience lagging or surging, it is probably time to re-adjust the carb jets. To ensure max performance and engine life, follow this procedure:
1) Locate the low and high RPM jets on the side of the carb - they are usually marked with a L and a H. Turn both jets completely CLOCKWISE ( to the fully closed position).
2) Rotate the Low jet counter-clockwise to 1 and 1/4 turns open.
3) Rotate the High jet counter-clockwise to approx 1 and 3/8 turns open.
4) Now, start the engine. You may need to turn the Low jet slightly one way or the other for the engine to start.
5) Adjust the Low jet as desired until the idle is where you like it. Turning clockwise ("CLOSING" THE JET) will produce a higher idle, and counterclockwise ("OPENING" THE JET) will produce a lower idle (and eventually flood and the engine will kill, if you turn it too far).
6) Open the throttle lever to full blast. Adjust the High jet until you get maximum RPMs. Note: this will probably be REALLY LOUD. Listen for the highest-pitched whine to tell you where max RPMs are hit. AFTER YOU FIND THE MAX RPM SETTING, TURN THE HIGH JET COUNTER-CLOCKWISE ("OPEN" THE JET) APPROX 1/16TH OF A TURN TO ENSURE YOU HAVE SUFFICIENT GAS/OIL MIX TO COOL THE ENGINE PROPERLY.

Note: The above are just general guidelines. You may need to adjust both the H and L screws once you begin driving, depending on engine loading, altitude, humidity, etc. The trick is to find settings that work well for you, and stick with them.

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.

What are the recommended carburetor needle settings for my engine?
DDM recommends the following tuning as a STARTING POINT for tuning your engine:
G230RC / G260RC / CY23RC / CY26RC / CY27RC / CY29RC / GP290 engines: 1 and 1/4 L, 1 and 3/8 H.

and link http://www.davesmotors.com/rccar-faq.htm
Click to expand...

Hi There!.
I am new to the forum and Rc motors. This sounds very informative. I have just bought an XRC-2 Buggy to start with to see if I like and can also use it before commiting to spend big money. I am struggling to get it to run properly. Is this guide pretty much for all 2 stroke motors or is there a different guide for the XRC. Any help appreciated. Cheers.
 
no, these guides are for pretty much all 2 stroke motors.
your motor is stock (stock exhuast can i suspect as well) so the DDM guide will be good to go on. but when you decide to start dropping some coin (and you will, its very adictive), and buy a modded monster, the guide i posted should be used for highly modified motors.

hth
Timmahh
 
It is so nice to have good advice on this forum, it makes this hobby so much more enjoyable! Thanx to all of you experts!!
 
Some good info in here. Hope it helps me. I got my new baja running yesterday after a long time of trying, same today too, once I got it running, it ran great for about 5 minutes then got boggy on the low end, I adjusted the low speed needle a little then it died and Ive not gotten it started since...
 
Oki have read and followed all the notes accordingly. I haven't ran m py TS motor in a good 2 months, I can't get the engine to idle. I was able to get a few half throttle refs in in my warm up attempt and then it bogs and dies. I did notice the return fuel line is broke in half. The rubber grommet that presses into the fuel tank, their is a fuel line broken off inside the tank this causing the primer to run out of fuel and loosing charge, I believe this is a key factor also. Any more advice fellas?? Im in Dallas tax about 6-700 feet above sea level.
 
Hello
I try to find same user guide about this engine Carson/Smartech 28 cc pt-engine with clutch \ which manufactory made ?
Hope you can help me
Thanks
 
I followed the explanation,and the video but I do not know why I have trouble every time to to start my engine
the prosses i do:
fuel ok half tank
spark ok i replace with new one
i open the chock (the read buton on 9:00-horizontal position)
i pump
i move the chock to vertical (6:00 )
no signal (i tray 5-8 time with the pull start)
car type smartech uno 28 cc
what is it so hard ....:mad:
 
If you have a carb with choke, it should be primed with the bulb a few times, then CLOSE the choke and pull until the engine 'just, nearly catches', then OPEN the choke and next pull it should start.
CLOSED - butterfly valve closes/blocks air into the carb.
OPENED - butterfly valve opens/permits air into the carb.
Al.
 
atom3624 said:
If you have a carb with choke, it should be primed with the bulb a few times, then CLOSE the choke and pull until the engine 'just, nearly catches', then OPEN the choke and next pull it should start.
CLOSED - butterfly valve closes/blocks air into the carb.
OPENED - butterfly valve opens/permits air into the carb.
Al.
Click to expand...

Its Not cause overflow in the engine to much pump ....?
 
atom3624 said:
If you have a carb with choke, it should be primed with the bulb a few times, then CLOSE the choke and pull until the engine 'just, nearly catches', then OPEN the choke and next pull it should start.
CLOSED - butterfly valve closes/blocks air into the carb.
OPENED - butterfly valve opens/permits air into the carb.
Al.
Click to expand...

Atom mate he posted in the fuel leak out the overflow/breather that he was fitting a kill switch and I think the smartech carb settings are different , his car was ok before he messed with the kill switch , il check the smartech factory carb settings and re-post
Hope this helps mate
Rob
 
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