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Apr 21, 2014, 08:35 AM
Scale Aircraft = Scale Crators
mikejr83's Avatar
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Magnum XL 70 RFS Loading Up With Fuel


Hi everyone,

Recent dealings with a new Magnum engine I purchased is giving me some serious stress. I having some trouble and after searching around with Google and looking through posts here and other forums I cannot find a solution or questions to the same effect. The title of the thread is the main issue. However, here is a bit of background info:

I recently got a Magnum XL 70RFS from Hobby People. I bolted it down to my test stand and ran about 3 tanks of fuel through it. At the specified two and one half turns out on the high speed it seemed like it was running too rich, but being in the brake-in phase I wanted to make sure the engine was getting good lubrication.

Everything seemed great while on the test stand. It had power, but since it was running rich I figured that when I had it all ready to go a good tune on the high speed would give it that last little bit of power.

I got this engine to put on my Edge 540 (Part 2). I ended up having to put the engine on the plane inverted in order not to make the cowling look like swiss cheese. According to the manual this shouldn't have any affect on the engine's performance.

Anyhow, after putting the engine on the plane I started running into a number of issues. It seemed fuel just wanted to pour through the carb. The tank and carb don't exactly line up on a center line. The actual carb may end up being near the bottom 1/3 of the tank. After working with the plumbing some it seems to have quit this. However, and this seems to be the issue that is preventing me from flying is that the engine just becomes inundated with fuel.

I'll start the engine which when cold isn't too difficult. After letting it run for a few seconds I'll open up the throttle and go to adjust the high speed. It does absolutely nothing. Adjusting it further and further in (clockwise) does nothing till I'm about 3/4 to 1/2 turn from closing the needle completely. Depending on how "lean" I've gone it will backfire and undo the prop nut. At this point the engine is full of fuel. Also, on the ground is a puddle of oil/fuel. It runs so rich that the whole front yard is full of smoke.

After one run I took the engine completely off the plane to start to look at it. When taking off the valve cover there must have been an ounce or more of fuel in there. It was basically full. Turning the crank back and forth shot fuel out of the exhaust and undoing the crankcase vent shot out fuel (or partially burnt fuel) all over the place.

Things I've noticed after the initial breakin:
* Unburnt fuel and oil just puddle where the exhaust hits. My 2-stroke Super Tiger produces doesn't produce anywhere near this amount.
* High speed does nothing in terms of leaning the mixture.
* Doesn't sip fuel, it guzzles it.
* Backfires (?) and breaks prop nut loose.
* The top of the valve cover was completely black as if there was some major blow back.
* oil coming out of: where the highspeed needle goes into the sleeve, coming out of the area around where the backplate meets the crank.

Things I've tried:
* Adjusting the values (the valve lash was horrible; was almost 2 the recommended amount)
* Pulled and disassembled the carb: Got some trash out of the carb and noticed that the o-ring on the high speed was cut up a bit

After going over the engine and "fixing" anything I could notice with the carb I put it all back to gether and got the same result.

At this point I'm ready to send it back and say its defective. I just want to cover everything before I do this (expecting shipping to be ridiculous or about 1/3 of the original cost of the engine). No one I've talked to in my club has had this problem. They all swear by Magnums and for the most part have them on almost every plane they fly.

Any idea on what gives?!

Edit - Prop and Fuel:
Running the 13x6 K-Series Master Airscrew as recommended in the instructions.
Cool Power Omega 15% nitro 17% oil
Last edited by mikejr83; Apr 21, 2014 at 10:48 AM.
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Apr 21, 2014, 09:45 AM
Registered User
First, two and half turns is way to rich. Nice setting for a couple of break in runs but you need to tune it down a bit, more like one and half turns. You need to use a TACH to set the carb on a four stroke unless you have exceptional ears.

Second, you will have to do something about the tank height as all you are doing is siphoning the fuel out of the tank. It will dribble right through the carb on to the ground. If it is not possible to change the tank height, then you may have to result in using a fuel demand regulator like a Cline System that will control the flow to a demand level from the carb. The Cline is a pressure delivery system (you do not really need the pressure part) that responds the demands of the carb. I believe Perry Carbs has the Cline business now days. The regulator will control the flow of fuel to the carb so that the tank will not sit there and siphon fuel through the carb. It is worth checking it out.

And yes, the engine does not care whether it is inverted or not, but the fuel system must be correctly situated, or set up. You have already experience the problems of the improper set up of a fuel system.
Apr 21, 2014, 09:59 AM
Scale Aircraft = Scale Crators
mikejr83's Avatar
Thanks Chip. I knew that 2 and a half turns was rich. It didn't bother me during the break-in period, but now I cannot get the engine leaned out even at a half a turn.

I did some quick Googling for "Cline" and "Cline fuel demand regulator" and didn't get any good results. I did check out Perry's page for regulating pumps. Would the VP-30 or VP-20 be basically the same as the "Cline system"? I need to order carb parts for another one of my engines from them anyhow so I may just throw that on the order. If I'm spending much more than $50 then I might just eBay this engine to go electric. Too much hassle...

EDIT: I just did some reading on the VP-30 over at Tower and saw that it needs a tap in the engine to get pressure off the crankcase. Would the crankcase return on the Magnum work for this? If I could add a T connector?
Latest blog entry: Finished My Sbach 342!
Apr 21, 2014, 10:29 AM
Registered User
surfer_kris's Avatar
Put it on test stand with the tank at the correct height. Once you have running properly on a test stand, then make sure the height of the tank is correct in the plane too and then it should run just fine.
Apr 21, 2014, 10:33 AM
Scale Aircraft = Scale Crators
mikejr83's Avatar
Quote:
Originally Posted by surfer_kris
Put it on test stand with the tank at the correct height. Once you have running properly on a test stand, then make sure the height of the tank is correct in the plane too and then it should run just fine.
Is there a way to solve the issue if I cannot move the tank in the plane? There pretty much isn't a way to get the carb down the centerline of the tank. Well, unless I went to some micro tank or cut the top of the cowling off so the engine wasn't inverted.
Latest blog entry: Finished My Sbach 342!
Apr 21, 2014, 10:37 AM
Dieselized User
gkamysz's Avatar
I'd pull the engine and run it on the bench to see if it can be tuned before spending money on equipment you may not need. I do use Cline regulators, but mainly to maintain a steady tune. I just noticed the Cline regulator site is gone. A friend of mine has a Magnum FS-70AR and it was very difficult to tune, also mounted inverted. I side mount to avoid tank height issues.

For some engines, 1/2-3/4 turn out on the main needle is normal. It also sounds as if you're adjusting the needle too quickly if it goes from sloppy rich to detonating. Copious amounts of fuel inside the engine is not surprising if it's being run extremely rich.

When posting about engine performance in general please include prop size and fuel type to help anyone reading understand what's happening. For glow engines this is very important.

Greg
Apr 21, 2014, 10:46 AM
TigreJohn
The Perry VP-30 doesn't work on a four stroke. You would have to use the VP-20.
Apr 21, 2014, 10:52 AM
Registered User
Are you blocking the crankcase breather? You mention this in your seventh paragraph. You haven't connected the breather to the fuel tank have you?
This vent should be free to let out the oil that passes the piston ring in normal running and ideally should have less than 2 inches of tube to allow the oil to be dumped outside the cowl. (Unless it's one of those that fit direct to either the inlet or exhaust pipes)
Last edited by Braddock, VC; Apr 21, 2014 at 10:58 AM.
Apr 21, 2014, 11:04 AM
Scale Aircraft = Scale Crators
mikejr83's Avatar
Quote:
Originally Posted by gkamysz
When posting about engine performance in general please include prop size and fuel type to help anyone reading understand what's happening. For glow engines this is very important.
Noted. OP updated.

Quote:
Originally Posted by gkamysz
I'd pull the engine and run it on the bench to see if it can be tuned before spending money on equipment you may not need. I do use Cline regulators, but mainly to maintain a steady tune. I just noticed the Cline regulator site is gone. A friend of mine has a Magnum FS-70AR and it was very difficult to tune, also mounted inverted. I side mount to avoid tank height issues.

For some engines, 1/2-3/4 turn out on the main needle is normal. It also sounds as if you're adjusting the needle too quickly if it goes from sloppy rich to detonating. Copious amounts of fuel inside the engine is not surprising if it's being run extremely rich.
On the test stand and on the plane I've done "one click adjustments". My Super Tigre is very, very sensitive to adjustments so I've learned to do no more than a click or two at a time.

Quote:
Originally Posted by Braddock, VC
Are you blocking the crankcase breather? You mention this in your seventh paragraph. You haven't connected the breather to the fuel tank have you?
This vent should be free to let out the oil that passes the piston ring in normal running and ideally should have less than 2 inches of tube to allow the oil to be dumped outside the cowl. (Unless it's one of those that fit direct to either the inlet or exhaust pipes)
The crankcase return came setup from the factory with a blue tube that connected from the crankcase to the updraft part of the engine. When disassembling the engine I removed the line and when turning the engine over in my hand it shot about 3/4 an ounce of "fuel" out.
Latest blog entry: Finished My Sbach 342!
Apr 21, 2014, 12:11 PM
Registered User
Thanks, mike. The other thing that springs to mind is the main jet. I've seen them opened up following the hi speed needle being turned in to hard. It's easy to check if it actually closes, turn it shut, put a piece of fuel pipe on the nipple and blow. If it does leak it's not a terribly hard job to change it. This happened on a saito of mine when I dropped it out of my hand onto the floor.
It's always a difficult one to call when the engine isn't in front of you, it's probably a combination of things with the tank level being potentially the most culpable and some mechanical fault with the needle valve always there to trip you up. I hope you get to sort it as the two magnum 4 strokes I had would run inverted without a problem.
Apr 21, 2014, 12:21 PM
Scale Aircraft = Scale Crators
mikejr83's Avatar
Quote:
Originally Posted by Braddock, VC
Thanks, mike. The other thing that springs to mind is the main jet. I've seen them opened up following the hi speed needle being turned in to hard. It's easy to check if it actually closes, turn it shut, put a piece of fuel pipe on the nipple and blow. If it does leak it's not a terribly hard job to change it. This happened on a saito of mine when I dropped it out of my hand onto the floor.
It's always a difficult one to call when the engine isn't in front of you, it's probably a combination of things with the tank level being potentially the most culpable and some mechanical fault with the needle valve always there to trip you up. I hope you get to sort it as the two magnum 4 strokes I had would run inverted without a problem.
Hmm. That sounds promising. I'll have to check that out.

The reason that I thought the regulator would be a good solution is that I have had it siphon fuel out when it's sitting there. I've had the tank and engine in and out of the plane so much that after the last time that I've had to re-do the plumbing a number of times. After I had it off the plane to take it apart when I put it back on the engine hasn't had that problem. The carb to centerline ration hasn't changed. I just thought perhaps I finally got the lines hooked up in a manner that suited it better.
Latest blog entry: Finished My Sbach 342!
Apr 21, 2014, 04:42 PM
Registered User
I had a world models midget mustang (my favourite plane) with a laser 80 mounted inverted.
The tank was centred on the crankcase and, on the laser the carb is centred on the cylinder head meaning there was about a couple of inches between the centre line of the tank and the carb below it.
Laser told me it shouldn't be a problem except maybe on negative g manoeuvres eg outside loop but to set the carb so that when the throttle trim was right back the carb was completely shut. I did and I had no major problems with the installation right up until the time the battery came loose and pulled out of the switch connector. I keep meaning to buy another midget mustang and I had to have a new crankshaft in the laser as it hit a rock when it reached Earth.
Apr 21, 2014, 11:10 PM
Registered User
I'd dump that Magnum and use an OS or a Saito. I had two Magnum 30's and they were junk. Sent them back to Hobby People and they couldn't make them run right so they gave me two more. I sold them and bought a Saito which solved all the problems.

You get what you pay for.
Apr 22, 2014, 07:18 AM
Scale Aircraft = Scale Crators
mikejr83's Avatar
Quote:
Originally Posted by datsunguy
I'd dump that Magnum and use an OS or a Saito. I had two Magnum 30's and they were junk. Sent them back to Hobby People and they couldn't make them run right so they gave me two more. I sold them and bought a Saito which solved all the problems.

You get what you pay for.
This is the first fuel motor I've purchased (the rest were "dead" by their owners and I fixed them). The reason I purchased it is that there is a significant number of club members at my local field that fly nothing but Magnum. Every weekend I see them fly with no troubles, etc.

I don't care what the powerplant is in the plane. I just want to fly it. If it came down to putting an OS or Saito in anything I flew then I'd never get in the air. This hobby costs too much as it is. That, however, is another discussion.
Latest blog entry: Finished My Sbach 342!
Apr 22, 2014, 07:57 AM
Registered User
surfer_kris's Avatar
There is no reason to change the engine, you don't even know if there is anything wrong with the engine yet. Broken o-rings on needles etc can/will happen to any engine brand.

Just put it upright on teststand to check if there is any problem with the engine itself. Then solve the problem you have when the engine is installed in the plane. Syphoning fuel is a direct evidence of a too high tank, no plumbing can change that fact.

From my own experience, the key to a successful inverted engine installation is in the tank level. Get that right and it runs just as well as an upright engine...


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