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Can I fit an 1150 engine in my 1100?


bobsdog

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Hi,

I am new to this forum, but not new to the superb world of BMW motorcycles. I truly believe that I found the best all round motorcycle the day I test rode a R1100RT.

Anyway My R1100RT is getting a little tired in the engine room. I have an immaculate engine and transmission from a 2003 R1150. My question is;

Can the 1150 engine be fitted into the 1100.

If so, can you retain the original gear box (transmission) or do you have to fit the complete power plant.

Has anyone done this conversion? What problems did they encounter?

I would be really gratefull for any info or help.

Thanks.

Martin. (in the UK)

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They are not interchangeable. The engine to tran. mount points are different. And them together as a system would pose be even greater difficulties as all the drive train to the rear is different. To say nothing about different engine management system, electronics, fuel injection, etc...

 

While anything is possible, I certainly wouldn't 'go there.'

 

Oh, and welcome to the board!

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Yes, so near, yet so far. As Ken said... fuhgetaboutit.

 

How many miles do you have on your bike? The oilhead engines last just about forever. If you are experiencing performance issues the cure is probably much simpler than any internal engine work.

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mikefigielski

Actually Martin, the 1150 engine itself(without trans) could be bolted up to the old 1100 bike as the engine trans mounting is the same on both bikes. I have verified this on a project bike I am building. Trying to put the whole 1150 engine/6 speed combo in an 1100 bike would not work since the trans case to rear subframe mounting is different. If you were to put the 1150 motor in your 1100 bike and used the 1100 throttlebodies/injectors and Motronic/wireharness it will work, no problem. The only potential issue will be which clutch pack to use. I have not got to that part of my project yet and I am not sure if it would matter. hope this helps.

Mike

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mikefigielski

After looking at it more closely and doing some quick measurements, it appears that you would need to use the entire 1100 clutch pack including the toothed starter wheel (clutch housing).

Mike

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Many many thanks to all for your replies.This forum is superb. So many BMW owners out there. Really appreiciate the effort you guys put in to help. My engine is not 'shot' The bike is still great to ride. Some of my riding buddies have said that my engine is breathing a bit when they follow me. (which is nearly always) I have a late (2002) tuned up engine and complete transmission etc etc just sitting in my Garage. I have all the motoronic unit throttle bodies etc etc etc as well. The bike that this lot came from really flew. The engine sounds awesome.

So if the gear box will mate to the 1150 engine, so long as I change the clutch/flywheel assy, this job could be possible.

Will keep you informed of my progress.

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If you were to put the 1150 motor in your 1100 bike and used the 1100 throttlebodies/injectors and Motronic/wireharness it will work, no problem.
The 1100 and 1150 ECUs are mapped the same?
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mikefigielski

No, the ECUs are different. What I am saying is to use everything from the 1100 and just put the 1150 bare engine in there. Basically it would be the same as putting a big bore 1150 kit in your 1100 which I have done and it works well. The 1150 and 1100 short block are basically identical except for the displacement. Using the wire harness and fuels inj system from the 1100 just simplifies the swap.

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Hi Mike,

I think you have just hit the nail on the head. Surely it makes sense here to just do a 'big bore' swap won't it?

The bottom end of my engine is sound, and if the bottom ends are basically identical, then if I swap just the bores up, then it'll be the same as swopping the engine. Am I correct in my thinking here Mike?

Also, if I did do that could I put the 1150 throttle bodies and motoronic unit on, or would I get problems in that area. Is it better to stick with 1100 throttle bodies, motronic etc etc.

You have a great wealth of knowledge about these things because you have actually done it. What difference does the 'big bore' conversion make?

Many many thanks for all your help. I can see the spanners coming out very soon.

Martin.

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mikefigielski

Martin,

Doing a big bore conversion requires that you get the outside of the 1150 cylinder sleeves(the portion that protrudes into the engine casing) turned down approx 1mm so that they will fit into the 1100 cases. Also, if your bike was built before 12/97 then the bottom of the piston pin bosses on the underside of the pistons will hit the crankshaft weights at bottom dead center.... don't ask how I know that! I used a dremel and buzzed off a little metal from the pin bosses and all was well. If your bike was built from 12/97 on then that won't be an issue. If you have a machine shop nearby that can turn down the cylinders, it is much easier than swapping motors. You need to keep the throttle bodies, injectors, and motronic consistant (all 1100 or all 1150). I kept the 1100 stuff on my '94 RS when I did it and it was fine. If you have an early model RT with the throttle cable then switching to the 1150 TBs will not be feasable as they use the 3 cable system. Hope this helps.

Mike

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James Clark
The bike that this lot came from really flew.

 

 

If that's all you have left of it, I take it the landing wasn't so smooth?

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The cylinder heads on the 1150 engine have two studs holding on each exhaust header, but the 1100 has three.

 

So, if swapping engines, you'd also have to swap exhaust headers, correct?

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Another question: If in the engine swapping department, why not modify the engine to R1100S specs, which as I recall is ~10hp more powerful?

 

Add GS intake tubes?

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mikefigielski

The exhaust stud issue could be a problem. You don't say which model the 1150 motor is from. R1150RS & RT bikes have the same 3 bolt exhaust header pattern as the R1100 bikes did. If the motor is from an R1150R or GS then the exhaust headers will be an issue. The only difference on the S models is the Motronic and the exhaust, cams, compression ration etc are the same as the RT. Most of the gain is in thge 500rpm higher redline and from the freer flowing exhaust. The exhaust can't be easliy duplicated on an RT.

Mike

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Many thanks Mike. Great info.

My bike is a 1999 reg, so hopefully the piston mod should not be nessasary.

As I have all the 1150 gear (throttle bodies etc) I think I will give it a go with that and see how it performs.

I have a good machine shop nearby who have done many machining jobs for me, so hopefully a mill or so should be ok off the liners.

As the 1150 engine is sitting on the floor in my workshop, it'll be an easy thing to get the work done before I touch my bike. Great.

Re the exhaust problem. This engine came from a GS. So even an exhaust from a 1150 RT would not fit. The GS system that I have here is a full Remus, sounds awesome. But because of the way in which the exhaust is routed it will not fit the RT.

Sounds like in order to achieve this conversion I will have to fabricate a one off exhaust system. If I do I will try to incorperate the remus system, then I will have the full potential from this engine. Or I would have to 'modify' the RT bodywork, to accomadate the GS system. Hmmm! Quite a bit of work, but hopefully worthwhile in the end.

Once again many thanks for all your info. You are a top guy.

Martin.

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ShovelStrokeEd

In regards the exhaust, although I confess I have been following this entire thing with interest, if you have access to a tig welder and some skills with same, you can fabricate your own or, send your RT exhaust to a header guy and have him duplicate the primary pipes in a one size larger diameter. Not a trivial task with all the bends in there but it could be done. You won't quite get as good as the R1100S exhaust but you can get close. An alternative might be to leave the bundle of snakes portion of the factory header alone, just provide a step up in size once the pipes have made the turn to the rear and more or less straightened out. Stepped headers are all the rage, dontchaknow. The flanges are pretty easily swapped with a band saw and tig welder. While you are in there, the transition piece from the exhaust port to the header pipe can be cleaned up quite a bit and provide real benefit to flow.

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mikefigielski

Martin,

You can reuse the heads on your RT with GS cylinders if you want. If the heads are a little tired have them redone or even ported like I did. That way you can use your headers. Perhaps you can get a cat eliminator crossover pipe (Two Brothers sells them seperately) and use the Remus end can you have. A lot less work than fabbing a custom exhaust. Don't forget that if you do use the GS heads those cams are less aggressive than the RT and you will lose some horsepower.

Mike

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Pardon my ignorance, but wouldn't it just be easier to put new rings and valves in the existing R1100RT than going through all this? confused.gif

 

I know fun is fun....but

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mikefigielski

Using the 1150 cylinders with the original heads is no more work than what you are suggesting (except the small amount of machining needed) and he'll end up with 50cc more displacement and 5hp and 5 lbs/ft of torque. If you enjoy this type of thing the project and all of the "figuring it out" and work involved is almost as much fun as riding the thing.

Mike

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