Just fitted monster 400 frame to monster 620 but shock does not line up with frame mounting

Raise the rear wheel off the ground and then with a no loss air pump apply more pressure to force any oil down the lines into the shocks, then release all air pressure and press the air line fitting collar in and disconnect the lines. THEN remove the upper shock mounting bolt and lockwasher and flat washer and then remove the lower shock mounting bolt and lockwasher and flat washer and remove the shock absorber assembly from the motorcycle. BUT do not lay it down as the oil will leak out and cannot be replaced so the shock would then be garbage. You could remove the air line fitting and plug the hole with a 1/8 NPT thread plug if the shock is to be retained and stored or etc.

If you have a dealer near by, go and measure the 2 bikes frame size. I think that would be the only difference. The 800 might have a bigger frame in pipe diameter size, The bolt pattern should be the same, but I don't know for sure. I have a 99 750 and 02 S4 and the difference in frame size is unbelievable. I think the 620 was built along the lines of the 400 frame, and the 750/ 800 was in a class all by itself. Then the 900's were another size up. Ask a mechanic at the dealer. They should know this stuff. Or call one up and bug them. I do it all the time. Hope this helps.

2 bolts on the top of shocks and 1 bolt on the bottom but the top 2 bolts are a pain in the neck

If you want an S4r then go for it and don't be put off by what others say. The engine mounts are identical on all Ducati engines, so you'll haev no worries there. I am not aware of any extra mounting tabs on the LC engines. The only problem you may have is that the later S4rs get 12mm engine mounts wheras the 620 will have 10mm. Not a problem if you have a 12mm drill bit. As far as swingarms are concerned, your 620 arm will fit fine. I wouldn't be worried about the frame twisting under the 996 grunt. Use the 620 ignition, & coils. Plug into the 996 injectors and use a powercommander to adjust the fuelling. The exhaust will be different - use an S4r exhaust and you'll be fine. Above all, be totally convinced that you can do this and don't let anyone put you off.

Have you selected a brand yet? I can strongly recommend the LeoVinces - they are stainless on the inside so no maintenance and the outsides can be carbon fiber Ti, or aluminum. Arrows are also highly recommended: both have a great fit-and-finish. Some might give you slightly better overall performance, but none will math them for longevity and customer satisfaction.,,,

Have you selected a brand yet? I can strongly recommend the LeoVinces - they are stainless on the inside so no maintenance and the outsides can be carbon fiber Ti, or aluminum. Arrows are also highly recommended: both have a great fit-and-finish. Some might give you slightly better overall performance, but none will math them for longevity and customer satisfaction.,,,