Topic: Minimum sleeve thickness

[dragracer]

Quick question, can anyone tell me the minimum allowable sleeve thickness in a big bore application?? I don't want to ruin a perfectly good cylinder because its been over bored to tin foil thin sleeves. I did a quick search here but didn't find a definite answer.

Thanks in advance. I'm just exploring some potential options for a new build.

[cbr954]

Kenny at cycle x told me not to go thinner than .075"  Mine would have been .055" with a bore to 72mm so I had to go with sleeves from dynoman as his would not have been thick enough.  I wish I would have measured the thickness before I put the motors together but I didn't.

[gschuld]

I am interested in the answer to that one as well.  I don't have the answer but I will measure and report back the thickness on my RC cast block at 73mm and RC factory cylinder at 70mm for reference.  That 70mm cylinder has LOTS of sleeve thickness, far more than the 73mm naturally.

FWIW, I think Jerry has 1.2mm thickness on his sleeves bored to 73.75 pistons. 

George

[Jerry Rxman Griffin aka MuthaF'er]

Correct, but I know less than you Frankie and most everyone else for that matter ;-). Mine was acquired this way and I have no background or knowledge. Sounds like a Big Jay kinda question!

[gschuld]

The RC cast cylinder at:                     73mm is 1.57mm or .062 inches.
The RC prepped factory cylinder at: 70mm is 2.98mm or .117 inches.

Both Sleeve sets are 3.000 inches O.D.

George

[dragracer]

Thanks for that info George. And Jerry, you know a helluva lot more about these engines than I do as far as details. I know just enough to get myself into trouble, but still maintain my bike to drag race it year after year. Don't short change yourself on the knowledge you do share.

[dragracer]

Big Jay, can you help me with an answer to this question? Or is anyone else willing to jump in with an answer.

[gschuld]

Again, nothing definitive.  But for reference, the consensus at RC Engineering back when wheels were square, was that up to 71mm was OK for street use, anything over that they considered race only.  They never seemed to stock 72mm pistons, but they did 70, 71, and 73s, and specifically recommended using their cast block for the 73mm bore.  The description for the 73mm sleeves still reads, RC sleeves to be installed in your cylinder.  So this presumes the factory cylinder.  And RC sleeves are just a shade over 1.5mm at 73mm bore in a factory cylinder.  Take that FWIW.

Using an RC cast cylinder should give more support for thinner sleeve walls, so this makes sense.

I looked through an Action Fours and an MTC catalog, neither made specific mention of minimal sleeve thickness.

The 1976 and 1978 RC catalogs had the same material below:

Hopefully, someone with actual real world experience can shed some light on this.

George.

[Big Jay]

I have always used .080" as the desired minimum. I have gone as low as .075" a few times.

[Jerry Rxman Griffin aka MuthaF'er]

Ouch, that would make mine like a hand grenade if the measurement of 1.2mm at the bottom is accurate all the up the sleeve.

Short lived but quick ;-)

 

[cbr954]

I just got a stroked motor with 73mm RC cast block, cylinder wall thickness averages .06" at the bottom of all 4 cylinders.

[joesmotos]

I was always told .080 thou was minimum(this from my days working at Star Racing and Cope Racing)

[754]

Jery , it depends if you are racing or riding on the street a bit.
 They may be necked down slightly at the bottom , so that less meat is carved out of the cases.

[754]

Anyone ever see a sleeve that let go during runnng..? Must start leaking a lot..?

[BPellerine]

I have a set of cyls where the sleeve pulled away from the top lip all the way around and pulled the sleeve downwards about 1/8 ins!!and that was only an 812.billp

[bear]

Blowing a head gasket is usually the flag for us.