Cylinder Sleeve and Head questions.

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Scra99tch

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Looking to see if anyone has come into a rebuild with a similar setup. The picture below is of my 1954 TWN (German Triumph) Super Tessy Moped engine. When I got the bike it had been sitting since the mid 90's in a barn and was fully frozen. I tried about 3 months of heating and soaking to get the piston out. But in the meantime buggered up the sleeve as the piston was not budging.

I am currently remaking the sleeve and wanted to know what a good clearance is needed between the recessed bore in the head to the sleeve protrusion shown in picture. When the sleeve is in the cylinder it protrudes above the gasket surface into the head. I have it currently at spec. from what I pulled from the engine. which has about a .006" difference from counterbore in head to OD of sleeve protrusion. Should I close that up more or keep it as is?


Bike is 150cc bore is about 58mm. I have the OD of the sleeve machined and am fairly heavy on the ID of the sleeve. Thinking I'll see what I can get away with for any increase in bore diameter.

Would there be any benefit to having a machine shop give the combustion chamber more of a dome shape and fit a custom piston with a tad higher compression?
tessy sleeve.jpg
 
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I just realized I had another question awhile ago about the Sleeve itself should have combined both threads sorry.
 
Is that an oilcan in the picture? Never seen one of those
 
Yeah, nice little unit still being made forget the make but I believe it was mentioned on here someplace.

Here it is.

www.hahn-kolb.de

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Nozzle fits nicely into the taiwan lathe oil dimples.
 
Scra99tch said:
Looking to see if anyone has come into a rebuild with a similar setup. The picture below is of my 1954 TWN (German Triumph) Super Tessy Moped engine. When I got the bike it had been sitting since the mid 90's in a barn and was fully frozen. I tried about 3 months of heating and soaking to get the piston out. But in the meantime buggered up the sleeve as the piston was not budging.

I am currently remaking the sleeve and wanted to know what a good clearance is needed between the recessed bore in the head to the sleeve protrusion shown in picture. When the sleeve is in the cylinder it protrudes above the gasket surface into the head. I have it currently at spec. from what I pulled from the engine. which has about a .006" difference from counterbore in head to OD of sleeve protrusion. Should I close that up more or keep it as is?


Bike is 150cc bore is about 58mm. I have the OD of the sleeve machined and am fairly heavy on the ID of the sleeve. Thinking I'll see what I can get away with for any increase in bore diameter.

Would there be any benefit to having a machine shop give the combustion chamber more of a dome shape and fit a custom piston with a tad higher compression?
View attachment 486788
Click to expand...
Wish I could help, Bet that bike is worth a pretty penny restored. I’m sure some of the automotive machinists will be along with some answers soon
 
Scra99tch said:
Looking to see if anyone has come into a rebuild with a similar setup. The picture below is of my 1954 TWN (German Triumph) Super Tessy Moped engine. When I got the bike it had been sitting since the mid 90's in a barn and was fully frozen. I tried about 3 months of heating and soaking to get the piston out. But in the meantime buggered up the sleeve as the piston was not budging.

I am currently remaking the sleeve and wanted to know what a good clearance is needed between the recessed bore in the head to the sleeve protrusion shown in picture. When the sleeve is in the cylinder it protrudes above the gasket surface into the head. I have it currently at spec. from what I pulled from the engine. which has about a .006" difference from counterbore in head to OD of sleeve protrusion. Should I close that up more or keep it as is?


Bike is 150cc bore is about 58mm. I have the OD of the sleeve machined and am fairly heavy on the ID of the sleeve. Thinking I'll see what I can get away with for any increase in bore diameter.

Would there be any benefit to having a machine shop give the combustion chamber more of a dome shape and fit a custom piston with a tad higher compression?
View attachment 486788
Click to expand...
My background is racing kart engines but I'll take a crack at this....

I'm assuming you have some sort of blank cast iron sleeve you are transferring the port dimensions from the old one. If that's what you're doing I would keep everything as close to stock as possible. While you might be able to squeeze more HP by modifying the head or ports, or by adding custom parts, without taking the whole engine into account you may run into trouble.

I'm also guessing you have sourced a stock piston to run and hopefully it's a standard bore or no more than .010 over. Changing the combustion chamber or the piston could also give you issues since without a known modification to follow you'll be guessing on what shape it should be. There's no guarantee it would make more power, and if it does will your bottom end hold up? Last thing you want to do is break a conrod or crank.

I also can't think of a good reason to change the top of the cylinder liner, it must have been done that way for a reason and changing it would also just be a guessing game. Best bet will be a conservative build and maybe even install a rev limiter to keep from pushing it too hard (assuming you're not planning on going racing with this scooter.

If you want a more detailed and thoughtful response try checking with the vintage snowmobile guys, you probably have some of them around where you are.

John
 
Thanks just by looking at the carbon build up around the ports it seems to me that there was some sort of leakage past this interface. I’ll make sure to run as close to stock as possible. Meaning same thickness head gasket. And grinding the ports correctly as they were. Even though from factory looks a bit jacked up.

Here is the sleeve which I bought as raw stock from LA Sleeve.
 

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Scra99tch said:
Thanks just by looking at the carbon build up around the ports it seems to me that there was some sort of leakage past this interface. I’ll make sure to run as close to stock as possible. Meaning same thickness head gasket. And grinding the ports correctly as they were. Even though from factory looks a bit jacked up.

Here is the sleeve which I bought as raw stock from LA Sleeve.
Click to expand...
I’m not saying it can’t be improved, just that without knowing how there’s no guarantee of not making it worse.

I used to have a book all about Italian (mainly) two stroke design theory with lots of examples. They were mostly going on trial and error although there are some definite calculations that can be done especially around expansion chambers.

On our race motors very significant changes can be made not just with jetting but also with header length before the expansion chamber. For a street application a compromise is needed to have something that will idle and run good at full throttle.

Before trying any mods from stock I’d want to have a complete spare motor on hand just in case something really bad happened.

John
 
The sleeve to head clearance of .006 you mentioned should also be left unchanged. That space should allow the engine to reach operating temp without issue. I wouldn't rush to raise compression, it could become a hard starter and it will affect the port tuning. John's right, it could be for the better, it could be for the worse, and your best bet is to leave it alone unless you have good information to follow. 2-strokes are sensitive little buggers.
 
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