True , you have to drill out the swingarm bolt holes on the frame. Then it will go in easy, if you are using the entire 650 swing arm rear wheel, shocks, chain guard and chain there will be no problem.
If you want to run the 550 wheel in the 650 swing arm , there will be issues. as I recall the rear axle is a larger diameter on the 650. and if you get past that , the different chain size may be an issue. I have never switched a 550 front sprocket into the 650 engine so I don't know if it'll be a direct fit or just another issue....I do know that the 650 and 550 rear sprockets do not switch. I hope the 650 donor has spoke wheels ,if not, the others work fine but take some getting used to visually.
The front end is the same way... You can switch the ENTIRE front end from 650 to 550 at the steering head. None of the parts that make a complete unit are interchangable between either unit...so it's either the 500/550 front end unit or the 650 front end unit.The 650 font forks are better than the 500/550... a touch longer too but if you hear that it'll throw off the numbers too much, fear not, you are only bringing it to stock 650 numbers . And to be frank , I feel that it is a total improvement over the 500/550's overall ride , without sacrificing nimbleness or stability.
If you have the 81 Custom model ( I think that's the one) it comes stock with dual front disc brakes. The spoke wheel model never did and no one here has been able to make one accept a dual front disc brake yet.
Wiring is a piece of cake if you swaped the entire front end over to 650 since the fuse box is right under the bars. There will be some customizing to do in the battery /air filter /CDI box area. 650 battery box ...will have to cut off the tool box and flip the RR to get it to fit under the sidcover on the shifter side. The battery box is not a direct fit but if you have a spare upper front engine mount bracket, it can be used at the rear of the battery box with stock isolatorsand attached with a standard 6mm or 8mm nut and bolt and washers drilled into the frame. The cdis can be attached in a similar fashion also using isolator rubber and washer...note I like to use a wide strip of old inner tube and wrap the cdi base and any area that the cdi boxes could touch if they were to get loose or jarred. The 650 coils should be used and will require threaded 6mmstock /6mm connectors and 6mmlock nuts , all avail at a good hardware store...will require a drilling.
The air filter unit is going to be a tight squeeze and will have to be installed while the rear fender removed, it makes it all possible. I can't remember if I used the 550 or 650 inner fender the last time I did it. But it will require home made mounting tabs to hold it against he frame on the brake side . I take the cover off the filter and cut down 3 hardware store bought screen door, screen /storm window stays and bolt them agaist the fiter and filter seal, just for a touch more air under the sidecover.
If you have an F frame you'll be in better shap than if you have a K frame.
Brake pedal....the 550 F is the one I used on my first K model 650 swap. The stock K pedal didn't give enough clearance for the bottom mounted clutch cable.
K sidecovers need to be cut around the carb area. The F model will look stock without cutting.
Well, that's all I got. good luck and have fun. RB
PS
If you are planning rearsets , disregard the F brake pedal.
" "pods forget the air box issue.
" " cafe seat electric pan disregard the battery box setup and most of the stock wiring.
but whatever you do , have fun doing it.
