Is my cylinder toast? need help...

[20774]

Any chance those R100 cylinders were post '81 with Nikasil coating on them? That might be why there was this type of reaction. If that's the case, then the cylinders are probably toast. There may be companies who can reapply the Nikasil coating....might be expensive.

[Polarbear]

You couild hone 'em yourself and see, but! A likely bore job is worthwhile with new pistons. I did this to first oversize on my R100/7 years ago. Nice improvement too. That year BMW was the end of the iron lungs and '79 brought the new non bore type ones, nikasil. You can switch over, buying new style but why? The older ones are quite servicable and I think you need the bore job. My last bore at 104000m, first over pistons and now at 380000m, same ones still pumping great ,all in iron sleeves. About 270000+m on a piston job is amazing to me....Randy

[AntonLargiader]

Wow. Toast. Might be interesting for a future repair, but certainly not usable. The other one looks OK?

[20774]

I did this to first oversize on my R100/7 years ago.

Randy -

Did you weigh in on the other thread re: going 1st over on the R100 pistons? Most that I've read about doing that is that it doesn't last, walls are too thin, it's unstable. You might be the poster child for actually doing this and it working!!

[Stan_R80/7]

I would get a cylinder hone - several auto parts stores loan them out - and see if the area etched can be honed out. If not, you have your answer. It doesn't look good from the photo's, but that area may hone right out. Good luck!

[BimmerCrab]

Wow. Toast. Might be interesting for a future repair, but certainly not usable. The other one looks OK?

The other one is perfect, with spot-on clearance specs.

[BimmerCrab]

I would get a cylinder hone - several auto parts stores loan them out - and see if the area etched can be honed out. If not, you have your answer. It doesn't look good from the photo's, but that area may hone right out. Good luck!

Just eyeballing it...it's deep enough to go to the next oversize.

Problem with boring it further...on closer inspection it seems these are 900 cylinders, bored out to 1000. So the iron sleeve is already pretty thin. These cylinders have a "9" stamped on them near the "KS" stamp. 900 heads, and pistons with 93.97 stamped on top.

There is a set of 900s on Ebay right now. I could buy those and have them bored to match my nice pistons. Thoughts?

OR...I could buy a matched set of Nikasil 1000s with pistons (two sets on ebay) and have the spigot machined down to 97mm so they'll fit in my case.

WWYD?

[GeorgeRyals]

Take the cylinders to a machine shop that does motorcycle cylinders. If they say .5 mm will clean them up, then buy a set of first over pistons. Take the pistons to the shop so they can fit the cylinders to them.

[8ninety8]

900 cylinders can be bored twice. I would never bore a 900 cylinder out to a 1000 without first taking advantage of the the first two over bores, IMHO, if you can find a used set of 900'rds.

A 900 goes almost like a 1000, and for all practical purposes, will git you on down the road like nothing else that is over 37 years old. IMHO.

[BimmerCrab]

900 cylinders can be bored twice. I would never bore a 900 cylinder out to a 1000 without first taking advantage of the the first two over bores, IMHO, if you can find a used set of 900'rds.

I'm considering two options. First, used 900s, and bore them to first-over with new pistons.

Cylinders - ~$275
Pistons ~$360
Machine work ~300

Or - get a used set of R100 Galnikal cylinders with pistons. Machine the spigot to 97mm

Cyl+pistons ~$450
Machine work ~150

The latter seems like a better option, unless I'm missing something.

[barryg]

If your going with nikasil cylinders your going to have to pull the engine to bore out the cylinder spigot. Just something else to think about.

[20774]

If your going with nikasil cylinders your going to have to pull the engine to bore out the cylinder spigot. Just something else to think about.

Or turn the cylinder base from 99 to 97...plus some other relief that's needed...

[BimmerCrab]

Or turn the cylinder base from 99 to 97...plus some other relief that's needed...

Does anyone have direct experience with having that done? Cost, for example...?

[BimmerCrab]

I found out that putting the newer R100 cylinders on my motor won't work without using R100 heads. And that is way to expensive and complicated.

I was referred to a machine shop by Dave Gardner and they can put a sleeve in my damaged cylinder and bore it to fit my piston for only $225. So I'm going with that solution. Simple and affordable.

[rstrauss]

Did you ever figure out what caused that damage to begin with? I found local engine shops know metal, and know what most marks and issues are. I'd just like to know how it happened to begin with.

I'm the guy with the piston thing on the other thread. Spent some time looking at options, but that was an R100.

Just out of curiosity, isn't that part of the cylinder that doesn't get touched, and doesn't really matter? Or does the piston skirt hit there? Is it actually going to cause issues? I'm just wondering if you could get a light hone and new rings (what I'm doing, cost: $130 for new rings, honing is probably $20 a jug) and call it good. But I'm asking if that is an option, not saying that is an option.