Max oversize on R60/2 cylinder bore

[schrader7032]

Related to my friend's refurb of his R60/2, what is the maximum oversize that one can reasonably expect to get away with? My Clymers shows the standard bore is 72mm and each oversize is 0.5mm. The book table only lists two oversizes. We were able to measure the bore reasonably well at the engine-side of the cylinder and measured pretty much 73mm...just using a simple micrometer. To be honest, I'm not sure if that's the best place to measure that...aren't the cylinders tapered as you get close to the skirt? He indicated he is aware that some engine work was done prior to his ownership...not sure of the extent. I don't believe the bike has that many miles on it...I don't recall at this point.

[wa1nca]

Related to my friend's refurb of his R60/2, what is the maximum oversize that one can reasonably expect to get away with? My Clymers shows the standard bore is 72mm and each oversize is 0.5mm. The book table only lists two oversizes. We were able to measure the bore reasonably well at the engine-side of the cylinder and measured pretty much 73mm...just using a simple micrometer. To be honest, I'm not sure if that's the best place to measure that...aren't the cylinders tapered as you get close to the skirt? He indicated he is aware that some engine work was done prior to his ownership...not sure of the extent. I don't believe the bike has that many miles on it...I don't recall at this point.


Bench Mark and Salis both have 73.5mm and also up to 74mm
Salis $154.00 x 2=308.00 plus 40.00 shipping
Bench Mark 199.00 x 2= 398.00 plus shipping

As you allready know Bench Mark is a liitle higher here but their tech support is worth it wait in gold

Did you get that BMZ rotor off

Tommy

[schrader7032]

I don't believe that the rotor has been pulled. Not sure he has a puller, although if I read right in the other thread that Joel provided a puller with his kits. This MZB kit was purchased more than 10 years ago and I think Joel was still involved.

My friend is probably focusing on getting the heads/cylinders/headers off first. We had discussed an approach to rotate the engine about the front engine mount to such an angle that the transmission could be pulled off and out. Then we would man-handle the case out of the frame. He has already received the shipping box from Vech so he's headed to getting the case into that box for shipping back. I'm just providing help when needed. I've at least done this once before when I did this on my R69S, so at least there is some experience with this process...albeit limited!

[ahistand]

Maybe in the old days when the manuals were written they only offered two oversizes. But now up to 74mm is available from all the usual suppliers as Tommy said so you got another mm to go.
The cylinders are not bored on a taper. The pistons are a little bigger at the skirt than at the ring area, but not the cylinders. To assess weather or not to bore the cylinders for the next oversize pistons, more accurate and multiple measurements will need to be taken with a bore gauge, or at the least a set of T-gauges and a micrometer.

[schrader7032]

We were just trying to get a general sense of where the cylinder might be. He's going to send the engine in the crate and the top end parts separately...Vech will decide what needs to be done.

[Jim D 5112]

If you measure the bore at the bottom of the cylinder below where the rings ran it will give you the size of the bore before any wear. Measuring it at the top just below where the rings ran will show the amount of wear in the cylinder. The difference between the two is the amount of wear. The taper in the cylinder is from wear. I once had a preunit Triumph that was drag raced hard and long. The cylinder would take a set of rings .020 bigger at the top than what the original bore was. You could feel the wear with you fingers. It also had a egg shaped crank on the rod journals.

[schrader7032]

One website documents a clutch change on a /2 that was done in something like 90 minutes. They tilted the rear of the engine up around the front engine mount. When I pulled the engine on my R69S, I was operating alone so I did the same thing. This shows basically what I was doing. I used the scissors jack from my car to carefully support and raise the rear of the engine. Seemed to work OK.

[wa1nca]

I don't believe that the rotor has been pulled. Not sure he has a puller, although if I read right in the other thread that Joel provided a puller with his kits. This MZB kit was purchased more than 10 years ago and I think Joel was still involved.

My friend is probably focusing on getting the heads/cylinders/headers off first. We had discussed an approach to rotate the engine about the front engine mount to such an angle that the transmission could be pulled off and out. Then we would man-handle the case out of the frame. He has already received the shipping box from Vech so he's headed to getting the case into that box for shipping back. I'm just providing help when needed. I've at least done this once before when I did this on my R69S, so at least there is some experience with this process...albeit limited!

I removed the front engine bolt loosened the rear then tilted front of the engine down and then remove the great box
Guess it may also work if you removed the rear engine bolt then also tilted front down to remove the gear box ??

Tommy
Kurt
I was wrong the rear gets removed as shown in you pic
PLEASE DELETE MY RESPONE
Tommy

[wa1nca]

Thanks for the pic Kurt
I tried this and was so easy
did not need any help

Installed the engine 1st with only front engine bolt
Added flywheel and torqued then added clutch assy and torqued
Then added transmission and lowered complete and installed rear engine bolt

Wish I knew this years ago

Tommy

[Daves79x]

You might have to do some more juggling - the shifter bolt is in upside down and cannot be changed with everything bolted in place. It will hit the exhaust pipe.

Dave