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Offline Rusty

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« on: May 25, 2021, 06:07:13 PM »
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« Last Edit: March 10, 2022, 07:19:49 PM by Air Master »

Online Dan McEntee

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Re: #1: Restoring a RING version Supertigre
« Reply #1 on: May 25, 2021, 07:02:28 PM »
Hello Guys,

I have been using Supertigre engines for several decades.   I try to avoid the ring engines that don't have a chromed liner.  The reason is that the non chromed liners are soft and when they wear it is nearly impossible to restore compression.  (for me anyway)

In February I sold 8 used Supertigre GS 40s for $20.00 at our swap meet just because I can't restore them to normal compression.  The issue I found is the cylinders wear egg shaped and just using a brake hone or sandpaper does not straighten it, if it is worn good.

I have a Supertigre S61 that I want to restore, so I decided to take a different approach.  I took the cylinder to my friend's house and we put it in the lathe.   He started with 1/2 a thousandth cut to see what it looked like.  That revealed the wear pattern.  We took another 1 thousandth out and that did not remove the wear.  We ended taking another 1 thousandth out to get it to where a hone would clean it up.

I reassembled it using a new Supertigre factory ring.   ZERO compression.   HB~>

I decide to run the engine today to see if that would improve the compression.   The engine runs well, and after 12 oz of fuel, the compression has improved, but low.

I was wondering if any of you guys have restored any  engines with this type construction?   Are you able by some means to get normal compression?

    I have never done it, but I think you are looking at needing to machine hone the liner to get it round, then maybe having the liner chromed. That takes the minimum metal out and with chroming you have a better chance of getting it back to the OEM bore dimension. Cutting it in a lathe takes more that you may realize and you would actually need a over size piston and ring to get back to OEM performance, I think. At least some sort of over size ring. Does the engine sound any different? Like it has some sort of piston slap noise?? Just curious.

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    Dan McEntee
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Online Dan McEntee

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Re: #1: Restoring a RING version Supertigre
« Reply #2 on: May 25, 2021, 08:42:22 PM »
  Yeah, I know Tom would do different heat treating treatments to cylinders and rings also. It would be cool to learn those techniques but I don't know if Tom left any notes or instructions. I think he heat treated cylinders first if they were not round, as this shrunk the cylinder a fraction, and then honed them round afterwards.  And not all Super Tigre engines had chromed liners, even though it says "chromed" on all the crank cases. They ended that practice early on as time consuming and expensive. But to keep some "truth in advertising" I think they still chromed something on the cranks shaft, maybe the main bearing surface, so that they could keep the chrome designation on the engine. For the engine in question that you are working on, I think the answer is to replace cylinder liner, I'm afraid.
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Offline katana

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Re: #1: Restoring a RING version Supertigre
« Reply #3 on: May 26, 2021, 03:54:11 AM »
Having no model engine rebuild experience I can't fathom how you can expect a 'bored out' cylinder to work as well as an un-bored one with regard to compression! A ring or rings can only expand so much to seal and an excessive ring end gap is somewhere for compression to leak. A static 6:1 CR cold engine won't become a 12:1 CR hot engine and running induces wear, so it can't get better! You may not hear piston slap but it will be happening. Chroming is an option but too much or too little makes it a skilled operation to get the tolerances correct again + does the std. ring work with chrome, some don't. Has anyone tried Nickel plating or one of the Nikasil type processes used to hard plate aluminium cylinders in modern bike engines?

Offline bob whitney

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Re: #1: Restoring a RING version Supertigre
« Reply #4 on: May 26, 2021, 09:56:47 AM »
First ,by boring a sleeve on a lathe u loose any taper u had. 2nd, 1-2 thousands is too much for our size motors. the ring is made to be round at a certain diameter. it would probly be worn out by the time it wore into the cyl

Never/Never run a chromed ring in a chromed liner

did u take a 1/2 thous cut which would be 1 thous overall or just a 1/4 thous cut???

if u can come up with an over size piston and ring ,the proper thing to do is hone the sleeve on a Sunnen Break Hone and keep the taper .Rad
« Last Edit: May 26, 2021, 04:29:11 PM by bob whitney »
rad racer

Online Dan McEntee

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Re: #1: Restoring a RING version Supertigre
« Reply #5 on: May 26, 2021, 11:49:24 AM »
Dan, straight up, I'm asking you if you ever rode a Penton 125cc 6 day trials motorcycle.  Sachs engine, 6 speed tranny, green tank, sunburst cylinder and head.  1971 to 1973.
   
      Oh, most definitely! I had one as my third bike in high school, after a 90cc Kawasaki to start out with, then a '68 Penton Berkshire steel tanker with the square cylinder. Then I was looking at buying a then new Hodaka Wombat when I ran across an add for a '72 Penton 125 Six Days with a blue printed engine. I raced that in local enduros for a few years, then moved up to a '75 Husqvarna 250WR. Took a long break from dirt bikes and raced karts for a while. Then around the year 2000 I got the bike bug again and got my Husky back from the guy I traded it to for some kart equipment. It was in pieces but I had a lot of fun rebuilding it. I didn't restore it, it was still a pretty good original condition, so I just went through it mechanically. I started to collect and rebuild vintage enduro bikes at that time and the heard got to about 47. Mostly European bikes but a few Honda, Yamaha, and Hodaka thrown in here and there.  At one time, I had a running and riding example of of each size Penton motorcycle which were 100 Berkshire, 125 Six Day, 175 Jackpiner, 250 Harescrambler, and 400 Mint. I got lucky and rescued a '97 KTM EXC 200 Special Edition Jackpiner off of Craig's List. There were only 133 of those built for world wide distribution.   I started to sell off bikes as circumstances dictated and I'm down to a mild manored collection of 14 right now, including a '70 100 Berkshire, a '73 250 Hare Scrambler, a '75 250 Hare Scrambler, and a '75 Mint400. Still have a couple of Hodaka projects to finish in retirement also. In later years I would just trail ride, ride some vintage observed trials competitions, and race in some ISDT Reunion Ride vintage enduros. I probably out to be selling off the rest of them, as my knees aren't quite what they need to be, but I still want to do at least a little bit of riding while I still can. At the ISDT Reunion Rides, I was racing with guys well into their 70's and 80's and they were an inspiration!! A heck of a lot faster than you may think!!
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    Dan McEntee
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Online Dan McEntee

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Re: #1: Restoring a RING version Supertigre
« Reply #6 on: May 26, 2021, 06:09:11 PM »
Dan, straight up, I'm asking you if you ever rode a Penton 125cc 6 day trials motorcycle.  Sachs engine, 6 speed tranny, green tank, sunburst cylinder and head.  1971 to 1973.

   You asked that question very specifically, and it made me wonder if our paths had crossed in our younger days here in the Mid West.. The 125 Six Days I have had recently was a very, very low time survivor so I did not ride or race that, mainly used for display and for pit bike duty some times. That bike, my last Jackpiner, and the '97 KTM were used at the display to promote the John Penton full length feature film that made by Todd Huffman back in 2014, I think it was, at that years Super Cross races here in town. I sent pictures of all 5 Penton/KTM bikes to Jack Penton when he was looking for display bikes in each town, and he picked those three of mine. I was very honored at that!!
  Type at you later,
   Dan McEntee
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Offline Chris Wilson

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Re: #1: Restoring a RING version Supertigre
« Reply #7 on: May 26, 2021, 10:18:17 PM »
 Do model engines with rings even require a cylinder taper?
I would think that cold they do but when at run temperature the walls should expand to parallel.
Chris.
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Offline Steve Helmick

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Re: #1: Restoring a RING version Supertigre
« Reply #8 on: July 08, 2021, 03:35:21 PM »
As a retired machinist and once a pretty good manual lathe operator, I'd wonder how you had the cylinder setup when you bored it out? Last place I worked they had a lathe guy that thought soft jaws would keep thin walled cylinders round, and they didn't. Setup is everything...or pretty close to everything!  y1 Steve

Edit: Saw that you had a Yam MX 175. I still have one, a 1980, that I used almost entirely for chasing free flight models. I consider it to be excellent for that purpose, partly because it will go pretty fast in a safe manner, and partly because it doesn't have or need a battery. The last point is key when you only run it every 10 years or so!   
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In 1944 18-20 year old's stormed beaches, and parachuted behind enemy lines to almost certain death.  In 2015 18-20 year old's need safe zones so people don't hurt their feelings.


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