Why no steel sleeves?

[Zombie]

Why dont some of you like steel-sleeved engines? I read some posts calling a CR a "steel-sleeved queen". I think a sleeve makes perfect sense, as its boreable and you dont have to send your cylinder away for replating. Ive sleeved all my bikes except for a 91 YZ 125, and Ive never had any trouble at all. So, whassup wit dat?

-Z

[Paul]

The tolerances are much tighter on a non-sleeved engine. The piston and the cylinder are made of the same material - aluminum. They expand at the same rate so your tighter tolerances yield morepower for a longer period of time with a higher rate of reliability. I desert race and my CR500 - with its iron-sleeve - deserved the title "iron sleeved sieze queen". Not to say I haven't blown a non-sleeved engine up, just haven't done it as often

[Rick]

I had one motor sleeved several years ago (an RM125, yuk), and it was a dismal failure.  Power was poor, and the bike just never performed again.  Also, with the work that RPM does on cylinder repairs/refinishing at low cost, an unsleeved cylinder can last for a long time.  

I will NEVER run a sleeved motor again.  Just not worth the tradeoff.

Rick

[Hogwylde]

I've also heard that since the heat transfer rate of the steel sleeve is different than the aluminum, that sleeved engines run hotter too.  
One thing that does happen when you sleeve.....Any porting work you may have had done in the past will be shot to hell.  Ports don't come in at 90 degree's to the cylinder, they come UP at an angle.  When you bore the cylinder, the ports will be lowered and the new sleeve will have stock port locations that will need matched to the cylinder.

Besides, when there are companies out there that can re-plate your cylinder back to stock dimensions with materials that are better than what they were originally plated with and allow tighter clearances, why wouldn't you replate instead of sleeve?  There isn't THAT much difference in the price.

[crazyryan]

I bought my 99' KX5 with a plated cylinder. It had been redone once since new by the first owner. I bought a 540 kit and had that sleeve ported. The new sleeve wasn't plated and worked great. I have three and a half thousandths tolerance. I say steel sleeve is better if built right.

[Paul]

I bought my 99' KX5 with a plated cylinder. It had been redone once since new by the first owner. I bought a 540 kit and had that sleeve ported. The new sleeve wasn't plated and worked great. I have three and a half thousandths tolerance. I say steel sleeve is better if built right.

I won't argue the point - I'm no engineer - but I think the guys that design these bikes (modern 2 and 4 strokes) have a reason for not using sleeves in any of them.

[doordie]

Guys,
you have plus and minus, whatever if you use sleeves or plated cylinders.
Trust me I have both!

//doordie

[GDubb]

I think Paul just made a very good point.  Maybe on a drag bike that you will rebuild often anyways, an iron sleeved, tight tolerance engine makes just as much sense... but as far as reliability in the practical world for those of us who want a bike that will last an entire season with hours upon hours of ride time on each outing... I'll vote for technology and hi-tech coatings.

[KXcam22]

Back in the old days (1976) my KX125's came with chrome plating which quickly chipped away. The fix was a steel resleeve but all the bikes were a lot slower afterwards. I never did figure out why.  I think the real difference is with friction and heat transfer. The plating has less friction than the steel liner and since the aluminum is right below, it conducts heat away far more efficiently.  This allows tighter clearances to be used.  As doordie said, there are pluses and minuses to both.  Nowadays there are more quality shops available who can re-plate which is a bonus.  I think both are good systems.  Dirtbike engineers have been shaving ounces on each new model for years.  Since the plating performs as well or better than steel liners, I think its likely that dirt bikes have mostly migrated to plated cylinders to save the weight of the steel liner. Cam.