Glow plug, Not burnt, but dont lite

[nitrotoys]

I have a MAC.21, I run a tank and or if i stop it, the glow plug just dont glow again, its not melted or burnt.

ALittle brown in color, engine is maybe a bit rich,

ANY SUGGESTIONS??

THanks

 

[[email protected]]

Maybe your glow ignitor is not chraged. Or sometimes the coil breaks way down inside and you can't tell that it's actually broken and the plug is bad. Do any of your other spare plugs glow when using this ignitor?

The browning sounds like early predetination and overheating of the engine caused by tight head clearance. Maybe raise the head clearance to about .012 or higher. Sounds like your at about .08

 

[[email protected]]

The other thing I was thinking about in regards to the browning is maybe your over proped? If you are go to a smaller prop like an X-437 this will reduce the load on the engine thus reduce heat.

 

[nitrotoys]

Glow ignitor is fine, The coil is there, but not making contitnuity, put a new plug in and it will run a full tank and when dies out from no fuel, plug same way.

and the engine isnt getting over 160 in temp.

I am running a 438 prop on it, alittle bar cut, stock dia and pitch.

 

[[email protected]]

Even though the plug is there the coil element is proboably broken deep inside. Take a pair of tweezers or something and pull on it a little and see if it was seperated near the bottom.

 

[nitrotoys]

The plug wire is shot, checked it.

I am running a stock mac .21, stock head clearence, 40% Red Max, MC-9 Plugs, about 3/4 gal fuel through it.

 

[[email protected]]

It must be your running the motor to lean. Fatten it up and break the motor in slowly. I'd run 4 or 5 tanks through thee motor before you can really run it lean.

What's the suggested needle setting for the break in process??

 

[Ron Olson]

What brand of plug are you using? The McCoy's have had problems in the past year with bad elements. K&B plugs need a lower amperage to start or they'll blow easily. One trick for longevity is to "Temper" the plug by heating it with your igniter then letting it cool and repeat several times.

 

[dwb2620]

What boat is this in? I run a Mac 21 in a 70 mph Eagle SG and it rarely blows a plug. And it always has a Brownish tint to it. Bad bearings, bad fuel, bad batch of McCoy plugs, excess driveline friction, pin hole in a fuel line, could be anything.

 

[TimD]

What pipe are you using?

 

[nitrotoys]

I am using MC-9 plugs, and fresh Red max 40%.

and I do temper the plugs.

Its in a Seaducer hull.

I am using a OS remote needle valve.

its i think rich, bearly runs at start and idle, gas shooting out carb.

have the Brown .21 nitro pipe

18 degree header,

Grims Fuel tank, 13.2 oz metal tank

all new fuel lines.

8 inch from plug center to weld on pipe

438 prop, sharpened and balenced, about a 1/4 barr cut.

runs GREAT, but after each shut down, kills the plug,

Is there another plug i could try?

 

[TimD]

Try shortening the pipe by 1/8 inch. Sometimes that works plus those motors and pipes like big rev's. The MC9's should be fine but if you want slightly more durable then you could try Cipolla 7's (red).

Have you checked the head for signs of detonation?

 

[nitrotoys]

You think to shorten the pipe another 1/8th inch??

Now when is it to get on the pipe, this one is about 1/2 throttle or alittle less.

What do you mean by checking the head for detonation? Please explain, I dont know what your talking about, or what to look for.

Thanks

 

[[email protected]]

Take the head bolts off the motor and examine the top of the piston and the bottom of the button. If it's pitted or scored you have excessive heat causing predetination.

The root cause of "Detonation" is excessive heat in the combustion chamber. Incressed combustion-chamber pressure causes excessive heat, so you can control detonation by controlling head pressure. To do so, add a head shim under the head button or open the bubble.

Or the most simplest way to control it is run it rich, but that's a big sacrifice in speed!

 

[nitrotoys]

I checked the piston and head button, No pitts, No scores, Its got a light redish/brown tint to it.

I think thats cause of the Maxie fuel i am running.

Would a lower nitro not burn the plug.

this is just pond playing boat

Can someone tell me HOW RICH it should be?

i has fuel spitting out the carb at idle, Runs great, just does the plug in, and it dont burn the plug eather.

thanks.

 

[TimD]

The pipe sounds too long to me. The MAC21 is capable of much higher RPM than most 21's.

Don't raise the head if it isn't detonating - you will loose power.

If your temp is only at 160 deg, you are not too lean. The colour of the plug element is the best way to tell - shiny= rich.

 

[[email protected]]

MACS like a lot of fuel. Go up to large fuel tubing, usually for the .21's you don't have to do that but worth a try if it's just a play boat.

 

[MikeP]

If it's not getting hot enough it will sound rich you will tend to try and lean it to get it to sound right, the MAC .21's I have seen here all needed restrictions in the water lines to get it to run hot enough. Good and hot to the touch but doesn't burn you.

-MikeP

 

[Anders_Martinelle]

I run a MAC 21in a Seaduser.

The setup i have is head clerance of 0,01, 40% nitro and 20% castor oil.

Brown nitro pipe set to 217mm or alittle over 8,5" and x440/3 std prop.

Runns 44 mph all day long with no burnd plugs.

I run Picco carb with low end adjustment so i don`t need to set it so rich at idle at the dock.

Anders

 

[nitrotoys]

Thanks guys for the info.

I got alot of mixed info.

Am going to try bigger fuel line, and richen it up.

I know for a fact its rich, but probably not rich enough, Just when gets under half tank, its now drawing from carb instead of being forced into it. Must be leaning out there.

and as far as runnning a 440 on it, it will not get on the pipe with a 440 two blade, am going to try the 3 blade once things are running right.

one person said take a 1/8 off the pipe, someone said 8.5. I am at 8 right now, and it seems to run great, just the plug problem.