tsnaylor1964

Hey guys and Pete Bergman, (I hope I got your name right, Pete).
I finally opened up the evo 77 to check for what I thought was a bend con rod. Well, there is good news and bad news. The good news is:
The con rod is not the problem and the overall insides show absolutely no corrosion or rust (always have been careful to use blue blocker after run oil)
The bad news is:
The cir clip on the master rod journal broke and got chewed up in the crankcase (as evidenced by all the nicks and scratches on the journal, rods and case walls). But it gets worse:
The broken pieces then got sucked into the intake ports of the # 2 and # 5 cylinders, destroying the pistons (breaking one piston ring) and eating up the tops of the cylinders and valves.
I have always followed Horizon's recommended fuel, break in, operation and maintenance on this beautiful engine and have around 100 hours on it since new. Unfortunately, I think it just had a defective part ( journal cir clip ) which started the bad chain of events.
I have not called Horizon yet, so I don't know if they will cover this under warranty but at the very least, I am looking at two new cylinder assemblies and pistons.
Anyway, I promised you guys on this great forum that would keep you informed on my misfortune after posting a few pages back that I had a problem.
Any input or advise would be welcome.
Tom

tsnaylor1964

Hey guys, while I am in the forum writing mood just though I would pass on some info for those who have expressed concerns on acquiring methanol in some of the older posts on this forum and others. I was in the fuel distributors office some time back paying my bill for my home heating oil and just thought I would ask if they knew where I could buy pure methanol. After getting some strange looks from the ladies, I explained that I just wanted to use it for fuel in my 'toy' r/c airplanes, not make crack cocaine! ( this is in California, after all) This seemed to put everyone at ease and she happily replied: sure, we sell it in 5 gallon and 55 gallon cans. Elated, I say, how much do you charge? After some amazing wizardry on her antique, crank type adding machine, (really, I'm not kidding) she gives a number that came out to about 5 bucks a gallon for the 5 gallon can and around 4 bucks a gallon for 55 gallon drum. Okay, now I am euphoric dreaming that I can now afford to buy and fly, all the Evolution radials on the planet, no worries. Then I come back to reality knowing that I will have to explain buying all these expensive 'toy" engines to my wife. Seriously though, I was thrilled to find that I could easily get enough fuel for the rest of my life at an affordable price.
So, the whole point of this rambling is to let others know, (who love these engines like I do) that you may have a source right in your own back yard like I did!
Check with your home heating oil distributer in your town to see if you can get it there also. Just be prepared to get some funny looks at first. (It helps to wear clean clothes and a fresh shave when you go in, though). Good luck!
Tom

Maxam

My Feedback: (62)

Well Tom, That is too bad. Yes it is time to call Horizon and get that thing fixed.....and to order more -Tom

badgerord

My Feedback: (6)

I just received my 7-77 back from CH, Adrian did a great job!!!

I am choosing to run it on Gas, running 32:1 and it blows a horrible black mess. I have run it for about 4 1/2 hours on set stand. How low can I run the oil content?

It runs great RPM wise, transitions and idle are great but it seems to be starved for air. When it was at full throttle, the high needle was at about one turn but it ran great, did not over heat, I realize it would
need to be richer for flight.

I wonder if a larger carb would help or make a back plate for a Walbro type card.

Any opinions?

Also, should one run muffler pressure? in my head I keep seeing a spark getting to the fuel somehow, then a scene out of a WW ll documentary as my Corsair heads to the deck in flames.

Marty
Badger Ordnance

mogman

My h/s needle is open about 1-1/4 turns, I haven't held full throttle for more than a few seconds. don't have that much run time on the engine yet. doesn't seem to matter where the low needle is, doesn't make much of a difference at all.

I've been thinking along the same lines as you...walbro carb and adaptor. How do we figure out which carb to use? I'll contact Adrian and see if he can help with the carb and adaptor.

Mine makes a big black mess also...32:1 with Stihl synthetic. I took the back off the engine to see how things were and it really wasn't that wet and oily inside. Obviously running rich as my plugs are all sooted up.

I'm not running any tank pressure, fuel flow seems ok. I still haven't figured how much choke it needs for a cold start yet.

Cheers,
Dave.

EDIT...I just sent Adrian an e-mail re: Walbro carb and daptor. I'll post his reply when I receive it.

In regards to your query on how low an oil content, the rod ends don't, as far as I can determine, have bearings. So they either have bushings or run the rod directly on the pins. In that case I wouldn't go any more than 30-32:1 and use a good quality synthetic oil. Stihl, Redline etc.

mogman

Adrian answered my e-mail.
If we go with a walbro carb we will have to use an electric fuel pump, as a radial has no crankcase pressure pulses to operate the carb diaphragm. I use the same set up on my Moki 400...no issues.

If I send him the glow carb dimensions he will make and adaptor and supply a carb.

Cheers,
Dave.

badgerord

My Feedback: (6)

Interesting... I would hate to have to run a pump. What do you think about a larger carb, bigger hole more air?

Marty
Badger Ordnance

Pull Up Now!

My Feedback: (3)

Pardon me, but this post confuses me. It has great RPM, good transition, and good idle, didn't overheat. What else is there? What is it doing wrong, that makes you think it needs a Walbro?

cymaz

If you put a Walbro carb on.....it has it's own fuel pump, doesn't it?

Pull Up Now!

My Feedback: (3)

The Walbro carb does have a fuel pump, but that pump is powered by a air-pulse-driven pump diaphragm. That pulse comes from a pressure tap (tube) running from the crankcase to the carb. The pressure wave comes from the piston moving up & down. 2 stoke crankcases possess a really nice pressure pulse, and 4-strokes are fairly good enough to work (note there is a breather tap). But the crankcase on a radial has a very poor pressure wave due to it's large size and very gradual progressive piston transitions.

Someone on here suggested an electric fuel pump to run the walbro. I could be wrong, but it seems to me you cannot just hook up an electric fuel pump to the fuel inlet on a walbro and expect it to work. Remember, when filling your gas tank with an electric filling pump how the gas doesn't come gushing out the walbro like it does a glow carb? (true with a simple filling tee in the fuel line running from the clunk to the walbro, than you plug after filling). The gas doesn't gush out because the pump diaphragm's reed valve is stopping the fuel. It must be pulsing to allow the fuel through.

For the electric pump mod, even if one poked a pin hole through the reed valve to let the gas through to the regulator side of a walbro, the electric pump is much higher volume than the walbro consumes, so that will lead to unpredictable fuel mix issues. The Walbro regulator has a pop-off spring valve that will pass fuel through unrestricted if the input pressure gets too high, like 10-15 psi if I remember. An electric pump can easily achieve this pressure. Alternatively, I'd think one could make a simple electric air pulse pump(hooked to the crankcase tap input on the walbro) that would use much less power than an electric pump and let the Walbro diaphragm pump function as intended.

Pull Up Now!

My Feedback: (3)

My apologies Dave, I edited out some stuff in your quote that didn't apply to my response.

One BIG question is what type of gasoline is everyone using with these radials? The general trend, though no one has reported symptoms that are consistent with it, is they're running lean. This is strange, because when converting from methanol to gas the usual issue is running too rich. Methanol contains it's own oxygen, compared to gasoline. So, with gasoline you need more gaseous air (than methanol) to get the right burn ratio. In other words, you have the lean the heck out of a gas-fed engine that is using a methanol carb to let in more of the air that the methanol didn't need. On my many gas converted glow engines, I like to use 87 octane 10% ethanol fuel because it does two things: 1) the alcohol cools the engine effectively during combustion due to evaporation; and 2)The added ethanol contains more oxygen, reducing the need to lean the carb beyond it's ability to physically spray the fuel evenly.

Think of a venturi-based paint airbrush. It has a happy zone where the spray is even. Too much air flow, it doesn't work. Too little, it also doesn't work. A methanol carb is designed to spray evenly at a richer setting than it needs if running gasoline. So, with gasoline, you're asking it to flow the gas evenly with the needle cranked in tighter than it was actually designed to flow. Ethanol delivers a bit more oxygen, allowing you to back out the needle valve into a better spray region.

If one has to use a Walbro, I'd think an 11mm venturi should be fine. It's only 77cc and the RPM isn't excessive with a radial.

One last thing, on my engines I run the very high quality Stihl synthetic oil that comes in those silver bottles. It's pricey, but I run right down to 50:1 and never have any black plug residue ever. Also, my conversions all have years of good service with plain rod journal bearings. We're talking Saitos, OS, four strokes, etc. A few years ago, I used to machine out the crankcases and made my own new rods with needle bearings but all this turned out to be unnecessary. Be careful of leaning, the engine can cook in seconds if the carb screws come loose. And using non-ethanol based fuel will also make it run like it's too lean because you're not getting the cooling need from the alcohol.

cymaz

You are absolutely correct P.U.N.
I had forgotten about the pulse from the engine..silly me.
Would Muffler pressure be enough to get the fuel through. I can't see why not, there are plenty of gass converted glows out there.

mogman

I use an APS electric pump on my Moki 400. It supplies a constant fuel pressure and supply to the carb. It also uses a return line, much like the pump in your car. Mine works flawlessly. They are sold through Vogelsang Aeroscale, a little pricey, but, IMHO, worth it.

Cheers,
Dave.

badgerord

My Feedback: (6)

Pull,

I know I said it seems to run fine, but it runs dirty, here is my thought...

If I run it lean to reduce soot, I run it too hot, if I can add more air, I can a more efficient ignition, more power w/o running lean so it will stay lubed, cleaner ignition, more reliability.

I am fairly new to gas, I have run nitro since 1976, so I know what I am doing there.

The thing I really want is reliability, over a $1000 in the engine and $2K in the airframe, I want to reduce the failure potential to only Pilot error.

Pull Up Now!

My Feedback: (3)

It would be hard to say for sure without seeing a proposed plumbing diagram for your concept. But a pressure tapped gas tank, just running to the standard unmodified Walbro carb, will not pass any fuel past the reed valve without a pulse from somewhere. But, you do have an interesting idea that may work if the pump diaphragm has both the reed valve parts cut off. That might have a chance of working. In fact, I would like to try that. If you do, please report the results.

I also read the post on here where the owner of the Moki said he uses that high end electric fuel pump. I don't have a Moki, and I don't know what kind of carb is on there. I'll research it, but I do wonder, IF it's a Walbro, if Moki has done some kind of mod on it to pass the gas thru it. I don't know, but wouldn't be surprised.

mogman

I have the Moki 400 with the APS electric pump.
It has a BIng carb, same as Walbro or Tillotsen(sp?). There are NO mods required to the carb. Just hook the gas line up as you would on any engine and go.
The pump was designed to work with the Walbro style carb.

Cheers,
Dave.

Pull Up Now!

My Feedback: (3)

Thanks for the info, Dave. It's all in the spirit of learning. So, BLNG carb? Is that an abbreviation?

mogman

Oops, misspelled, should be BING, made in Germany, I believe.

I wonder if we should move these posts about gas and ignition over to the gas engine thread, so as not to clutter up the glow thread.
Maybe Tom, (maxam) will let me know as it's his thread.

Maxam

My Feedback: (62)

All Moki radials use Walbro carbs. The APS Power Fuel pump is simply hooked to the Walbro carb. The carb will accept the fuel just fine. The pump flappers will let the fuel flow through to the diaphragm. Yes the stock carb would need to be leaned for gas use. The needle will become much more sensitive! Gas conversions for these engines is appropriate to this thread as long as Evolution engines is the subject. I have concern for gas conversion with a plain main bearing. The Saito radials on gas have been seizing. There is a gentleman that has been machining the master rod in these engines and presses in a phosphor bronze plain bearing. -Tom

Pull Up Now!

My Feedback: (3)

I REALLY like this forum because it challenges me to do the EVO 77 research I otherwise wouldn't. I've been suffering from a misconception at least one of the pump reed valves must have been what was opposing the inlet pressure from fueling the plane(thru a simple tee). But, MOGMAN and MAXAM are exactly correct. The arrangement of reed valves does NOT oppose free flow of fuel past them. It is in fact the metering valve that is the last point of free flow of fuel when induced from some source of inlet fuel pressure. I prepared this labeled diagram to show just that, to promote understanding. So the electric pump will work fine, as long as the pop-off pressure (bend lever in Walbro) isn't set to open too easily. In fact, the instructions for the Moki electric pump actually says to disconnect the air pump pulse line. I think the fuel return line on the Moki electric pump is to make sure the fuel pressure never rises to the level it will trip the metering valve in the Walbro. Since the Evolution doesn't have the air pulse pump on the front of the engine, the electric idea is about the only alternative(not sure about the muffler tap-to-tank idea, might have to prime with a bulb).

Now I've been running lots of gas four strokes and never suffered a seized main rod bearing. There might be other contributing causes. Maxim, on the Evolution, what is the material of the master bearing? I haven't taken mine apart yet.

Maxam

My Feedback: (62)

I do not know. Sorry. -Tom

mogman

Does anyone know if the main crank bearing, the big on in the case, is sealed or open.
I ask this because on the Moki, the front gearcase is lubed by grease. Now, most people know grease in a gearbox is not really that good, because the grease will be slung to the sides of the case by centrifugel force.
In my Moki 400, I remove a pushrod and lifter from cyl #1 and remove a pushrod and lifter from a cylinder that is just below the centerline of the crank.

I add some 90w gear oil through the top lifter hole and when it runs out of the lower lifter hole the case has sufficient oil.
I discovered this early on in the life of the moki when I removed a couple of lifters and they were bone dry. Now with the oil added, I'm getting some seepage /leakage past the lifters so I know things are getting lubed.

Just curious to see if you think this would work for the 7-77 etc. If the gear case is open to the intake chamber then obviously this is probably not a good idea.

Cheers,
Dave.

badgerord

My Feedback: (6)

Does anyone know of an exploded diagram of the Evo motor.

Maxam

My Feedback: (62)

The timing chest is open to the crankcase. All cams and lifters get oiled from the fuel directly.

mogman

Thank you. One less thing to worry about.

Cheers,
Dave.