NEW CYLINDERS for R100/7

[dougjordan]

I have 78 R100/7 in need of new jugs. Has anybody put on Nikasil ? Any speical maching needed ? If this can be done what year bike should the cylinder and piston come from ?

[lostboy]

The latest cylinders from BMW (since about 1988) have a ridge at the bottom of the cylinder to match a counterbore in the case. You'll need to have this ridge turned on a lathe or hand cut a relief in the case. I've done this with a die grinder and a carbide burr. The ideal choice of piston would be one with the flat squish band, but many R100s are being run with the tapered sqish band without any problems.

[Polarbear]

How many times have you bored the old ones? They last nearly forever and can take afew bores. Mine is on its first oversize piston and 345000 miles, still in spec.:). I did the 1st over at 104000 and now at 345k, whats up with this? They have a long life! I have met only a few with more miles than me. Randy

[dougjordan]

How many times have you bored the old ones? They last nearly forever and can take afew bores. Mine is on its first oversize piston and 345000 miles, still in spec.:). I did the 1st over at 104000 and now at 345k, whats up with this? They have a long life! I have met only a few with more miles than me. Randy

The problem being oil consumption...from day 1. Has been bored 1 time , rings never seated after 30000 miles. So this time bore was in spec so with a cross hatch and new rings I put it together. After 1000 miles and rideing like I slole it, oil consumption is still hight. Heads have been done. Pulled the plugs and could see a fare amount of oil around the edge of the pistons . Rings were new but...the end gap was on the high side of tolerance.

[krehmkej]

I have been helping a friend with his 1979 R100 project, and it most assuredly did not have the Nikasil jugs. I had always heard they were phased in beginning in about 1981.

[lkchris]

BMW changed to Nikasil cylinders on the /7 with the introduction of the 70hp variant.

Nikasil cylinders arrived with the 1981 models. Not before.

[mymindsok]

After checking into the prices for a bore and new pistons and then looking around for used Niks, I bit the bullet and bought new jugs and pistons. The pistons come complete with rings pins and clips.

I'm putting them on my R-90 so they'll be getting the lathe treatment but I'm thrilled to know that I'll never be repalcing any of that stuff again! :nyah

[47512]

I don't know what new cylinders and pistions cost for a BMW, But this is what I have done many times on motorcycle engines with aluminum cylinders, this incudes BMW's, BSA's, most japanese and others. I bore out the iron liner and replace it with one made from aluminum pipe generaly 6061 and have it plated with nickasil. This way you can run standard pistons, and cast iron rings and tighter clearence than with iron bores. Total seal makes 3 piece oil rings to fit older BMW's, some sets have a 2 piece scraper or compression rings, these rings have much better oil control than the standard old fashoned oil ring.

I have a friend that races a R75/6 in AHRMA events and this set up has worked great for him with no issues. I'll bet this is less expensive than new cylinders and pistons. I have made liners for old motorcycles that cylinders or over size pistons are no longer available, Standard pistons are easyer to find because over size are what are what people are looking for. I am not soliciting business as there are businesses that do this process, like Bore Tech. Just food for thought

Ken G.