DIY repinching (with pics)

[EvhCo]

My Kyosho ran excellent even with mildly low compression, but I had to try this. I used a hose clamp to shrink the sleeve, then heated it, and then cooled it with water.

Here is a pic of it with the clamp on.

This is the most I could push the piston inside the sleeve after repinching.

Has heaps lot compression (hell, I can even hold the car by the pullstart).
It was arguably risky, but extremely rewarding.

 

[Rolex]

What you might think is compression is most likely an out of round cylinder. By it's very design, a worm gear clamp can not exert even pressure.
Pinching is a precise process down to a few thousandths of an inch to a perfectly round shape.
If you can't push the piston by hand any farther than you show in that photo, you've damaged the cylinder.

 

[griff7373]

just out of curiosity have you ran it since you attempted this? The setup is flawed as it's not going to be completely round and will probably damage the connecting rod when you try and run it.

 

[EvhCo]

If you can't push the piston by hand any farther than you show in that photo, you've damaged the cylinder.

I can actually, it just needs more force to go through.

 

[EvhCo]

So I started the engine today. Fired right up and felt strong. I just need to fix the faulty fuel system and then I'll start the break in.

 

[cbaker65]

No doubt it can destroy the piston ,I did it once on a 28 with a hose clamp ,I just slightly tighten the clamp ,
it did work for about 3 runs ,so I tighten it even harder for the second time ,that time it destroyed the sleeve .

The clamp does not tighten perfectly in circle ,so it causes an egg shape!

 

[EvhCo]

So I put it on the car and fired it up. She was hauling ass, sure as hell. It sounded as usual and there was a fine line of smoke with a slightly rich tune.
At the same time, the fuel tank ruptured, my spur gear cracked and I realized I completely ran out of fuel.
Back to work, then.

 

[NinoS]

So I started the engine today. Fired right up and felt strong. I just need to fix the faulty fuel system and then I'll start the break in.

Thanks for posting about this, ill be trying this myself, mainly because with the cheaper engines i run, there is absolutely nothing to lose in trying it. Getting a pro repinch is not worth the price of the engine, no point in pouring money into it.

Sure the pressure will not be even, but if it works to get the engine back running for a bit longer then i'd call that a success.

I'm curious to see how it goes after the engine has warmed up fully. Can you restart it easily? What about the next day? That will say alot about whether this method can really squeeze some extra life out of a worn engine.

 

[EvhCo]

Thanks for posting about this, ill be trying this myself, mainly because with the cheaper engines i run, there is absolutely nothing to lose in trying it. Getting a pro repinch is not worth the price of the engine, no point in pouring money into it.

Sure the pressure will not be even, but if it works to get the engine back running for a bit longer then i'd call that a success.

I'm curious to see how it goes after the engine has warmed up fully. Can you restart it easily? What about the next day? That will say alot about whether this method can really squeeze some extra life out of a worn engine.

Engine preservation is an art, and the greater the artist, the greater the doubt. Doubt is what helps us preserve, in this case.

Poetry mode deactivated.

I let the engine sit for 2 days after the last time I ran it. I ran it 10 minutes ago, cold-started from around the 3rd pull, which is quicker than the usual 6-7 pulls required to cold-start before the repinching.
When the engine is warm, the fun begins. It restarts from literally the first pull, each and every time. I also noticed the RPM range is now larger. It can idle at lower RPM and rev up at noticeably higher speeds.
I almost hit the sweet spot, too. Just that the smoke is invisible (but plenty of it, I was literally choking after 5 minutes of idling in a small room), but I'll keep the tuning for after the break-in.
My engine wasn't worn before, but I wanted to see if I could bring it to factory-new condition. Out of this extensive 3-day testing, I can call it a great success.

Mind what cbaker65 said, though. The temptation to tighten it for even more compression is big, but I only tightened the clamp a tiny little bit, so it didn't turn into an egg. It takes 2 millimeters to make the difference between a powerful engine and a wrecked one.

If you do it, definitely post some pics.

 

[NinoS]

Thanks @EvhCo for the details and tips. I actually have the right size hoseclamps coming from Amazon, mainly because i would always forget to grab 'em at the auto parts store when there - if one of my nitro rc's was broken down, you can bet i wouldn't forget, but since these couple of worn out engines are just sitting with no chassis to put 'em in, there was no urgency...so finally when i recalled "oh yeah, i want to try that" I just ordered on amazon, interestingly the night before i saw your thread here, so great timing. I've looked at the proper pinching kits available, but couldn't find one guaranteed to be the right size or that i wanted to blow the cash on.

I'll post back here when i try it out, good to have a bit of a road map here for sure! Both the engines i have in mind would no longer start once they were fully warmed up, so essentially both are in fully "worn out" status, which will give a good comparison if I can actually get them running reliably.

 

[mrbones]

Evhco, this thread on pinching a cylinder with a hose clamp is almost as entertaining as the one you started on using peroxide as a booster.

 

[cbaker65]

They do sell a repinching tool!
Been watching this one for my 21's ,they sell different sizes ,been wanting to try it out for myself!...

https://www.ebay.com/itm/Piston-Sle...e=STRK:MEBIDX:IT&_trksid=p2060353.m1438.l2649

 

[mrbones]

Your entertainment is least important to me.
Thanks for posting!

What should be important to you is that you need to take into consideration that a lot of novice RC people come to this web site looking for good information and guidance in learning about how to run RC equipment and they don't need information such as pinching a cylinder with a hose clamp. Mr Rolex gave you a very good explanation of what needs to happen for a good pinch and all your procedure is going to do is destroy whats left of someone engine. You should not be posting anything that is going to result in being detrimental to anyone's equipment.

 

[EvhCo]

What should be important to you is that you need to take into consideration that a lot of novice RC people come to this web site looking for good information and guidance in learning about how to run RC equipment and they don't need information such as pinching a cylinder with a hose clamp. Mr Rolex gave you a very good explanation of what needs to happen for a good pinch and all your procedure is going to do is destroy whats left of someone engine. You should not be posting anything that is going to result in being detrimental to anyone's equipment.

If the first thing people do with their engine is try to repinch the cylinder because they saw a post on the internet, that is their problem, pal. Matter of fact, I'm not the first to try, and I'm not the first to succeed.

They do sell a repinching tool!
Been watching this one for my 21's ,they sell different sizes ,been wanting to try it out for myself!...



https://www.ebay.com/itm/Piston-Sleeve-Pincher-Hobao-Ofna-Hyper-21-4p-8p-Race/380361593576?ssPageName=STRK:MEBIDX:IT&_trksid=p2060353.m1438.l2649

That's awesome! Might try it for the completely worn Tamiya I'm buying.

 

[mrbones]

If the first thing people do with their engine is try to repinch the cylinder because they saw a post on the internet, that is their problem, pal. Matter of fact, I'm not the first to try, and I'm not the first to succeed.

I'm pretty sure that the only thing that you have posted on this site that you were successful at was tooting your own horn! So far you get 100% fail on being able to validate success in cylinder pinching and for using peroxide as a booster (which is obviously a dead subject that you realized you might as well drop!). What's next Pal? You know, you told me that the remaining water in the peroxide blend would make steam, maybe you can figure out a way to convert a nitro into a steam engine.

 

[NinoS]

So far so good on the .15 after trying this out. After reassembly the pinch has a nice pop to it. One of these days i'll either set up a test bench to try it out or grab a roller to put it in and see what happens.

Due to the preceding poop storm, sounds like it will be good one to post a video on, whether this engine remains a paperweight or not.

 

[EvhCo]

I'm pretty sure that the only thing that you have posted on this site that you were successful at was tooting your own horn! So far you get 100% fail on being able to validate success in cylinder pinching and for using peroxide as a booster (which is obviously a dead subject that you realized you might as well drop!). What's next Pal? You know, you told me that the remaining water in the peroxide blend would make steam, maybe you can figure out a way to convert a nitro into a steam engine.

I don't need to prove anything to you. Guys like NinoS have recently tried repinching and may soon confirm if it worked or not.
As for the peroxide, I, once again, brought up a topic that has been debated on another forum. I thought it would be interesting.
I'm not here to try and revolutionize the nitro engines. If you fail to understand that, fine, we don't have to be friends, and I'm not here to argue. If I offended you in any way, I am deeply and sincerely sorry. Can we drop it?

So far so good on the .15 after trying this out. After reassembly the pinch has a nice pop to it. One of these days i'll either set up a test bench to try it out or grab a roller to put it in and see what happens.

Due to the preceding poop storm, sounds like it will be good one to post a video on, whether this engine remains a paperweight or not.

Can't wait for the results. I'll try and post a video of my repinch, too. I will soon finish the break in, and if everything goes well, this technique definitely saved me some hefty bucks.

 

[mrbones]

I don't need to prove anything to you. Guys like NinoS have recently tried repinching and may soon confirm if it worked or not.
As for the peroxide, I, once again, brought up a topic that has been debated on another forum. I thought it would be interesting.
I'm not here to try and revolutionize the nitro engines. If you fail to understand that, fine, we don't have to be friends, and I'm not here to argue. If I offended you in any way, I am deeply and sincerely sorry. Can we drop it?



Can't wait for the results. I'll try and post a video of my repinch, too. I will soon finish the break in, and if everything goes well, this technique definitely saved me some hefty bucks.

Yeah I didn't agree with our discussion that we had concerning combustion. I will drop it. Sorry.

 

[cbaker65]

Theres nothing wrong with experimenting with old worn out engines!

I have several worn out engines out in the shed ,they been out there for 10 years ,they are nothing
but paper weights! I also have several engines sitting new in a box that I'm not using yet!

I've been involved in RC's for 20 years ,I built some an destroyed some ,An I enjoyed doing so ,it
was a good learning experience.

You can not enjoy something that lays up in a box or sits on a shelf ,that's no fun ,
you will enjoy it better if you toss it up in the air an use it for target practice!....

 

[NinoS]

^^^ what he said

I've ordered manifold, pipe, and fuel tank from the far east to set up a little test bench...will come in handy with or without hose clamp experiments, at least thats how i justify the $15.

I have a feeling ill get impatient on the shipping and do some disassembly of my running fleet to try it out first though.