Going to install a true steel sleeve in DAX 70

[hot70cc]

Me and my buddy have been discussing about installing a steel sleeve in the cylinder, by doing some machine work to make this engine dependable for a long time. Stronger rings and piston. With no mysterious metal shavings appearing in the engine. He is a master journyman grinder at a factory where i work and it can be done. It won't cost me a dime. So i am going to go ahead and do it. He just wants the cylnder to start it. We are going to order the piston and rings before we do it to get the correct dimentions. Cross your fingers and i Will post pics when completed. hopefully no more scarred cylinder and no more destroyed pistons, and everlasting compression.

 

[andyinchville1]

Looking forward to hearing how it goes. Could be the beginning of a new era for durability...FWIW the bearings/bushings have also been a problematic area as well ;-)
Andrew

 

[hot70cc]

got my bearings at a small engine repair place Stihl,

 

[andyinchville1]

You Da Man!
Andrew

 

[OldPete]

Consider a cast iron sleeve over steel. Fit it to a counterbore at the top and shrink it inplace, then do the final bore cutting. Just my $0.02.

Cast sleeves should be avalible off the shelf.

 

[ChrisHill]

You may want to get a laser thermometer to keep an eye on your heat after your done and it's up and running. One of the reasons that the happy-times use an alloy cast cylinder (without a sleeve) is to better distribute heat. The sleeve will hold heat, and will likely cause you more problems with other things failing sooner...especially bearings, rings, pistons, con-rod, etc...stock or aftermarket parts are subject to failure from the heat that will be produced.

The idea of the sleeve is a good one, and has been tried and tested several times before but the end result was that it creates more problems then it cures.

I'm definitely interested in seeing how you make out with this. Please keep us all informed.

 

[Egor]

I like the steel or cast sleeve idea. You can cut the ports pry-er to dropping into the barrel. You will have to fit the piston carefully, as the materials will expand at a different rate. The steel sleeve will be harder to hone to size. I would look into using a piston from a Stihl saw engine. They use the 10mm wrist pin. If you chose to go with their piston you could make the deck height and the ports more effective. I used to sleeve Honda's, and you just have to get the interference correct. Cool down the sleeve and warm up the barrel if I remember it was about .003 interference. Have fun, Dave

PS: Have the Stihl dealer show you a cylinder to get an idea of some good ports. I have a piston from one at work I will try and get a pic of it up. Those German bearings will last forever.

 

[hot70cc]

Thanks all , my buddy already knows about the heat issue, I guess thats why he is a master journyman grinder lol, i wasn't sure until i asked him. He said something about cast wearing to easily from the heat, even though cast is better with the heat issue so he's doing steel. He said in the long run steel is the way to go for this engine type. Its no different than a steel sleeve for a pulling tractor with 3x the rpm's with a steel sleeve rather than an original sleeve. I'm just going with what he thinks is best. Any other opinions will be a help.

 

[OldPete]

Cast iron is much more porous than steel and retains a film of oil MUCH better.
Cooling might be an issue because the HT engines are not heavily finned.

 

[andyinchville1]

Are you planning on doing any porting work to the cylinder design?....Might be the perfect time while you're "in there" anyways.

Andrew