Alright, I have a newbie question. Can four stroke glow plugs be used in a two stroke engine? The reason I ask is, the manufacture recomends a long through, med - hot glow plug and all I can find locally are four stroke lgow plugs.

Yes, you can use them. The os 4 stroke plug is great. Ive heard that they burn hotter than 2 stroke plugs. It did the trick for a few bad running engines i had

be sure to check that it does not strike the piston though...

A four stroke plug is the best fix for the ST big 2500 thru 4500 engines.

Why bother to use a 4 stroke plug when you can always buy a hotter 2 stroke plug? It does not make any sense.

A 4-stroke plug runs much hotter than a 2-stroke plug. A 4-stroke plug needs to retain the heat of each combustion cycle longer than in a 2-stroke engine because it only fires every other stroke. They do work good in some larger 2-strokes as mentioned but you have to make sure it clears the piston. I would not use it in a small 2-stroke.

a small 2 stroke, 40-90 size probably will not benifit well from a 4 stroke plug

But if a four stroke plug is all you can find locally, then give it a shot.
Dennis-

All glowplugs are created equal. 4 stroke plugs are just hot two stroke plugs. As far as plug length goes 2 stroke plugs can be long or short, depends what the munufacturer decides to use. Just look down the plug hole and you can see whether it's long or short.

Thanks to all, I feel better about using the plug. However; I am chasing a grimlin in that engine. It runs great on the ground and when I hold the plane stait up in the air... no change. It's a strong running engine. It's when I get it off the ground that wierd things happen. somewhere in the flight, it will die. I mean die, no sputtering or warning. It may be 10 minutes into the flight or it might happen on take-off. It is very frustrating, to say the least. Has anyone had this happen, or do you have any advice?

A little more detailed info would help. Does it die with a throttle change or while the throttle is steady? What engine? What fuel and is it fresh? Is the engine new or has it been used awhile? You get the picture. List all the info you can, it helps to narrow things down a bit.

Throttle change doesn't effect it on the ground. In the air, it will die with the throttle steady. The engine is a new VMAX 046, RCU did a review, which included the engine and it's still on the site. I'm running 10% in it right now and it is fresh. I broke the engine in on a test stand and did it strait out of the manual. It took about 4 tanks of fuel. I appriciate all the help from you guys here and if we figure this out, all the virtual beer is on me !!!

Check the tank and fuel lines. You may have a small air leak. Otherwise It sounds like the low speed needle is a little lean. Try richening up the low speed needle just a tiny bit. Around 1/8 of a turn and see what happens. A different plug is also a good thing to try. When a plug starts to fail it could give you the same symptoms. Good luck with the engine.

Mark Shuman

sounds a bit like overheating to me

Yah I'm with Spaceclam... is the engine cowled? Exit area at a minimum 2X intake area.....

Andy

It does sound like it could be overheating except for the fact that you mentioned it sometimes dies on takeoff. Try running a full tank of fuel through the engine on the ground while you vary the throttle to simulate flying. Check for any air bubbles going through the fuel lines, if there is, you have a leak somewhere. If it doesn't die during that test then I suspect the needles aren't set correctly, probably too lean but it's hard to say.

First thing I will say is that you are running too lean, hence ok on the groung and then dies in flight when the prop unloads. Try the pinch test ... or point the plane veritical and then tune the high end. After that give it a few clicks rich.

Sorry to have to tell you this but the VMAX engine sucks big time, they are lovely 1st or 2nd gallon, after that its kinda like hell. Tuning is most difficult, a few flyers here have that problem. Experienced flyers facing problems tuning that engine.