The Secret of Engine Tuning

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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...
This is real good stuff, transcribed half of it to my field notes!
 
Timmahh said:
ya, colemans is so much cleaner burning than gas, regardless of oil used. its not surprising it has very little deposits left behind.
been thinking of giving it a go.
Click to expand...
Dumb question but do you mean Colman camp fuel (white fuel)
 
this guide it total bs....
tuning low - says to tune it to get desired idle rpm, but idle screw sets idle rpms - ayfkm?
bogging down when transitioning from low rpms - again, total bs. I was following this guide and driving way too rich all the time, beacuse it was bogging from idle when i added throttle - so i was constantly richening high until it finally didnt do that. But thats not what you should do.
Today i finally figured it out by trial and error - when that happens it means your low is too lean.... getting high right is much more difficult, you need to observe many things like power, max speed. Doing this by sound is again total bs, theres was absolutely no sound difference between way too rich and just right. She was just getting higher rpms.
Its really sad that some "guide" on such big forum is used and confusing new people getting experience with 1/5 petrols.
If i was to follow this guide blindly i would probably destroy engine from having high too rich all the time and low too lean FFS!......
Only when i took things into own hands she finally runs like it should
 
Lebron James Eating GIF by NBA
 
Roni92 said:
this guide it total bs....
tuning low - says to tune it to get desired idle rpm, but idle screw sets idle rpms - ayfkm?
bogging down when transitioning from low rpms - again, total bs. I was following this guide and driving way too rich all the time, beacuse it was bogging from idle when i added throttle - so i was constantly richening high until it finally didnt do that. But thats not what you should do.
Today i finally figured it out by trial and error - when that happens it means your low is too lean.... getting high right is much more difficult, you need to observe many things like power, max speed. Doing this by sound is again total bs, theres was absolutely no sound difference between way too rich and just right. She was just getting higher rpms.
Its really sad that some "guide" on such big forum is used and confusing new people getting experience with 1/5 petrols.
If i was to follow this guide blindly i would probably destroy engine from having high too rich all the time and low too lean FFS!......
Only when i took things into own hands she finally runs like it should
Click to expand...
wow who are you who is so wise in the ways of engine tuning
 
Tuning by ear and response has always been a thing with 2 stroke engines. Off idle bog, is typically too lean. Setting idle with the idle mixture screw is stupid. Setting high speed screw is honestly pretty easy if you know what to listen for. Arguably harder on an rc car then most 2 stroke applications where the engine is in your hands or between your legs.
 
Roni92 said:
this guide it total bs....
tuning low - says to tune it to get desired idle rpm, but idle screw sets idle rpms - ayfkm?
bogging down when transitioning from low rpms - again, total bs. I was following this guide and driving way too rich all the time, beacuse it was bogging from idle when i added throttle - so i was constantly richening high until it finally didnt do that. But thats not what you should do.
Today i finally figured it out by trial and error - when that happens it means your low is too lean.... getting high right is much more difficult, you need to observe many things like power, max speed. Doing this by sound is again total bs, theres was absolutely no sound difference between way too rich and just right. She was just getting higher rpms.
Its really sad that some "guide" on such big forum is used and confusing new people getting experience with 1/5 petrols.
If i was to follow this guide blindly i would probably destroy engine from having high too rich all the time and low too lean FFS!......
Only when i took things into own hands she finally runs like it should
Click to expand...
Could really do with some example here, I forget trial and error is better than a good baseline.

You are trash talking with zero back up, I give you 5 more posts max.

Go pedal your snake oil advice somewhere else, maybe you could join your attitude which is about as low as snake spit. Good luck.👍🏾
 
how thats zero backup? i specifically pointed out whats wrong with that "guide". 4 pages of posts and nobody see obvious errors,
and following this "awesome" advice on first pageit almost ruined my 2 new engines i feel like i have right to be a lil salty....
and im not saying im great at tuning or anything, on the contrary im almost completely new and finally after about 8l of burned petrol figured out why my engines kept bogging from idle despite constantly richening high like this guide says... but when high was almost 3 turns out i knew somethings wrong so i started to mess with them on my own.
So maybe better fix that guid instead of being so defensive before some other noob like me totally ruins his engine?
 
You are shouting in your first few posts and by your own admission you don’t have a clue what you are doing or talking about.

The OBR advice is good advice and they are very well renowned and respected engine tuners and builders.

You can’t come one here and say twisted the needle this then that and eventually it worked. That is BS advice.

Also where is your rig? What motor are you running and which carb and pipe?

It helps if you are constructive rather than critical with no back up.

Up to you which direction you want to go now? Me as well I suppose. 🤔👍🏾
 
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