New magnum .15 wont shut off
03-23-2010, 07:24 PM
#1
New magnum .15 wont shut off
I noticed during my break in that I am unable to shut this motor off. I can see the throttle barrel is all the way closed but it continues to run at an idle. This is mounted on a combat plane and the tank is mounted very high, could this be my problem? Any thoughts would be great.
03-23-2010, 11:00 PM
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RE: New magnum .15 wont shut off
It is usually air flow that pulls fuel mix into the engine, as we all know. High fuel pressure (high tank) plus loose barrel could do it I guess.
03-24-2010, 08:27 AM
#5
RE: New magnum .15 wont shut off
The more I think about it the more I am leaning torwards leaking needle, because I can put my finger over the carb when it is idleing and it will not stop so the air is getting in somewhere other than the carb intake. I also checked the head bolts they are tight as well.
03-24-2010, 08:41 AM
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RE: New magnum .15 wont shut off
G'day
If an engine won't stop when you choke it by totally covering the air inlet, then air MUST be getting in somewhere else. The usual places are -
1. Round the bottom of the carby because it is not pushed down or the O ring is damaged.
2. Air being sucked in round the fuel inlet - loose fitting, damaged gasked (quite common with engines that have a soft gasket)
3. Air being sucked in via the needle (usually the high speed needle but could also be the low speed needle as they have O rings too - because the O ring is worn or damaged. Sometimes a small piece of fuel tube round the needle helps here.
4. Air being sucked in because the barrel of the carby is a loose fit in the body of the carby. A temporary fix here is to grease the barrel and see if that works. Silicon grease lasts longer as is does not dissolve.
5. Even possibly a damaged back plate gasket allowing air to get into the crank case but usually this sort of leak stops the engine working as crank case compression is needed to force a fuel load up the transfer ports.
Hope this helps a bit.
If an engine won't stop when you choke it by totally covering the air inlet, then air MUST be getting in somewhere else. The usual places are -
1. Round the bottom of the carby because it is not pushed down or the O ring is damaged.
2. Air being sucked in round the fuel inlet - loose fitting, damaged gasked (quite common with engines that have a soft gasket)
3. Air being sucked in via the needle (usually the high speed needle but could also be the low speed needle as they have O rings too - because the O ring is worn or damaged. Sometimes a small piece of fuel tube round the needle helps here.
4. Air being sucked in because the barrel of the carby is a loose fit in the body of the carby. A temporary fix here is to grease the barrel and see if that works. Silicon grease lasts longer as is does not dissolve.
5. Even possibly a damaged back plate gasket allowing air to get into the crank case but usually this sort of leak stops the engine working as crank case compression is needed to force a fuel load up the transfer ports.
Hope this helps a bit.
03-24-2010, 01:42 PM
#7
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RE: New magnum .15 wont shut off
ORIGINAL: mike109
G'day
If an engine won't stop when you choke it by totally covering the air inlet, then air MUST be getting in somewhere else. The usual places are -
1. Round the bottom of the carby because it is not pushed down or the O ring is damaged.
2. Air being sucked in round the fuel inlet - loose fitting, damaged gasked (quite common with engines that have a soft gasket)
3. Air being sucked in via the needle (usually the high speed needle but could also be the low speed needle as they have O rings too - because the O ring is worn or damaged. Sometimes a small piece of fuel tube round the needle helps here.
4. Air being sucked in because the barrel of the carby is a loose fit in the body of the carby. A temporary fix here is to grease the barrel and see if that works. Silicon grease lasts longer as is does not dissolve.
5. Even possibly a damaged back plate gasket allowing air to get into the crank case but usually this sort of leak stops the engine working as crank case compression is needed to force a fuel load up the transfer ports.
Hope this helps a bit.
G'day
If an engine won't stop when you choke it by totally covering the air inlet, then air MUST be getting in somewhere else. The usual places are -
1. Round the bottom of the carby because it is not pushed down or the O ring is damaged.
2. Air being sucked in round the fuel inlet - loose fitting, damaged gasked (quite common with engines that have a soft gasket)
3. Air being sucked in via the needle (usually the high speed needle but could also be the low speed needle as they have O rings too - because the O ring is worn or damaged. Sometimes a small piece of fuel tube round the needle helps here.
4. Air being sucked in because the barrel of the carby is a loose fit in the body of the carby. A temporary fix here is to grease the barrel and see if that works. Silicon grease lasts longer as is does not dissolve.
5. Even possibly a damaged back plate gasket allowing air to get into the crank case but usually this sort of leak stops the engine working as crank case compression is needed to force a fuel load up the transfer ports.
Hope this helps a bit.
Then there is the place that no one wishes to go - around the crankshaft's nose because of a poor fitting crankshaft/crankcase bore.
It is possible to switch to a sealed front bearing and hope for the results that you are looking for, but most likely you will just have to live with it as most manufacturers do not consider the inability to stop the engine via throttle command as a defect. I have had many engines over the last five decades, even top brands, that would not stop via throttle.
Ed Cregger
03-24-2010, 01:47 PM
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RE: New magnum .15 wont shut off
ORIGINAL: twostroke
The more I think about it the more I am leaning torwards leaking needle, because I can put my finger over the carb when it is idleing and it will not stop so the air is getting in somewhere other than the carb intake. I also checked the head bolts they are tight as well.
The more I think about it the more I am leaning torwards leaking needle, because I can put my finger over the carb when it is idleing and it will not stop so the air is getting in somewhere other than the carb intake. I also checked the head bolts they are tight as well.
MJD
* (or two, sometimes telescoping it can solve size problems)
03-24-2010, 06:03 PM
#9
RE: New magnum .15 wont shut off
The carb has an o-ring around the needle so it should not draw any air through there, unless it is damaged.
I have found another odd place for a leak thought, which I have never seen on any other engine.
Mine actually leaks between the liner and case!
If I take of the muffler and rotate the engine back and forth there is a very clear leak between the case and liner, sometimes bubbles but definitely oil being drawn back and forth. The liner does have an unusually sloppy fit in the case, when the head is off the liner just drops right out and there is wiggle room in there too. On a good engine one should normally have to push the liner out by using a wooden stick and the piston. It might be possible to seal this with a thin layer of JB weld on the outside of the liner but I have not tried that yet...
Such a leak cannot keep the engine running for a long time of coarse, but it is likely enough to prevent the engine from immediately shutting down when the barrel is closed.
By running full castor, the leak might also seal up a bit with time...
I have found another odd place for a leak thought, which I have never seen on any other engine.
Mine actually leaks between the liner and case!
If I take of the muffler and rotate the engine back and forth there is a very clear leak between the case and liner, sometimes bubbles but definitely oil being drawn back and forth. The liner does have an unusually sloppy fit in the case, when the head is off the liner just drops right out and there is wiggle room in there too. On a good engine one should normally have to push the liner out by using a wooden stick and the piston. It might be possible to seal this with a thin layer of JB weld on the outside of the liner but I have not tried that yet...
Such a leak cannot keep the engine running for a long time of coarse, but it is likely enough to prevent the engine from immediately shutting down when the barrel is closed.
By running full castor, the leak might also seal up a bit with time...
03-24-2010, 07:08 PM
#10
RE: New magnum .15 wont shut off
Well after supper I went out and ran this thing again and treated it like a regular two stroke and I found that when I spray between case and the thrust washer on the front of engine it shuts right down, the front bearing is leaking air sooooooo will they cover this under the warranty being it is only a month old or do they consider this normal?
03-24-2010, 07:57 PM
#12
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RE: New magnum .15 wont shut off
I found that Magnum was very accommodating. If you send it in for warranty repair they will likely send you back a new engine. However, there is a chance that the new engine will have the same problem or maybe even a worse problem.
If it runs reliably and holds a mixture setting then I would consider myself lucky and hold on to it. Keep an old towel in your flight box to stop it.
If it runs reliably and holds a mixture setting then I would consider myself lucky and hold on to it. Keep an old towel in your flight box to stop it.
03-24-2010, 09:43 PM
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RE: New magnum .15 wont shut off
My mag 25 also wouldnt shut off but I replaced the front being with a sealed one and no more drama. I know it doesnt fix the cause but it fixes the prob., Leave both seals intact and see how you go. Cheers the pope
03-25-2010, 09:21 AM
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RE: New magnum .15 wont shut off
Throw a rag into the prop. Or if it has a spinner take your hand, make a fist...and use the cup (indx finger and thumb) and snuff it out that way.
Or pull the fuel line off. Or plug the muffler with your thumb.
Or pull the fuel line off. Or plug the muffler with your thumb.
03-25-2010, 08:51 PM
#17
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RE: New magnum .15 wont shut off
With a new engine I doubt the gaskets will give you any trouble.
There are detailed step-by-step instructions for replacing bearings somewhere on RCUniverse. You may be able to find it with a search or maybe someone else will post a link. You will need to put the case in an oven to get the old bearings out and the new bearings in. When you install the new bearings you should only apply force to the edge of the outer race, not the inner race. Aside from a few tricks, bearing replacement is not difficult and only takes an hour or so.
I don't know if a puller is needed to get the thrust washer off your engine. On some engines the washer comes off by hand, other engines require a puller.
There are detailed step-by-step instructions for replacing bearings somewhere on RCUniverse. You may be able to find it with a search or maybe someone else will post a link. You will need to put the case in an oven to get the old bearings out and the new bearings in. When you install the new bearings you should only apply force to the edge of the outer race, not the inner race. Aside from a few tricks, bearing replacement is not difficult and only takes an hour or so.
I don't know if a puller is needed to get the thrust washer off your engine. On some engines the washer comes off by hand, other engines require a puller.
03-25-2010, 10:11 PM
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RE: New magnum .15 wont shut off
Someone alluded to this earlier. Run straight castor oil in your fuel. The added viscosity might be all it needs to seal up those air leaks. I've seen it happen before. Besides, your engine will love it.
Ed Cregger
Ed Cregger
03-26-2010, 08:55 AM
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RE: New magnum .15 wont shut off
ORIGINAL: JPMacG
With a new engine I doubt the gaskets will give you any trouble.
There are detailed step-by-step instructions for replacing bearings somewhere on RCUniverse. You may be able to find it with a search or maybe someone else will post a link. You will need to put the case in an oven to get the old bearings out and the new bearings in. When you install the new bearings you should only apply force to the edge of the outer race, not the inner race. Aside from a few tricks, bearing replacement is not difficult and only takes an hour or so.
I don't know if a puller is needed to get the thrust washer off your engine. On some engines the washer comes off by hand, other engines require a puller.
With a new engine I doubt the gaskets will give you any trouble.
There are detailed step-by-step instructions for replacing bearings somewhere on RCUniverse. You may be able to find it with a search or maybe someone else will post a link. You will need to put the case in an oven to get the old bearings out and the new bearings in. When you install the new bearings you should only apply force to the edge of the outer race, not the inner race. Aside from a few tricks, bearing replacement is not difficult and only takes an hour or so.
I don't know if a puller is needed to get the thrust washer off your engine. On some engines the washer comes off by hand, other engines require a puller.
Basically, the puller needs something to grab on to...and more often than not that "something" can go in the jaws of the vice. It's not like these things require huge torque to pop off.
03-26-2010, 09:05 AM
#21
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RE: New magnum .15 wont shut off
ORIGINAL: ArcticCatRider
Throw a rag into the prop. Or if it has a spinner take your hand, make a fist...and use the cup (indx finger and thumb) and snuff it out that way.
Or pull the fuel line off. Or plug the muffler with your thumb.
Throw a rag into the prop. Or if it has a spinner take your hand, make a fist...and use the cup (indx finger and thumb) and snuff it out that way.
Or pull the fuel line off. Or plug the muffler with your thumb.
03-26-2010, 09:15 AM
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RE: New magnum .15 wont shut off
At idle speed??? If the barrel's all the way closed the motor parts can't have a ton of "inertia"
This is a .15 we're talking about
This is a .15 we're talking about
03-26-2010, 11:51 PM
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RE: New magnum .15 wont shut off
ORIGINAL: fizzwater2
throwing a rag in the prop is a good way to break engine parts.. the sudden stop can be hard on things.
ORIGINAL: ArcticCatRider
Throw a rag into the prop. Or if it has a spinner take your hand, make a fist...and use the cup (indx finger and thumb) and snuff it out that way.
Or pull the fuel line off. Or plug the muffler with your thumb.
Throw a rag into the prop. Or if it has a spinner take your hand, make a fist...and use the cup (indx finger and thumb) and snuff it out that way.
Or pull the fuel line off. Or plug the muffler with your thumb.
I admit that it is not the best method, nor is it the first method that I would choose. On the otherhand, in over fifty years of running glow engines and having to stop them once in a while with a tossed rag, I have yet to break an engine part other than when the rag snags the needle valve, etc. Haven't even broken a prop. No, I don't recommend this method as ones first method, but there are times when a running engine must absolutely be stopped. In these cases, the rag works just fine.
Ed Cregger
03-29-2010, 03:47 PM
#25
RE: New magnum .15 wont shut off
I got a message that my bearing was shipped friday and I received it today, I think it took me longer to heat up the case to install the new bearing than assembling the rest of the engine. I also used some loctite 518 on the bearing to ensure a great seal put it all together and mounted it. I runs like it should now and shuts off, much easier to tune the top end also. I am very inpressed with Boca
Bearing they are in florida and Im in Minnesota and the us mail got my bearing here that fast. The only thing I noticed is on there site if you order a bearing kit which is two bearings it is much more money than if you order the bearings by themselves?!?![sm=confused.gif] anyway Thanks everyone for there input!!!! Twostroke
Bearing they are in florida and Im in Minnesota and the us mail got my bearing here that fast. The only thing I noticed is on there site if you order a bearing kit which is two bearings it is much more money than if you order the bearings by themselves?!?![sm=confused.gif] anyway Thanks everyone for there input!!!! Twostroke