It can be done, but sometimes it shouldn't.
Motorcycle frames can sustain damage from a variety of unfortunate situations, not the least of which are the occasional crashes we find ourselves involved in. What do we do about frame damage, though? Can it be fixed? Should it be fixed?
The short answer is, yes, it can usually be fixed! The longer answer is yes, the frame can be fixed, but you, the owner of said motorcycle, will have to do some cost-benefit calculations in order to weigh whether it is worth it to fix. If it’s not, you’ll have to decide whether whole-frame replacement is a better option, or if it’s simply time for an entirely new motorcycle.
The method of damage is your first and biggest clue when it comes to method of repair. Usually, a crash is the culprit, and that is the one that is often overlooked, but very much needs to be fixed. Sometimes, time and improper storage results in frame damage.
When it comes to very old steel-framed motorcycles, frame rust can be a real problem. Small patches can be sanded and painted without too much trouble or danger. Very large patches, or internal rust and holes, often mean a fix is impossible or prohibitively expensive. The “good” news is, if the frame is in that kind of shape, the rest of the bike most likely isn’t worth rescuing, either. Pull off what can be salvaged, and send the rest to a recycler.
The very best—for various metrics of “best”—way to damage a motorcycle frame is to crash the bike. In many states the mere presence of a scratch on the frame will total a motorcycle in an insurance adjuster’s eyes, so the decision might be made for you. If you notice a crack in the frame, or the bike doesn’t track the way it used to, or you notice a wobble that wasn’t there before the crash, or there are any other changes in handling that did not exist before the crash, have it checked.
Often, a crashed motorcycle is a much-loved motorcycle, and a damaged frame is the thing that stands between fixing it and riding it, or sending it to the scrap heap. If the bike might have a bent or damaged frame but you are not sure, the only reliable way to know is to bring it to a professional. Even if no damage to your motorcycle’s frame is obvious, if you ask very much from your motorcycle (and we do), it is worth it to have it measured. Often a frame can be twisted or bent but display no visible cracks, stress marks, or paint chips.
Frame restoration specialists use an instrument called a theodolite, which measures angles from a distance, and is the same tool land surveyors use. With this tool and some computer software specific to the task, they can detect bends and twists in a frame that otherwise looks just fine to the naked eye. The bike does not need to be stripped to the frame to do so.
If the frame is not straight, a technician can secure it in a jig and re-true it. This will ensure the frame, swingarm, front suspension and wheels are all properly aligned to work together perfectly.
If the bike remains misaligned, at best it will wear out its tires unevenly and “pull” to one side of the road. At worst, its brakes, suspension, bearings, and any other moving parts will be misaligned, causing unexpected premature wear and handling problems that can be very dangerous, especially at high speed.
If you are riding a bike that was ever crashed harder than a parking lot tip-over, you will probably want to find a reputable chassis repair technician in your area. Since a frame can be measured for damage with minimal prep, it’s worth your time to have it checked out.
Source: Computrack Boston