I have a few question on pinching sleeves. Why would you want to pinch a sleeve tighter then a new sleeve would be? I would think that too tight of a pinch would wear out the piston faster then if the sleeve was lightly pinched for compression. As for the break in sheets, I can't think of one motor manufacture that recommends heating the block with a torch, hair dryer, or a heat gun. I would think that if you had to go to all this trouble just to get it to turn over with a recoil to start it, you have already wore out a new con rod before the wheels even touch the ground. Can you imagine the stress on the con rod breaking in an over pinched sleeve? You all have to remember, these little/big motors run on compression not how tight the pinch is. The pinch is only there to seal the very top of the compression stroke. The oil content begins to build the compression just above the intake port. At this point the piston has to have very close tolerences. Not tight but snug enough to make a seal. The above is just my 2 cents worth.
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questions about piston sleeve resizing on all .12 through .28 engines
- Thread starter osrocket1
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Widdy, I do not know if anyone is pinching new engines but I can tell you that I got mine pinched after it had lost most of it's compression. I did use a hair dryer to heat it up but only to make using the pullstarter easier. I was able to pull it wihtout heating it but it was not easy.
Buncrana said:
I think Widdy was talking about the reference stating that when it's re-pinched, it's tighter than the engine was when it was new. Not to pinch an already new piston/sleeve.
Sorry if anyone mis read me. Olds is correct. I'm not talking about pinching a new motor. I just don't understand why anyone would pinch a sleeve to the point where its too hard to start with either a recoil or a box. There is no need for a tighter pinch then what comes with a new sleeve. It just seems to me a tighter pinch puts more stress on the con rod and piston then needs to be. As i stated above all the pinch does is seal the compression stroke at the very top of the stroke. It has nothing to do with building compression. Compression starts to build just above the ports. That area is where the tolerences are crucial. Minimal drag but enough to allow for the fuel to seal the space between the piston and sleeve to allow it to compress and then at the top where the pinch is, is to seal for detination. Granted the tighter the pinch the better seal, but, i don't think tighter is better in this case. If the motor manufactures wanted or thought that the sleeve needs to be tighter then they are making them, wouldn't they be doing it? I'm all for repinching a sleeve, i'm just not sure about a tighter pinch then what would be called normal or to manufactures specs.
I'm not trying to dis anyone here, its just my thoughts on this subject.
I'm not trying to dis anyone here, its just my thoughts on this subject.
widdy, we try to pinch them as close to the way they were when new, and in some cases they are a little tighter, but that is also true when you buy brand new engines alot of guys will testify that they have purchased the same engine for a backup and they cannot believe the difference in the way the new one feels compared to the one they already have, and if in case they are matched up there is probably a tolerance that they are able to hold,
i think that i will open up 5 sets of new ones as soon as i get some time and see exactly how much difference there is on them,(i am sure that some guys are also curious) i hope that helps, and i do agree that a overtight engine is hard on the conrod, but its also good to check the rod out closely because if a engine is in need of a pinch after several gallones the rod may also need attention, thanks for asking, jb
i think that i will open up 5 sets of new ones as soon as i get some time and see exactly how much difference there is on them,(i am sure that some guys are also curious) i hope that helps, and i do agree that a overtight engine is hard on the conrod, but its also good to check the rod out closely because if a engine is in need of a pinch after several gallones the rod may also need attention, thanks for asking, jb
ZANDOR
RCTalk VIP
I will back that up with three of us had the same mill.
1 of them would stop a ofna crome top starter box dead.As the other two would work just fine. So that showes there is a difference between the same mill from the same maker.
On the pinch.. And I will back that up.
1 of them would stop a ofna crome top starter box dead.As the other two would work just fine. So that showes there is a difference between the same mill from the same maker.
On the pinch.. And I will back that up.
"widdy, we try to pinch them as close to the way they were when new, and in some cases they are a little tighter, but that is also true when you buy brand new engines alot of guys will testify that they have purchased the same engine for a backup and they cannot believe the difference in the way the new one feels compared to the one they already have,"
OS as i have stated in my posts, I'm not here to dis anyone. I'm just trying to clarify the reason for a tight pinch. The above quote has me a little baffled. Anyone can by the same engine and i'm sure the pinchs are not the same. But, i'm almost sure they don't say to heat the motor for breaking it in.
As for the con rod, I have had sleeves pinched maybe as tight if not a little looser as a brand new sleeve, and still have ran the same con rod. I do agree that the con should be checked. Now, just my opinion here, if the sleeve is tighter then it should be i would think it would cost a person more money in the long run. one con rod for break in and one for run time. I just can't seem to understand the reason for a tighter sleeve pinch, and have to endure all the trouble just to get it to turn over. JMHO
OS as i have stated in my posts, I'm not here to dis anyone. I'm just trying to clarify the reason for a tight pinch. The above quote has me a little baffled. Anyone can by the same engine and i'm sure the pinchs are not the same. But, i'm almost sure they don't say to heat the motor for breaking it in.
As for the con rod, I have had sleeves pinched maybe as tight if not a little looser as a brand new sleeve, and still have ran the same con rod. I do agree that the con should be checked. Now, just my opinion here, if the sleeve is tighter then it should be i would think it would cost a person more money in the long run. one con rod for break in and one for run time. I just can't seem to understand the reason for a tighter sleeve pinch, and have to endure all the trouble just to get it to turn over. JMHO
widdy, you are right they shouldn't be tighter than a new one that is on the snug side, i just think that even with a brand new engine it is much easier on the lower end of the rod if you heat the block up, especially if the starter box is not one of the stronger ones, our winter indoor track is cold in the pits and guys still use something to preheat the block just to help it start easier, even on engines that have never been resized, again i am just trying to help answer questions, any and all are welcome i hope that this helps because alot of guys are not as experienced as others with the engines, and thanks for your input. jb
OS, Thank You for confirming that the "on the SNUG side" engine requiring heat to turn over on the box or with a recoil is too tight. Out of all the engines that i have bought new, i don't ever recall having to heat or use a drill to start. Should I ever buy a new engine that requires a drill motor to turn over, I now know It will be shipped back to the manufacturer. I would consider a motor that a good starter box or to have a drill used to turn it over a manufactures flaw. Thanks for responding to my posts.
.21Rc10GT
Hardcore RCTalk User
I think the higher end engines have really tight pinch. My sirio .27r was super tight and i heated it up to start. I know the collari's are pretty tight as well, tight enough to snap pull start cords... The ofna .27 is also a tight engine... i think it just depends on the manufacturer...
Sure thing Buncrana,
I own a dirt oval track that, oh i'd say maybe 15 - 20 of us run AE GT's with a mixture of motors. For example we have some that run the stock AE 15, OS 15 CV and CV R, 12 CV and CV R and a few Fantoms. We don't race under a lap counter. We do it for the fun of it.
I do own a pinching machine that I use for pinching the guys sleeves.I don't do it for a business or for the money. Our "group" just likes to save $$where we can. We have no problem running pinched sleeves.
I have learned that a tight pinch kills a piston and sleeve in the long run. I've played with different pinchs from light to tight. Say what you like but what i have learned is this, the light to medium pinch at the top with a very light pinch just above the ports will make these engines last for 4-6 gallons. You see the compression stroke starts just above the ports. The fuel and oil mixture starts to seal the compression and the pinch holds the compression for the combustion. Also I have learned that better sealing just above the ports with a minimal drag and a light pinch makes a faster motor. Less drag on the piston and sleeve makes more RPMS. Now before you jump up and down, i have used only the engines that i have listed above, and the fuel milage and life of the motor depends on the person that tunes the motor. Some like to have a screaming motor where others like it a little rich. Rich seems to make the car a little slower but make the motor last longer. Screaming seems to wear out the piston faster. We have run sleeves that have been pinched 2-3 times and changed the con rod maybe once. After that we throw the motor away due to the fact that by the time you replace bearings, crank, and a new P&S, you can buy a whole new motor. I guess you could label us budget racers.
I could be wrong about the bigger motors like the .27's. I have never owned one. But, as big as they are i'm quite sure that they do have a tighter pinch. But not to the point where you have to use a drill motor as one person here stated he had to use just to turn it over with out a GP in it.
My findings and opinions are mine and in no way i'm I trying to offend anyone. I'm just learning as much as i can about different motors. I do appreciate all the info that has been posted. But what really impresses me is the respectable way that it has been done
.
I own a dirt oval track that, oh i'd say maybe 15 - 20 of us run AE GT's with a mixture of motors. For example we have some that run the stock AE 15, OS 15 CV and CV R, 12 CV and CV R and a few Fantoms. We don't race under a lap counter. We do it for the fun of it.
I do own a pinching machine that I use for pinching the guys sleeves.I don't do it for a business or for the money. Our "group" just likes to save $$where we can. We have no problem running pinched sleeves.
I have learned that a tight pinch kills a piston and sleeve in the long run. I've played with different pinchs from light to tight. Say what you like but what i have learned is this, the light to medium pinch at the top with a very light pinch just above the ports will make these engines last for 4-6 gallons. You see the compression stroke starts just above the ports. The fuel and oil mixture starts to seal the compression and the pinch holds the compression for the combustion. Also I have learned that better sealing just above the ports with a minimal drag and a light pinch makes a faster motor. Less drag on the piston and sleeve makes more RPMS. Now before you jump up and down, i have used only the engines that i have listed above, and the fuel milage and life of the motor depends on the person that tunes the motor. Some like to have a screaming motor where others like it a little rich. Rich seems to make the car a little slower but make the motor last longer. Screaming seems to wear out the piston faster. We have run sleeves that have been pinched 2-3 times and changed the con rod maybe once. After that we throw the motor away due to the fact that by the time you replace bearings, crank, and a new P&S, you can buy a whole new motor. I guess you could label us budget racers.
I could be wrong about the bigger motors like the .27's. I have never owned one. But, as big as they are i'm quite sure that they do have a tighter pinch. But not to the point where you have to use a drill motor as one person here stated he had to use just to turn it over with out a GP in it.
My findings and opinions are mine and in no way i'm I trying to offend anyone. I'm just learning as much as i can about different motors. I do appreciate all the info that has been posted. But what really impresses me is the respectable way that it has been done
.jc2stroke2
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ah finaly I'm needing a pinch on a force .26 force .25 can i get prices to do this do i send the hole engine or just the sleeve I'm thinking a pinch will be best for me cause i dont wanna spend a fortune on new mill right now send info to [email protected]
But he does have a website now: http://www.osrocketracing.com/
Found it in my subscription to Xtreme RC last month. He's started making engine heads now too.
Besides, it's $20 for one shipped regardless of brand. Although, you might want to email him to make sure he can do those engines: [email protected]
Found it in my subscription to Xtreme RC last month. He's started making engine heads now too.
Besides, it's $20 for one shipped regardless of brand. Although, you might want to email him to make sure he can do those engines: [email protected]
