Okay guys,

so here is the issue. At the beginning of the build I obviously had to change the rear structure of my k100 frame to make it fit the new seat. As the german tüv does not like having non-professionals work with frames I gave it to a local motorcycle shop. The quickly called back and informed me that the frame was non-aligned and extremely expensive to repair, so I was kind of forced to find a new one. Long story short: I bought a frame, the bill calls it a 1985 frame. I couldn't bring it back home since I was in the process of being taught how to teach other soldiers our weaponry and was hung up on that. My parents were in the area so they brought it in and to the motorcycle job. Since both the shop and my parents didn't know that there are differences between a 2v K100 and a 4V K100 the didn't look after that. And everything fits so far so I just came across when looking at all my registrations just now. It a '91 4V Frame, they sold me the wrong frame.

While this might not make a difference for many other countries, german tüv is build different. And since my POC has no idea what the differences in the k100's are he won't allow me to use the newer frame.

So what actually are the differences? From what I've found in the 4V the steering tube has been strengthened, it's a duolever frame but no other changes. But that's it. I asked BMW classic which tried to answer me properly but they are probably more knowledgeable in the R-Series and couldn't really help apart from sending the technical drawings and telling me that there is no difference in the steering tube angle

Am I missing something?

The problem you have is that as far as the authorities are concerned it is a 1991 K100 4V so you cant put an 85 2V engine into it and meet the regulations in force when the 91 model was made. Probably pollution requirements. Where as I have a 1999 K11LT with a 2000 K1200 engine which requires some mods to get it going well but that way round is OK. The design rules really apply much more to cars than bikes but don't argue with them as its like mud wrestling with a pig. You both get covered in mud and shit but the pig enjoys it.

Yeah, I am aware. It also comes with a few other issues as well, more power, probably ABS that the k4v mostly of the time had and I also planned driving the k with a throttle reduction which differs between the two engines aswell.

But while the mud games might be a loosing battle it is still far less expensive than paying another 200€ for the frame and 2,5k for the modification. I still need to get a license at that cost another 3k here

Ah I don't know. It is just annoying. I just hoped that some of you had some good resources that might support my claim that there is not much difference frame-wise

There is an immediate and visible difference - the fuel tank mountings. An early (pre-87) tank with the screw-on fitting at the rear won't fit the later frame which has a push-in type fitting secured by C-clips. It's possible to make a bracket that screws to the early frame using the existing tank mounts and so allowing the mounting of a late tank, so no frame mods Herr TuV Man, but you can't do it the other way around. That requires making early-style mounts and welding them to the frame.

Mechanically, I believe that the frames are identical.  There may be some slight difference in front end geometry to accommodate different forks and front wheel, but the mounting points for the engine, transmission and rear suspension are the same.  A side by side comparison will show any differences.

The fairings are interchangeable between models so I believe that geometry is the same as well.  The only real difference between the frames would be the mounting points for the Motronic and ABS components which are in different locations from the Jetronic.  These items would be the ABS brain, the coils, Ignition control unit, and the air plenum.  There might also be some differences in the radiator and tank mounting points between the early K100 and the 4 valve model.

Structurally, both frames are carrying the same amount of weight with similar weight distribution and drive trains with similar power output so the forces on the frame will be similar.  If anything, the late model frame would be stronger than the early one.  As far as I can tell, the engine block and transmission, which are stressed members in the frame, are identical between models, so there is no stregth difference.

Since the major difference between frames would be in the front end geometry, and the danger of tank slappers, you might want to do some research and document the front end geometry of the bikes that use those frames.  Heck, while you are at it, you could get a K1100 front fork assembly and Paralever swing arm.  

Seems strange that you can modify the frame to accommodate a different seat, and install different forks, wheels, handlebars, pegs and rear suspension to build a custom, but can't use a different year frame that is virtually identical.

Rear fender mounts are different - and so are the rear fenders.

Z racks are the same but they mount differently to the frame. (This why you need a 240 Reynolds Rack for a 2V and a 241 Reynolds Rack for a 4V.)

The rear hoop MIGHT be a little longer on the 4V since the paralever FD is longer than the monolever FD but I'm not positive of that.

According to me, there are 3 types of frames:
- K100 8V
- K1 (and K100 16V)
- K1100

The K1 has a specific angle of the direction : so the trail value is 90mm for the K1 vs 110mm for the others.
It also has no silent blocs at the front engine fittings  like K100 8V:


Another essential difference is on the K11 frame vs the others :


The triangle at the top of the frame is only on the K11. The K100 16v and 8V share the same design but the tubes thickness are different.

There also are other slight differences, about brackets, particularly around the top fixation of the rear damper.


About the initial issue of a deformed frame:
I've been told, from a former BMW chief mechanic, that when the K100 was issued, they noted huge deformations in new frames, from a bike to another.  They could have more than 2cm différences at the rear end, measured at the frame, and the same value at the rear wheel offset.
The information was sent upwards and BMW, after considering the problem, took the necessary decision, in the spirit of responsibility that characterizes German industry and sent a technical note to the dealers network to solve the problem  with elegance and efficiency: deny the problem by increasing the allowable deformation tolerances.

A last thing: don't chop your K100. It sucks.

Not all K1100s have the "V" frame. 1993 and earlier K1100LTs use the same frame as the K100RS4V.

Part 46512310661

I was about to add the K1100 frame changed in 1994.

This was also the change from ABS1 to ABS2. Fuel tank from up to 93 does not fit 94 on.

My K100-K1200-engined/5 speed "Big Block" originally used a 1987 K100RS frame when I initially put it all together, but when 'pushed' it exhibited a noticeable weave on long, fast sweeping corners - new steering head bearings were fitted in both frames, all fasteners correctly torqued, and Paralever rear used, same shockie & Marzocchi forks. 

I sourced a 1993 frame from a K1100RS with V backbone and with no other changes the irregular handling entirely went away.

First of all, thank you all for your input.

Since the only change I made to the K-Frame is the rear and I don't plan on changing the front forks (specifically due to the high offset of the stock forks, there is no USD that I know of that has tripletrees that come close to ~55mm. The custom tripletrees from powerbrick and the likes are not tested by german tüv. It's quite hard to get those permitted. And better suspension isn`t worth it, if I can't turn my bike.)

Thank you @JBT for the short history on the different frames in the k1002v-K1100.

I obviously kept searching only for more information and also took a closer look at my registration papers. Something I found, mainly in the papers, is the allgemeine betriebserlaubnis (ABE) Number(Early K1002v: D100; Early 16V and later 2V: D100/1 but they are further distinguished by Versions A/B/C) . Since the early K100RS16V have the same ABE as the K100 after '85 (?) I might have a chance to support my claim that the frames are almost equal by using that.

But I think it is of more use to ask a german forum for that.

Though if you can help with that claim, feel free to answer that

This is a request for explanation of this thread and the applicable legal rationales. My understanding is the OP is modifying his K100 and ran into some issues which necessitated replacing the frame. He purchased a new/used frame but it was technically for a different variant of the K100 and is now stuck legally unable to properly register the bike??? Did I get that right? Just wondering at the cultural and legal differences. I powder coated one of my K-75's frame. Decent job but the shop covered up the VIN number. Not ever been bothered by it. And I've mixed and matched frames and engines. Never even had questions raised. And I thought California rather - dare I say - anal about such details. Just being curious.

It's the VIN number that seems to be the important one over here. It's checked at start of the annual test (MOT) to make sure you're not trying to pass off a ringer, but I don't recall ever having an engine checked. Certainly, one Guzzi frame of mine had three different engines in it over its lifespan and was never questioned, even though the logbook had a different number on.

Dai wrote:It's the VIN number that seems to be the important one over here. It's checked at start of the annual test (MOT) to make sure you're not trying to pass off a ringer, but I don't recall ever having an engine checked. Certainly, one Guzzi frame of mine had three different engines in it over its lifespan and was never questioned, even though the logbook had a different number on.

Dai, check me, you're in the UK? What is the MOT? Years ago when I lived in Memphis autos/trucks and the like were checked quarterly or yearly for brakes and headlight alignment. That's pretty much gone by the by. And motorcycles weren't ever checked for anything. Certainly here in California the only thing that gets checked on a motorcycle is the color and amount of money you send in to pay for the license sticker. Frankly even the rudimentary air pollution equipment on modern BMW's was regularly stripped off. Just trying to learn the differences.

UK, yes. MOT = Ministry of Transport, an annual test for most vehicles over four years old but for some vehicle classifications it's after three years. It's gotten tighter over the years and (maybe surprisingly) I approve of that approach. However, it's nowhere near as bad as the German TuV test. Cost varies by vehicle type. Additionally you then have to pay an annual Vehicle Excise Duty (VED - commonly and incorrectly referred to as 'the road tax'), the cost of which also varies by vehicle type and engine pollution levels.

Vehicles over forty years old from the date of first registration (not the date of build) neither have to take the MOT test, nor pay the VED. Two of my Moto Guzzis fall into this band and LFB (built November 1983, first registered May 1984) rolls over next year. The thinking behind this was that any vehicle that reaches that age has been properly maintained. You still have to apply annually for the VED exemption but it's painless. You are still expected to maintain the vehicle to MOT standards; if you fail to do this the police have the right to impound the vehicle and take you to court.

We also have an SVA test (single vehicle approval) for custom stuff that is either completely homebuilt or deviates in specific ways from the vehicle as it left the factory. It's really a super-MOT and is nothing to be bothered about if you've done the job properly. Once the vehicle has passed the SVA it then assumes normal MOT procedures immediately - no four year break. Oddly, a bit of a legal slip-up means that a vehicle that has just passed an SVA now has to go through the less restrictive MOT before it can be issued with the VED and be legally classified as roadworthy.

Lastly, there is the IVA (individual vehicle approval) for as-built vehicles that are e.g. being brought in from overseas and are going to be registered in the UK. It's a simple inspection that then also requires an MOT as a follow-up.

With the exception of the forty year rule, you cannot get vehicle insurance nor the VED certificate unless the vehicle has a valid MOT certificate. If the MOT certificate expires during the insurance period, the insurance is automatically invalidated until a new MOT test has been passed. The VED is unaffected. You are legally required to have valid road vehicle insurance at all times when you are driving/riding. The consequences of not having it and getting caught can be very severe. It's not just the court case and the fines and the endorsements on your driving licence and the increase in the insurance premium for the next few years; the knock-on effects of losing your driving licence through getting too many endorsements can and has led to the loss of jobs though not being able to get to a place of work and consequently, homelessness through not being able to pay a mortgage. It just isn't worth the risk, but people still do it.

When I was at school in KY, there was no vehicle checking at all, except to re-register a vehicle that was being brought in from out of state. 'Rust buckets' does not adequately describe some of the pickups that lived up the hollers.

It is quite pathetic what passes as a form of inspection in most of the US states, which I've had experience of living in (multiple over 40 years). Massatucky being the exception where a motorbike gets an annual 'inspection' which is quite rudimentary. 

In Washington state, when I put together "Big Block" in 2014 and early '15, I simply used a frame that was appropriate with a known good VIN. No one checked on the modified later model brakes, different gearbox, 1200cc engine, customised fuel injection system, later models wheels, sliced and re-welded subframe, shock or Marzocchi forks, & etc. I paid the rego & insurance for the type of bike the frame represented and away I rolled 

- just the way I like it 

Does it mean there's rubbish rolling over the roads that could be deemed illegal or unsafe? Yep, you betcha. There could also be some masterly engineered projects, much improved upon over 'stock' vehicles. But this here's 'Merica.

Yeah, in 2018 my K100RS was totalled.  The insurance gave me cash to replace the bike with enough left over to completely rebuild the original using the engine and some of the other stuff. 

The frame was trashed so I got a replacement from Colorado that came with a clean title so I was able to register it without a salvage title. 

Motorcycle inspection in New York is a lot easier than autos.  Lights, horn, turn blinkers, brakes and tires.  The guy I take my bikes to can get the job done along with the paperwork in about 10 minutes.

Idaho and South Dakota will let you re-rego a salvage title from another state that essentially 'washes' the wreck from the vehicle's history. You only need a PO box as an address. An acquaintance of mine has cleaned several over the years. Plus, if you're a resident of the three counties near the Seattle metro area you can get a licence and rego in So. Dakota and avoid the excessive yearly RTA additional tax added to your registration. That's a transit tax to pay for the light rail project that's been going on for yonks now. It doubles my rego fee for bikes and cars and I will never ever step a foot onto their platform, but my neighbours might, so it's possibly gunna keep them off the road. Sure. Nudge. Wink.