Bored out R11

shreddr · shreddr's Garage

I have found a few threads on this topic here, but nothing that answers my question. I know SJBMW makes the 1150 kit for the R11 that gets you 50cc for $1500 plus labor. My question? Is it necessary to buy the cylinders to do a bore increase, and if not is it necessary to use the 101mm pistons? Bottom line, can you use a larger diameter custom piston, and bore out the stock cylinders and get a true 1200cc motor? I have machinist friends who can do the bore job for nothing, and I can probably break the topends down, so the total cost to me would be pistons, rings, wrist pins and gaskets. Any thoughts?

AndrewA · 05-04-2007, 06:09 PM

You would at least loose the Nikasil cylinder lining.

R111S · R111S's Garage

Maybe you could insert a new liner?

Chris Canning · 05-04-2007, 10:58 PM

Have spent some time thinking about a big bore kit,there are 3 suppliers that i've managed to find,it's a grey area to say the least,plenty of opinions,but not to many people actually done it.
What you suggest maybe possible providing you can get someone to recoat the cylinders,and can find pistons that will work,without to much exspensive R+D,but certainley a risk that may end up costing a lot more than you hoped to save.

captainasty · 05-04-2007, 11:40 PM

The difference on the cylinders is that the kits have been turned down to fit the cases. The way BMW gets the '1200' is to change the bore & stroke. I have a 1200 crank to do just that. Find some used 1150cc cylinders and clean them up. Have your friend turn the OD on the lower section to fit the cases.

VetteRacer · 05-05-2007, 08:40 AM

Heres a quick question on the whole bigger CC idea..
Will a the R1200 motor, from the R1200C not the new R1200, fit into the R1100S frame? I am guessing the heads/cams could be swapped over, and pistons changed to a higher compression...
Is that a feasible way to do the big bore and stroke our bikes to get more power?
OR
Can the old 1200 crank be fit into the R1100S motors?

captainasty · 05-05-2007, 09:19 AM

Yes, either way. BUT the pistons in the R12C are cast and not forged. The trick is to get R1150RS pistons. Those are the larger bore (101mm) and forged at the higher compression.

captainasty · 05-05-2007, 09:20 AM

I have both ways here at my shop. Just more time d#@nit.

roger albert · 05-05-2007, 09:28 AM

I'd ditto all captainnasty said.

Don't even think about just boring.
Losing the lining would give you and engine life of a couple hundred miles, maybe, if you baby'd it. Then you'd need a new crank and top end too.

A liner makes no sense here. Poor thermally, and no room for it in any event.

Mod'd factory jugs are indeed the way to go, and maybe a stroked crank. But if you think the Ss vibe now...

VetteRacer · 05-05-2007, 10:05 AM

Quote:

Originally posted by roger albert
and maybe a stroked crank. But if you think the Ss vibe now...

It only vibrates around idle RPMs... Who stays in that range anyways?

Captain, look forward to hearing the final results of your tinkering.

roger albert · 05-05-2007, 10:22 AM

Wait til you ride stroker or heavier piston'd S.
I'm pretty sure you'll feel the vibes well above idle.
But if you like that kind of thing ...

VetteRacer · 05-05-2007, 10:31 AM

Roger, If I ever get the opportunity I will take one for a spin.

Any pictures of your R90 Cafe? I miss my R90/6

Chris Canning · 05-05-2007, 10:39 AM

Quote:

Originally posted by roger albert
Wait til you ride stroker or heavier piston'd S.
I'm pretty sure you'll feel the vibes well above idle.
But if you like that kind of thing ...

So if you have Roger,what was it like??,i haven't but i'd be interested to hear from someone who has.

roger albert · 10:58 AM

Done it on a solid-bar mount conversion big-bored RS.
Wasn't for me. Low power increase, moderate vibe increase.
Works for some better than for me. I'm at the limit of tolerance on a stock S. For you tough guys, it could be cool. At this point, I'd grab a bone stock 12S if I were looking for power gains. Much cheaper, and it leaves a roadmap for more in the future.
But if you realize it's mostly for fun, and you just like twiddling with what you have, and can handle vibes, then more power to you.

I filled in on a raceteam last weekend and road a bored and stroked mini that was basically a 50% displacement increase, but with, near as I could tell, stock crank throws. Even on a tiny motor, it was a lot to deal with on an endurance race. OK for sprints, but not my choice for endurance.

Vettracer, one of my R90/6s is for sale. You know you _need_ it. No, not the cafe, Just the 'regular' one (still chock full of upgrades)

And sorry, but I couldnt' find any cafe/6 photos. I'll have to look some more. Been wanting to put it on the web.

Chris Canning · 05-05-2007, 02:00 PM

Buying a 12S wouldn't be cheap for me!!!,telling my wife the horsepower was better and persuading her the thing that passes off as a pillion seat is ok,she may me be a little crazy putting up with me,but she ain't crazy!!!

Hence,when the 1200 came out,gave it a quick sideways glance,shrugged my shoulders, and carried on modding my S.

David · David's Garage

Just have the cylinders bored and recoated: http://www.langcourt.com/

JonyRR · 05-30-2007, 09:05 AM

all this is doable.
the question, is it worth it.
a poster here, joe, from back east, was supposed to be building a 'true' 1200 R259 engine, with a 1200C crank, 1136CC cylinders and I think using 1100S rods and custgom pistons.
I think a careful balance job would help.
I alos think headwork will be in order here.
the real question here is WHAT gains are to be had here.I was gonna do all this govno at one time, but you know what? It ain't worth it. Just ride it until it crumbles

and add some nitro