WRX

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I have a new big mig .061
I broke it in with PowerMaster 20% because Powermaster fuel is what I run in my car. I use Powermaster primarily because of the high oil content. It extends the longevity of my car engines which are susceptible to heat soak and that blue thunder crap is 90% caster and 10% synth. not good for engine life, but they stay cool and those who do not know any better think every thing is fine until their crank jutts out the side of their crank case.

During break in I followed the directions on the pamphlet supplied with the engine. Fat for few minutes then tuned for a few minutes then fat again et cetera.

The engine ran as expected during break in (not very well), but I did notice some bubbles around the glow plug. I thought it was fuel boiling off the head.

I only had about 8 ounces of Powermaster left so I used all of it for break in. Last Saturday I got some Norvel 15%. I notice the head getting a bit warmer than I like on the new fuel and the engine will only run for about a minute regardless of how fat I have the needle setting.

After reading the norvel website I have determined that there is an airleak. I can even hear it leaking out through the top of the head when I have the piston at TDC. I tighten the head but not overly because I fear to strip the aluminum threads.

I have tried removing one of the copper shims and got the same result.

What can I do?
Is my glow plug combustion chamber warped?

Andrew

Hi WRX --

Sometimes you can get a little machining chip embedded in one of the copper gaskets or in the shoulder at the top of the cylinder. Remove the head, plug and gaskets. Make sure the shoulder at the top of the cylinder is completely clean -- I sometimes cut a toothpick in half and use the flattened end to go around the rim to pop loose any debris. Wipe the gaskets on a paper towel and also make sure they have no burrs or edges turned up. Sometimes, the gasket will catch an edge in the cylinder threads and get deformed. Also make sure the plug base is clean and flat. Reinsert the gaskets and use your toothpick to seat them so one side is not hung in the cylinder threads.

Reassemble and tighten. You would have to have a pretty good arm to strip the threads, especially if you are holding the engine in one hand and the wrench in the other.

To check for leaking around the plug, fill the relief around the plug with fuel, turn thru TDC and watch for bubbles.

Your engine still sounds like it is getting too hot -- fix any leaks and continue to breakin at a 2 cycle/4 cycle setting. I have seen some engines that will start to slow as they get hot and not respond to richening, but when started cold and cycled back and forth, run thru a complete tank.

The NORVELs tend to like higher castor content, especially during breakin and will run well up to 20% castor. However, some of the guys here who wring out their engines will run all synthetic. I prefer a minimum of 10% castor.

Lastly, make sure the carb is seated and tight and that the o-ring is in place and compressed.

the "other" andrew

WRX

My Feedback: (1)

Checked for burrs. Used my little finger to make sure there were no protrusions or intrusions on all the machined surfaces that make the seal and found no problems. From the factory the head was not very tight so I was a bit cautious with torquing the head down (cold engine only).

Even after all this I torqued the head down relatively tight and still have a compression leak. []

Edit:
I always run at least 10% castor. I usually try to find a fuel that has 15% to 30% castor else I have to run too fat to keep the temp down and have problems with loading up at idle too soon.

The carbatooter is tight. That the first thing I felt compelled to examine. The backing plate also exibits no signs of a vacume leak.

flyinrog

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is it running yet and could it be spent fuel accumulating down in the glow head area that is boiling off?, Ive seen that happen to....Rog

WRX

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I can get bubbles on a cold head and I can hear the air slowly coming out when I crank it to TDC.

ptulmer

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Just curious, have you tried a new glow plug?

WRX

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I have not tried a new glow plug as of yet. I was wondering if that could be the problem I will likely contact Norvel and ask for a new plug. I don't feel that I should have to pay for a new plug for a bran new engine. I realize that they probably get inquiries like this all the time caused by user error, but I have been working with scale RC 2 stroke engines for more than five years. I am quite familiar with tuning, breaking in, and mainiaining these little wonders. This is however my first airplane motor (cox .049 line control planes not counted here)

Japanman

My advice would be to have another look at the plug, copper shims and seating area. This area needs to be absoulutely clean- If a tiny bit of aluminium was in there to start with, it has likely been squashed into the seating area and would not be removerd by just your finger. I would not get in there with anything paper as bits of paper catch on the threads and then turn transparent in the oil- making the problem worse if you don`t spot them. I think using the cut toothpick or something similar to scrape around the area, then flushing with fuel (or a blast of compressed air etc) with the piston near the top of the stroke is your best bet to get the area clean. Then I`d individually inspect and clean the shims, and the plug in a similar manner.

If all of this does not fix the problem, then get in touch with norvel-

J.M

WRX

My Feedback: (1)

Update:

Found the leak to be between the top of the glowplub and the inside ring of the head. This is where taper seal is and it is beyond me how it was leaking. I removed one of the copper rings from the cylinder (now there are 2) and put it over the top of the glow plug
No more leak

Andrew

WRX --

I'm glad your leak has stopped, however, the head's (inside ring of the head) sole function is to place pressure on the top of the plug, not to form a gas seal. The taper on the bottom of the head is not a seal, but a champfered relief to eliminate interference with the plug body and allow full contact with the plug flange.

Your leak was due to a failure of the bottom of the plug and shims to form a good seal -- air, fuel mixture, etc. was leaking and migrating around the plug flange and out around the plug body. The movement of a shim may have done one of two things: The shim was the culprit and you have no leakage at all or you blocked the leakage around the plug body and have forced migration around the head threads.

Also keep in mind that removing a shim will increase the compression ratio -- if you have been experiencing heating problems, this may aggrevate that. I would suggest that you consider getting another shim set and replace all three.

A lot of the posters here have had extensive experience with these engines and may have other suggestions.

Attached below is a comment by Ed Stevens of NORVEL that appeared in an earlier thread concerning leakage.

*******************

I occasionaly read posts for comments on NORVEL motors, although I don't post often to try to stay out of everyone's hair. In this gentleman's case, a leaking head is the problem. It's notable that a leaking head will almost always reduce power and cause overheating. You would see this even more on hot days, with big props, etc.

Leaking can happen for a variety of reasons: deformed gasket, piece of "stuff" stuck somewhere on the gasket, etc.

We have more issues with leaking heads when a motor is bored out to make a bigger displacement. For example, if you bore out a .049 (like we did) to make a .061, the "shelf" that the gasket sits on becomes about 1/2 as wide. That means 1/2 the seating area for the gasket, and more tendency to be prone to leaking issues. It is very rare for us to see a .074 head leak because there is ample seating area on that space.

Tightening the head will rarely help once the leaking has started. Hot oil and fuel burns onto the copper in the space where the leaking takes place, creating residue. The residue prevents the gasket from ever sealing again.

Sometimes you can rescue a gasket by gently sanding it between two pieces of very fine sandpaper, wet. But I have to admit sometimes this ends up deforming the gasket. (In desperation, it's worth a try). As with any gasket that has leaked, the best thing to do is get a new gasket.

I can't always be around to reply to questions, but email at our site if you need more clarification.

That's for this opportunity to explain a common issue that is pretty easy to fix.

******************

the "other" Andrew

WRX

My Feedback: (1)

Thanks a million Andrew. That was the information I needed.