New Engine head loose
 

I got a new super tigre engine yesterday. It is a G90 ringed. I put it in the test stand to break it in today. I got everything ready and started the thing up. It started right up but didn't seem to be acting quite right and would not respond to the needle valve. Then i noticed fuel leaking from the engine. I thought it was coming out of the exhaust port like the muffler wasn't on tight.
Anyway to make a long story short, i decided i would check the headbolts. They were all almost a complete turn loose. Has anyone else every recieved a new engine with the head loose? I tightened them up and the leak was gone.
I love super tigre engines, I have 4, but this just seems like something they would check before sending an engine to a customer. I'm glad it didn't ruin it.

RE: New Engine head loose
 

Can't say it surprises me, I am sure they don't run the engines prior to sale. Shtuff happens, I used to be a quality supervisor.

RE: New Engine head loose
 

I've had a couple of new engines that had somewhat less than tight bolts...either head or backplate.
It pays to check them before you run it...especially if you don't test run the engine, and have it already installed in the airplane, then find out that the backplate screws are loose![:@]:D:eek:

RE: New Engine head loose
 

Yep, two out of four G90s here had head-bolts that were not even finger-tight.

Don't you just love Chinese quality control? (sorry, that's an oxymoron).

RE: New Engine head loose
 

With these engines coming out of china, it pays to take them apart anyway, and clean out the left over swarf before starting them. That way, you know they are clean, and that everything is tight.

RE: New Engine head loose
 

Not just the Chinese engines. I lost the piston on my new K&B Sportster last week from contamination.

RE: New Engine head loose
 

My 51 was the same, it would only run at full throttle. I reassembled the carb correctly and then noticed a lot of oil coming from the head, all the head bolts were less then finger tight.
Tightened them up and she runs lovely, but it will not shut off at idle, suspect an air leak around the mounting lug area.

RE: New Engine head loose
 

I have never seen it on a Head before, but I have seen back cover screws and intake screws that were only finger tight on a few magnum's.;)

RE: New Engine head loose
 

My Thunder Tiger .46 Pro had a loose head and backplate. Tightened it up and everything was fine.


Ed Cregger

RE: New Engine head loose
 

I've had loose screws through the years on most every brand of engine. It ain't just the Chinese, however they may be worse than the others.

RE: New Engine head loose
 

My BGX 3500 had loose head bolts. Backfired and what the heck is going on for about a half hour.

RE: New Engine head loose
 

I learned to fly with a Senior Tele with an Irvine Q 72, its head came loose after about a half gallon of fuel, it can happen any engine.

RE: New Engine head loose
 

Gents,

Excuse a little scolding, please?

Our engines are miracles of modern technology... at least the pieces turned out by hi-tech processes are. Assembly, particularly in low hourly wage parts of the world, may not be everything we wish it were. That leaves some of the responsibility up to us...

Even if you buy a new car, these days, a read of the owner's manual will suggest a "break-in" process for a certain period of time. It is, today, much less involved and crucial than it once was, but you'll gain by following the recommended precautions.

So, I recommend checking that the engine is bolted together well enough to run. I've been surprised (- shocked, SHOCKED, Rick -) to read that some of us don't bother!

Further, I recommend pulling the backplate - at least - off a 2-cycle to check whether there's any loose bits from the manufacturing and assembly processes floating around in the crankcase. If there are, a flush with rubbing alcohol should remove them. Oil the moving parts, and re-install the backplate.

"Torquing" the head is less critical now than it had been, but is still pretty important. Try backing off all the head bolts until they are loose, then running them in until they "just touch". Then back each out a half turn.

I.e., for a six bolt head, use a Star of David type pattern. Select one of the front bolts and call it 12 o'clock. Turn it in 1/4 turn, then go to the bolt at 4 o'clock and do the same, Then to the 8 o'clock bolt - same. Now, cross the head to the opposite - 2 o'clock - bolt and give it a quarter turn. Then 6 o'clock... Then 10 o'clock... Then diametrically across to the 4 o'clock for another 1/8 turn.

And, with this sequence, continue with ever decreasing increments, to draw the head down. In two or three more passes, you should feel definite resistance at each bolt. Continue to pull-in even increments, with a small handle diameter screwdriver, or the short tang of an Allen hex key, until you can't add any further draw-in. The head should be on square, evenly tight, and well-sealed for running, now.

(For four bolt heads, try to keep crossing the diameter as well as possible, say a sequence of 2 o'clock, 8 o'clock, 4 o'clock, 10 o'clock, then from 10 o'clock to 4 o'clock and round and round we go...)

A helpful thing to check is how free the shaft turns (before the 'pinch' zone in AAC/ABC or ABN engines). After each increment in tightening the head, roll the shaft back and forth to assure that you haven't pulled in any distortions. Again, this is less likely with more recent engines, but it can happen. Checking as I recommend at least gives confidence that we haven't bound up the engine by ham-handedness...

After the first few runs, test stand on in a model, go around the head bolts and backplate bolts, as above, to correct for any gasket 'settling' or compression from running loads, etc. This should last a long time...

Finally, every engine I've had in my hands came with some form of mfr's recommended break-in procedure. Try it: you'll probably appreciate it when your engine outlasts those of others who expected their toy to be ready to play with in the box, and performs better while lasting longer.

I first opened up a model engine back in the early-1950's, and have always found something that could be improved...

RE: New Engine head loose
 

I have ben using model engines for over 35 years, and in that time I have never ever had one that had the head bolts not tight, or would not run, straight from the factory and out of the box, untill I brought this Super Tigre.
The bolts were just placed in the head, not loose, but completely undone.
Now in this day and age, even if you use the valid points Lou suggests, this is unacceptable, especially for a newcomer to the hobby who does not understand anything about engines.
Even the cheaper engines on the market are better put together then these ST's.
The carb was also completely misassembled, and had to be stripped and put together correctly before the engine would even run.
What happened to even the most basic quality control.
ST have to be careful because other manufacturers produce engines as good/better for less money and they work straight out of the box.
Besides that, the engine is very good, once I actually got it running, and now I have to work out how to get it to idle slowly and shutoff when the throttle barrel is completely closed, but again I have to spend time messing about with it when I would rather just be able to start the engine and fly.
Just my unbiased observations on this subject,, so please no nasty rude comments about this post, I am not putting down ST, just explaining my one and only experience with them.
Darryl

RE: New Engine head loose
 

As affluence comes to China, so will some of its consequences. Your engine must have been the first assembled on Monday morning, between numerous sessions of calling for Earl.

Yes, it is frustrating.

This is one reason that I am for robots assembling our engines. They seldom have a need to call for Earl.


Ed Cregger

RE: New Engine head loose
 

Dave, you're obviously very good at avoiding anywhere near a lean run, lean runs will knock any head loose in a few minutes. When the one on my Q 72 came loose I was a newber and peaked them to max. I've never had a loose one from the factory.

RE: New Engine head loose
 

Well I started this thread and would like to defend super tigre. I tightened the head up and I am happy to say that after about 30 mins of break in the engine is runnin great with no ill effects. It's idling well and was dragging my saw horse around at wide open. Maybe all that is needed is for manufacturer's to add a line to their manuals. "Before starting check all bolts for tightness". Problem solved. I know i'll check them every time from now on.

Well i'm off to burn some holes in the sky with the skrike,
Matt

RE: New Engine head loose
 

Glad it worked out OK. I consider myself a most cautious engine guy but I have been bitten before. I will be going through all my engines both new and used from now on to check for trouble to include a partial tear down. That new piston and cyl taught me a hard one.

RE: New Engine head loose
 

I always remove the backplates on new engines

RE: New Engine head loose
 

I look at engines as just another "kit" to put together before it can be used.

It is very common to find chips, old coolant, and/or tapping oil that were never properly cleaned off the parts before it was put together, and doesn't make a very good first gulp the engine takes on its first fire-up.

Loose screws from the factory should be a total imbarresment for the company, but probably is the most common manufacturing defect.

Maybe that is why some instructions advise checking the tightness of all the screws after its first use...they are too ashamed to say "check them but only after we are ruled out as the culprit".

Heat expansion and contraction on model engines is common for making steel screws to loosen or freeze up, but finding them two turns out after you find the engine doesnt run the first time isnt good.

RE: New Engine head loose
 

I cringe when I think of all the engines that I did that to as a newbie, Hobbsy. Mine used to smoke. I'll bet yours did too. I still suspect that this tuning technique coupled with little or no castor oil in the fuel is what gave most McCoy engines a bad name in the sixties. We didn't know any better.


Ed Cregger

RE: New Engine head loose
 

Ed, that smoke actually saved my big yellow Telemaster abck in 91 when I was learning ot fly. I had a Fox .74 on it and was running it pretty rich so it made quite a smoke trail. A friend Andy Bonner was teaching me to fly, we got to talking about somrthing and the next thing I know plane is almost a dot in the sky. I had enough experience to know how much stick made it roll for a perfect slow turn without losing any altitude. I banked it to the left a little and soon could see that the smoke trail was behind the plane, I just let it turn until the smoke trail disappeared and new it was headed straight toward us. in about 3 minutes it was back, it was time to take a deep breath. Thank Goodness for TeleMasters and their great flight characteristics.

RE: New Engine head loose
 

Jetpack, Ed and Hobbsy...

I think it was when Carlsen or MECOA were first bringing in AME engines - the half-A's - that I saw a recommendation in the instructions to pull backplate (and head if a glow) to soak the opened engine several hours in 'white gasoline' before attempting to operate the beast. (I may have seen similar recommendation with one or two other Russian or mainland-Chinese-engines.) Then: clean, wipe dry, oil and reassemble. I've done this with several engines, particularly from those parts of the world, since, and invariably found some dissolved gunge soaked from the exposed innards. Subsequent running-in went pretty much as described in the manual - without problem, unless the engine had something else specific "off".

(To JP particularly) having the headbolts tight is not always enough. If they are socked home the way I heard had been done as a matter of course at one mfr's factory, it's worth going through the alternating triangular sequence I mentioned above. That one company had powered Phillips head tools on extension drives overhead, and the relatively low-skill line installers just went around the bolts in sequence, once. Not alternating. Just 12-2-4-6-8-10 (o'clock) and done! I don't even like the shape of Pringles in potato chips...

Further, some factories do initial bench runs before boxing up the units for shipping and sale. PAW and FOX, I believe, for sure. PAW claims an engine is not sold unless it meets the factory benchmark RPM. I haven't found swarf or crumbs inside either make's new engines, but a bench run may have blown such stuff through and away. No serious apparent damage ever conclusively noted...