Terryh6336

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I purchased an .46 nitro engine made in China at a swap meet. The engines runs great: however, I starting having mid-range problems and adjusted the low end adjustments. Did not help. I backed out the main needle valve and attempted to take out the low end valve to make sure trash was not the problem. Can anyone tell a a starting point for the low end? I know to start at about 1 1/2 turns out.

Terry

JohnBuckner

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No one will ever be able to answer you questions with so little information. So far we know its a .46 and made in china. That takes in a hugh variety.

What brand or marking are displayed on the side?

Is it a four or two stroke?

Is it a bleeder carb (important question)?

Or is it a double needle carb (important question)?


Concerning chinese engines, there are many fine engines produced there however there are just as many klinkers. This almost always is caused by poor quality control and inconsistancy.

Also please note it is unlikely that a main needle one and one half turns out is a good starting point for an engine of that displacement. That is a very lean start setting.

If you can,t answer any of the above questions the you will need to post photos of both sides and that way you may get plenty of good information.

John

Terryh6336

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Ok here are the facts. This is a Direct Connection .40 two stroke. It has both needle valves no airbleed. I am running a Fox long glow plug and 15% Wildcat with a small amount of castor oil.

kenh3497

Have you tried a new glow plug? What sort of "problems" are you having. With the engine running pinch the fuel line. The engine should speed up a bit then die. If it just dies then the mix is too lean. How is the idle? same pinch method there to get you in the ball park setting.

JohnBuckner

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OK now we are cooking, I suspect it is a rebranded double needle SC. Everything above is appropriate. First run the main needle valve all the way out and turn the midrange screw to where it is flush with the rotating barrel. Now close the throttle completely and screw the main needle valve back in till it stops. Back the needle out two and one half turns and these should be good rich starting positions.

Now after starting it will be rich and not likely to take any throttling so you lean the main needle a little at a time untill you can gradually open the throttle completely without the engine dying.

The next steps are what is called pinch tuning and there are variations of the technique. This technique is not often taught and seldom seen on these forums. It is a very effective method and well worth learning and practice by anyone operating glow two strokes. It is not an effective method for glow four strokes except possibley setting the low range.

Like Kenh spoke of above after you have leaned the main needle enough to open the throttle fully it will likely still be to rich. Do a rapid pinch and quickly let go of the fuel inlet line and as mentioned if it instantly wants to stop the engine then you need to back off the needle a click or two then pinch agine and keep doing this untill the engine will display an almost imperceptible momentary increase in rpm. This will be very close to that sweet spot. If at full throttle at the pinch it gain a lot of rpm then you are still to rich and need to run the needle valve in.

Now to move on to the low range needle and we have the engine running well at full throttle. Let the engine move to a low idle speed and let it run for at least about 15 seconds or more then open the throttle smoothly without stop to full if the engine stops immediatly the low range is too lean and it should be opened slightly (no more than a 1 eighth turn of a conventional double needle carb).

The next situation and by far the most common is when you open the throttle smartly from idle is, there will be much stammering but still runs eventually going to full throttle. This is a situation where the midrange is to rich and that little barrel mid range needle screw needs to be turned in slightly no more than an eighth at a time then check agine by the throttle opening.

The high speed setting and the low speed setting are closely interelated so after setting the high speed and low speed it may well be neccessary to do the high speed agine after setting the low speed (most often just a quick pinch to check and just a click leaner or richer.

Some folks and posters here suggest a little different form of mid range pinch setting and that is fine but the full system I outlined above has held me in good stead for a lot of years and I teach it to all my students who seem to become excellent engine tuners.

John

Terryh6336

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Thank you John. This sounds like a good technique. I will retune the engine when the weather lets up here in WV. I wil post my results asap. Thank you also for being patient.