Can i fit a zzr 600 engine into my zzr 400 frame ,as my head has cracked and have a 600 engine which is a 1991 as well, would it fit straight in without any major problems if not what problems could i come accross thanks ****

Not without a lot of work
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Hello and welcome to Fixya, It can be done, one of our competitor's race teams did it with some pretty drastic modification's. Its definitely a challenge.But seen it accomplished. I could give you there info, they may be able to give you some hints. Let me know, Thanks for using Fixya

Im not sure about "bolt straight on" but it should be very close. most times bike models run for years without much major change. You may have to change a few brackets, or do a bit of bending and filing to get it to fit. The 06 ZZR has the twin headlights. I looked at some pictures carefully of the two different models. The frame is the same for both, so there is a good chance it will bolt straight on.

zzr 600 haynes .com

Take a spark plug out go buy 4 and put them in.

you wont find one but all exept the head and carbs are the same as the zzr 600 use this instead availiable at haynes .com

there is not a manual for the zzr 400 so use the zzr 600 everything is the same except from the carbs and the head

The frame mounting points are completely different. A zx 636 frame wraps around the motor where as a zx10r frame goes directly over the motor. That's how they keep the zx10r nimble enough to feel like a 600cc sport bike. But in this day and age if you have enough time and money you can accomplish anything. Honestly it's just easier to sell your 6 and buy a 1 liter.

zzr 600 manual is the same except the head and carbs

ello m8,, i havent tried these guyz yet,, but they do downloadable manuals,as well as sell yuh one, but try em,, its www.repairmanual.com nice 1 ,,hope it helps,,