Good day to highly reputable forum people!

I have a running project K75 RT and I just took it to first longer drive after I bought it. The bike had motor swap 10 years ago and was left to sit for 10 years. Motor was changed because the clutch was literally ripping itself apart every 20 to 200km. Best guess being there was something off in engine-clutch-gearbox alignment. The engine that was swapped out has one of the engine's aluminum mount rebuilt. Also fairings have seen some fixing on the other side. So it has been crashed at some point.

I suspect that I might have slightly damaged frame geometry. I took one of the front engine mounts loose and it was 2 to 3 cm of the line. When I put it back I had to bend the front mounting bar to get it on spot. Should the engine mounts be perfectly lined by standard? Also on my resent ride I noticed that the bike is slightly pulling to the right. On straight and even highway I had to keep light counter steering pressure to the left. If I took my hands of the bar the bike started to tilt right.

2/3 cm out of line would worry me   However before scraping the frame, you can inspect the front forks for alignment, tyre condition/wear pattern/pressure 38psi. Also, steering head bearings for condition 

moriarti wrote:2/3 cm out of line would worry me   However before scraping the frame, you can inspect the front forks for alignment, tyre condition/wear pattern/pressure 38psi. Also, steering head bearings for condition 

Thanks for answer!

I ride brand new BT-46 tyres with proper pressures. Steering head is solid. There could be some misalignment when it comes to forks but I'm afraid that the actual problem comes from the frame. The engine mount off-set and steering abnormalities would suggest that.

I could
1. live with the imperfect frame but it doesn't feel safe when it affects the handling.

2. get some (hopefully) straight second-hand frame but the change work would be huge

3. try to straighten the frame on some frame bench. Local restrictions allow frame-straightening by bending in case of regular steel frame. However I would still be left with frame that has extra tensions in its structure. Probably not a big problem since the frame is quite sturdy. Still a 'TYÖMAA' which means a hell lot of work.

4. Scrap the bike and sell parts. I have a running bike with spare engine so I could have some money out of it. Maybe I would buy a new K75 and proceed to my original closed-loop EFI project I had in mind. 

I am considering options 3 and 4 for now. Anyway it seems quite a setback and while trying to just enjoy a hobby it still seems like enormous amount of wasted time and resources on this bike.

I spent many years working on bikes for a living. Many crash repairs and after a few very bad experiences with straightening frames I came to the conclusion that a bent frame was not to be fixed. Bending a frame back into shape causes more problems down the track as you have just discovered. Feed it to the scrap metal bin and put some time into a good frame.

I had a bike totaled in a collision with an automobile and the frame was seriously bent.  I was able to purchase a used frame in good condition with a title from a bike breaker for something like $400 which included shipping 2400km from Colorado to New York State. 

Having a bare frame made it very easy to do a paint job on the whole frame as well as changing the steering head bearings. 

I would check around, frames shouldn't be that hard to find, and if you can avoid shipping costs by picking it up yourself, they can be pretty inexpensive for what you get as well.

flying finn & brick wrote:Good day to highly reputable forum people!

Should the engine mounts be perfectly lined by standard? Also on my resent ride I noticed that the bike is slightly pulling to the right. On straight and even highway I had to keep light counter steering pressure to the left. If I took my hands of the bar the bike started to tilt right.

Yes, the frame should line up with the mounting points on the engine.

When I made a custom K75 with a motor from one K75 and a frame from another K75 everything lined up perfectly at the front of the motor, at the top of the bellhousing and at the transmission.

Many K bikes pull to the right slightly.

It should all line up perfectly but there are shims required and its possible there is an issue there. As in lack of shims, not to mention some have a damper rubber mounting.

I have not taken a K engine out but I know the shims should exactly fill the space between engine and frame, there is not a need for the bolts to pull them together. That is going to introduce a stress into the frame, thats not good.

The only frame bolt that should need any shimming is the one at the top of the bellhousing.

I put this graphic together from the BMW manual when I built my K75 Frankenbrick: