Tower .75 won't stop ??
10-29-2006, 03:12 PM
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Tower .75 won't stop ??
Hello
I just finished the break in on the .75 and when I try to kill the motor by closing throtal it will run on for a while at a very low idle. I fully seated carb and have a good seal on o-ring. I also checked back plate where o-ring seals it, it looked liked as if the o-ring wasn't sealing good so I put some RTV sealant to make sure.
I still have the run on so where else might air be coming in ? The engine seems to run well other wise. I have two .46's and a .61 that don't have this problem.
Thanks
Frank
I just finished the break in on the .75 and when I try to kill the motor by closing throtal it will run on for a while at a very low idle. I fully seated carb and have a good seal on o-ring. I also checked back plate where o-ring seals it, it looked liked as if the o-ring wasn't sealing good so I put some RTV sealant to make sure.
I still have the run on so where else might air be coming in ? The engine seems to run well other wise. I have two .46's and a .61 that don't have this problem.
Thanks
Frank
10-29-2006, 03:34 PM
#2
RE: Tower .75 won't stop ??
Before you start changing a bunch of things, I would wait and fly it for a while. My experience with several Chinese made engines, although not the Tower .75, is that they need a fairly long run in before their mid range comes around and they start shutting down. I normally find that it takes 15-20 tanks of fuel for the engine to really run well. The top end will run well, but the mid and low end will be chancy depending on how tight the engine was.
I have seen people get totally frustated trying to get a perfect adjustment after a break-in consisting of 2 or 3 tanks. As I mentioned, I don't have a Tower .75, but I do have many .46-.52 size engines, as well as 3 .91s, all Chinese, and they have all gotten around to running well. My Tower .46 was like that, as other engines that size. The .91s, which are on the same size case as the .75, all took a gallon or more of fuel to fully break-in.
I have seen people get totally frustated trying to get a perfect adjustment after a break-in consisting of 2 or 3 tanks. As I mentioned, I don't have a Tower .75, but I do have many .46-.52 size engines, as well as 3 .91s, all Chinese, and they have all gotten around to running well. My Tower .46 was like that, as other engines that size. The .91s, which are on the same size case as the .75, all took a gallon or more of fuel to fully break-in.
10-29-2006, 04:20 PM
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RE: Tower .75 won't stop ??
Hello Ed
thanks for the reply
yes I heard that about these engines. I have about 7-8 tanks threw it. It's running pretty well at idle, midrange and top end, it transistions pretty well. I guess I will give it more time as you say. It's just weird how it keeps runnig even with my finger blocking the card.
Thanks
Frank
thanks for the reply
yes I heard that about these engines. I have about 7-8 tanks threw it. It's running pretty well at idle, midrange and top end, it transistions pretty well. I guess I will give it more time as you say. It's just weird how it keeps runnig even with my finger blocking the card.
Thanks
Frank
10-29-2006, 05:11 PM
#4
RE: Tower .75 won't stop ??
Some of those carbs are so tight in the mount, that you have to clamp them down tight
then tighten the cinch bolt. If it is still running with your finger over the carb, there is
a chance it is still leaking air there, even though you think it is sealing.
FBD. [sm=regular_smile.gif]
then tighten the cinch bolt. If it is still running with your finger over the carb, there is
a chance it is still leaking air there, even though you think it is sealing.
FBD. [sm=regular_smile.gif]
10-29-2006, 05:22 PM
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RE: Tower .75 won't stop ??
ORIGINAL: Flyboy Dave
Some of those carbs are so tight in the mount, that you have to clamp them down tight
then tighten the cinch bolt. If it is still running with your finger over the carb, there is
a chance it is still leaking air there, even though you think it is sealing.
FBD. [sm=regular_smile.gif]
Some of those carbs are so tight in the mount, that you have to clamp them down tight
then tighten the cinch bolt. If it is still running with your finger over the carb, there is
a chance it is still leaking air there, even though you think it is sealing.
FBD. [sm=regular_smile.gif]
I checked that, I took off oring, the carb sealing surface touched engine case. When I put on carb with o-ring I pushed carb down with wood block to it was fully seated.
Is there anyplace else it could be pulling in air?
thanks
Frank
10-29-2006, 05:57 PM
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RE: Tower .75 won't stop ??
ORIGINAL: fc911c
Is there anyplace else it could be pulling in air?
Is there anyplace else it could be pulling in air?
10-29-2006, 06:10 PM
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RE: Tower .75 won't stop ??
ORIGINAL: Zombie
You might check the o rings on both needles, if you haven't already done so. If you have the remote High end needle, check the washer under the nut that's on the opposite side of the carb from the low end needle.
ORIGINAL: fc911c
Is there anyplace else it could be pulling in air?
Is there anyplace else it could be pulling in air?
Haven't done that, I was thinking of switching carbs with my .61, I think the problem might be with the carb itself as you suggested.
thanks
Frank
10-29-2006, 06:12 PM
#8
RE: Tower .75 won't stop ??
Yes, it could be pulling air in from the front bearing....you might have to live with it,
or...put a sealed bearing in the front....if that is the case. [
]Loosen the headbolts using a cross pattern, and tighten them back down using a
cross pattern....just to eliminate a head, or liner leak.
FBD. [sm=regular_smile.gif]
10-29-2006, 06:29 PM
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RE: Tower .75 won't stop ??
ORIGINAL: Flyboy Dave
Yes, it could be pulling air in from the front bearing....you might have to live with it,
or...put a sealed bearing in the front....if that is the case. []
Loosen the headbolts using a cross pattern, and tighten them back down using a
cross pattern....just to eliminate a head, or liner leak.
FBD. [sm=regular_smile.gif]
Yes, it could be pulling air in from the front bearing....you might have to live with it,
or...put a sealed bearing in the front....if that is the case. [
]Loosen the headbolts using a cross pattern, and tighten them back down using a
cross pattern....just to eliminate a head, or liner leak.
FBD. [sm=regular_smile.gif]
Frank
10-29-2006, 06:34 PM
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RE: Tower .75 won't stop ??
ORIGINAL: rainedave
Frank, did your engine come with all these red washers? This is a brand new Tower .61, but the .75 should have these seals as well. If your engine doesn't have these, I'd try to Tower to send you a set.
Frank, did your engine come with all these red washers? This is a brand new Tower .61, but the .75 should have these seals as well. If your engine doesn't have these, I'd try to Tower to send you a set.
yes I have those I think. I will check for sure.
Thanks
10-29-2006, 08:08 PM
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RE: Tower .75 won't stop ??
ORIGINAL: Flyboy Dave
Yes, it could be pulling air in from the front bearing....you might have to live with it,
or...put a sealed bearing in the front....if that is the case. []
Loosen the headbolts using a cross pattern, and tighten them back down using a
cross pattern....just to eliminate a head, or liner leak.
FBD. [sm=regular_smile.gif]
Yes, it could be pulling air in from the front bearing....you might have to live with it,
or...put a sealed bearing in the front....if that is the case. [
]Loosen the headbolts using a cross pattern, and tighten them back down using a
cross pattern....just to eliminate a head, or liner leak.
FBD. [sm=regular_smile.gif]
--------------
IF it is pulling air around the front bearing, the crankcase bore is out of spec and it is a warranty issue. Ball bearings do not determine the fit around the crankshaft and the permissable leakage level. The crankcase bore does this each and every time.
If none of the carb sealing tricks work and the backplate isn't leaking, it is time to return the engine for warranty repair with a note of explanation.
Ed Cregger
10-29-2006, 08:29 PM
#13
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RE: Tower .75 won't stop ??
I understand there is a weep hole (?) between the crankcase and the front bearing. I've heard that sometimes this hole, if oversized, can cause the problem.
All I can say is good luck. I had a similar problem with a Magnum 46XLS that would not shut off. After trying everything I had it replaced under warranty. The replacement wouldn't shut off either. I've learned to live with it.
All I can say is good luck. I had a similar problem with a Magnum 46XLS that would not shut off. After trying everything I had it replaced under warranty. The replacement wouldn't shut off either. I've learned to live with it.
10-29-2006, 08:36 PM
#14
RE: Tower .75 won't stop ??
My .75 has ten gallons through it this summer and feels like new, and has never dead sticked once. It is the most reliable engine I have ever owned. It starts with a two finger snap of the spinner and does not miss a beat.
But mine too has a 900-1,000 rpm diesleling thing going on once in a while too even when the barrel is closed, but it does not bother me one bit.
My back cover and carb throat were sealed with silocone since day one. I would use another .75 in a heart beat if I had a application for it. In fact another club member just bought one after watching mine scream all summer. I cannot even count how many compliments I had this summer at all the different flyins I attended about how that engine pulls the plane.
I have more comfidence in the this engine than any I have ever owned.
I have seen every thing from OS's (yes OS's) Saito's, ZDZ's, 3W's land dead stick this summer, but that cheap TH.75 never miss's a beat, and really screams to boot.
But mine too has a 900-1,000 rpm diesleling thing going on once in a while too even when the barrel is closed, but it does not bother me one bit.
My back cover and carb throat were sealed with silocone since day one. I would use another .75 in a heart beat if I had a application for it. In fact another club member just bought one after watching mine scream all summer. I cannot even count how many compliments I had this summer at all the different flyins I attended about how that engine pulls the plane.
I have more comfidence in the this engine than any I have ever owned.
I have seen every thing from OS's (yes OS's) Saito's, ZDZ's, 3W's land dead stick this summer, but that cheap TH.75 never miss's a beat, and really screams to boot.
10-29-2006, 10:06 PM
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RE: Tower .75 won't stop ??
I've seen this time after time about GMS engines won't die. As quoted there are ways to fix them. But why? I've never seen a plane crash because the engine runs. I've got five GMSs. None of them die at idle. Wouldn't change that for anything. I've had the brands that died. Planes died with them.
10-29-2006, 10:25 PM
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RE: Tower .75 won't stop ??
ORIGINAL: A1
I've seen this time after time about GMS engines won't die. As quoted there are ways to fix them. But why? I've never seen a plane crash because the engine runs. I've got five GMSs. None of them die at idle. Wouldn't change that for anything. I've had the brands that died. Planes died with them.
I've seen this time after time about GMS engines won't die. As quoted there are ways to fix them. But why? I've never seen a plane crash because the engine runs. I've got five GMSs. None of them die at idle. Wouldn't change that for anything. I've had the brands that died. Planes died with them.
yes I agree, it would be worse not being able to hold an Idle.
Frank
10-29-2006, 10:33 PM
#17
RE: Tower .75 won't stop ??
I don't think it has anything to do with the design of the engine. My Tower .61 cuts off when I close the throttle all the way without hesitation. As far as I know, the bore and stroke are the only actual differences between these two engines. If that's true, then it must be due to variations in parts fit, i.e., a QC issue. Either that, or something is not assembled correctly, which I doubt, because Frank has checked just about everything. Maybe try replacing the length of fuel tubing that runs from the remote NV to the carb?
10-30-2006, 05:59 AM
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RE: Tower .75 won't stop ??
Although I don't have a .75,I do have 3 Tower .46 and one does the same as your .75. The other 2 are as reliable as the day is long with many flights on them. I did the break in as instructions and the motor is perfect except I can't shut it off. I brought it to the field to have our club "motor guy" take a look and he could get it either. After a morning of trying to resolve it, he told me to leave it be a fly it. It will idle flawles for a whole tank if I leave it and transition to full power without skipping a beat. I looped the fuel line up a little higher and slid one of those fuel line clamps over it. When I bring the plane in I throw the throttle kill and it slows down below idle, then I come form behind and clamp the fuel. It shuts down in seconds after that. I have been running it this way for a year and it still runs great!
I say fly it and enjoy it, you'll love it,
Peter
I say fly it and enjoy it, you'll love it,
Peter
10-30-2006, 06:13 AM
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RE: Tower .75 won't stop ??
ORIGINAL: pcinc
Although I don't have a .75,I do have 3 Tower .46 and one does the same as your .75. The other 2 are as reliable as the day is long with many flights on them. I did the break in as instructions and the motor is perfect except I can't shut it off. I brought it to the field to have our club "motor guy" take a look and he could get it either. After a morning of trying to resolve it, he told me to leave it be a fly it. It will idle flawles for a whole tank if I leave it and transition to full power without skipping a beat. I looped the fuel line up a little higher and slid one of those fuel line clamps over it. When I bring the plane in I throw the throttle kill and it slows down below idle, then I come form behind and clamp the fuel. It shuts down in seconds after that. I have been running it this way for a year and it still runs great!
I say fly it and enjoy it, you'll love it,
Peter
Although I don't have a .75,I do have 3 Tower .46 and one does the same as your .75. The other 2 are as reliable as the day is long with many flights on them. I did the break in as instructions and the motor is perfect except I can't shut it off. I brought it to the field to have our club "motor guy" take a look and he could get it either. After a morning of trying to resolve it, he told me to leave it be a fly it. It will idle flawles for a whole tank if I leave it and transition to full power without skipping a beat. I looped the fuel line up a little higher and slid one of those fuel line clamps over it. When I bring the plane in I throw the throttle kill and it slows down below idle, then I come form behind and clamp the fuel. It shuts down in seconds after that. I have been running it this way for a year and it still runs great!
I say fly it and enjoy it, you'll love it,
Peter
Thanks, sounds like the thing to do.
Frank
10-30-2006, 10:18 AM
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RE: Tower .75 won't stop ??
Frank, you have one heck of an engine here and it sould like you have checked it over pretty well. I think I know the cause of your problem. The idle stop screw is set too long.
My 75 had the idle screw set to long and the carb barrel wouldn't rotate closed enough. One word of caution here, use Locktite on this little screw or it can vibrate out. I bet if you adjust the idle limiting screw you will see this problem go away.
My 75 had the idle screw set to long and the carb barrel wouldn't rotate closed enough. One word of caution here, use Locktite on this little screw or it can vibrate out. I bet if you adjust the idle limiting screw you will see this problem go away.
10-30-2006, 11:00 AM
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RE: Tower .75 won't stop ??
ORIGINAL: buzzingb
Frank, you have one heck of an engine here and it sould like you have checked it over pretty well. I think I know the cause of your problem. The idle stop screw is set too long.
My 75 had the idle screw set to long and the carb barrel wouldn't rotate closed enough. One word of caution here, use Locktite on this little screw or it can vibrate out. I bet if you adjust the idle limiting screw you will see this problem go away.
Frank, you have one heck of an engine here and it sould like you have checked it over pretty well. I think I know the cause of your problem. The idle stop screw is set too long.
My 75 had the idle screw set to long and the carb barrel wouldn't rotate closed enough. One word of caution here, use Locktite on this little screw or it can vibrate out. I bet if you adjust the idle limiting screw you will see this problem go away.
I did look into that because it did seem that the barrel was barley closing so did as you say but it didnt work, even when I place my finger over carb and seal it , it keeps running.
thanks
Frank
10-30-2006, 11:26 AM
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RE: Tower .75 won't stop ??
ORIGINAL: rainedave
Maybe someone would be willing to move their NV to the carb and try it out. It would at least eliminate or isolate the remote NV as a cause or not.
Maybe someone would be willing to move their NV to the carb and try it out. It would at least eliminate or isolate the remote NV as a cause or not.
thanks
Frank
10-30-2006, 02:55 PM
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RE: Tower .75 won't stop ??
ORIGINAL: JPMacG
I understand there is a weep hole (?) between the crankcase and the front bearing. I've heard that sometimes this hole, if oversized, can cause the problem.
All I can say is good luck. I had a similar problem with a Magnum 46XLS that would not shut off. After trying everything I had it replaced under warranty. The replacement wouldn't shut off either. I've learned to live with it.
I understand there is a weep hole (?) between the crankcase and the front bearing. I've heard that sometimes this hole, if oversized, can cause the problem.
All I can say is good luck. I had a similar problem with a Magnum 46XLS that would not shut off. After trying everything I had it replaced under warranty. The replacement wouldn't shut off either. I've learned to live with it.
----------------
Not shutting off with the throttle barrel fully closed was not considered a defect for many, many years. Like you said, you just learned to live with it. There were several engines, very popular ones, that were made in the past that had this affliction, but darned if I can remember them at the moment.
Plugging the vent, putting your finger over the carb (sometimes), or pulling the fuel line was quite common with such engines. I used to grab the spinner (very carefully) and stop them that way. I no longer recommend that strategy. No, I never got bitten from doing that, but that was just pure luck.
Lots of engines have a spiral groove ground in the crankshaft. That was put there to pump escaping oil back into the crankcase. Sometimes, if this spiral comes back too far, this will cause the engine not to stop even when your finger is plugging the carb intake hole.
Engines that do not have this groove, but are still experiencing not stopping at barrel closure can have a worn crankcase crankshaft bore.
I'm not saying that things cannot be influenced by using sealed bearings once a situation exists. I am saying that I don't know of any manufacturer that is relying on sealed bearings to seal this area of a TWO-STROKE engine. Of course, the world changes and there are lots of things that I do not know. <G>
Ed Cregger
10-30-2006, 03:07 PM
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RE: Tower .75 won't stop ??
ORIGINAL: Ed Cregger
----------------
Great post Thanks
Frank
Not shutting off with the throttle barrel fully closed was not considered a defect for many, many years. Like you said, you just learned to live with it. There were several engines, very popular ones, that were made in the past that had this affliction, but darned if I can remember them at the moment.
Plugging the vent, putting your finger over the carb (sometimes), or pulling the fuel line was quite common with such engines. I used to grab the spinner (very carefully) and stop them that way. I no longer recommend that strategy. No, I never got bitten from doing that, but that was just pure luck.
Lots of engines have a spiral groove ground in the crankshaft. That was put there to pump escaping oil back into the crankcase. Sometimes, if this spiral comes back too far, this will cause the engine not to stop even when your finger is plugging the carb intake hole.
Engines that do not have this groove, but are still experiencing not stopping at barrel closure can have a worn crankcase crankshaft bore.
I'm not saying that things cannot be influenced by using sealed bearings once a situation exists. I am saying that I don't know of any manufacturer that is relying on sealed bearings to seal this area of a TWO-STROKE engine. Of course, the world changes and there are lots of things that I do not know. <G>
Ed Cregger
ORIGINAL: JPMacG
I understand there is a weep hole (?) between the crankcase and the front bearing. I've heard that sometimes this hole, if oversized, can cause the problem.
All I can say is good luck. I had a similar problem with a Magnum 46XLS that would not shut off. After trying everything I had it replaced under warranty. The replacement wouldn't shut off either. I've learned to live with it.
I understand there is a weep hole (?) between the crankcase and the front bearing. I've heard that sometimes this hole, if oversized, can cause the problem.
All I can say is good luck. I had a similar problem with a Magnum 46XLS that would not shut off. After trying everything I had it replaced under warranty. The replacement wouldn't shut off either. I've learned to live with it.
----------------
Great post Thanks
Frank
Not shutting off with the throttle barrel fully closed was not considered a defect for many, many years. Like you said, you just learned to live with it. There were several engines, very popular ones, that were made in the past that had this affliction, but darned if I can remember them at the moment.
Plugging the vent, putting your finger over the carb (sometimes), or pulling the fuel line was quite common with such engines. I used to grab the spinner (very carefully) and stop them that way. I no longer recommend that strategy. No, I never got bitten from doing that, but that was just pure luck.
Lots of engines have a spiral groove ground in the crankshaft. That was put there to pump escaping oil back into the crankcase. Sometimes, if this spiral comes back too far, this will cause the engine not to stop even when your finger is plugging the carb intake hole.
Engines that do not have this groove, but are still experiencing not stopping at barrel closure can have a worn crankcase crankshaft bore.
I'm not saying that things cannot be influenced by using sealed bearings once a situation exists. I am saying that I don't know of any manufacturer that is relying on sealed bearings to seal this area of a TWO-STROKE engine. Of course, the world changes and there are lots of things that I do not know. <G>
Ed Cregger