Are there any 4 stroke tuning gurus out there that can give some tips on tuning. I have a new O.S. 70 Surpass and I'm not too sure what to look for or listen for while tuning. TIA

You really should get a tachometer to help with tuning four stroke engines. When it goes from peaked to too lean, the rpm will drop a little before it starts to overheat. That point is hard for me to hear. A tachometer will tell you when you're going too far and you can back off a few clicks.

You will definately need a tach unless you do not mind over leaning the engine. Also, try this Saito Guru's site, it will help you. www.saito-engines.info

Hi!
A tach is not needed at all!!
Just listening to how the engine sounds...as simple as with a two stroke! You can tune a two-stroke can you?

Regards!
Jan K
Sweden

I agree with Jaka. There is no mystery. Just tune it just the same as your 2 stroker. I have never used a tach. Just take your time and all will be fine.

Mark Shuman

Same here, I own a tach, but I only bought it to show the RPM in a review I once did. Haven't touched it since.

Plus, you really CAN'T go by RPM! The engine is going to swing different props at different RPM. So what may be a perfect setting with one prop, may be too rich or lean with another.

Just lean it out until you hear it reach it's peak, then back it off to where it first hit it's peak, or one or two clicks richer. Point the nose up at full throttle. If it goes sick make it a little richer.

If you are tweaking it, and you get it too lean, it's not going to hurt anything for as short a time as you're tuning it. The worst that can happen is if you get it way too lean, it may back-fire and throw the prop (A good reason to keep yourself and others away from the front of any running engine). But you'll usually hear it go sick long before that happens

I think the biggest mistake made with newcommers to 4 strokes is NOT CHECKING VALVE SETTINGS. I've seen new engines right out of the box with missadjusted valve clearances. Check before operating the first time and then again after the first half hour of break in. After that, just checking once or twice a year is adequate in most cases. If you see a change in power output or ease of starting, it may also be time to recheck valve clearances. Read and heed the manufacturers instruction sheet.

You beat me to it Rodney. If those valves arent set right you wil not get all the power out of the engine no matter what you do with the needles. Just be sure and either get REAL familiar with the procedure for adjusting or get some help. It is easy to adjust valves but you have to know exactly what the valve settings are and where to check them at in the stroke. Usually its at Top Dead Center, when the piston is at its highest point. Ill stop there because you really need to read your manual but its easy to do.

Needle settings are just like a 2 stroke as Minn said. If it runs great at full throttle but it doesnt idle well you can adjust your low speed idle settings but you need to read the manual on how to do it if you dont know how. More times than not the mfg settings are perfect but they werent set to mfg settings at the factory. Its just a good idea to learn and double check.

I use a tach but only to check my max rpms to make sure I don't blow the darn thing up. Since i do not fly a 4 stroke in the typical 4 stroke fashion, this is a must have. I swing smaller props with more pitch for speed and you need to keep an eye on the rpms.

MinnFlyer. Most comprehensive advice of all. Very clear. TNX as I'm about to break in a new 52 4S.